CN105200337A - High-strength wear-resistant steel plate and production method thereof - Google Patents

Abstract

A high-strength wear-resistant steel plate and its production method, its chemical composition wt% is: C0.25-0.30%, Si0.3-0.5%, Mn0.40-1.00%, Cr0.6-1.2%, Mo0.15 ～0.4%, Nb0.01～0.03%, Ni≤0.50%, Cu≤0.50%, B0.0005～0.0022%, Ti0.025～0.04%, Als0.020～0.045%, P≤0.015%, S≤0.005 %, and Ti/N≥3.4. Refining control of molten steel [N]≤0.0080%, [O]≤0.0020%, to ensure effective boron content is 0.0010~0.0020%, stacking slow cooling after continuous casting ≥48h; adopt two-stage controlled rolling, the final rolling temperature of the first stage is 980 ~1050°C. In the second stage, the off-line quenching is adopted for the thickness > 50mm, and the swing is performed in the low-pressure section of the quenching machine; the online quenching is adopted for the thickness ≤ 50mm, and self-tempering is carried out by using the residual temperature. The invention has lower carbon and manganese content, good weldability, surface hardness greater than 550HB, -40°C low-temperature toughness greater than 30J, and maximum thickness up to 120mm.

Description

A kind of high-strength wear-resistant steel plate and its production method

technical field

The invention belongs to the metallurgy field of metal materials, and in particular relates to a 550HB grade high-strength wear-resistant steel plate and a production method thereof.

Background technique

Wear-resistant steel plates can be widely used in fields such as energy, transportation, agricultural machinery, mining equipment, engineering machinery, and cement equipment. High-carbon and high-manganese series have been widely used as classic wear-resistant steels for more than a hundred years. However, when the impact of the crushed material is not strong, because the work hardening performance of high manganese steel cannot be fully exerted, the high manganese steel liner shows the weakness of fast wear and short service life; Grinding steel has the characteristics of good wear resistance and toughness, simple production process and reasonable economy, and its development and application develop rapidly.

The wear-resistant steel plate with a surface hardness of 550HB is a high-strength wear-resistant steel plate with high surface hardness and wear resistance. It is generally supplied in the state of quenching and low temperature tempering. It is mainly used in construction machinery and mining machinery that require high wear resistance. used under working conditions.

The production of high-strength wear-resistant steel plates at home and abroad has formed a number of patents. For example, the Chinese Patent Publication No. CN1775983 provides a "high-strength cast air-cooled bainitic wear-resistant steel and its preparation method", and its chemical composition is (weight % ): C0.32～0.65, Si0.8～3.0, Mn1.2～3.0, Cr0.5～0.8, Cu0.3～0.8, B0.001～0.008, Al0.18～0.35, Y0.05～0.15, Ti0.05～0.20, Mg0～0.12, Ca0～0.12, Zn0～0.15, and 0.10<Mg+Ca+Zn<0.25, the rest is Fe and unavoidable trace impurities. The manufacturing process is as follows: heat and melt scrap steel, pig iron, ferrochrome and copper plate, add ferrosilicon and ferromanganese for pre-deoxidation and alloying after melting; Final deoxidation and alloying, and then out of the furnace; crush the compound modifier containing yttrium, boron, titanium, magnesium, calcium and zinc into small pieces with a particle size of less than 25mm, place them at the bottom of the ladle, and use the method of pouring into the ladle to clean the molten steel Carry out compound modification treatment; after modification treatment, pour molten steel into castings in ordinary molds. Compared with the traditional high-manganese steel, the wear-resistant steel of this invention has significantly lower carbon and manganese content and higher surface hardness. The Rockwell hardness is 55.7. Due to the higher surface hardness, it can significantly increase the service life, improve the working efficiency of equipment, and reduce production costs. Has good economic benefits. The patent belongs to medium-carbon, high-silicon alloy wear-resistant steel with complex alloy system, high content of aluminum, silicon and titanium, difficult smelting and continuous casting, and can only be used to produce castings.

