CN118726852A - A wide and thick specification high-toughness wear-resistant steel based on hot rolling production line and production method - Google Patents

Abstract

A wide and thick specification high-toughness wear-resistant steel based on a hot rolling production line, the components and wt% of which are: C: 0.17-0.25%, Mn: 0.5-2%, P≤0.020%, S≤0.010%, Als: 0.03-0.06%, Ti: 0.010-0.02%, Si not exceeding 0.3% or Cr not exceeding 0.6% or B not exceeding 0.0003% or any two or more thereof are added in any proportion; the production method is: heating the ingot after conventional smelting and continuous casting; rough rolling; finish rolling; cooling; coiling; quenching; tempering; and standby. Compared with the prior art, the present invention overcomes the difficulty of coiling and cross-cutting in traditional hot rolling production lines, and significantly reduces the difficulty of production; it has excellent low-temperature toughness, that is, the impact energy at -40°C can reach more than 40J, and it will not crack when used in a low-temperature environment; because it is coiled at high temperature, the plate quality of the hot-rolled coil is significantly improved, the optimal unevenness can reach less than 2mm/m, and the qualified rate of the finished plate shape is increased by no less than 30%.

Description

A wide and thick specification high-toughness wear-resistant steel based on hot rolling production line and production method

Technical Field

The invention relates to a hot-rolled wear-resistant steel and a production method, and specifically to a wide and thick specification high-toughness wear-resistant steel and a production method based on a hot-rolled production line, which is suitable for the hot-rolled production line to produce wear-resistant steel with a width of 1500-2100 mm and a thickness of 10-30 mm.

Background Art

Low-alloy high-strength wear-resistant steel is widely used in mechanical equipment such as metallurgy, mining, building materials, railways, electricity, coal, etc. The use environment is harsh, and the quality requirements for strength, toughness, hardness and wear resistance are increasing day by day. In particular, low-temperature toughness has a far-reaching impact on the risk of cracking during the application process. Traditional thin-gauge wear-resistant steel is optimized through rolling and cooling processes. The lower coiling temperature is conducive to refining the microstructure, thereby improving low-temperature toughness. However, with the increase in thickness, at a lower coiling temperature, the strength of thick-gauge steel coils poses a greater challenge to coiling and cross-cutting equipment. Therefore, for hot-rolled thick-gauge wear-resistant steel, in order to ensure equipment safety, its coiling temperature is usually high, the original grains are coarse, and the low-temperature toughness at -40°C can only reach 10 to 20J, which is difficult to meet the application requirements of low-temperature environments.

After searching:

The document with Chinese patent publication number CN102605234A provides "A wear-resistant steel plate and its manufacturing method", whose components by weight percentage are: C: 0.08-0.24%, Si: 0.10-0.30%, Mn: 0.70-1.70%, P: ≤0.050%, S: ≤0.030%, Cr: ≤1.00%, Mo: ≤0.60%, Al: 0.01-0.10%, B: 0.0005-0.0040%, Ti: 0.005-0.06%, and satisfying: 0.15≤Cr+Mo≤1.20%, 0.011%≤Al+Ti≤0.15%, and the balance is Fe and unavoidable impurities. It is produced by casting-controlled rolling-quenching and tempering heat treatment process, with excellent performance, and is suitable for manufacturing easily worn equipment in engineering machinery. The disadvantage is that its low-temperature toughness is generally low, only reaching about 10 to 20J at -40℃, and there is a high risk of cracking when used in a low-temperature environment of -40℃.

The document with Chinese patent publication number CN108546874A discloses a low-cost HB400-grade medium-thick plate wear-resistant steel plate and a manufacturing method, wherein the chemical element composition and weight percentage thereof are: C: 0.19-0.22%, Si: 1.1-1.3%, Mn: 3-3.3%, Ni: 0.30-0.36%, Mo: 0.15-0.32%, V: 0.15-0.25%, P≤0.012%, S≤0.009%, satisfying 0.35%≤V+Mo≤0.45%, and the rest is Fe and unavoidable inclusions, and the thickness of the steel plate is 20-70mm. The wear-resistant steel plate has good hardenability, uniform microstructure and performance, small residual stress, avoids the microcrack source that may be caused by repeated high-temperature heating of the wear-resistant steel, significantly reduces the risk of cracking during application, and has a tensile strength of more than 1200MPa and a Brinell hardness of more than 380. The disadvantage is that its alloy cost is relatively high, which will increase the production cost and the promotion cost of downstream users.

