DESC:FIELD OF THE INVENTION
The present invention relates to a process for production of a high strength reinforcement alloy bar. More particularly present invention relates to the high strength reinforcement alloy bar using sponge iron and scrap. These high strength reinforcement alloy bars will make available better quality reinforcement bars (‘rebars’) acutely needed in the constructions of Reinforced Cement Concrete (‘RCC’) structures across the industry.
BACKGROUND
With the rapid expansion of the world population and different economies, the need for homes and other infrastructure has increased exponentially. Most of the structures to meet this growing demand used reinforcement rebar. Therefore, the demand for the metal rebar is very high and the resources are limited. Technology for the production of rebar has improved a lot. Rebars may be manufactured by either (i) Micro alloying, (ii) Low alloy steel (iii) cold twisting (cold working) or (iv) Thermo-Mechanical Treatment (TMT). However, out of these choices, TMT processing has been the most popular now-a-days due to inherent advantages of producing high strength rebars with excellent strength and ductility combination. TMT bars have indeed filled in the gap but there will still a huge gap between demand and supply. None of the existing technology is able to use scrap iron and sponge iron for production of rebars.
2279/CHENP/2011 discloses that a composite reinforcing bar is formed from a series of inner rovings with first and second helical wrappings of at least one roving wrapped around the inner rovings in opposed directions of wrapping with the resin permeated there through. The bar structure is formed to allow torsional bending sufficient to allow the formed bar to be wound to form a coil of the bar wrapped a series of times around an axis at right angles to the length of the bar. The bar is forwarded into a rotating winding frame formed by a series of posts around a vertical rotation axis. The coil is held in place while the frame is removed for transporting the coil to a remote location. At the remote location the coil is placed in a similar winding frame and the bar is pulled from the coil and cut to a required length.
25/KOL/2010 relates to developing high strength (YS:640MPa Min.) Thermo Mechanically Treated (TMT) bar and a process for its production. The TMT bars of the invention is having yield strength above 640MPa, UTS/YS ratio of 1.15 Min., with super toughness (18% elongation Min.) properties of said TMT rebars through selective alloy design and optimizing process parameters. The alloy design comprising C-Mn chemistry wherein manganese content of steel is maintained in the range of 0.8-1.3 wt %, and no micro-alloying element is added so that cost of production remains competitive. The process parameters for the instantaneous quenching by accelerated cooling of the hot deformed rebars are adapted to provide thick martensitic structure at the periphery and the core containing predominantly acicular ferrite/bainite structure along with pearlite ensuring desired combination of strength and ductility properties, favoring wide scale application in RCC structures or as rock bolts for effective roof support in tunnel construction and the like.
1322/KOL/2007 relates to a modified method of welding of thermomechanically treated (TMT) welded metal rebars for uniform strength maintained throughout the thickness of welded rebars and welded rebars produced thereof comprising the steps of welding lap joint (single side) of TMT rebars of same or different diameter at horizontal, vertical or sloping position on striking electrode somewhere in the middle of and of the joint according to the procedure as laid down in paragraph 10.5.4 of IS 9417-1989 with actual welding current of 180 amperes as against proprietor specified current of 140/180 amperes; selecting test TMT rebar composition in weight % of C-0.15, Mn-0.06, S- 0.018, P-0.016, Si-0.141, S+P-0.034 according to the specification as laid down in IS 1608:2005/IS0 6892:1998 and electrode specification confirming to AWS/SFAS.SE 8018 having composition in weight % C- 0.05-0.10, Mn 1.4-1.85, S-0.030 Max, P-0.030 Max, Si-0.20-0.48, Ni-0.45- 0.80 and size of 4 mm x 450 mm; sel ecting test TMT rebar composition in weight % of C-0.15, Mn-0.06, S- 0.018, P-0.016, Si-0.141, S+P-0.034 according to the specification as laid down in IS 1608:2005/ISO 6892:1998 and electrode specification confirming to AWS/SFAS.SE 8018 having composition in weight % C- 0.05-0.10, Mn 1.4-1.85, S-0.030 Max, P-0.030 Max, Si-0.20-0.48, Ni-0.45- 0.80 and size of 4 mm x 450 mm; carrying on determination of tensile properties before and after welding of the TMT rebar test specimens on conformation of uniform strength throughout the thickness of the welded rebars as specified in IS 9417-1989 after welding.
