Claims:We claim:

1. A method for reducing roll forces during cold rolling of a steel, the method comprising:
casting a steel slab comprising an alloy composition in weight percentage (wt.%) of:
carbon (C) at about 0.04 wt. % to about 0.065 wt.%,
manganese (Mn) at about 0.15 wt. % to about 0.5 wt. %,
silicon (Si) up-to 0.04 wt. %,
sulphur (S) up-to 0.03 wt. %,
phosphorous (P) up-to 0.03 wt. %,
aluminum (Al) up-to 0.055 wt. %,
nitrogen (N) up-to 120ppm,
titanium (Ti) at about 0.012 wt. % to about 0.025 wt. %,
balance being Iron (Fe) optionally along with incidental elements;
heating, the steel slab to a first predetermined temperature for a first predetermined time;
subjecting the steel slab to a hot rolling at the first predetermined temperature to reduce thickness of the steel slab to a first predefined thickness to produce a hot rolled steel sheet,
wherein presence of titanium at about 0.012 wt. % to about 0.025 wt. % in the alloy composition scavenges free nitrogen from interstitial sites of steel matrix and induces favourable crystallographic texture, forming microstructure comprising predominantly a ferrite phase and marginally a pearlite phase, wherein the hot rolling results in reducing yield strength and tensile strength of the steel thereby reducing roll forces during subsequent cold rolling.

2. The method as claimed in claim 1, wherein the first pre-determined temperature ranges from 1100°C to 1200°C.

3. The method as claimed in claim 1, wherein the first predetermined time ranges from 15minutes to 45minutes.

4. The method as claimed in claim 1, wherein the hot rolled steel sheet exhibits tensile strength less than or equal to 500 MPa.

5. The method as claimed in claim 1, wherein the microstructure of the hot rolled steel sheet comprises majority of ferrite phase.

6. The method as claimed in claim 1 and 5, wherein microstructure of the hot rolled steel sheet comprises greater than 80% of the ferrite phase and less than 20% of the pearlite phase.

7. The method as claimed in claim 6, wherein the ferrite phase in the hot-rolled steel sheet is substantially polygonal shaped.

8. The method as claimed in claim 7, wherein average grain size of the polygonal shaped ferrite phase ranges from 5 microns to 25 microns.

9. The method as claimed in claim 1, wherein the hot rolling includes finish rolling of the steel at temperatures greater than Ar3 and/or Ae3 temperature, wherein Ae3 is the temperature at which transformation of austenite to ferrite starts at equilibrium.

10. The method as claimed in claim 1, wherein the casting is a continuous casting process and is performed in a thin slab caster.

11. The method as claimed in claim 1, wherein the cold rolling is performed in a reversing cold-rolling mill.

12. The method as claimed in claim 1, wherein the Ti in the chemical composition of steel is governed by the equation:
[Ti]-(48/14)*[N]-(48/32)*[S]<0%
wherein, N is the wt.% of Nitrogen and S is wt.% of Sulfur.

13. The method as claimed in claim 1, wherein the hot rolling is performed in a thin slab casting and rolling (TSCR) mill.

14. The method as claimed in claim 1, wherein the heating of the steel slab is performed in a reheating furnace.

15. An advanced low strength hot rolled steel sheet with a tensile strength up to 500 MPa, the hot rolled steel sheet comprising:
an alloy composition in weight percentage (wt.%) of:
carbon (C) at about 0.04 % to about 0.065 %,
manganese (Mn) at about 0.15 % to about 0.5 %,
silicon (Si) up-to 0.04 %,
sulphur (S) up-to 0.03 %,
phosphorous (P) up-to 0.03 %,
aluminum (Al) up-to 0.055 %,
nitrogen (N) up-to 120ppm,
titanium (Ti) at about 0.012 % to about 0.025 %,
balance being Iron (Fe) optionally along with incidental elements,
wherein presence of titanium at about 0.012 wt. % to about 0.025 wt. % in the alloy composition scavenges free nitrogen from interstitial sites of steel matrix and induces favourable crystallographic texture, forming microstructure comprising predominantly a ferrite phase and marginally a pearlite phase.

16. The steel sheet as claimed in claim 15, wherein the microstructure of the hot rolled steel sheet comprises majority of ferrite phase.

17. The steel sheet as claimed in claim 15, wherein the microstructure of the steel sheet comprises greater than 80% of the ferrite phase and less than 20% of the pearlite phase.

18. The steel sheet as claimed in claim 16, wherein the ferrite phase in the steel sheet is substantially polygonal shaped.

19. The steel sheet as claimed in claim 18, wherein average grain size of the polygonal shaped ferrite phase ranges from 11 microns to 12 microns.

20. A method for manufacturing an advanced low strength steel sheet with a tensile strength up to 500 MPa, the method comprising:
casting a steel slab comprising an alloy composition in weight percentage (wt.%) of:
carbon (C) at about 0.04 wt. % to about 0.065 wt. %,
manganese (Mn) at about 0.15 wt. % to about 0.5 wt. %,
silicon (Si) up-to 0.04 wt. %,
sulphur (S) up-to 0.03 wt. %,
phosphorous (P) up-to 0.03 wt. %,
aluminum (Al) up-to 0.055 wt. %,
nitrogen (N) up-to 120ppm,
titanium (Ti) at about 0.012 wt. % to about 0.025 wt. %,
balance being Iron (Fe) optionally along with incidental elements,
heating, the steel slab to a first predetermined temperature for a first predetermined time;
subjecting the steel slab to a hot rolling at the first predetermined temperature to reduce thickness of the steel slab to a first predefined thickness to produce the hot rolled steel sheet; and
subjecting the steel sheet to the cold rolling to further reduce the thickness of the steel sheet to a second predetermined thickness to form the cold rolled steel sheet,
wherein, the hot rolled steel sheet includes microstructure comprising predominantly a ferrite phase and marginally a pearlite phase.