Summary of the invention

The present invention aims to overcome the shortcomings of the prior art and provide a wide and thick specification high-toughness wear-resistant steel based on a hot rolling production line, which is produced on a hot rolling production line with a width of 1500-2100 mm, a thickness of 10-30 mm, a steel plate Brinell hardness of not less than 370, so as to reduce the production difficulty, not cause damage to production equipment, and a low-temperature impact energy of -40°C of not less than 40J and a production method.

Measures to achieve the above objectives:

A wide and thick specification high-toughness wear-resistant steel based on a hot rolling production line, the components and weight percentage contents of which are: C: 0.17-0.25%, Mn: 0.5-2%, P≤0.020%, S≤0.010%, Als: 0.03-0.06%, Ti: 0.010-0.02%, Si not exceeding 0.3% or Cr not exceeding 0.6% or B not exceeding 0.0003% or any two or more thereof are added in any proportion, and the rest are Fe and impurities.

A method for producing wide and thick high-toughness wear-resistant steel based on a hot rolling production line, the steps of which are:

1) After conventional smelting and continuous casting, heat the ingot: control the heating temperature at 1180-1230℃ and the heating time at

120-150 minutes, during the heating time: the heating time in the high temperature section shall not be less than 60 minutes;

2) Perform rough rolling and control the reduction rate of at least one of the first three passes to be no less than 20%;

3) Finish rolling is performed, and the total cumulative reduction rate in the finishing rolling stage is controlled to be not less than 60%, and the cumulative reduction rate in the last three passes is not less than 40%; the final rolling temperature is controlled at 780-820°C;

4) Cooling to the coiling temperature at a cooling rate of 3 to 10°C/s;

5) Coil the steel sheet and control the coiling temperature at 700-750°C;

6) Perform quenching, control the quenching temperature at 790-830°C, and keep it at this temperature for 5-10 minutes;

7) Tempering, controlling: tempering temperature at 150-200°C, tempering time at 10-30min;

8) Set aside.

Preferably, the heating time in the high temperature section is 63 to 66 minutes.

Preferably, the quenching temperature is between 790°C and 810°C.

Functions and mechanisms of various raw materials and main processes in the present invention

C: C is the cheapest element to improve material strength. As the carbon content increases, hardness and strength increase, but plasticity, toughness and welding performance decrease. Taking all factors into consideration, the C weight percentage is 0.17-0.25%;

Si: Si can reduce the diffusion rate of carbon in ferrite, promote the formation of ferrite, and also deteriorate the surface quality. Taking all factors into consideration, the Si weight percentage is preferably 0-0.3%;

Mn: Mn significantly reduces Ar1 temperature and austenite decomposition rate, improves the stability of supercooled austenite, promotes stress release of austenite, increases the residual austenite content in the final structure, and improves cold bending performance. However, if the Mn content is too high, it will increase temper brittleness and cause serious center segregation. Taking all factors into consideration, the Mn weight percentage should be 0.5-2%.

Als: Als can deoxidize steel, reduce inclusion content, and also play a role in grain refinement. Taking all factors into consideration, Als is 0.03-0.06%;

Ti: Ti has a strong affinity with C and N in steel, forming a stable Ti(C, N) compound, which can be induced to precipitate during controlled rolling, effectively preventing recrystallization, and has a significant effect on precipitation and grain refinement. Considering all factors, the Ti weight percentage is preferably 0.010-0.020%;

Cr: Cr can improve hardenability and tempering stability, and reduce the cooling rate of martensite. However, too high Cr reduces processability and weldability. Considering comprehensively, the Cr weight percentage is preferably 0 to 0.6%;

B: Adding a small amount of B to B steel can greatly improve the hardenability, but when B is too much, it is easy to be enriched at the grain boundary, which will reduce the grain boundary binding energy, making the steel plate more inclined to fracture along the grain when subjected to impact load, and reducing the low-temperature impact energy of the steel plate. Therefore, the addition amount of B in the present invention is ≤0.0003%.

P, S: P and S are harmful impurity elements in steel. P in steel is easy to form segregation in steel, reducing the toughness and welding performance of steel. S is easy to form plastic sulfide, causing stratification of steel plate and deteriorating the performance of steel plate. Therefore, the lower the P and S content, the better. Taking comprehensive consideration, the P and S content of steel is P≤0.020%, S≤0.010%.

