WO2020098306A1

WO2020098306A1 - Thick nm500 wear-resistant steel and production method therefor

Info

Publication number: WO2020098306A1
Application number: PCT/CN2019/097829
Authority: WO
Inventors: 姜在伟; 王升; 侯中华; 闫强军; 张仪杰; 姜辉; 王思聪
Original assignee: 南京钢铁股份有限公司
Priority date: 2018-11-12
Filing date: 2019-07-26
Publication date: 2020-05-22
Also published as: ZA202103239B; AU2019101844A4; AU2019381094A1; CN109280852A

Abstract

A thick NM500 wear-resistant steel, relating to the field of metallurgical technology and comprising the following chemical components by mass percentage: 0.26%-0.30% of C, 0.20%-0.60% of Si, 0.60%-1.00% of Mn, P ≤ 0.012%, S ≤ 0.003%, 0.60%-0.90% of Cr, 0.35%-0.50% of Mo, 0.40%-0.60% of Ni, 0.008%-0.030% of Ti, 0.015%-0.050% of Nb, 0.0008%-0.0025% of B, Ceq≤0.75%, with the balance being Fe and inevitable impurities. The production process of the present wear-resistant steel is short, the cost is low, and the produced steel has excellent mechanical properties, large thickness, high hardness, good toughness, and great welding performance.

Description

Large thickness NM500 wear-resistant steel and production method

Technical field

The invention relates to the technical field of metallurgy, in particular to a large-thickness NM500 wear-resistant steel and a production method.

Background technique

Compared with traditional wear-resistant cast steel, low-alloy wear-resistant steel plate has the advantages of low alloy content, high low-temperature impact toughness, bendable forming and other comprehensive properties, as well as flexible and convenient production and low production cost. It is widely used in work The harsh conditions require high-strength and hardness, good wear-resistant engineering, mining, construction, agriculture, cement, port, power and metallurgy machinery equipment manufacturing, such as bulldozers, loaders, excavators, dump trucks, ball mills and various Mining machinery, grab, stacker and reclaimer, conveying bending structure, etc. Such components generally work under extremely harsh conditions such as wet and dry environments, and replacement is difficult. The steel plates are required to have high strength, hardness, excellent wear resistance, and good welding performance. High service life.

At present, there have been many patent reports on low-alloy wear-resistant steel, but its thickness is thin, and the uniformity of cross-sectional hardness is not ideal, and the welding performance is poor. It can not have both excellent wear resistance and corrosion resistance, which is difficult to meet The demand for large-scale, light-weight and long-life manufacturing of equipment manufacturing, especially for low-alloy wear-resistant steel NM400 thick plates with a thickness of 90mm and a uniform hardness, there are very few technologies that can be referenced.

Considering that the best performance of the 90mm large thickness wear-resistant steel plate requires not only high hardness and toughness properties, but also good welding performance, all requirements must be easy to produce and low cost; therefore, this application is for 90mm The chemical composition and production process of the large-thickness NM500 wear-resistant steel plate were studied, and a large-thickness NM500 wear-resistant steel and its production method were designed.

Summary of the invention

In order to solve the above technical problems, the present invention provides a large thickness NM500 wear-resistant steel, the chemical composition and mass percentage are as follows: C: 0.26% ~ 0.30%, Si: 0.20% ~ 0.60%, Mn: 0.60% ~ 1.00%, P≤0.012%, S≤0.003%, Cr: 0.60% to 0.90%, Mo: 0.35% to 0.50%, Ni: 0.40% to 0.60%, Ti: 0.008% to 0.030%, Nb: 0.015% to 0.050%, B: 0.0008% to 0.0025%, Ceq≤0.75%, Ceq = C + Mn / 6 + (Cr + Mo + V) / 5 + (Cu + Ni) / 15, the balance is Fe and inevitable impurities.

Technical effect: The large-thickness NM500 wear-resistant steel and production method provided by the present invention are simple and easy to implement, the production process is short, the cost is low, the produced steel has excellent mechanical properties, large thickness, high hardness, good toughness and good welding performance.