21. The method as claimed in claim 20, wherein the first pre-determined temperature ranges from 1100°C to 1200°C

22. The method as claimed in claim 20, wherein the first predetermined time ranges from 15mins to 45mins.

23. The method as claimed in claim 20, wherein the microstructure of the hot rolled steel sheet comprises majority of ferrite phase, preferably the microstructure of the hot rolled steel sheet comprises greater than 80% of the ferrite phase and less than 20% pearlite phase.

24. The method as claimed in claim 20, wherein the ferrite phase in the steel sheet is substantially polygonal shaped.

25. The method as claimed in claim 24, wherein average grain size of the polygonal shaped ferrite phase ranges from 11 microns to 12 microns.

26. The method as claimed in claim 20, wherein the hot rolling includes finish rolling of the steel at temperatures greater than Ar3 and/or Ae3 temperature, wherein Ae3 is the temperature at which transformation of austenite to ferrite starts at equilibrium.

27. The method as claimed in claim 20 comprises coiling the steel sheet at second predetermined temperature, wherein the second predetermined temperature is greater than 550°C.

28. The method as claimed in claim 20 comprises feeding the steel slab through a primary descalers to remove oxide scale layers on the steel slab formed during the casting.

29. The method as claimed in claim 20, wherein the cold rolling is performed in a reversing cold-rolling mill.

30. The method as claimed in claim 20, wherein the heating of the steel slab is performed in a reheating furnace.

31. The method as claimed in claim 20, wherein the casting is a continuous casting process and is performed in a thin slab caster.

32. The method as claimed in claim 20, wherein the hot rolling is performed in a thin slab casting and rolling (TSCR) mill.

33. The method as claimed in claim 20, further comprising performing a pickling and cold rolling on the steel sheet after the hot rolling.

34. The method as claimed in claim 20, wherein the first predefined thickness ranges from 1.2 mm to 6 mm.

35. The method as claimed in claim 20, wherein the second predefined thickness ranges from 0.1 mm to 1.6 mm.

36. The method as claimed in claim 20, wherein the Ti in the chemical composition of steel is governed by the equation:
[Ti]-(48/14) *[N]-(48/32) *[S]<0%
wherein, N is the wt.% of Nitrogen and S is wt.% of Sulfur.

37. The method as claimed in claim 20, wherein the difference between the first predefined thickness and second predefined thickness is greater than 70%.
, Description:TECHNICAL FIELD

Present disclosure relates in general to a field of material science and metallurgy. Particularly, but not exclusively, the present disclosure relates to an advanced low strength hot rolled steel sheet. Further embodiments of the disclosure disclose a method for manufacturing an advanced low strength hot rolled steel sheet with tensile strength of up-to 500 MPa with reduced rolling forces during cold rolling.

BACKGROUND OF THE DISCLOSURE

Steel is an alloy of iron, carbon, and other alloying elements. Because of its strength and low cost, steel is considered as a major component in wide variety of applications. Some of the applications of the steel may include buildings, ships, tools, automobiles, machines, bridges, and numerous other applications. Steel obtained from steel making process may not possess all the desired properties. Therefore, the steel may be subjected to secondary processes such as heat treatment, cold working for controlling material properties to meet various needs in the intended applications.

Generally, heat treatment may be carried out using techniques including but not limiting to annealing, normalising, hot rolling, quenching, and the like. During heat treatment process, the material undergoes a sequence of heating and cooling operations, thus, the microstructures of the steel may be modified during such operation. As a result of heat treatment, the steel undergoes phase transformation, influencing mechanical properties like strength, ductility, toughness, hardness, drawability etc. The purpose of heat treatment is to increase service life of a product by improving its strength, hardness etc., or prepare the material for improved manufacturability.

Further, cold Rolling Mills (CRM) are generally used to reduce the thickness of steel sheets and impart properties as per the requirements of the end customers. The input Steel sheet used as substrate for these CRMs are sourced from the upstream hot rolling plants and these steels have conventionally plane Carbon-Manganese chemistry design with a typical chemical composition: Carbon < 0.10 wt%, Manganese < 0.6 wt%, Silicon < 0.15 wt%, Sulphur < 0.03 wt%, Phosphorus < 0.03 wt% Aluminum < 0.06wt%, Nitrogen < 120ppm. The reduction in thickness is done by repeated cold rolling passes in the reversing cold rolling mills which are operated with huge capacity motors using large amount of electrical energy. In any cold rolling mill, the productivity of the CRMs is very crucial for not only enhancing the cold rolled products business (including FHCR [full hard cold rolled] and CRCA [closed rolled cold annealed] Products) but also no compromises can be made on product quality but at the same time, the increase in the carbon footprints due to large electrical energy consumption, is not an ecologically sustainable practice.

Main hurdle in increasing the productivity of CRMs is high roll forces during cold rolling process, which directly determines number of roll passes during cold rolling in the reversing mill. Hence it is directly affecting the processing time. Higher the roll forces during cold rolling, more electrical energy would be required to run the CRM, thus increasing the energy consumption. Various options currently have been tried to decrease the roll forces at CRM, but most of them are associated with certain constraints, limitations, and compromises.

Some of the conventional techniques used to increase the productivity of cold rolling mills include, motor-capacity enhancement, reducing the work roll diameter of cold rolling mill, using higher lubrication, increasing strip-tension, increasing the cold rolling mill speed, reducing the thickness of input hot rolled steel substrate, using extra low carbon interstitial free (IF) steel, etc. But all these options are associated with many constraint, limitations, and compromises, and require major capital investment and resources and also known to increase the carbon footprints.

There are various process in the art for producing rolled blank/sheets. One such conventional process is disclosed in US10590506 B2 [506B2]. Document 506 B2 teaches about precipitation hardened hot rolled steels which are strengthened by extremely fine nano sized Ti (C, N) precipitates. Increasing the amount of TiC precipitation will increase strength. Increase in strength of hot-rolled steel will impact the cold formability of hot rolled steel sheet.