47/KOL/2004 discloses a process for manufacturing of improved corrosion resistant TMT rebars, in particular, copper-molybdenum TMT rebars having improved strength and corrosion resistant properties suitable for applications in chloride containing environment. The process comprises providing steel ingots having compositions comprising 0.14 to 0.18 wt% carbon 1.0 to 1.2 wt% manganese, 0.2 to 0.3 wt% silicon, up to 0.03 wt% sulphur, up to 0.03 wt% phosphorous, 0.3 to 0.4 wt% copper and 0.15 to 0.2 wt% molybdenum, the balance being iron, soaking said steel ingots and processing to billets, cooling the surface of said billets in Thermix Unit with water pressure between 15 to 22 kg/mm2 and equalization temperature between 600 to 680 degree C and finish rolling said surface cooled steel bars between 950 to 1060 degree C.
551/KOL/2003 discloses a process for manufacturing of high strength micro alloyed TMT rebar with improved sub-zero impact toughness which is provided by suitably selecting the levels of micro alloying elements in the steel. The process comprises providing steel billet having a composition of 0.05 to 0.1 wt% carbon, 0.3 to 0.5 wt% manganese, 0.05 to 0.2 wt% silicon, upto 0.035 wt% sulfur and atleast 0.008 wt% of microalloying elements comprising niobium and phosphorus wherein the level of phosphorus is in the range of 0.08 to 0.1% when niobium is not present or upto 0.04 wt% when niobium is present in the range of 0.005 to 0.015 wt%, the balance being iron, heating said steel billet at a temperature between 1200 to 1250 degree C, rolling heated billet to rebar, short intensive cooling the rolled rebar and further cooling in atmosphere. The rebars of this invention have wide applications in the construction sector such as general concrete reinforcement in buildings, bridges and various other concrete structures and especially high rise buildings.
5/KOL/2003 relates to a thermo mechanical process for the manufacture of copper phosphorous bearing corrosion and earthquake resistant Thermo Mechanically Treated (TMT) rebar which comprises the steps of melting a steel composition (by weight %) containing: C-0.25 max.; Mn-1.50 max.; S-0.04 max.; P- 0.07-0.12%; Si-0.50 % max.; Cr+Mo + Nb 0.50% max ; Cu-0.25 min. and the balance being Fe in a furnace; tapping the melt in a preheated ladle at 1630 ± 10 °C, provided with Ferro alloy of quantity Fe-Mn 1.0- 3.0 T; Fe-Si 0.5-1.5T; Fe-P 0.5-2.0 T and copper cathode homogenizing the steel in the ladle by purging of argon; casting the homogenized steel either into ingots or as billet by continuous casting; soaking the ingots at 1300 ± 20 °C as required; processing the soaked ingots into billets, where after; the billets are reheated at temperature of 1230 ± 20°C and processed through a known TMT line.
In the prior art, in none of the existing processes, the scrap or sponge iron is used all processes in the invention covered in prior art use various methods which relate to material treatment and are certainly not environmental friendly compared to the present invention. All the existing inventions are very less energy efficient and consume large quantity of energy. These existing inventions also end up consuming huge quantity of natural resources and are not resulting in reduction of wastage of natural resources. Thus there is a gap for inventing a new process for production of high strength reinforcement alloy bars which recycles scrap and uses sponge iron in place of the finished products to develop the desired product. This gap is sought to be filled in by the present invention which is very energy efficient, flexible in terms of micro alloying parameters uses recycling and saves natural resources as well as consumes less energy.

