Preparation method of bainite high-strength steel hot-rolled coil plate for mining machinery

Abstract

The invention discloses a hot rolling method for producing a bainite high-strength steel coil plate for mining machinery, the continuous casting speed of bainite high-strength steel is 1.0-1.2 m / min, and a casting blank with the thickness of 230 mm is obtained. And the soaking process conditions are as follows: the casting blank enters a soaking pit furnace at 1230-1270 DEG C, and the cold charging soaking time is 25-60 minutes. The initial rolling temperature is 1210-1230 DEG C, and the final rolling temperature is 890 + / -15 DEG C. The final thickness of the hot rolled plate is 8.0 mm, and the granular bainite structure is uniform in size and good in distribution. According to the method, on the basis of a double electromagnetic stirring process, the alloy components, the heating schedule and the rolling process of the bainite high-strength steel are creatively optimized and adjusted, the consistency and the stability of the structure and the performance of granular bainite are obtained, then it is guaranteed that the bainite high-strength steel which serves can be stably produced, and the quality and the competitiveness of products are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for preparing a bainite high-strength steel hot-rolled coil for mining machinery. Background Art

[0002] Mining machinery operates under complex and harsh working conditions, and the performance requirements of the materials used are extremely high. As a new type of material, the application of bainitic high-strength steel coil in the field of mining machinery has an important technical background. First of all, the mining operating environment is usually characterized by high wear, high impact and high pressure. Traditional materials are prone to fatigue cracks, excessive wear and other problems under such conditions, resulting in shortened equipment life and increased maintenance costs. Secondly, with the continuous expansion of mining scale and the increasing requirements for operating efficiency, mining machinery requires stronger load-bearing capacity and higher reliability. Bainitic high-strength steel coil has excellent strength and toughness, which can meet these needs. With the continuous deepening of research on bainite structure, its performance can be better controlled, thus providing technical support for the application of mining machinery. It makes the production of bainitic high-strength steel coil more efficient and quality controllable, creating conditions for its wide application in the field of mining machinery.

[0003] After searching, the document with Chinese patent application number CN108531810B discloses "A hot-rolled ultra-high strength steel substrate and its preparation method". The method is suitable for: carbon 0.10-0.30%, silicon: ≤0.40%, manganese: 0.60-1.60%, phosphorus: ≤0.015%, sulfur: ≤0.0015%, niobium: 0.010-0.050%, chromium: 0.010-0.50%, molybdenum: 0.010-0.90% 、Vanadium: 0.010%~0.10%, Titanium: 0.010~0.040%, Aluminum: 0.015~0.040%, Nickel: 0.0025~0.40%, Copper: 0.0025~0.40%, Calcium: 0.0010~0.0050%, Boron: 0.0010~0.0030%, Nitrogen: ≤0.006%, Oxygen: ≤0.004%, Hydrogen: ≤0.00020%, The balance is iron and inevitable impurities. Although the invention can produce large thickness specifications and good plate shape; Higher qualified rate: The qualified rate of the present invention can be increased by more than 25% compared with the thin-gauge substrate produced by the wide and thick plate mill and the furnace coil mill; The unevenness of the hot-rolled steel coil after the whole coil is cut and flattened is ≤3mm / m. The yield rate reaches more than 96%, and the comprehensive qualified rate reaches more than 95%; High production efficiency. However, the disadvantage of this document is that although the performance is good, the presence of molybdenum and nickel elements, which have high market prices, increases the cost by 500-1000 yuan per ton, so the relative cost is higher than that of the present invention.

[0004] After searching, the document with Chinese patent application number CN107779766A, "Ultra-high strength thin hot-rolled steel sheet with excellent formability and its manufacturing method", is suitable for C: 0.15% ~ 0.25%, Si: 0.005% ~ 0.20%, Mn: 0.5% ~

[0005] 2.0%, Ti: 0.005%~0.05%, P: 0.005%~0.02%, S≤0.01%, Cr: 0.005%~0.5%, Al: 0.01%-0.15%, B: 0.0005-0.005%, the rest is Fe and inevitable impurities. The microstructure contains more than 95% by area of ​​martensite, and the KAM (Kernel Average Misorientation) of the martensite is 0.5-0.75. The tensile strength is 1.3-1.5GPa. The uniform elongation is more than 3%. The disadvantage of this document is that the yield strength is high and the elongation is low. In order to achieve a higher elongation, it is necessary to increase the tempering process, increase the manufacturing cost, and the strength will decrease.

