Claims:We claim:
1. A process for producing low alloy steel comprising steps of:
casting a steel alloy with composition (all in wt. %): 0.10 to 0.25 Carbon, 1.0 to 1.8 Manganese, 0.40 to 0.6 Silicon, 0.15 to 0.25 Chromium, 0.10 to 0.15 Molybdenum, 0.40 to 0.65 Nickel, 0.34 to 0.69 Carbon equivalent, 0 to 0.10 Vanadium, 0 to 0.08 Titanium, 0 to 0.01 Boron, and balance being Iron and residual impurities;
homogenizing the steel alloy by austenitizing at 1150-1200 °C for 2-4 hours; and
hot rolling the steel alloy in the range of 68-75% followed by water quenching to room temperature.
2. The process as claimed in claim 1, wherein the low alloy steel comprises 100% martensite.
3. The process as claimed in claim 1, wherein hardness (at 1 kg load) of the low alloy steel is 430 Hv-520 Hv.
4. The process as claimed in claim 1, wherein Yield Strength of the low alloy steel is 900-1100 MPa.
5. The process as claimed in claim 1, wherein Ultimate Tensile Strength of the low alloy steel is 1400-1600 MPa.
6. The process as claimed in claim 1, wherein total elongation of the low alloy steel is 11-18 %.
7. A low alloy steel comprising:
0.10 to 0.25 carbon, 1.0 to 1.8 Manganese, 0.40 to 0.6 Silicon, 0.15 to 0.25 Chromium, 0.10 to 0.15 Molybdenum, 0.4 to 0.65 Nickel, 0.34 to 0.69 Carbon equivalent, 0 to 0.01 Vanadium, 0 -0.08 Titanium, 0 to 0.01 Boron, and balance being Iron and residual impurities (all in wt.%).
8. The low alloy steel as claimed in claim 7, wherein the low alloy steel comprises 100% martensite.
9. The low alloy steel as claimed in claim 7, wherein hardness (at 1 kg load) of the low alloy steel is 430 Hv-520 Hv.
10. The low alloy steel as claimed in claim 7, wherein Yield Strength of the low alloy steel is 900-1100 MPa.
11. The low alloy steel as claimed in claim 7, wherein Ultimate Tensile Strength of the low alloy steel is 1400-1600 MPa.
12. The low alloy steel as claimed in claim 7, wherein total elongation of the low alloy steel is 11-18 %.
, Description:HOT ROLLED AND DIRECT QUENCHED LOW ALLOY STEEL AND A PROCESS OF PRODUCING THE SAME

TECHNICAL FIELD
[0001] The present disclosure relates generally to a field of metallurgy. Particularly, but not exclusively, the disclosure relates to a design and development of newly designed low alloy steel grades exhibiting ultra-high strength and good ductility, and further relates to a process for producing low alloy steel.
[0002] The present disclsoure further relates to controlled thermo-mechanical processing of the alloy followed by direct water quenching process that led to improved mechanical properties.

BACKGROUND
[0003] Background description includes information that may be useful in understanding the present subject matter. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed subject matter, or that any publication specifically or implicitly referenced is prior art.
[0004] A process of wear involves gradual and progressive loss of material from the surface of a component due to relative motion between the active and counter body species either by mechanical action or chemical reaction. Depending upon the environment of application, the material interacts with different kinds of abrasives and as a result wears out. Therefore, abrasive wear resistant materials become highly desirable in the industrial applications such as agriculture, earth moving, excavation, mining, mineral processing, transportation etc.
[0005] The increasing cost of replacing worn parts in mining and earth moving equipment confronts a continual challenge to materials development. As per the report of a national survey in 1997, for UK industries who have wear problem, the cost of wear was typically about 0.25% of their turnover. Out of this, abrasive wear alone contributes to around 63% [M.J. Neale, M. Gee, William Andrew Inc., 2001]. This undesirable loss, particularly due to the process of wear, can be reduced to at least half by replacing the currently used materials with new ones and/or by selecting a better design of the components. However, a new design of a component is often coupled with other associated risk, and also does not always make an economically viable alternative. To the contrary, the use of new material can be considered as a better option.
[0006] Components in wear resistant applications, particularly in mining and earthmoving sectors, are essentially required to have adequate abrasion resistance along with the ability to resist chemical attacks. As impact loading is mostly unavoidable in such applications, the requirement for good impact toughness also becomes one of the major concerns. Pressently, most of these applications uses medium to high carbon steels containing martensitic or tempered martensitic microstructure. The tempering treatment requires an additional facility after hot rolling for heat treatment. Although the toughness of steel can be improved by tempering, this leads to reduction in the strength of the material. On the other hand, the high carbon steels with martensitic microstructure are hard and brittle. Hence, these materials are limited by low impact toughness, which leads to the generation of cracks while experiencing sudden impact loading [H. Mohrbacher, Molybdenum in steels for abrasion resistant applications, Niobelcon bvba, Schilde,Belgium].
[0007] Thus, there is a need to avoid tempering treatment and develop new grade of material with low carbon content as well as substitutional aditions to achieve high strength while maintaining the good ductility.