Patent Publication No. CN1140205 discloses "a medium-carbon medium-alloy wear-resistant steel", its chemical composition is: C0.45-0.65%, Si0.3-0.8%, Mn0.4-1.0%, Cr4.0-5.5% , Mo0.3～0.7%, V0.2～0.5%, Re0.02～0.05%, P·S≤0.040%. The patent is produced by casting steel, which is suitable for making liners, compartment plates, rolling crushing drums, hammer heads and blow bars of hammer and impact crushers for medium-sized ball mills that are subject to relatively large loads. For tooth plates of jaw crushers with strict magnetic separation requirements, the service life is 3-4 times that of high manganese steel. The patented product has low content of manganese and silicon, but the content of alloys such as carbon and chromium molybdenum is still high, so it can only be produced by casting, and the smelting of rare earth-containing steel is difficult, and the production process is not easy to control. The surface hardness of the patented wear-resistant steel is Rockwell 52, which is low in hardness and poor in wear resistance.

Patent Publication No. CN101250673 provides "a super-high-strength wear-resistant steel and its production method", its composition is (weight percent): C0.10-0.17%, Si0.25-0.50%, Mn1.20-1.50%, P≤0.018%, S≤0.008%, Cr0.20～0.50%, Ni0.25～0.50%, Mo0.10～0.40%, Als0.02～0.06%, B≤0.005%, RE≤150g/ton steel, The balance is Fe and unavoidable impurities, and the carbon equivalent Ceq(%)≤0.60, Ceq(%)=C+Mn/6+(Mo+Cr+V)/5+(Ni+Cu)/15. The specific production methods of the steel include: smelting by ultra-pure steel process—desulfurization of molten iron—compound blowing at the top and bottom of converter—vacuum treatment—feeding rare earth (RE) wire in crystallizer—casting into slab—slab heating—rough rolling—finishing Rolling—air cooling or medium pressure water cooling—steel quenching and tempering treatment. This patent has low carbon and alloy content and can be produced by continuous casting. Although it has ultra-high strength and high toughness, the hardness of the steel plate is only 400HB and cannot reach 550HB, so it cannot be widely used in mines and mines with harsh working conditions and high wear resistance requirements. On construction machinery products, tempering treatment is required after quenching, the process is complicated and the cost is high.

Baoshan Iron and Steel Co., Ltd. Li Hongbin, Yao Liandeng, Liu Zicheng, Zhao Xiaoting and others applied for "a wear-resistant steel plate" with the publication number CN10234682A. : 0.20～1.50%, P: ≤0.050%, S: ≤0.030%, Cr: 0～1.50%, Mo: 0～0.80%, Al: 0.02～0.20%, B: 0.0005～0.0040%, Ti: 0～ 0.10%, Ca: 0-0.030%, 0.10%≤Cr+Mo≤1.80%, 0.05%≤Al+Ti≤0.18%, and the balance is Fe and unavoidable impurities. The manufacturing method of the wear-resistant steel plate includes the steps of smelting, refining, casting, rolling, quenching and tempering. The 550HB grade wear-resistant steel plate obtained through the above composition and process has high hardness (≥550HB), can be welded and bent, and its microstructure is martensite or martensite and retained austenite. This kind of steel has excellent wear resistance and is very suitable for working in a strong abrasive environment, especially on vehicles or facilities that are in contact with high-strength ore and other high-hardness materials, such as buckets, loaders, and mining electric wheel dump trucks. The surface Brinell hardness of the patented steel plate is above 550HB, and the maximum thickness is 60mm. It is produced by the heat treatment process of quenching and low temperature tempering. The carbon content of this patent is relatively high at 0.31-0.4%, and the tendency to crack is large, and steel plates above 60mm cannot be produced. It is suitable for the requirements of large-thickness wear-resistant liners in mines; this patent requires tempering after quenching, the process is complicated and the cost is high.

U.S. Patent Publication No. US2012134872 (A1) invention patent "Manufacturing method of wear-resistant steel plate and parts" (ABRASION RESISTANTSTEEL, METHODOFMANUFACTURINGANABRASIONRESISTANTSTEELANDARTICLESMADETHEREFROM), its composition content is expressed by weight: 0.20-0.30%C, 0.40-1.25%Mn,≤0.05% Production The method is heating to 1650-1700°F. after hot rolling; quenching; at tempering temperature 350-450°F., the surface hardness of the steel plate is greater than 440HBW, the hardness of the core is greater than 90% of the surface hardness, and the transverse impact of the steel plate is at 60° F. Greater than 20ft-lbs, room temperature ≥ 40ft-lbs. This patent has low carbon and alloy content and good low-temperature toughness, but the surface hardness is only 440HB, the maximum thickness is 20mm, and offline tempering is required, the process is complicated and costly.