[0006] After searching: the document with Chinese patent application number CN114657462A discloses a "Ultra-high strength wear-resistant steel plate and its manufacturing method", which is applicable to: C0.35%~0.40%, Si0.20%~0.40%, Mn0.20%~0.60%, P≤0.012%, S≤0.002%, Al0.020%~0.050%, V0.040%~0.070%, Ti0.010%~0.030%, Cr1.20%~1.40%, Mo0.4%~0.6%, Ni0.40%~0.60%, B0.0012%~0.0030%, and the rest is Fe and unavoidable impurities. 4-20mm ultra-high strength wear-resistant steel plate with good plasticity and toughness. After the steel plate is cut into sections, it is subjected to quenching heat treatment, with a quenching heating temperature of 910°C and a holding time of 30 minutes. After being taken out of the furnace, it is quenched to room temperature with water; the tempering heating temperature is 220°C and the holding time is 35 minutes. Although the overall performance is excellent, the precious elements in the alloy cost are relatively high, and the heat treatment process does not specify the heat treatment process for different thicknesses. If the same heat treatment process is used, the relative manufacturing cost will increase, which is not conducive to long-term development. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing a bainite high-strength steel hot-rolled coil for mining machinery, which improves the comprehensive performance and service performance of the finished strip while meeting the comprehensive performance requirements.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for preparing a hot-rolled bainite high-strength steel coil for mining machinery, comprising:

[0010] The continuous casting process adopts constant casting speed, argon blowing protection and light pressure control throughout the process;

[0011] Select bainite high-strength steel, smelt and cast it into slabs, heat it to 1230-1270℃, and place it in the furnace for 180-270min; the soaking temperature is 1240-1260℃, the soaking time is 25-60min, and then rough rolling is carried out at 1220±10℃;

[0012] The finishing rolling temperature range is 1000-1100℃, the cumulative reduction of finishing rolling is 78-82%; the final rolling temperature of finishing rolling is guaranteed to be 890±15℃;

[0013] The slab after finish rolling is cooled to the coiling temperature for coiling, and the coiling temperature is 500±25℃;

[0014] The continuous casting billet drawing speed is 1.0-1.2 m / min, and a continuous casting slab with a thickness of 230 mm is obtained;

[0015] The composition of the bainitic high-strength steel used is C: 0.16-0.18%, Si: 1.45-1.65%, Mn: 1.35-1.55%, Nb: 0.020-0.030%, Ti: 0.020-0.035%, Cr: 1.40-1.60%, B: 0.0007-0.0017%, and the balance is Fe and other inevitable impurities, among which P≤0.018%, S≤0.008%, O≤0.005%, and the rest is Fe and inevitable impurities.

[0016] Furthermore, after heating to 1230-1270°C, the cold charging and soaking time is 25-60 minutes, and the first descaling treatment is carried out.

[0017] Furthermore, the composition of the bainitic high-strength steel used is C: 0.17%, Si: 1.56%, Mn: 1.42%, Nb: 0.023%, Ti: 0.039%, Cr: 1.44%, and the balance is Fe and other inevitable impurities, including P: 0.011%, S: 0.001%, B: 0.0017%, O: 0.004%, and the rest is Fe and inevitable impurities.

[0018] Furthermore, the intermediate billet thickness is 32-50 mm.

[0019] Furthermore, the finished product has a thickness of 8.0 mm.

[0020] Furthermore, the cumulative reduction in finish rolling was 80%.

[0021] Furthermore, the temperature is lowered to the coiling temperature by laminar cooling.

[0022] Compared with the prior art, the beneficial technical effects of the present invention are:

[0023] Based on the dual electromagnetic stirring process, the present invention creatively adjusts the alloy composition of high-strength steel at the micro level, and uses Nb, Cr, and Ti elements to inhibit the growth of austenite grains and promote nucleation during austenite transformation to refine grains, control the thickness core structure, improve the uniformity of the structure, and ensure that the hardness and tensile properties of the rolled plate meet the standard requirements. According to the distribution of the structure at different positions in the steel, the consistency and stability of the granular bainite structure and performance are evaluated, which can stably produce bainite high-strength steel for service and improve the quality and competitiveness of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below in conjunction with the accompanying drawings.

[0025] Figure 1 This is the metallographic microstructure diagram of the slab at 1 / 2.

[0026] Figure 2 This is the metallographic microstructure diagram of the slab at 1 / 4. DETAILED DESCRIPTION

[0027] The present invention is described in more detail below with reference to examples. These examples are merely descriptions of the best mode for carrying out the present invention and are not intended to limit the scope of the present invention in any way.

[0028] The following example 1 hot rolled ingot has a thickness of 230 mm, after R1 rough rolling and R2 rough rolling, the thickness is 32-50 mm, and after finishing rolling F1-F7, the thickness is 8.0 mm. The microstructure metallographic diagram of the finished product at 8.0 mm1 / 2 is as follows Figure 1 As shown, the microstructure metallographic diagram at 1 / 4 is as follows Figure 2 As shown, the metallographic organization diagram shows that the granular bainite structure at different positions is uniform and fine, with good uniformity and consistency. The actual production performance is shown in Table 4, and the results show that the performance is relatively stable.