The technical solution further defined by the present invention is:

The chemical composition and mass percentage of a large thickness NM500 wear-resistant steel mentioned above are as follows: C: 0.27%, Si: 0.28%, Mn: 0.83%, P≤0.009%, S≤0.0015%, Cr: 0.80% , Ni: 0.48%, Mo: 0.45%, Ti: 0.013%, B: 0.0015%, Alt: 0.033%, Ceq: 0.69%.

The chemical composition and mass percentage of a large thickness NM500 wear-resistant steel mentioned above are as follows: C: 0.28%, Si: 0.27%, Mn: 0.83%, P≤0.009%, S≤0.0020%, Cr: 0.79% , Ni: 0.49%, Mo: 0.43%, Ti: 0.015%, B: 0.0016%, Alt: 0.033%, Ceq: 0.70%.

The chemical composition and mass percentage of a large thickness NM500 wear-resistant steel mentioned above are as follows: C: 0.28%, Si: 0.27%, Mn: 0.83%, P≤0.009%, S≤0.0020%, Cr: 0.78% , Ni: 0.47%, Mo: 0.42%, Ti: 0.014%, B: 0.0015%, Alt: 0.033%, Ceq: 0.70%.

Another object of the present invention is to provide a large thickness NM500 wear-resistant steel production method, including the following processes: hot metal desulfurization pretreatment-converter smelting-LF + RH refining-continuous casting-casting billet stack slow cooling-casting billet inspection- Cast billet determination-casting bill acceptance-casting billet preheating-casting billet heating-descaling-rolling-air cooling-flaw detection-shot blasting-quenching-tempering-straightening-cutting, sampling-spray marking-inspection-storage ,among them

When the slab is heated, the temperature of the heating section is 1180 ° C-1230 ° C, the temperature of the soaking section is controlled at 1215 ° C-1220 ° C, the tapping temperature is between 1180 ° C-1200 ° C, and the furnace time is 350min-420min;

Rolling adopts the two-stage rolling method. The two-stage open rolling temperature is ≤950 ° C, the thickness of the finished product is 90mm, the thickness of the ingot to be warm is controlled at ≥130mm, the second-stage final rolling temperature is 850 ° C to 860 ° C, and the air is cooled after rolling;

During quenching and tempering, the quenching temperature is controlled at 900 ℃ ～ 930 ℃, the heating rate is 1.5 ± 0.1min / mm, and the furnace time is 170min ～ 190min; the tempering temperature after quenching is controlled at 150 ℃ ～ 220 ℃, and the heating rate is 2.5 ± 0.1min / mm, the furnace time is 360min ～ 450min, slowly cool to room temperature;

When straightening in the hot-rolled state, pre-straightening is first performed at 790 ° C to 830 ° C.

As mentioned above, a large thickness NM500 wear-resistant steel production method, when rolling, the rolling in the recrystallization zone requires a pass reduction rate of ≥12%, the final rolling temperature is ≥980 ° C, and the rolling in the recrystallization zone requires cumulative reduction The rate is ≥50%, rolling in the non-recrystallized area requires cumulative reduction rate ≥40%, open rolling temperature ≤950 ℃, final rolling temperature ≥830 ℃.

As mentioned above, a large thickness NM500 wear-resistant steel production method, the thickness of the blank is 320mm.

The beneficial effects of the present invention are:

(1) The invention is designed by adding a small amount of chromium, nickel, molybdenum alloy, Nb + Ti + V + B micro-alloying components, carbon equivalent ≤0.75, short production process flow, low cost;

(2) The present invention uses a reasonable controlled rolling process to produce wear-resistant steel with a thickness of up to 90mm. Through the optimal heat treatment process, each mechanical performance index has reached the standard requirements for material design of large domestic and foreign machinery and equipment companies. The surface hardness is ≥470HB , The core hardness is greater than 360HB, -20 ℃, Akv impact energy value ≥ 17J;

(3) The present invention successfully solves the technical difficulties of high hardness and low plasticity, low impact energy value and high carbon equivalent of 90mm large thickness wear-resistant steel, which affects the welding performance. The prepared steel has excellent mechanical properties, large thickness and high thickness Hardness, good toughness and good welding performance;

(4) In the present invention, due to the high strength of the 90mm steel plate after rolling, it needs to be pre-corrected at 790 ℃ ~ 840 ℃ to ensure the original shape, on the basis of adherence to low-cost production requirements, to ensure that the quenching can be hardened, in the composition In the design, medium carbon plus a small amount of Cr, Mo, and B elements to improve hardenability are adopted, so as to improve the cooling speed design idea to solve the production of high-grade equipment requirements;