OBJECTIVE
The main objective of the present invention is to produce high yield strength and high ductility rebar with a new process not known so far.
The principal objective of the present invention is to use scrap metal and sponge iron to produce a high strength rebar.
Another objective of the present invention is to reduce energy consumption in the production of rebars.
Yet another objective of the present invention is to produce unique alloy design that has high ductility and strength.
Yet another objective of the present invention is to reduce manufacturing cost of the rebar.
Still another objective of the present invention is to have flexibility in micro alloying to produce varying qualities of rebars while minimising consumption of natural resources as is not known so far.
Further objectives, advantages and features of the present invention will become apparent from the detailed description provided herein below, in which various embodiments of the disclosed invention are illustrated by way of examples and with appropriate reference to accompanying drawings.

SUMMARY OF THE PRESENT INVENTION

The present invention relates to a production process for high strength reinforcement alloy bar using sponge iron and scrap iron. The process includes: a process of the melting and preparation alloy mixture, a process of continuous casting of molten metal and a process of rolling and metal treatment.
The process of the melting and preparation of alloy mixture includes: a scrap iron is being melt inside a furnace and a first chemical analysis is performed to determine the composition of the melted scrap iron. A sponge iron is added to the melted scrap iron to form a molten metal. The chemical analysis is further performed on the molten metal to determine the composition of carbon in the molten metal. The sponge is iron further added to the molten metal based on the second chemical analysis. Then deslaging is performed to remove the slag from the molten metal. The further excess oxygen from the molten metal is removed by adding the deoxidization agent. A necessary amount of silicon and manganese is added to the molten metal. A ferro-chrome and a copper is added in order to achieve desired composition of molten metal.
The process of continuous casting of molten metal includes: After few minutes of homogenization process in the furnace, the molten metal is being tapped into a ladle. A molten metal is purged with nitrogen in order to remove trapped gases. After achieving a particular temperature, the ladle is sent to a continuous casting machine for casting. The molten metal is casted into a billet and the billet is further send for rolling.
The process of rolling and metal treatment includes: The billet is transferred to the rolling mill without preheating. The billet is rolled into a rebar. A short duration intense water quenching is done on the rebar by passing the hot rolled rebar though the series of water pipes. The surface of the rebar is converted into hard martensite. The rebar is further air cooled that subsequently tampers the hard martensite surface of the rebar.
One of the advantages of the present invention is that the present invention scrap iron and low quality sponge to produce high yield strength iron rebar.
Yet another advantage of the present invention is that the present invention uses less energy to produce rebar.
Yet another advantage of the present invention is that the present invention is having unique alloy design and processing route.
Yet another advantage of the present invention is reduction of pollution it uses scrap and also efficient of utilization of natural resources as it uses low quality sponge iron thus in totality it is extremely environment friendly and good for conserving of the resources for the planet.

Further objectives, advantages and features of the present invention will become apparent from the detailed description provided herein below, in which various embodiments of the disclosed invention are illustrated by way of example and appropriate reference to accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings are incorporated in and constitute a part of this specification to provide a further understanding of the invention. The drawings illustrate one embodiment of the invention and together with the description, serve to explain the principles of the invention.
Fig. 1 illustrates the microstructure of a developed rebar at core in an embodiment of the present invention.
Fig. 2 illustrates the microstructure of a developed rebar at rim in an embodiment of the present invention.
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DETAILED DESCRIPTION OF THE INVENTION

While this invention is open for being adopted in many forms with small variations, there is shown in the drawings and will herein be described in detail specific, with the understanding that the present disclosure of such embodiments is to be considered as an example of the principles and not intended to limit the invention to the specific embodiments as shown and described herein. In the description below, like reference numerals are used to describe the same, similar or corresponding parts in the several views of the drawings. This detailed description defines the meaning of the terms used herein and specifically describes embodiments in order for those skilled in the art to practice the invention.
Definition
The terms “a” or “an”, as used herein, are defined as one or as more than one. The term “plurality”, as used herein, is defined as two or as more than two. The term “another”, as used herein, is defined as at least a second or more. The terms “including” and/or “having”, as used herein, are defined as comprising (i.e., open language). The term “coupled”, as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically.

The term “comprising” is not intended to limit inventions to only claiming the present invention with such comprising language. Any invention using the term comprising could be separated into one or more claims using “consisting” or “consisting of” claim language and is so intended. The term “comprising” is used interchangeably used by the terms “having” or “containing”.

Reference throughout this document to “one embodiment”, “certain embodiments”, “an embodiment”, “another embodiment”, and “yet another embodiment” or similar terms means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of such phrases or in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics are combined in any suitable manner in one or more embodiments without limitation.

