Production method of high-toughness SA387Gr11CL2 steel plate

Abstract

The invention belongs to the technical field of heat treatment processes, and particularly relates to a production method of a high-toughness SA387Gr11CL2 steel plate, which comprises a steel billet heating process, a steel billet rolling process, a water cooling process and a tempering process, and solves the problems that in the production process of the existing SA387Gr11CL2 steel plate, the hardness and the impact strength cannot be coordinated, and the capacity of a quenching furnace cannot be released. The heat treatment capacity is released, the production cost is reduced, the hardness and the impact strength of the steel plate are optimal, and the production quality of the SA387Gr11CL2 steel plate is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of heat treatment processes, and in particular relates to a production method of a high-toughness SA387Gr11CL2 steel plate. Background Art

[0002] With the development of high-temperature pressure container industry, the quality requirements for steel plates in the production process are getting higher and higher. In order to improve the comprehensive mechanical properties of finished container equipment and make the steel plate's surface Brinell hardness and lateral impact under different environments standard, strict process methods are required for production.

[0003] However, in the production process of existing steel plates, there are problems such as: the hardness exceeds the upper limit when ensuring impact performance, the strength performance fails to meet the requirements when ensuring surface hardness indicators, and the production capacity of the quenching furnace cannot be released, which will lead to a decrease in the quality of the produced steel plates.

[0004] Therefore, the present invention provides a method for producing a high-toughness SA387Gr11CL2 steel plate. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that the hardness and impact strength of the existing SA387Gr11CL2 steel plate cannot be coordinated during the production process and the quenching furnace production capacity cannot be released, thereby releasing the heat treatment capacity, reducing the production cost, and making the hardness and impact strength performance of the steel plate reach the best, thereby greatly improving the production quality of the SA387Gr11CL2 steel plate.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A production method of a high-toughness SA387Gr11CL2 steel plate, comprising a heating process, a rolling process, a water cooling process and a tempering process, wherein in the heating process, the temperature of the steel billet heating section is ≤1280°C, the temperature of the soaking section is between 1220°C and 1260°C, and the total heating time in the furnace is ≥0.9 min / mm; In the rolling process, the starting temperature of rough rolling is ≥1000°C, the thickness of the intermediate billet is ≥2mm, the starting temperature of the austenite non-recrystallization zone is ≤920°C, and the final rolling temperature is ≤820°C; In the water cooling process, the steel billet is quickly water-cooled after rolling, and the steel billet is cooled to 620±20°C, and the water-cooled steel billet is sent to hot straightening for straightening, and then sent to a cooling bed for air cooling to room temperature; In the tempering process, the tempering furnace temperature is between 752°C and 758°C, the total tempering time in the furnace is 3.5min / mm+20-30min, and the tempered billet is sent to the cooling bed to cool to room temperature; The chemical composition of the steel billet production contains, by weight wt%, C: 0.08-0.16%, Si: 0.20-0.80%, Mn: 0.40-0.65%, Nb: <0.01%, V: <0.01%, Ti≤0.02%, Al: 0.03-0.06%, Ni<0.1%, Cu: <0.1%, Cr: 1.05-1.30%, Mo: 0.50-0.65%, B: <0.0007%, Ca: 0.0001-0.005%, P: ≤0.01%, S: ≤0.008%, O: <0.002%, N: ≤0.004%, H: ≤0.00015%, and the balance is Fe and unavoidable impurity elements.

[0007] Preferably, the rolling process adopts austenite non-recrystallization zone controlled rolling.

[0008] Preferably, the water cooling process uses an ultra-fast cooling device for water cooling.

[0009] Preferably, in the water cooling process, the roller speed of the ultra-fast cooling device is 1.8±0.1 m / s.

[0010] Preferably, in the tempering process, the total tempering time in the furnace is not less than 120 minutes.

[0011] Preferably, the rolling in the austenite non-recrystallized region is finish rolling.