Hence, there is a need for an economically attractive and technically viable way of developing hot rolled steel sheet with reduced roll forces during cold rolling.

The present disclosure is directed to overcome one or more limitations stated above or any other limitation associated with the prior arts.

SUMMARY OF THE DISCLOSURE

One or more shortcomings of the prior art are overcome by method as disclosed and additional advantages are provided through the method as described in the present disclosure.

Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.

In one non-limiting embodiment, there is provided a method for reducing roll forces during cold rolling of a steel. The method starts from casting a steel slab of a composition comprising in weight percentage (wt.%) of carbon (C) at about 0.04 wt. % to about 0.065 wt.%, manganese (Mn) at about 0.15 wt. % to about 0.5 wt. %, silicon (Si) up to 0.04 wt. %, sulphur (S) up to 0.03 wt.%, phosphorous (P) up-to 0.03 %, aluminium (Al) up to 0.055 wt.%, nitrogen (N) up-to 120ppm, titanium (Ti) at about 0.012 wt.% to about 0.025 wt.% balance being Iron (Fe) optionally along with incidental elements. Heating, the steel slab to a first predetermined temperature for a first predetermined time, and then subjecting, the steel slab to a hot rolling to produce a hot-rolled steel sheet. The steel slab is subjected to hot rolling at the first predetermined temperature to reduce thickness of the steel slab to a first pre-defined thickness to produce a hot rolled steel sheet. The presence of titanium at about 0.012 wt.% to about 0.025 wt.% in the alloy composition scavenges free nitrogen from interstitial sites of steel matrix and induces favourable crystallographic texture in the microstructure. The favourable crystallographic texture comprises of crystal orientations such as {554} <225>, {332} <113>, {111} <112>, are induced in the hot rolled steel micro-structure, predominantly containing a ferrite phase and a marginally a pearlite phase. The obtained textured hot-rolled steel results in reduced yield strength and tensile strength of the steel thereby reducing roll forces during subsequent cold rolling.

In an embodiment, the first predetermined temperature ranges from 1100°C to 1200°C and the first predetermined time ranges from 15 minutes to 45 minutes.

In an embodiment, the hot-rolled steel sheet exhibits tensile strength less than or equal to 500 MPa.

In an embodiment, microstructure of the hot rolled steel sheet comprises majority of ferrite phase. The microstructure of the hot rolled steel sheet comprises greater than 80% of the ferrite phase and less than 20% of the pearlite phase. The ferrite phase in the hot-rolled steel sheet is substantially polygonal shaped. Average grain size of the polygonal shaped ferrite phase ranges from 5 microns to 25 microns.

In an embodiment, the hot rolling includes finish rolling of the steel at temperatures greater than Ar3 and/or Ae3 temperature. Ae3 is the temperature at which transformation of austenite to ferrite starts at equilibrium.

In an embodiment, the casting is carried out in a continuous casting process and is performed in a thin slab caster.

In an embodiment, the cold rolling is performed in a reversing cold rolling mill.

In an embodiment, the Ti in the chemical composition of steel is governed by the equation:
[Ti]-(48/14) *[N]-(48/32) *[S]<0%; where, N is the wt.% of Nitrogen and S is Wt.% of Sulfur.

In an embodiment, the hot tolling is performed in a thin slab casting and rolling (TSCR) mill.

In an embodiment, the heating of the steel slab is performed in a reheating furnace.

In another non-limiting embodiment, an advanced low strength hot-rolled steel sheet with a tensile strength up to 500MPa is disclosed. The hot-rolled steel sheet comprising an alloy composition in weight percentage (wt.%) of carbon (C) at about 0.04 % to about 0.065 %, manganese (Mn) at about 0.15 % to about 0.5 %, silicon (Si) up-to 0.04 %, sulphur (S) up-to 0.03 %, phosphorous (P) up-to 0.03 %, aluminum (Al) up-to 0.055 %, nitrogen (N) up-to 120ppm, titanium (Ti) at about 0.012 % to about 0.025 %, balance being Iron (Fe) optionally along with incidental elements. The presence of titanium at about 0.012 wt. % to about 0.025 wt. % in the alloy composition scavenges free nitrogen from interstitial sites of steel matrix and induces favourable crystallographic texture with crystal orientations such as {554} <225>, {332} <113>, {111} <112>, in the hot rolled steel micro-structure predominantly containing a ferrite phase and marginally a pearlite phase.

In yet another non-limiting embodiment, a method for manufacturing an advanced low strength steel sheet with a tensile strength up to 500 MPa is disclosed. The method includes casting, a steel slab comprising an alloy composition of a composition comprising in weight percentage of composition in weight percentage (wt.%) of carbon (C) at about 0.04 % to about 0.065 %, manganese (Mn) at about 0.15 % to about 0.5 %, silicon (Si) up-to 0.04 %, sulphur (S) up-to 0.03 %, phosphorous (P) up-to 0.03 %, aluminum (Al) up-to 0.055 %, nitrogen (N) up-to 120ppm, titanium (Ti) at about 0.012 % to about 0.025 %, balance being Iron (Fe) optionally along with incidental elements. Further, heating the steel slab to a first pre-determined temperature for a first pre-determined time. Subjecting the steel slab to a hot rolling at the first predetermined temperature to reduce thickness of the steel slab to a first predefined thickness to produce the hot rolled sheet. The hot rolled steel sheet includes microstructure comprising predominantly a ferrite phase and marginally a pearlite phase. The hot rolled sheet is then subjected to the cold rolling to further reduce the thickness of the steel sheet to a second pre-determined thickness to form the cold rolled steel sheet.

In an embodiment, the method comprises coiling the hot-rolled steel sheet at a second pre-determined temperature. The second pre-determined temperature is greater than 550°C.

In an embodiment, the method comprises feeding the steel slab through a primary descalers to remove oxide layers on the steel slab formed during the casting. The method further includes performing a pickling and cold rolling on the steel sheet after the hot rolling.