The present production process relates to a process for high strength reinforcement alloy bar using sponge iron and scrap iron. The process includes: a process of the melting and preparation of an alloy mixture, a process of continuous casting of molten metal and a process of rolling and metal treatment.
The process of the melting and preparation alloy mixture includes:
First, scrap is being melted inside a furnace and a first chemical analysis is performed to determine the composition of the melted scrap iron. Thereafter, sponge iron is added to the melted scrap iron to form a molten metal. The chemical analysis is further performed on the molten metal to determine the composition of carbon in the molten metal. The sponge iron may further be added to the molten metal based on the second chemical analysis. In the preferred embodiment of the present invention, the scrap iron and the sponge iron are being used in a nearly 50-50 proportion. In the preferred embodiment, 50% scrap iron is first added in the furnace to start with and melting is done. After the first chemical analysis, 30% sponge iron is added initially. Further addition of sponge iron is made after second chemical analysis taking care of carbon. Then deslaging is performed to remove the slag from the molten metal. The further excess oxygen from the molten metal is removed by adding the deoxidization agent. A necessary amount of silicon and manganese is added to the molten metal. A ferro-chrome and a copper is added in order to achieve desired composition of molten metal. In the preferred embodiment, the molten metal composition (by weight %) is containing C: 0.15 max.; Mn: 1.5 max.; S:0.04 max.; P:0.12 max; Si: 0.5% max, Cr+Cu+P: 0.40% min and the balance being Fe in the furnace, provided with ferro-alloys of quantity Si-Mn 0.05 - 0.30 T; Fe-Si upto 0.05T; Fe-Cr 0.005 – 0.050 T and copper as per requirement. In an embodiment, the scrap iron and the sponge iron is melted by an induction furnace. In the preferred embodiment, a 20 ton air induction furnace is being used to melt the scrap iron and the sponge iron.
The process of continuous casting of molten metal includes:
After few minutes of homogenization process in the furnace, the molten metal is being tapped into a ladle. A molten metal is purged with nitrogen in order to remove trapped gases. After achieving a temperature of 1650-1660?C, the ladle is sent to a continuous casting machine for casting. The molten metal is casted into a billet and the billet is further send for rolling. In the preferred embodiment, the molten metal is purged with nitrogen for at least 3 minutes at a pressure of 15 kg/cm2. In the preferred embodiment, the required temperature is in the range of 1650-1660?C.
The process of rolling and metal treatment includes:
The billet is transferred to the rolling mill without preheating. The billet is rolled into a rebar. A short duration intense water quenching is done on the rebar by passing the hot rolled rebar though the series of water pipes. The surface of the rebar is converted into hard martensite. The rebar is further air cooled that subsequently tampers the hard martensite surface of the rebar. Herein, water of water pipes has following optimized quenching parameters that are average inlet temperature average, outlet temperature, water flow rate and pressure.
In an embodiment, the present invention produces the rebar of high yield strength ranging from 450MPa to 600 MPa. In the preferred embodiment, the high yield strength is 550 MPa. In an embodiment, the present invention substantially uses scrap iron and low quality sponge iron to produce the high yield strength rebar.
In yet another embodiment of the present invention, 8 ton scrap iron followed by 8 ton sponge iron were added in an induction furnace for initial melting. After complete melting, bath sample from molten metal was analysed for chemical analysis. Trim additions of necessary ferro-alloys were made and a second chemical analysis done. Once, the chemistry was achieved as per desired specification in terms of C, Mn and Si, necessary addition of copper and ferro-chrome were made to the furnace before tapping. Final chemical analysis is shown in Table 1.
The temperature of ladle at Co is taken was around 1620±10?C. Liquid steel was continuously cast into 110x110 mm2 billet in a 2-strand billet caster at a speed of 2.5 meter/minute. The continuously cast billets were directly transferred to the rolling mill without any reheating and were rolled in series of rolling stands with the finish rolling speed of 6.5 m/s. After finish rolling, the bar passes through the water quenching boxes where following quenching parameters were maintained. The tensile properties obtained are given in Table 2. Typical microstructure at rim responsible for high strength and soft core is shown in Fig.1 and Fig.2.
Average inlet temperature 940C
Average outlet temp 575C
Water Flow Rate 108 kg
Water pressure 11 kg/cm2
Fig. 1 illustrates the microstructure of a developed rebar at core in an embodiment of the present invention. Microstructure at core is showing ferrite + pearlite structure responsible for high ductility.
Fig.2 illustrates the microstructure of a developed rebar at rim in an embodiment of the present invention. Microstructure at rim is showing well tempered martensite structure responsible for high strength.
Table 1 Typical Chemistry
C Mn Si S P Cr Cu Alloying Elements CE
0.15 0.38 0.13 0.040 0.061 0.33 0.08 0.47 0.28