OBJECTS OF THE DISCLOSURE
[0008] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed hereinbelow.
[0009] A general object of the present disclosure is to provide low alloy steel grades with ultra high-strength and good ductility, which can be produced directly from hot rolling mill.
[0010] Another object of the present invention is to propose a thermo-mechanical processing schedule followed by direct water quenching to room temperature.
[0011] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

SUMMARY
[0012] This summary is provided to introduce concepts related to a design and development of newly designed low alloy steel grades exhibiting ultra-high strength and good ductility. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0013] The present disclosure relates to a process for producing low alloy steel comprising steps of: casting a steel alloy with composition (all in wt. %): 0.10 to 0.25 Carbon, 1.0 to 1.8 Manganese, 0.40 to 0.6 Silicon, 0.15 to 0.25 Chromium, 0.10 to 0.15 Molybdenum, 0.40 to 0.65 Nickel, 0.34 to 0.69 Carbon equivalent, 0 to 0.10 Vanadium, 0 to 0.08 Titanium, 0 to 0.01 Boron, and balance being Iron and residual impurities; homogenizing the steel alloy by austenitizing at 1150-1200 °C for 2-4 hours; and hot rolling the steel alloy in the range of 68-75% followed by water quenching to room temperature.
[0014] In an aspect, the low alloy steel comprises 100% martensite.
[0015] In an aspect, hardness (at 1 kg load) of the low alloy steel is 430 Hv-520 Hv.
[0016] In an aspect, Yield Strength of the low alloy steel is 900-1100 MPa.
[0017] In an aspect, Ultimate Tensile Strength of the low alloy steel is 1400-1600 MPa.
[0018] In an aspect, total elongation of the low alloy steel is 11-18 %.
[0019] The present disclosure further relates to a low alloy steel comprising 0.10 to 0.25 carbon, 1.0 to 1.8 Manganese, 0.40 to 0.6 Silicon, 0.15 to 0.25 Chromium, 0.10 to 0.15 Molybdenum, 0.4 to 0.65 Nickel, 0.34 to 0.69 Carbon equivalent, 0 to 0.01 Vanadium, 0 -0.08 Titanium, 0 to 0.01 Boron, and balance being Iron and residual impurities (all in wt.%).
[0020] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
[0021] 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 to form a further embodiment of the disclosure.
[0022] 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 DRAWINGS
[0023] The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system and/or methods in accordance with embodiments of the present subject matter are now described, by way of example only, and with reference to the accompanying figures, in which:
[0024] FIG. 1 illustrates a process for producing a low alloy steel, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0025] 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.
[0026] While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has 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 forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.
[0027] The terms “comprises”, “comprising”, “includes” or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, device or method that includes a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or apparatus proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or method.
[0028] In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the disclosure may be practised. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.
[0029] Hereinafter, a description of an embodiment related to designing and casting of two different alloys at, say, 40 kilogram (kg) scale which are subsequently hot forged. In order to ensure the complete homogenization, the forged steel plates are first austenitized at 1200 °C for about 2-4 hours. After that, the plates are hot rolled and subsequently quenched in water to room temperature.
[0030] The present subject matter is based on studies and experimentations that were required to develop low alloy steel grades exhibiting high strength while maintaining the good ductility.
[0031] In accordance with some embodiments of the present disclosure, two alloys are designed considering the following factors:
1. Higher Ms temperature.
2. Low carbon equivalent to eliminate the problem of weldability and low carbon content to improve impact toughness.
3. Higher hardenability to eliminate bainite or pearlite formation during quenching.
4. Addition of substitutional additions to achieve the desired strength levels.