In an embodiment, the first predefined thickness ranges from 1.2mm to 6mm and the second thickness ranges from 0.1mm to 1.6mm. The difference between the first pre-defined thickness and second pre-defined thickness is greater than 70%.

It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the disclosure.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

The novel features and characteristics of the disclosure are set forth in the appended description. The disclosure itself, however, as well as a preferred mode of use, further objectives, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:

FIGS.1a and 1b are flowcharts illustrating a method for manufacturing an advanced low strength steel sheet, according to an exemplary embodiment of the present disclosure.

FIG.2a and FIG.2b illustrates a graphical representation of difference in yield strength and ultimate tensile strength of conventional hot rolled steel and the advanced low strength steel sheet of the present disclosure, respectively.

FIG.3a illustrates SEM microstructure of hot rolled plane-carbon manganese coil.

FIG.3b illustrates SEM microstructure of hot rolled steel sheet with titanium, according to an exemplary embodiment of the present disclosure.

FIG. 4 illustrates ODF plot comparison between plane-carbon manganese hot rolled steel sheet and titanium added hot rolled steel sheet.

FIGS.5a to 5c illustrate a fiber plot of comparison between crystallographic texture of plane-carbon-manganese and titanium-added hot rolled steel sheet.

Figure 6 illustrates a graphical representation of comparison of roll forces during cold rolling of plane-manganese vs. titanium-added hot rolled steel sheet.

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION

The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the description of the disclosure. It should also be realized by those skilled in the art that such equivalent methods do not depart from the scope of the disclosure. The novel features which are believed to be characteristic of the disclosure, as to method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.

In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the spirit and the scope of the disclosure.

The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a method that comprises a list of acts does not include only those acts but may include other acts not expressly listed or inherent to such method. In other words, one or more acts in a method proceeded by “comprises… a” does not, without more constraints, preclude the existence of other acts or additional acts in the method.

Embodiments of the present disclosure discloses an advanced low strength steel sheet and a method for manufacturing or producing the advanced low strength steel sheet. Also, the present disclosure provides a method which results in reduced roll forces, improved mill speed, increase in productivity and product quality.

The method of manufacturing advanced low strength steel sheet, includes first step of producing a steel slab of an alloy composition including in weight percentage [wt.%] of carbon (C) at about 0.04 % to about 0.065 %, manganese (Mn) at about 0.15 % to about 0.5 %, silicon (Si) up-to 0.04 %, sulphur (S) up-to 0.03 %, phosphorous (P) up-to 0.03 %, aluminum (Al) up-to 0.055 %, nitrogen (N) up-to 120ppm, titanium (Ti) at about 0.012 % to about 0.025 %, balance being Iron (Fe) optionally along with incidental elements by any manufacturing process including but not limiting to casting. Once the steel slab is casted, it may be immediately subjected to heating. The steel slab may be heated to a first pre-determined temperature for a first pre-determined time. Subsequently, the steel slab may be subjected to hot rolling to achieve a first pre-defined thickness to produce hot rolled steel sheet. In an embodiment, presence of titanium at about 0.012 wt. % to about 0.025 wt. % in the alloy composition scavenges free nitrogen from interstitial sites of steel matrix and induces favourable crystallographic texture with crystal orientations such as {554} <225>, {332} <113>, {111} <112>, in the hot rolled steel micro-structure predominantly containing a ferrite phase and marginally a pearlite phase. The obtained textured hot-rolled steel results in reduced yield strength and tensile strength of the steel thereby reducing roll forces during subsequent cold rolling. The hot rolling may be carried out in multiple steps i.e., under roughing mill and finishing mill. The hot rolled steel sheet may be subjected to the cold rolling process to further reduce the thickness of steel sheet to a second pre-determined thickness to form cold rolled steel sheets.

Henceforth, the present disclosure is explained with the help of figures for a method of manufacturing low strength steel sheet. However, such exemplary embodiments should not be construed as limitations of the present disclosure since the method may be used on other types of steels where such need arises. A person skilled in the art may envisage various such embodiments without deviating from scope of the present disclosure.

Figs.1a and 1b are exemplary embodiments of the present disclosure illustrating a flowcharts depicting a method for manufacturing advanced low strength hot-rolled steel sheet. In the present disclosure, mechanical properties such as rollability of the steel may be improved. The steel produced by the method of the present disclosure, includes a microstructure comprising predominantly a ferrite phase and marginally a pearlite phase. The method is now described with reference to the flowchart blocks and is as below. The order in which the method is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method. Additionally, individual blocks may be deleted from the methods without departing from the scope of the subject matter described herein. The method is particularly applicable to advanced low strength steel and it may also be extended to other type of steels as well.
The method of manufacturing the advanced low strength steel sheet according to the present disclosure consists of a casting step followed by a hot rolling process, coiling, cooling & cold rolling using a steel material which satisfies the component composition described below. The various processing steps are described in their respective order below:

As shown in block 101 [in FIG.1a and 1b], the method starts with the process of casting. In the method of present disclosure, the steel of the specified composition including in weight percentage of 0.04 - 0.065 % of carbon (C), 0.15 % – 0.5 % of manganese (Mn), maximum up to 0.04 % of silicon (Si), maximum up to 0.03 % of sulphur (S), maximum up to 0.03 % of phosphorous (P), maximum up to 0.055 % of aluminium (Al), maximum up to 120 ppm of nitrogen (N), 0.012 % to about 0.025 % of titanium (Ti), the balance being iron and other incidental elements like impurities, is first continuously cast either in a conventional continuous caster or a thin slab caster. In an embodiment, the continuous casting may be performed using funnel mold of thickness ranging from 50 to 80 mm. Further, the casting speed for continuously casting the steel may range from 4.5 m/min to about 6.0 m/min. In an embodiment, presence of titanium (Ti) in the chemical composition of steel may be governed by the equation [Ti]-(48/14) *[N]-(48/32) *[S]<0%,
Where, N is the weight percentage if nitrogen and S is the weight percentage of sulphur.