The US Patent Publication No. US2008/0247903Al is an invention patent "a wear-resistant steel plate and its manufacturing method" (METHOD FORMAKING ANA BRASION-RESISTANTSTEEL PLATE AND PIATE OBTAINED), and its composition wt% is: 0.35%≤C≤0.8%, 0%≤Si≤2%, 0%≤Al≤2%, 0.35%≤Si+AL≤2%, 0%≤Mn≤2.5%, 0%≤Ni≤5%, 0%≤Cr≤5%, 0%≤Mo≤0.50%, 0%≤W≤1.0%, 0.1%≤Mo+W/2≤0.50%, 0%≤B≤0.02%, 0%≤W≤2%, 0%≤Zr≤4%, 0.05%≤Ti+Zr /2≤2%, 0%≤S≤0.15%, N≤0.03%; over AC3, cool to room temperature at a cooling rate greater than 5°C/s, the thickness of the steel plate is 2-150mm, and the surface roughness of the steel plate is 5-12mm/m, Tempering at 250-350°C, the hardness of the obtained steel plate is 280-650HB. The patent has a large hardness span, and in its examples, there are 3 cases with a hardness greater than 550HB, but the carbon content is 0.59-0.69%, which is still in the range of high-carbon steel, with poor weldability and a large tendency to crack. The patent has a large alloy content and a complex system. Off-line tempering heat treatment is required, and the cost is relatively high.

In summary, the current production of 550HB high-strength wear-resistant steel plates has the following deficiencies:

1. The content of alloys such as carbon, manganese and silicon is high, and smelting is difficult, so only castings can be produced;

2. The surface hardness is lower than 550HB, and the thickness is lower than 60mm;

3. The production process is complicated, and tempering heat treatment is required after quenching.

Contents of the invention

The object of the present invention is to provide a high-strength wear-resistant steel plate with a thickness of 8-120mm, a surface hardness greater than 550HB, a low-temperature toughness greater than 30J at -40°C, low carbon and manganese content, and no need for tempering, and its production method .

For this reason, the solution that the present invention takes is:

A high-strength wear-resistant steel plate, its chemical composition wt% is: C: 0.25%-0.30%, Si: 0.3%-0.5%, Mn: 0.40%-1.00%, Cr: 0.6%-1.2%, Mo: 0.15 %～0.4%, Nb: 0.01%～0.03%, Ni≤0.50%, Cu≤0.50%, B: 0.0005%～0.0022%, Ti: 0.025%～0.04%, Als: 0.020%～0.045%, the balance is Fe and unavoidable impurities; control of impurity elements in steel: P≤0.015%, S≤0.005%, [N]≤0.0080%, [O]≤0.0020%, and Ti/N≥3.4.

C: In order to ensure the ultra-high surface hardness of the steel plate and the hardenability of the thick steel plate when it is water-cooled, a considerable amount of carbon content is required. Within a certain range, the hardness of the steel increases with the increase of the carbon content. At the same time, a certain carbon content can be Form carbide precipitation with Nb, Ti, Cr, Mo, etc. to increase wear resistance. If the carbon content is too high, the plastic toughness will be reduced and the welding performance will be reduced. In order to ensure the high hardness, welding performance and low temperature toughness of the steel plate, the C content in the present invention is controlled at 0.25-0.30%.

Si: The main function is solid solution strengthening and deoxidation, and it is a non-carbide forming element. When the Si content is high, it will inhibit the precipitation of carbides, but if it is too much, it will reduce the welding performance and affect the toughness. Therefore, the Si content in the present invention is controlled at 0.3 ~0.5%.

Mn: The main function is solid solution strengthening. When the content is greater than 0.4%, it can improve hardenability and increase the supersaturation of carbon in martensite, which is beneficial to the improvement of strength and hardness, and the cost is low, but when the content is higher than 1.0, it is easy to The formation of central segregation will make the slab prone to cracks; therefore, the content of Mn in the present invention is controlled at 0.4% to 1.0%.