[0032] Furhter, the chemical composition of the proposed alloys, their carbon equivalent (CE) values and Ms temperature calculated empirically as well as through dilatometry experiment are shown in Table 1:

Element (wt %) C Mn Si Cr Mo Ni V Ti B N Fe CE Ms (°C)
Empirical Experimental
Alloy-1 0.15 1.20 0.5 0.2 0.1 0.5 0.03 - - 0.0120 Bal. 0.45 426 454
Alloy-2 0.20 1.47 0.5 0.2 0.1 0.5 - 0.025 0.0009 0.0048 Bal. 0.54 393 390
Table 1: Chemical composition, carbon equivalent (CE) and Ms temperatures of Alloy 1 & 2.
[0033] FIG. 1 illustrates a process 100 producing low alloy steel, according to an embodiment of the present disclosure. The order in which the process 100 is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any appropriate order to carry out the process 100 or an alternative method. Additionally, individual blocks may be deleted from the process 100 without departing from the scope of the subject matter described herein.
[0034] At block 102, the process 100 includes casting a steel alloy with composition (all in wt. %): 0.10 to 0.25 Carbon, 1.0 to 1.8 Manganese, 0.40 to 0.6 Silicon, 0.15 to 0.25 Chromium, 0.10 to 0.15 Molybdenum, 0.40 to 0.65 Nickel, 0.34 to 0.69 Carbon equivalent, 0 to 0.10 Vanadium, 0 to 0.08 Titanium, 0 to 0.01 Boron, and balance being Iron and residual impurities.
[0035] At block 104, the process 100 includes homogenizing the steel alloy by austenitizing at 1150-1200 °C for 2-4 hours.
[0036] At block 106, the process 100 includes hot rolling the steel alloy about 70% followed by water quenching to room temperature.
[0037] The low alloy steel obtained with the implementation of the process 100 has mechanical properties (on American Society for Testing and Materials (ASTM) standard) shown in Table 2:

Properties Water Quench (WQ)
Alloy 1 Alloy 2
Hardness (HV 1 kg) 430-470 505-525
Yield Strength (MPa) 900-1000 1050-1100
Ultimate Tensile Strength (MPa) 1400-1500 1550-1600
Uniform elongation (%) 7-9 7-8
Total elongation (%) 12-18 11-12
Table 2: Mechanical properties of Alloy 1 & 2

[0038] Thus, with the implementation of the present disclosure, a need is eliminated for any extra facility to perform tempering heat treatment, i.e. to obtain steel product directly from the hot strip mill.
[0039] Also, the present disclosure provides a ow alloy composition, particularly the carbon content exhibiting higher strength with good ductility. In an aspect, the low alloy steel comprising 0.10 to 0.25 carbon, 1.0 to 1.8 Manganese, 0.40 to 0.6 Silicon, 0.15 to 0.25 Chromium, 0.10 to 0.15 Molybdenum, 0.4 to 0.65 Nickel, 0.34 to 0.69 Carbon equivalent, 0 to 0.01 Vanadium, 0 -0.08 Titanium, 0 to 0.01 Boron, and balance being Iron and residual impurities (all in wt.%).

Equivalents:
[0040] The specification has described a process for producing low alloy steel. The illustrated steps are set out to explain the exemplary embodiments shown, and it should be anticipated that on-going technological development will change the manner in which particular functions are performed. These examples are presented herein for purposes of illustration, and not limitation. Further, the boundaries of the functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternative boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the disclosed embodiments. Also, the words "comprising," "having," "containing," and "including," and other similar forms are intended to be equivalent in meaning and be open-ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.
[0041] Finally, the language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based here on. Accordingly, the embodiments of the present invention are intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.