The method then includes the step of heating as shown in block 102 [in FIG.1a and 1b]. After casting the steel slab with the specified composition, the slabs are heated to a first predetermined temperature for a first predetermined time. In an embodiment, the first predetermined temperature is greater than 1000 °C, preferably in the range of 1100 °C to 1200 °C, and the first predetermined time ranges from 15 minutes to 45 minutes. The casted steel slab may be heated or hot charged in a tunnel furnace. In an embodiment, heating the steel slab at the first pre-determined temperature i.e., about 1100 °C to 1200 °C homogenises composition and microstructure of the steel slab. Also, directly, and immediately heating the cast steel slab for the first pre-determined temperature for the first pre-determined time ensures that the austenite grain size does not coarsen.

Once the steel slab is heated as per the block 102, the heated steel slab may be passed through high-pressure water jets which may act as primary descalers or scale breakers to remove oxide scale layers that may be formed during the casting and heating. Upon completing the preceding steps, the heated steel slab may be subjected for hot rolling as shown in block 103 [in FIG.1a and 1b] to form a steel sheet. The hot rolling may be performed in a thin slab casting and rolling [TSCR] mill. As shown in block 103, after casting and heating the steel slab with the specified composition, it is hot rolled. The hot rolling may constitute two steps of deformation via the first hot rolling process and the second hot rolling process. In some embodiments, the hot rolling process may constitute one step to produce hot rolled steel. In an embodiment, the first hot rolling process is a deformation process of steel slab in a roughing mill at the first predetermined temperature. The first rolling process may be carried out om a first rolling stand. The first hot rolling process reduces the thickness to the highest. In the roughing stage, the cast structure may be broken down, and the new structures may be formed. In an embodiment, the steel slab may be subjected to second hot rolling process. The second hot rolling process is a further deformation process of the steel slab carried out in four or more strands of the finishing mill, and temperatures in all strands of the finishing mill are such that microstructure of the material consists of single-phase austenite. In an embodiment, the second hot rolling process may be carried out at a temperature range of Ae3 to Ae3 + 70 °C., wherein Ae3 is the temperature at which transformation of austenite to ferrite starts at equilibrium. Subjecting the steel slab to the hot rolling process at the first predetermined temperature reduces the thickness of the steel slab to a first pre-defined thickness to produce the hot rolled sheet. In an embodiment, the first predefined thickness may be ranging from about 1.2mm to 6mm. Use of lower first predefined thickness may be beneficial in additionally reducing the roll forces along with the presence of titanium upon subjecting the hot rolled steel sheet to cold rolling process, as the cold-rolling draught may be lowered. Further, use of higher first predefined thickness may substantially increase the roll forces during the cold rolling, this may be countered by addition of titanium in the specified range. Higher %reduction/draught may increase the roll forces during cold rolling process due to higher accumulation of strain and higher strain hardening which may be countered by the addition of titanium in the specified range as disclosed in the present disclosure. Lower %reduction/draught decreases the roll forces during cold rolling due to lower accumulation of strain and lower strain hardening.

Conventionally, addition of titanium is known to increase yield strength and tensile strength of hot rolled steel coil manufactured from conventional hot strip mills [HSM]. But processing conditions of the present disclosure are substantially different from TSCR hot rolling mills and hence the effect of titanium in TSCR mills may be observed to be substantially different. Coarse titanium nitride (TiN) precipitate does not provide any precipitation strengthening to hot rolled steel but is known to restrict coarsening of prior-austenite grain size and improves strength by grain refinement which is evident in conventional HSM. Conventionally, thick slabs obtained from continuous casting are usually first cooled to room temperature. Then the slabs are reheated in the furnace at 1250 to 1240 °C, and residence time of approximately 3 hours, wherein TiN precipitate restrict the austenite grain coarsening, leading to finer prior-austenite grains subsequently transforming to finer ferrite grains. Hence increasing the yield strength of the hot rolled steel. Due to higher amount of grain refinement in conventional HSM, the effect of lower yield strength [by titanium addition by nitrogen scavenging and favourable crystallographic texture] is subdued, while the phenomenon of grain-refinement becomes dominating which increase yield strength.

However, yield strength and tensile strength of hot rolled steel coil manufactured from TSCR mill according to present disclosure may be reduced by titanium addition in the range of about 0.012 wt.% to about 0.025 wt.%. Formation of TiN in the TSCR mill according to the present disclosure may not strengthen the hot rolled steel due to grain refinement but reduces the strength by approximately 20 Mpa. FIG.2a and 2b clearly indicate the drop in strength of hot-rolled steel due to the addition of titanium in the specified range.

During the hot rolling, the presence of titanium at about 0.012 wt.% to about 0.025 wt.% in the alloying composition scavenges free nitrogen from interstitial site of steel matrix and inducing favourable crystallographic texture. The first predetermined temperature should be above 1100 °C, to ensure scavenging of nitrogen from the interstitial sites, thus forming titanium nitride (TiN) precipitates. A first predetermined temperature greater than 1200 °C is also not desirable because it may lead to grain coarsening of austenite and/or excessive scale loss. Due to the presence of titanium in the specified range, yield strength and tensile strength of the hot rolled steel sheet may be reduced. FIG.2a and FIG.2b clearly depicts the drop in strength of hot rolled steel due to the above specified level of titanium addition. In an embodiment, maximum tensile strength of the hot rolled steel sheet manufactured according to the present disclosure may be 500 MPa.

The microstructure of the titanium added hot rolled steel sheet may be predominantly of ferrite phase with marginal pearlite phase uniformly distributed in the microstructure. In some embodiments, the microstructure of the hot rolled steel sheet may include 80% or greater of ferrite phase and less than 20% of pearlite phase. Preferably, the microstructure of the hot rolled steel sheet may comprise minimum of 90% of ferrite phase and less than or equal to 10% of pearlite phase. In an embodiment, the microstructure of the hot rolled steel sheet may include about 90% to 97% of the ferrite phase and less than 5% of the pearlite phase. In another embodiment, the ferrite phase in the hot rolled steel sheet may be substantially polygonal shaped. Average grain size of the polygonal shaped ferrite phase ranges from 05 microns to 25 microns. FIG.3a and 3b represents comparison of hot-rolled steel microstructure of conventional plane carbon manganese sheet and the titanium added hot rolled steel sheet using EBSD [electron back-scattered diffraction] image quality map, respectively.