(5) In the present invention, due to the high strength of the experimental steel, the 90mm steel plate is controlled and rolled using a high temperature and large reduction mode, and the overall compression ratio is greater than 3 times. Therefore, a 320mm thick billet is selected, and the soaking temperature is controlled at about 1220 ° C. Appropriate extension to ensure that the steel temperature of the blank is uniform throughout, avoiding the occurrence of "red and black" steel temperature;

(6) In the present invention, since the thickness of the finished product is 90 mm, in order to avoid the occurrence of core segregation during the rolling process and affect the strength and impact value, the two-stage rolling method is adopted, and the first-stage rolling deformation rate ≥50%, two The total deformation rate of the stage is ≥40%, to ensure that there is no obvious difference between the surface and the heart tissue;

(7) The invention successfully solves the problem that the production line with a rolling force of 12,000 tons can produce wear-resistant steel with high hardness, high toughness and large thickness, which is applied to domestic large-scale machinery and equipment, which greatly reduces the cost of relying on imported high costs.

BRIEF DESCRIPTION

Figures 1 and 2 are photos of the metallographic structure of the NM500 wear-resistant steel at a tempering temperature of 180 ° C, a heating rate of 2.6min / mm, and a tempering time of 420min and a thickness of 1/4 and 1/2 thickness respectively.

detailed description

Example 1

The chemical composition and mass percentage of a large thickness NM500 wear-resistant steel provided by this embodiment are as follows: C: 0.27%, Si: 0.28%, Mn: 0.83%, P≤0.009%, S≤0.0015%, Cr: 0.80 %, Ni: 0.48%, Mo: 0.45%, Ti: 0.013%, B: 0.0015%, Alt: 0.033%, Ceq: 0.69%, Ceq = C + Mn / 6 + (Cr + Mo + V) / 5 + (Cu + Ni) / 15, the balance is Fe and inevitable impurities.

The production method includes the following processes: hot metal desulfurization pretreatment-converter smelting-LF + RH refining-continuous casting-casting billet stack slow cooling-casting billet inspection-casting billet determination-casting billet acceptance-casting billet preheating-casting billet heating- Descaling-rolling-air cooling-flaw detection-shot blasting-quenching-tempering-straightening-cutting, sampling-spray marking-inspection-storage, including:

The thickness of the billet is 320mm. When the billet is heated, the temperature of the heating section is 1200 ℃ ～ 1220 ℃, the temperature of the soaking section is controlled at 1215 ℃, the tapping temperature is 1195 ℃, and the furnace time is 405min;

Rolling adopts the two-stage rolling method. The two-stage rolling temperature is 886 ℃, the finished product thickness is 90mm, the thickness of the ingot to be warm is controlled at 150mm, the second-stage final rolling temperature is 856 ℃, and the air cooling after rolling; Secondary reduction rate ≥12%, final rolling temperature ≥980 ℃, rolling in the recrystallization zone requires cumulative reduction rate ≥50%, rolling in the non-recrystallization zone requires cumulative reduction rate ≥40%, open rolling temperature ≤950 ℃ , The final rolling temperature ≥830 ℃;

During quenching and tempering, the quenching temperature is controlled at 912 ℃, the heating rate is 1.4min / mm, and the furnace time is 185min; the tempering temperature after quenching is controlled at 200 ℃, the heating rate is 2.4min / mm, and the furnace time is 410min. Slowly cool to room temperature;

When straightening in the hot-rolled state, pre-straightening is first performed at 828 ° C.

Example 2

The chemical composition and mass percentage of a large thickness NM500 wear-resistant steel provided by this embodiment are as follows: C: 0.28%, Si: 0.27%, Mn: 0.83%, P≤0.009%, S≤0.0020%, Cr: 0.79 %, Ni: 0.49%, Mo: 0.43%, Ti: 0.015%, B: 0.0016%, Alt: 0.033%, Ceq: 0.70%, Ceq = C + Mn / 6 + (Cr + Mo + V) / 5 + (Cu + Ni) / 15, the balance is Fe and inevitable impurities.