Nb: It is a strong carbon and nitrogen compound forming element. Its main function is to inhibit the grain growth during heating by forming fine carbonitrides in the steel, and it has a certain precipitation strengthening effect when it is air-cooled; Nb is added to the steel. Tensitic grain interface movement, thereby increasing the recrystallization temperature of the steel plate. When an appropriate amount of Nb is added to the steel plate, the undissolved NbC plays the role of pinning the austenite grain boundary during high-temperature austenitization, thereby hindering the excessive coarsening of the austenite grain boundary. Nb dissolved in austenite inhibits austenite recrystallization and refines austenite grains during two-stage rolling. However, if the Nb content is too high, coarse NbC will be formed, which will affect the mechanical properties of the steel plate. Therefore, the addition amount of Nb in the present invention is 0.01-0.03%.

Ti: It can form compounds with nitrogen, carbon and sulfur. The main function is to inhibit grain growth during heating by forming fine carbonitrides in steel. The formation temperature of titanium and nitrogen compounds is higher, and the precipitation temperature of vanadium carbide and niobium carbide It is lower than titanium carbide and titanium nitride. When adding titanium, by controlling the ratio of titanium and nitrogen (Ti/N≥3.4), niobium is mainly combined with carbon, and at the same time, it can prevent free N and B in the steel from forming compounds and improve acid-soluble boron. Yield fully exerts the effect of B to improve hardenability, but when the content is too high, coarse TiN will be formed, which will reduce the low-temperature toughness and fatigue performance of the steel plate. Therefore, the addition of Ti in the present invention is controlled at 0.025% to 0.04% and Ti /N≥3.4.

Mo, Cr: The main function is to reduce the critical cooling rate, improve the hardenability of the steel plate, and form a completely fine martensitic structure. In addition, chromium and molybdenum can form a variety of carbides in the steel to improve the strength and hardness of the steel plate, ensuring The hardness of the thick gauge steel plate is above 550HB, the Mo content is more than 0.15%, and the effect is obvious when the Cr content is more than 0.6%. Weldability decreases, so the present invention controls Cr: 0.6-1.2%, Mo: 0.15-0.4%.

B: Adding a small amount of boron to the steel can greatly improve the quenching hardenability. Since the amount of boron added is very small and has a strong affinity with oxygen and nitrogen in molten steel, it is easy to have a chemical reaction with it, thus losing Improve hardenability. Therefore, before adding boron in smelting, the content of oxygen and nitrogen in molten steel should be reduced as much as possible, but when the B content is too much (≥0.0025%), it is easy to enrich at the grain boundary, which will reduce the binding energy of the grain boundary, and make the steel plate more stable when subjected to impact load. It tends to fracture intergranularly, reducing the low-temperature impact energy absorbed by the steel plate. Therefore, the addition amount of B in the present invention is 0.0005-0.0022%, and [N]≤0.0080%, [O]≤0.0020%.

Cu, Ni: Add 0.3-0.5% Cu to the steel plate with a thickness greater than 50mm. The self-tempering process after quenching can form ε-Cu precipitation, which can effectively improve the strength and hardness of the steel. It is easy to cause surface quality defects such as edge overburning and surface warping due to copper brittleness. In order to improve the surface quality of Cu-containing steel, high-melting-point Ni elements are often added to steel to form high-melting-point Cu and Ni binary alloy phases, reduce low-melting-point Cu-rich phases, and increase the solubility of Cu in steel. In order to completely suppress copper brittle defects in Cu-containing steel, the ratio of Ni:Cu is generally controlled to be greater than 1:2. Ni is also an element that simultaneously improves the hardness and low-temperature toughness of steel plates with a thickness greater than 50 mm. Ni will form FeNi compounds with Fe. , when the steel plate is subjected to low-temperature impact load at a lower temperature, solid solution Ni can improve the low-temperature impact energy absorption of the steel plate, but the cost of Ni is higher, so the addition of 0.5% or less Ni to the medium-thickness steel plate of the present invention can ensure the stability of the steel plate. The mechanical properties, especially the low temperature toughness at -40°C, make it competitive in the market.