Also due to titanium addition, the favourable orientations of gamma fibre {554} <225>, {332} <113>, {111} <112> increases in intensity, which increases the plastic strain ratio, which indicates that material flow occurs easily, primarily parallel to the plane surface in sheet metal. For BCC alpha-Fe [close to ferrite] the strength is highest along the cube diagonal (111), lower along the face-diagonal (110), and lowest along the cube edge (100).

Referring now to FIG.4 and FIG(s) 5a to 5c, which illustrate the formation of favourable crystallographic texture orientations and increase in the intensity of gamma fibre orientations [shown in FIG.5a] such as {554} <225>, {332} <113>, {111} <112>. FIG.5b and FIG.5c illustrates comparison of crystallographic texture fibre plot for plane-carbon-manganese coil and titanium-added coil an alpha fibre plot and theta fibre plot respectively. Due to titanium addition, favourable orientations of gamma fibre {554} <225>, {332} <113>, {111} <112> increased in intensity, which increases the plastic strain ratio [Lankford coefficient], which indicates that material flow may occur easily. Primarily parallel to the plane surface in sheet metal [or low flow-strength in the plane of the sheet].

After finish rolling, the steel sheet is subjected to intensive cooling or laminar cooling until the hot rolled steel sheet may reach coiling temperature. The cooling is performed on a run-out-table. The method further includes the second step of cooling. Upon cooling the hot rolled steel sheet, it may be subjected to coiling may be carried out at a coiling temperature. In an embodiment, the coiling temperature may be maintained above 550°C. This ensures that the microstructure consists of ferrite-pearlite only.

The method optionally comprises cleaning the steel sheet by acid pickling and skin pass treatment. In an embodiment, the steel sheet may be uncoiled and pickled in a pickling line and then skin passed in a skin pass mill and then coiled. The pickling is performed in a pickling line to remove oxides and the skin pass is performed by a compressive deformation.

As shown in block 104 [in FIG.1b], the hot rolled steel sheet may be subjected to cold rolling process to further reduce thickness of the steel sheet to a second pre-determined. The second pre-determined thickness may be ranging from about 0.1mm to 1.6mm. Use of higher second pre-defined thickness [say more than 0.43mm] may aid in additionally reducing the roll-forces of during cold rolling process along with presence of titanium, as the cold rolling draught may be lowered. However, using lower second pre-defined thickness may substantially increase the cold-rolling draught which may increase the roll-forces. The increase in roll forces may be countered by the addition of titanium which may be added in the specified range. In an embodiment, the difference between the first predefined thickness and the second predefined thickness is greater than 70%. The cold rolling may be performed in a reversing cold-rolling mill. In the reversing cold rolling mill, the titanium added hot rolled steel sheet is an advanced low strength steel, which is marginally lower in strength than conventional plane carbon-manganese steel chemistry in hot rolled steel sheet. Said feature along with the formation of favorable crystallographic texture in the hot rolled steel due to titanium addition may provide an added advantage for reducing the roll-forces during cold rolling with no adverse effect to product quality. The lower strength of the steel may significantly be easy to be cold rolled into thinner sheets, thus making the cold rolling process faster and reducing the roll forces, thus leading to improved rollability. As a result, the roll forces of reversing cold rolling mill may be reduced by 650 to 900KN in majority of cold rolling passes. In case, the number of cold rolling passes are constant, due to the lesser amount of force required, the motor current of the reversing cold rolling mill may be reduced by 10% to 35%.
In an embodiment, the advanced low strength steel sheet exhibits tensile strength of maximum 500 MPa. To achieve the required mechanical properties as proposed in the disclosure, it may be required to obtain a very homogenous microstructure. In the present disclosure, the microstructure consists of ferrite-pearlite structures.

The following portion of the present disclosure provides details about the proportion of each alloying element in a composition of the steel and their role in enhancing properties.

Carbon (C) may be added in the range of about 0.04 wt.% to about 0.065 wt.%. Carbon is one of the most effective and economical, interstitial solid-solution strengthening elements in hot-rolled steel coil and FHCR [Full Hard-Cold Rolled] coil. Thus, it helps in achieving the minimum required hardness of FHCR coil. Carbon also combines with Ti to form carbides (or carbonitrides) which bring about precipitation strengthening in hot-rolled steel, especially TiC. But TiC precipitation will be restricted, if all Ti content is consumed for TiN formation in hot-rolled steel. However, increasing Carbon will further increase the strength of hot-rolled steel coil due to solid-solution strengthening, which will increase the roll-forces during subsequent cold-rolling operation. In order to have good rollability during cold rolling, the carbon content has to be restricted to less than 0.10%.

Manganese (Mn) may be added in the range of about 0.15 wt.% to about 0.5 wt.%. Manganese not only imparts substitutional solid-solution strengthening to the ferrite in Hot-rolled steel coil and resultant strengthening of FHCR coil, but it also lowers the austenite to ferrite transformation temperature thereby refining the ferrite grain size in hot-rolled steel. However, increasing the Mn further will raise the strength of hot-rolled steel coil, which will increase the roll-forces during subsequent cold-rolling operation. Hence, in order to have good rollability during cold rolling, the Manganese content has to be restricted to less than 0.60%.

Silicon (Si) may be added maximum up to 0.04 wt.%. Silicon like Mn is a very efficient substitutional solid-solution strengthening element in hot-rolled steel coil and FHCR steel coil. But increasing the Si further will raise the strength of hot-rolled steel coil, which will increase the roll-forces during subsequent cold-rolling operation. Hence, to have good rollability during cold rolling, the Silicon content has to be restricted to less than 0.15%.