The billet thickness is 320mm. When the billet is heated, the heating section temperature is 1220 ℃ ～ 1230 ℃, the soaking section temperature is controlled at 1220 ℃, the tapping temperature is 1190 ℃, and the furnace time is 373min;

Rolling adopts the two-stage rolling method, the two-stage rolling temperature is 890 ℃, the finished product thickness is 90mm, the thickness of the ingot to be warm is controlled at 150mm, the second-stage final rolling temperature is 854 ℃, and the air cooling after rolling; Secondary reduction rate ≥12%, final rolling temperature ≥980 ℃, rolling in the recrystallization zone requires cumulative reduction rate ≥50%, rolling in the non-recrystallization zone requires cumulative reduction rate ≥40%, open rolling temperature ≤950 ℃ , The final rolling temperature ≥830 ℃;

During quenching and tempering, the quenching temperature is controlled at 910 ℃, the heating rate is 1.5min / mm, and the furnace time is 180min; the tempering temperature after quenching is controlled at 180 ℃, the heating rate is 2.5min / mm, and the furnace time is 400min. Slowly cool to room temperature;

When straightening in the hot rolled state, pre-straightening is performed at 810 ° C.

Example 3

The chemical composition and mass percentage of a large thickness NM500 wear-resistant steel provided by this embodiment are as follows: C: 0.28%, Si: 0.27%, Mn: 0.83%, P≤0.009%, S≤0.0020%, Cr: 0.78 %, Ni: 0.47%, Mo: 0.42%, Ti: 0.014%, B: 0.0015%, Alt: 0.033%, Ceq: 0.70%, Ceq = C + Mn / 6 + (Cr + Mo + V) / 5 + (Cu + Ni) / 15, the balance is Fe and inevitable impurities.

The billet thickness is 320mm. When the billet is heated, the heating section temperature is 1210 ℃ ～ 1220 ℃, the soaking section temperature is controlled at 1220 ℃, the tapping temperature is 1189 ℃, and the furnace time is 378min;

Rolling adopts the two-stage rolling method, the two-stage rolling temperature is 887 ℃, the finished product thickness is 90mm, the thickness of the ingot to be warm is controlled at 150mm, the second-stage final rolling temperature is 858 ℃, and the air cooling after rolling; Secondary reduction rate ≥12%, final rolling temperature ≥980 ℃, rolling in the recrystallization zone requires cumulative reduction rate ≥50%, rolling in the non-recrystallization zone requires cumulative reduction rate ≥40%, open rolling temperature ≤950 ℃ , The final rolling temperature ≥830 ℃;

When quenching and tempering, the quenching temperature is controlled at 910 ℃, the heating rate is 1.5min / mm, and the furnace time is 125min; the tempering temperature after quenching is controlled at 180 ℃, the heating rate is 2.6min / mm, and the furnace time is 420min, Slowly cool to room temperature;

When straightening in the hot rolled state, pre-straightening is performed at 825 ° C.

The mechanical properties of the wear-resistant steel produced in Example 1, Example 2 and Example 3 are as follows:

With reference to Figures 1 and 2, it can be seen that from 1/4 thickness to 1/2 metallographic structure, the microstructure is tempered martensite, and from 1/4 thickness to the heart are tempered horses Austenitic structure, and uniform grain structure.

The present invention develops a 90mm-thick NM500 wear-resistant steel through the design of medium carbon and a small amount of chromium, nickel, molybdenum alloy, niobium + vanadium + titanium + boron microalloying, combined with a reasonable controlled rolling process and heat treatment process. After rolling and heat treatment, its mechanical properties include surface hardness ≥470HB, core hardness ≥360HB, -20 ℃, Akv impact energy value ≥17J; as the national standard does not have mechanical performance standards for 70mm thickness NM500 wear-resistant steel, the present invention The obtained hardness and toughness indexes have reached the design standards of mechanical properties of large foreign companies. Due to the high hardness and large thickness, in the actual industrial production process, the cooling capacity of rolling equipment and quenching machine is higher, and wide and thick plates are used. 5,000 mills with a rolling force of 12,000 tons. Fully utilize the large-pressure rolling mode to obtain mechanical properties with uniform grains and matching structure and properties. It successfully solved the production line with a rolling force of 12,000 tons to produce high hardness, Wear-resistant steel with high toughness and large thickness is applied to large domestic machinery and equipment, which greatly reduces the high cost of relying on imports.