A production method of high-strength wear-resistant steel plate, its production process: molten iron pretreatment - converter smelting - refining - vacuum degassing - micro-Ti treatment - B alloying - continuous casting - stacking slow cooling - cleaning with temperature - plate Billet heating - rolling - online quenching (finished steel plate thickness ≤ 50mm) - straightening - stacking - offline quenching (finished steel plate thickness > 50mm). The specific method is:

Smelting and continuous casting process:

Pretreatment of molten iron, using converter smelting, refining treatment through top blowing or top-bottom composite blowing, and microalloying, control of impurity content in steel and effective B control. During refining, control the molten steel [N]≤0.0080%, [O]≤0.0020%, add Ti microalloying, and control the Ti/N≥3.5 in the steel to ensure that the content of effective boron in the steel is 0.0010%～0.0020% , Continuous casting uses electromagnetic stirring to reduce element segregation; after continuous casting, stacking and slow cooling ≥ 48h, effectively remove the hydrogen content and casting internal stress in the slab; then clean the slab with temperature to reduce casting defects, and the temperature of the slab during cleaning Control at 100-200°C to avoid cutting cracks.

Rolling and heat treatment process:

Billet heating temperature 1200～1250℃;

Two-stage controlled rolling is adopted during rolling. In the first stage of rolling, austenite undergoes dynamic recrystallization, static recrystallization and dynamic recovery process, which refines the austenite grains; in the second stage, austenite further A large number of dislocations are refined and enriched, providing a large number of nucleation sites for in-line quenching or phase transformation.

In the first stage, the rough rolling start temperature is 1050-1100°C, and the finish rolling temperature is 980-1050°C.

The second stage of finishing rolling adopts different rolling processes according to the thickness of the finished steel plate: for the slab with the thickness of the finished steel plate > 50mm, the second-stage rolling temperature is <870°C, the final rolling temperature is ≤860°C, air cooling after rolling; offline after cooling Quenching, quenching heating temperature 850-900°C, heat preservation 2-3min/mm; when quenching, swing in the low-pressure section of the continuous quenching machine, swing time 100-200s, quenching final cooling temperature 150-250°C, and then stack and air-cool to room temperature , time ≥ 24h;

For slabs with a finished steel plate thickness ≤ 50mm, the starting rolling temperature is controlled at ≤ 930°C, the final rolling temperature is controlled at < 850°C, online quenching is carried out after rolling, the water inlet temperature is 790-850°C, the cooling rate is ≥10°C/S, and the red The temperature is 200-250°C. Immediately after rolling, roll off the assembly line for stacking or slowly cool in the trough, and use the residual temperature for self-tempering for a time ≥ 24 hours, which can effectively avoid quenching and cracking of the steel plate and reduce the tempering heat treatment process.

The beneficial effects of the present invention are:

1. Low carbon and manganese content; the carbon content is less than 0.30%, the alloy composition is simple, the weldability is good, and the crack tendency is low.

2. The surface hardness is greater than 550HB; it can be used in severe wear conditions such as mining machinery.

3. The maximum thickness of the finished steel plate can reach 120mm; it can meet the use requirements of larger thickness wear-resistant steel plate.

4. The low-temperature toughness at -40°C is greater than 30J. The steel plate has good low-temperature crack arrest ability and can be used in a low-temperature environment of -40°C.

Description of drawings

Figure 1 is a diagram of the hardness distribution of a 100mm thick steel plate section.

Detailed ways

The process flow of the production method of the high-strength wear-resistant steel plate of the present invention is: molten iron pretreatment—converter smelting—refining—vacuum degassing—micro-Ti treatment—B alloying—continuous casting—stacking and slow cooling—temperature cleaning—slab Heating—rolling—online quenching (thickness of finished steel plate ≤50mm)—straightening—stacking—offline quenching (thickness of finished steel plate>50mm).

The present invention will be further described below in conjunction with embodiment.