Phosphorus (P) content should be restricted to 0.03 wt.% maximum as higher phosphorus levels may lead to reduction in toughness and weldability due to segregation of phosphorus into grain boundaries.

Sulphur (S) content must be limited otherwise it results in a very high inclusion level that deteriorates formability. Sulphur (S) may be kept 0.03 wt% maximum.

Aluminium (Al) may be restricted to 0.055 wt.% maximum. Aluminium is primarily utilized in liquid steel making for de-oxidation and for making de-oxidized/killed steel. Aluminium also combines with Nitrogen in steel to form fine AlN precipitates, which have a weak precipitation strengthening effect. But in the presence of Titanium, the AlN precipitation is restricted, and TiN precipitation dominates. Moreover, Aluminum should be restricted to 0.06% max so that any additional solid-solution strengthening of hot-rolled steel can be avoided.

Nitrogen (N) may be restricted to 0.012 wt.% maximum. Similar to Carbon, Nitrogen (in free state) is also an excellent interstitial solid-solution strengthener in hot-rolled steel coil and FHCR steel coil. But when Nitrogen combines with Titanium to form TiN, the solid-solution strengthening contribution of free Nitrogen is lost, resulting in the strength-loss of hot-rolled steel, which would be beneficial for reducing the roll-forces during subsequent cold-rolling. Nitrogen should be preferably restricted to 70ppm maximum, so that all of it exist only exist in combined state (as TiN precipitates), and not in free state.

Titanium (Ti) may be added in the range of 0.012 to 0.025 wt.%. Titanium addition in steel lead to the formation of TiN precipitate during solidification of liquid steel during Continuous casting process. These TiN precipitates coarsen during subsequent processing steps of slab re-heating and hot-rolling and are widely known for not contributing to Precipitation strengthening. Instead, the Nitrogen scavenging by Titanium reducing the overall strength of ferrite matrix in hot-rolled steel. This reduction in strength in hot-rolled steel due to Nitrogen scavenging, will help in lowering the roll forces and improving the rollability during cold-rolling.

The chemical composition of the hot-rolled steel should also satisfy the below mentioned criteria in the present disclosure as below:
[Ti] - 48/14 X [N] - 48/32 X [S] < 0%
Where, a content (weight %) of the corresponding element is substituted for the respective symbols of elements in Formula.

Examples:

Further embodiments of the present disclosure will be now described with an example of a particular composition of the steel. Experiments have been carried out for a specified composition of the steel formed by using method of the present disclosure.

The results that are shown in Table-1 below depict chemical compositions achieved, and also may include average finish rolling temperatures achieved and average coiling temperature achieved for the hot rolled steel sheets. Subsequently, the hot rolled steel sheets are used as input substrate for cold rolling on six high reversing cold-milling mill to achieve required cross section thickness.

Table-2 depicts average roll forces data for each cold-rolling pass taken on the reversing col-rolling mill to achieve final thickness. Inputs thickness and actual widths of the hot rolled steel sheets may also be included. Further, the Table-2 depicts actual output thickness and average hardness of the final cold-rolled steel sheet.

Table 1. Examples of the hot-rolled coils rolled in accordance with the present invention. CT (°C) 645 641 645 640 646 649 648 648 649 647 647 572 570
FRT (°C) 878 877 907 876 880 904 904 907 880 906 904 878 909
Ca (ppm) 33 28 27 19 27 31 25 22 22 31 31 33 33
Cu (wt%) 0.004 0.008 0.005 0.004 0.005 0.006 0.005 0.006 0.006 0.005 0.005 0.010 0.006
Ni (wt%) 0.015 0.015 0.015 0.015 0.018 0.019 0.015 0.020 0.020 0.017 0.017 0.019 0.024
Cr (wt%) 0.020 0.015 0.033 0.020 0.023 0.018 0.023 0.022 0.019 0.020 0.020 0.025 0.029
Mo (wt%) 0.001 0.001 0.002 0.001 0.001 0.001 0.001 0.001 0.000 0.001 0.001 0.001 0.001
N (ppm) 48 38 60 41 60 62 66 51 45 55 55 55 63
Nb (wt%) 0.0002 0.0002 0.0003 0.0002 0.0034 0.0008 0.0003 0.0007 0.0003 0.0002 0.0002 0.0002 0.0002
Ti (wt%) 0.0008 0.0012 0.0134 0.0012 0.0135 0.0134 0.0135 0.0142 0.0017 0.0148 0.0148 0.0006 0.0167
V (wt%) 0.0002 0.0003 0.0014 0.0004 0.0012 0.0010 0.0012 0.0010 0.0005 0.0009 0.0009 0.0001 0.0008
Al (wt%) 0.052 0.051 0.042 0.068 0.054 0.047 0.040 0.039 0.039 0.041 0.041 0.064 0.040
B (wt%) 0.0003 0.0003 0.0003 0.0003 0.0001 0.0003 0.0002 0.0003 0.0001 0.0002 0.0002 0.0002 0.0004
Si (wt%) 0.01 0.01 0.02 0.01 0.01 0.01 0.01 0.01 0.03 0.01 0.01 0.01 0.02
S (wt%) 0.003 0.003 0.002 0.003 0.004 0.003 0.004 0.002 0.002 0.003 0.003 0.004 0.003
P (wt%) 0.022 0.011 0.016 0.015 0.017 0.019 0.019 0.013 0.015 0.016 0.016 0.013 0.013
Mn (wt%) 0.20 0.21 0.19 0.21 0.19 0.19 0.18 0.21 0.17 0.24 0.24 0.41 0.43
C (wt%) 0.044 0.046 0.046 0.047 0.048 0.045 0.047 0.045 0.045 0.043 0.043 0.054 0.056
Example type Comparative Example Comparative Example Present Invention Example Comparative Example Present Invention Example Present Invention Example Present Invention Example Present Invention Example Comparative Example Present Invention Example Present Invention Example Comparative Example Present Invention Example
Coil ID Plane C-Mn Coil 1 Plane C-Mn Coil 2 Titanium added Coil 1 Plane C-Mn Coil 3 Titanium added Coil 2 Titanium added Coil 3 Titanium added Coil 4 Titanium added Coil 5 Plane C-Mn Coil 4 Titanium added Coil 6 Titanium added Coil 7 Plane C-Mn Coil 5 Titanium added Coil 8