In addition to the above embodiments, the present invention may have other embodiments. All technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of protection required by the present invention.

Claims

A large thickness NM500 wear-resistant steel, characterized in that its chemical composition and mass percentage are as follows: C: 0.26% ~ 0.30%, Si: 0.20% ~ 0.60%, Mn: 0.60% ~ 1.00%, P ≤ 0.012%, S≤0.003%, Cr: 0.60% to 0.90%, Mo: 0.35% to 0.50%, Ni: 0.40% to 0.60%, Ti: 0.008% to 0.030%, Nb: 0.015% to 0.050%, B: 0.0008% to 0.0025%, Ceq≤0.75%, Ceq = C + Mn / 6 + (Cr + Mo + V) / 5 + (Cu + Ni) / 15, the balance is Fe and inevitable impurities.
A large thickness NM500 wear-resistant steel according to claim 1, the chemical composition and mass percentage are as follows: C: 0.27%, Si: 0.28%, Mn: 0.83%, P ≤ 0.009%, S ≤ 0.0015%, Cr : 0.80%, Ni: 0.48%, Mo: 0.45%, Ti: 0.013%, B: 0.0015%, Alt: 0.033%, Ceq: 0.69%.
A large thickness NM500 wear-resistant steel according to claim 1, the chemical composition and mass percentage are as follows: C: 0.28%, Si: 0.27%, Mn: 0.83%, P ≤ 0.009%, S ≤ 0.0020%, Cr : 0.79%, Ni: 0.49%, Mo: 0.43%, Ti: 0.015%, B: 0.0016%, Alt: 0.033%, Ceq: 0.70%.
A large thickness NM500 wear-resistant steel according to claim 1, the chemical composition and mass percentage are as follows: C: 0.28%, Si: 0.27%, Mn: 0.83%, P ≤ 0.009%, S ≤ 0.0020%, Cr : 0.78%, Ni: 0.47%, Mo: 0.42%, Ti: 0.014%, B: 0.0015%, Alt: 0.033%, Ceq: 0.70%.
A large thickness NM500 wear-resistant steel production method, characterized by the following process: hot metal desulfurization pretreatment-converter smelting-LF + RH refining-continuous casting-casting billet stack slow cooling-casting billet inspection-casting billet determination- Cast slab acceptance-casting slab preheating-casting slab heating-descaling-rolling-air cooling-flaw detection-shot blasting-quenching-tempering-straightening-cutting, sampling-spray printing identification-inspection-storage, which

When the slab is heated, the temperature of the heating section is 1180 ° C-1230 ° C, the temperature of the soaking section is controlled at 1215 ° C-1220 ° C, the tapping temperature is between 1180 ° C-1200 ° C, and the furnace time is 350min-420min;

Rolling adopts the two-stage rolling method, the two-stage open rolling temperature is ≤950 ℃, the finished product thickness is 90mm, the thickness of the to-be-heated slab is controlled to be ≥130mm, the second-stage final rolling temperature is 850 ℃ -860 ℃, and air cooling after rolling;

During quenching and tempering, the quenching temperature is controlled at 900 ℃ ～ 930 ℃, the heating rate is 1.5 ± 0.1min / mm, and the furnace time is 170min ～ 190min; the tempering temperature after quenching is controlled at 150 ℃ ～ 220 ℃, and the heating rate is 2.5 ± 0.1min / mm, the furnace time is 360min ～ 450min, slowly cool to room temperature;

When straightening in the hot-rolled state, pre-straightening is first performed at 790 ° C to 830 ° C.
The production method of NM500 wear-resistant steel with large thickness according to claim 5, characterized in that: during rolling, rolling in the recrystallization zone requires a pass reduction rate of ≥12%, a final rolling temperature of ≥980 ° C, and recrystallization Zone rolling requires cumulative reduction rate ≥50%, rolling without recrystallization zone requires cumulative reduction rate ≥40%, open rolling temperature ≤950 ℃, final rolling temperature ≥830 ℃.
A method for producing a large-thickness NM500 wear-resistant steel according to claim 5, wherein the thickness of the blank is 320 mm.