Table 2 Typical Tensile Properties
YS, MPa UTS, MPa Elongation, % UTS/YS
535 635 18 1.19

Further objectives, advantages and features of the present invention will become apparent from the detailed description provided herein below, in which various embodiments of the disclosed present invention are illustrated by way of example and appropriate reference to accompanying drawings. Those skilled in the art to which the present invention pertains may make modifications resulting in other embodiments employing principles of the present invention without departing from its spirit or characteristics, particularly upon considering the foregoing teachings. Accordingly, the described embodiments are to be considered in all respects only as illustrative, and not restrictive, and the scope of the present invention is, therefore, indicated by the appended claims rather than by the foregoing description or drawings. Consequently, while the present invention has been described with reference to particular embodiments, modifications of structure, sequence, materials and the like apparent to those skilled in the art still fall within the scope of the invention as claimed by the applicant.

CLAIMS:
1. A process for high strength reinforcement alloy bar using sponge iron and scrap the process comprising:
a process of the melting and preparation alloy mixture, the process having

First scrap iron is being melt inside a furnace and a first chemical analysis is performed to determine the composition of the melted scrap iron,

then sponge iron is added to the melted scrap iron to form a molten metal,
a second chemical analysis is further performed on the molten metal to determine the composition of carbon in the molten metal,
the sponge iron further added to the molten metal based on the second chemical analysis,
deslaging is performed to remove the slag from the molten metal,
further excess oxygen from the molten metal is removed by adding the deoxidization agent,
necessary amount of a silicon and a manganese is added to the molten metal, and
ferro-chrome and copper is added in order to achieve desired composition of the molten metal;
a process of continuous casting of the molten metal, the process having
after few minutes of homogenization process in the furnace, the molten metal is being tapped into a ladle,
a molten metal is purged with nitrogen in order to remove trapped gases,
after achieving a required temperature, the ladle is sent to a continuous casting machine for casting, and
the melted is casted into a billet and the billet is further send for rolling;
a process of rolling and metal treatment, the process having
the billet is transferred to the rolling mill without preheating,
the billet is rolled into a rebar,
short duration intense water quenching is done on the rebar by passing the hot rolled rebar though the series of water pipes,
the surface of the rebar is converted into hard martensite, and
the rebar is further air cooled that subsequently tampers the hard martensite surface of the rebar;
wherein, water of water pipes has following optimized quenching parameters that are average inlet temperature average, outlet temperature, water flow rate and pressure .

2. The molten metal as claimed in claim 1, wherein the molten metal composition (by weight %) containing C: 0.15 max.; Mn: 1.5 max.; S:0.04 max.; P:0.12 max; Si: 0.5% max, Cr+Cu+P: 0.40% min and the balance being Fe in the furnace, provided with ferro-alloys of quantity Si-Mn 0.05 - 0.30 T; Fe-Si upto 0.05T; Fe-Cr 0.005 – 0.050 T and copper as per requirement,

3. The furnace as claimed in claim 1, wherein the furnace is selected from an induction furnace.
4. The process as claimed in claim 1, wherein the process produces the rebar of high yield strength ranging from 450MPa to 600 MPa.

5. The high yield strength as claimed in claim 4, wherein the high yield strength is 550 MPa.

6. The process as claimed in claim1, wherein the process substantially uses scrap iron and low quality sponge iron to produce the high yield strength rebar.

7. The process of rolling as claimed in claim 1, wherein the process of rolling saves energy by rolling the billet without preheating.

8. The process of continuous casting of the molten metal as claimed in claim1, wherein the required temperature process of continuous casting of the molten metal in the range of 1650 to 1660.