Table – 1

Table 2. Examples of the cold-rolled coils obtained after cold-rolling of hot-rolled coils (or present invention). Hardness Rockwell-B 95 93 94 94 94 92 92 92 95 93 94
Roll Force Pass 8 (KN) Not applicable Not applicable Not applicable Not applicable Not applicable Not applicable Not applicable Not applicable 7161 6573 Not applicable Not applicable Not applicable Not applicable
Roll Force Pass 7 (KN) 8431 8401 7682 Not applicable Not applicable Not applicable Not applicable Not applicable 6965 6573 6200 Not applicable Not applicable Not applicable
Roll Force Pass 6 (KN) 8065 7711 7444 8104 7514 7752 Not applicable Not applicable 6965 6377 6278 7715 6675 Not applicable
Roll Force Pass 5 (KN) 8257 8091 7237 8198 7578 7862 7814 7826 6867 6573 6965 7543 6700 6786
Roll Force Pass 4 (KN) 8228 7884 7135 8211 7671 7924 7985 8026 7063 6671 6573 7456 6783 6884
Roll Force Pass 3 (KN) 8265 7930 7307 8425 7775 8148 8032 8132 7652 7308 7358 7568 6619 7286
Roll Force Pass 2 (KN) 7993 7530 6966 8039 7391 7815 7592 7880 7259 7063 7259 8179 7266 7366
Roll Force Pass 1 (KN) 7230 6945 6715 7392 7311 7564 7391 7525 7456 7456 7112 7952 7983 8736
Number of Passes during Cold Rolling 7 7 7 6 6 6 5 5 8 8 7 6 6 5
Output Coil Thickness (mm) 0.43 0.43 0.43 0.43 0.43 0.43 0.43 0.43 0.423 0.423 0.423 0.274 0.274 0.274
Input Coil Thickness (mm) 2.2 2.2 2.2 2.2 2.2 2.4 2.2 2.4 2.8 2.8 2.8 2 2 2
Coil width (mm) 1220 1220 1220 1220 1220 1220 1220 1220 1365 1365 1365 1040 1055 1055
Example type Comparative Example Comparative Example Present Invention Example Comparative Example Present Invention Example Present Invention Example Present Invention Example Present Invention Example Comparative Example Present Invention Example Present Invention Example Comparative Example Present Invention Example Present Invention Example
Coil ID Plane C-Mn Coil 1 Plane C-Mn Coil 2 Titanium added Coil 1 Plane C-Mn Coil 3 Titanium added Coil 2 Titanium added Coil 3 Titanium added Coil 4 Titanium added Coil 5 Plane C-Mn Coil 4 Titanium added Coil 6 Titanium added Coil 7 Plane C-Mn Coil 5 Titanium added Coil 8 Titanium added Coil 9

Table-2

Table-3
Table-3 depicts average motor current data for each cold-rolling pass taken on the reversing cold-rolling mill to achieve final thickness. In the Table-3, it is clear that the average motor current for titanium added hot rolled steel sheet according to present disclosure requires significantly lesser than the conventional plane-carbon manganese steel sheet.

Table-4
Table-4 shows mill speed data for each cold rolling pass taken on the reversing cold-rolling mill to achieve final thickness. As shown in Table-4, the number of passes during cold rolling required for titanium added steel sheet coil may be significantly lesser than that of the plane carbon manganese steel sheet.
Referring now to FIG.6, which illustrate a comparison of average roll forces during cold-rolling of plane-carbon-manganese coil vs cold-rolling titanium added steel sheet according to the present disclosure. Average roll-forces for very large number of coils [of both plane-carbon -manganese steel sheet and titanium added steel sheet] are plotted in the box plots for statistical validation of the present disclosure. FIG.6 clearly illustrate roll forces are reduced during cold rolling of the present disclosure which improves rollability during cold-rolling and lead to reduction in the number of cold-rolling passes at reversing cold-rolling mill. Number of plane carbon-manganese steel sheets (2.2mm cold rolled to 0.43mm in 7 passes) considered for plotting boxplot is 1960. Number of titanium-added steel sheets (2.2mm cold rolled to 0.43mm in 7 passes) considering for plotting box-plot is 395. Number of titanium-added steel sheets (2.2mm cold-rolled to 0.43mm in 5 passes) considered for plotting box plot is 40. Number of titanium-added steel sheets (2.4mm cold-rolled to 0.43mm in 5 passes) considered for plotting boxplot is 36.
In an embodiment of the present disclosure, roll forces of the reversing cold rolling mill may be reduced by 650-900 KN in majority of passes due to scavenging of nitrogen by titanium during hot rolling process. Further, the motor current of reversing cold rolling mill may be reduced by 10% to 35% in majority of passes, if the number of cold rolling passes are kept same. The reduction in roll forces were sufficient in decreasing the number of passes for cold rolling in a reversing cold-rolling mill. Thereby, increasing the productivity due to reduction in processing time at CRM. As a result of reduced roll forces, the mill speed may be significantly increased. During cold-rolling, the reduction in roll-forces and/or reduction in motor-current results in the increase of productivity of cold-rolling mill. Increase in draught during cold rolling of present disclosure may result in allowable use of 3% higher thickness of hot rolled coil for achieving the same output thickness after cold rolling, without adversely impacting the roll-forces, mill-speed, product quality or mill-productivity.

Equivalents:

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Referral Numerals

Referral Numerals Description
101-104 Flowchart blocks
101 Casting stage
102 Heating stage
103 Hot rolling stage
104 Cold rolling stage