The chemical composition wt% of the embodiment is shown in Table 1; the rolling process parameters of the embodiment are shown in Table 2; the quenching heat treatment process of the embodiment is shown in Table 3; the performance test results of the embodiment are shown in Table 4;

Table 1 Example chemical composition wt%

example C Si mn Cr Mo Ni Nb Ti B als Cu N Ti/N 1 0.26 0.4 1.0 0.60 0.15 - 0.03 0.04 0.0015 0.020 - 0.0035 11.4 2 0.27 0.3 0.8 0.80 0.20 - 0.02 0.025 0.0020 0.035 - 0.0040 6.3 3 0.28 0.4 0.6 1.00 0.30 0.40 0.018 0.036 0.0022 0.030 0.40 0.0045 8.0 4 0.30 0.5 0.4 1.20 0.40 0.50 0.024 0.033 0.0012 0.035 0.50 0.0060 5.5

During refining, control the molten steel [N]≤0.0080%, [O]≤0.0020%, add Ti microalloying, and control the Ti/N≥3.5 in the steel to ensure that the content of effective boron in the steel is 0.0010%～0.0020% , Continuous casting adopts electromagnetic stirring to reduce element segregation; after continuous casting, stacking is slowly cooled for ≥48h, and then the slab is cleaned with temperature, and the temperature of the slab is controlled at 100-200°C during cleaning.

Table 2 embodiment rolling process parameter list

In Table 2, Examples 1-1 and 1-2 refer to two examples of different rolling process parameters of Example 1 in Table 1, and the rest are analogous. Table 3 and Table 4 are the same.

Table 3 embodiment quenching heat treatment process parameter list

Table 4 embodiment performance inspection result

Claims (2)

1. a high-strength abrasion-proof steel plate, it is characterized in that, its chemical composition wt% is: C:0.25% ~ 0.30%, Si:0.3% ~ 0.5%, Mn:0.40% ~ 1.00%, Cr:0.6% ~ 1.2%, Mo:0.15% ~ 0.4%, Nb:0.01% ~ 0.03%, Ni≤0.50%, Cu≤0.50%, B:0.0005% ~ 0.0022%, Ti:0.025% ~ 0.04%, Als:0.020% ~ 0.045%, surplus is Fe and inevitable impurity; Impurity element in steel controls: P≤0.015%, S≤0.005%, [N]≤0.0080%, [O]≤0.0020%, and Ti/N >=3.4.

2. a production method for high-strength abrasion-proof steel plate as claimed in claim 1, is characterized in that, its concrete grammar is:

Smelt and continuous casting process:

During refining, control molten steel [N]≤0.0080%, [O]≤0.0020%, add Ti microalloying, control Ti/N >=3.5 in steel, to ensure that the content of effective boron in steel is 0.0010% ~ 0.0020% simultaneously, continuous casting adopts induction stirring, reduces element segregation; Stacking slow cooling >=48h after continuous casting, then carry out the cleaning of slab band temperature, during cleaning, board briquette controls at 100 ~ 200 DEG C;

Rolling and thermal treatment process:

Billet heating temperature 1200 ~ 1250 DEG C; Two benches controlled rolling is adopted: first stage roughing start rolling temperature is 1050 ~ 1100 DEG C, finishing temperature 980 ~ 1050 DEG C during rolling; Subordinate phase finish rolling takes different rolling technologys according to finished steel plate thickness difference: for the slab two-stage start rolling temperature < 870 DEG C of finished steel plate thickness G reatT.GreaT.GT 50mm, finishing temperature≤860 DEG C, roll rear air cooling; Out-line quenching is carried out, quenching temperature 850 ~ 900 DEG C, insulation 2 ~ 3min/mm after cooling; During quenching, swing, time of oscillation 100 ~ 200s at continuous quenching machine low-pressure stage, quenching final cooling temperature 150 ~ 250 DEG C, then stacking air cooling is to room temperature, time >=24h;

Slab start rolling temperature for finished steel plate thickness≤50mm controls at≤930 DEG C, finishing temperature control is < 850 DEG C, press quenching is carried out after rolling, enter water temp 790 ~ 850 DEG C, speed of cooling >=10 DEG C/S, red temperature is 200 ~ 250 DEG C, and immediately roll off the production line after rolling stacking or enter groove slow cooling, remaining temperature is utilized to carry out self-tempering, time >=24h.