[0029] Example 1

[0030] The composition of the bainitic high-strength steel used in the embodiment of the present invention is C: 0.16-0.18%, Si: 1.45-1.65%, Mn: 1.35-1.55%, Nb: 0.020-0.030%, Ti0.020-0.040%, Cr 1.40-1.60%, B: 0.0007-0.0017%, and the balance is Fe and other inevitable impurities, among which P≤0.018%, S≤0.008%, O≤0.005%, B: 0.0007-0.0017%, and the actual detection of the ladle composition is shown in Table 1.

[0031] In the embodiment of the present invention, the heating temperature is 1230-1270° C., the cold charging time in the furnace is 180-270 min, the soaking temperature is 1240-1260° C., and the cold charging soaking time is 25-60 min.

[0032] The starting rolling temperature in the embodiment of the present invention is 1210-1230° C., and the cumulative reduction of the rough rolling is 78-86%.

[0033] In the embodiment of the present invention, the cumulative reduction of the finishing rolling is 75-84%, and the final rolling temperature of the finishing rolling is ensured to be 890±15°C.

[0034] The coiling temperature in the embodiment of the present invention is 500±25°C.

[0035] In the embodiment of the present invention, the thickness of the intermediate blank is 32-50 mm, and the thickness of the finished product is 8.0 mm.

[0036] In the embodiment of the present invention, the laminar cooling method is used to cool the temperature to the coiling temperature.

[0037] The performance results in the embodiments of the present invention fully meet the standard requirements.

[0038] Table 1 Composition of molten steel in the middle package

[0039]

[0040] Table 2 Heating furnace process parameters

[0041]

[0042] Table 3 Key rolling process parameters

[0043]

[0044] Table 4 Mechanical properties of trial products

[0045]

[0046] Based on the dual electromagnetic stirring process, the present invention creatively optimizes and adjusts the alloy composition, heating system and rolling process of bainite high-strength steel, utilizes Nb, Cr, Ti element precipitation strengthening to ensure strength and hardness, adopts large reduction rolling technology to control the thickness core structure, improves the uniformity of the structure, and selects the layer cooling mode to ensure the hardness and surface quality of the coil. The consistency and stability of the granular bainite structure and performance are obtained, thereby ensuring the stable production of bainite high-strength steel in service, improving the quality and competitiveness of the product, and having significant economic and social benefits for the development, promotion and application of high-strength coils in my country.

[0047] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a hot-rolled bainite high-strength steel coil for mining machinery, characterized in that: include: The continuous casting process adopts constant casting speed, argon blowing protection and light pressure control throughout the process; Select bainite high-strength steel, smelt and cast it into slabs, heat it to 1230-1270℃, and place it in the furnace for 180-270min; the soaking temperature is 1240-1260℃, the soaking time is 25-60min, and then rough rolling is carried out at 1220±10℃; The finishing rolling temperature range is 1000-1100℃, the cumulative reduction of finishing rolling is 78-82%; the final rolling temperature of finishing rolling is guaranteed to be 890±15℃; The slab after finish rolling is cooled to the coiling temperature for coiling, and the coiling temperature is 500±25℃; The continuous casting billet drawing speed is 1.0-1.2 m / min, and a continuous casting slab with a thickness of 230 mm is obtained; The composition of the bainitic high-strength steel used is C: 0.16-0.18%, Si: 1.45-1.65%, Mn: 1.35-1.55%, Nb: 0.020-0.030%, Ti: 0.020-0.035%, Cr: 1.40-1.60%, B: 0.0007-0.0017%, and the balance is Fe and other inevitable impurities, among which P≤0.018%, S≤0.008%, O≤0.005%, and the rest is Fe and inevitable impurities.

2. The method for preparing a bainite high-strength steel hot-rolled coil for mining machinery according to claim 1, characterized in that: After heating to 1230-1270℃, the cold charging and soaking time is 25-60min, and the first descaling treatment is carried out.

3. The method for preparing a bainite high-strength steel hot-rolled coil for mining machinery according to claim 1, characterized in that: The composition of the bainite high-strength steel used is C: 0.17%, Si: 1.56%, Mn: 1.42%, Nb: 0.023%, Ti: 0.039%, Cr: 1.44%, and the balance is Fe and other unavoidable impurities, among which P: 0.011%, S: 0.001%, B: 0.0017%, O: 0.004%, and the rest are Fe and inevitable impurities.

4. The method for preparing a bainite high-strength steel hot-rolled coil for mining machinery according to claim 1, characterized in that: The thickness of the intermediate billet is 32-50mm.

5. The method for preparing a hot-rolled bainite high-strength steel coil for mining machinery according to claim 1 or 4, characterized in that: The finished product thickness is 8.0mm.

6. The method for preparing a hot-rolled bainite high-strength steel coil for mining machinery according to claim 1, characterized in that: The cumulative reduction in finish rolling was 80%.

7. The method for preparing a hot-rolled bainite high-strength steel coil for mining machinery according to claim 1, characterized in that: The laminar cooling method is used to cool down to the coiling temperature.

Images