Compared with the prior art, the present invention has the following effects:

1. It overcomes the difficulty of coiling and cross-cutting in traditional hot rolling production lines, and the production difficulty is significantly reduced.

2. Excellent low-temperature toughness, the impact energy at -40℃ can reach more than 40J, and it will not crack when used in low-temperature environment.

3. Under high-temperature coiling conditions, the shape quality of the hot-rolled coil is significantly improved, the optimal unevenness can reach less than 2mm/m, and the qualified rate of the finished product shape is increased by more than 30%.

DETAILED DESCRIPTION

The present invention is described in detail below:

Table 1 is a list of chemical components of various embodiments and comparative examples of the present invention;

Table 2 is a list of main process parameters of various embodiments and comparative examples of the present invention;

Table 3 is a table of performance test results of various embodiments of the present invention and comparative examples.

Each embodiment of the present invention is produced according to the following steps

1) After conventional smelting and continuous casting, heat the ingot: control the heating temperature at 1180-1230℃ and the heating time at

120-150 minutes, during the heating time: the heating time in the high temperature section shall not be less than 60 minutes;

2) Perform rough rolling and control the reduction rate of at least one of the first three passes to be no less than 20%;

3) Finish rolling is performed, and the total cumulative reduction rate in the finishing rolling stage is controlled to be not less than 60%, and the cumulative reduction rate in the last three passes is not less than 40%; the final rolling temperature is controlled at 780-820°C;

4) Cooling to the coiling temperature at a cooling rate of 3 to 10°C/s;

5) Coil the steel sheet and control the coiling temperature at 700-750°C;

6) Perform quenching, control the quenching temperature at 790-830°C, and keep it at this temperature for 5-10 minutes;

7) Tempering, controlling: tempering temperature at 150-200°C, tempering time at 10-30min;

8) Set aside.

Table 1 Chemical composition list of various embodiments and comparative examples of the present invention (wt%)

Table 2 List of main process parameters of various embodiments of the present invention and comparative examples

Table 2

Table 3 Performance test results of various embodiments of the present invention and comparative examples

It can be seen from Table 3 that the embodiment can produce wide and thick high-toughness wear-resistant steel based on the hot rolling production line with lower composition, and its performance is better than that of the comparative example, especially the -40°C impact energy, which is more than twice that of the comparative example, and the whole process cost is reduced by more than 10%.

This specific implementation is only the best example and is not a restrictive implementation of the technical solution of the present invention.

Claims (4)

1. A wide and thick specification high toughness wear-resistant steel based on a hot rolling production line, the components and weight percentages of which are: C: 0.17～0.25%, Mn: 0.5～2%, P≤0.020%, S≤0.010%, Als: 0.03～0.06%, Ti: 0.010～0.02%, Si not exceeding 0.3% or Cr not exceeding 0.6% or B not exceeding 0.0003% or any two or more thereof added in any proportion, and the rest being Fe and impurities. 2. A method for producing a wide and thick specification high-toughness wear-resistant steel based on a hot rolling production line as claimed in claim 1, comprising the following steps: 1) After conventional smelting and continuous casting, heat the ingot: control the heating temperature at 1180-1230℃ and the heating time at 120-150 minutes, during the heating time: the heating time in the high temperature section shall not be less than 60 minutes; 2) Perform rough rolling and control the reduction rate of at least one of the first three passes to be no less than 20%; 3) Finish rolling is performed, and the total cumulative reduction rate in the finishing rolling stage is controlled to be not less than 60%, and the cumulative reduction rate in the last three passes is not less than 40%; the final rolling temperature is controlled at 780-820°C; 4) Cooling to the coiling temperature at a cooling rate of 3 to 10°C/s; 5) Coil the steel sheet and control the coiling temperature at 700-750°C; 6) Perform quenching, control the quenching temperature at 790-830°C, and keep it at this temperature for 5-10 minutes; 7) Tempering, controlling: tempering temperature at 150-200°C, tempering time at 10-30min; 8) Set aside. 3. A method for producing wide and thick high-toughness wear-resistant steel based on a hot rolling production line as described in claim 2, characterized in that the heating time in the high-temperature section is 63 to 66 minutes. 4. A method for producing wide and thick high-toughness wear-resistant steel based on a hot rolling production line as described in claim 2, characterized in that the quenching temperature is between 790 and 810°C.