[0012] Beneficial effects of the present invention: 1. The present invention improves the impact toughness by increasing the tempering temperature and rapidly reducing the surface hardness. At the same time, due to the grain refinement and dislocation caused by the early controlled rolling, the strength reserve is achieved, so that the Brinell hardness of the SA387Gr11CL2 steel plate surface is between 165-182HB, the 0°C impact average is ≥280J, the tensile performance is good, and the plate flatness is ≤3mm / 2m, which effectively omits the quenching process and releases the heat treatment capacity.

[0013] 2. The present invention fully refines the original austenite grains through rough rolling and finish rolling, forms a large number of dislocations and deformed nuclei, provides nucleation fulcrums for subsequent organizational transformation, refines the transformation organization, and thus improves the impact performance and strength of the SA387Gr11CL2 steel plate.

[0014] 3. The present invention ensures that the temperature of the steel plate is about 800°C after final rolling, so that the steel temperature is within the complete austenitization temperature range, and is quickly cooled to obtain a bainite structure similar to that obtained by accelerated cooling (quenching) after normalizing, thereby achieving the effect of offline normalizing accelerated cooling.

[0015] In summary, when producing SA387Gr11CL2 (American standard chromium-molybdenum steel) steel plates, the present invention heats, rolls, water-cools, tempers and air-cools the steel billets. During the heating and rolling processes, the steel billets at different stages are processed at different temperatures, and the cooling temperature is controlled, thereby improving the performance indicators of the surface of the SA387Gr11CL2 steel plates, ensuring the impact toughness of the SA387Gr11CL2 steel plates, and optimizing the hardness and impact strength performance of the SA387Gr11CL2 steel plates, thereby greatly improving the production quality of the SA387Gr11CL2 steel plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the metallographic structure diagram of Example 1 of the present invention after tempering.

[0017] Figure 2 This is the metallographic structure diagram of Example 5 of the present invention after tempering. DETAILED DESCRIPTION

[0018] The method of using the present invention is further described below.

[0019] A production method of high-toughness SA387Gr11CL2 steel plate, comprising a heating process, a rolling process, a water cooling process and a tempering process, wherein the heating process adopts a stepping heating furnace for heating, the slab specification is 220 mm, the temperature of the steel slab heating section is ≤1280°C, the temperature of the soaking section is between 1220°C and 1260°C, and the total heating time in the furnace is ≥0.9 min / mm; By heating, the plasticity of the steel billet is improved, the deformation resistance is reduced, the temperature inside and outside the steel billet is made uniform, the crystal structure of the metal is improved, and the internal structural defects of the steel billet are eliminated or alleviated. Lowering the heating temperature in the soaking section mainly achieves the effect of preventing the grain from growing and coarsening at low temperature. At the same time, a longer time in the furnace is used to further homogenize the alloy element segregation in the core of the casting, thereby improving the homogenization of the impact original structure of the steel billet and providing the original structure reserve for the later controlled rolling and tempering to maintain the impact toughness.

[0020] In the rolling process, the starting temperature of rough rolling is ≥1000°C, the thickness of the intermediate billet is ≥2mm, the starting temperature of the austenite non-recrystallization zone is ≤920°C, and the final rolling temperature is ≤820°C; By combining the rolling in the austenite recrystallization area (rough rolling) and the rolling in the austenite non-recrystallization area (finishing rolling), the original austenite grains are fully refined, a large number of dislocations and deformation nuclei are formed, which provide nucleation fulcrums for subsequent organizational transformation, refine the transformation organization, and achieve the purpose of improving impact performance and strength.

[0021] In the water cooling process, the steel billet is quickly water-cooled after rolling, and the steel billet is cooled to 620±20°C, and the water-cooled steel billet is sent to hot straightening for straightening, and then sent to a cooling bed for air cooling to room temperature; After final rolling, the temperature of the steel plate is guaranteed to be around 800°C, so that the steel temperature is within the complete austenitization temperature range, and then enters the ACC (ultra-fast cooling device) for cooling, so as to achieve the purpose of organizational transformation through online rapid cooling, and obtain a bainite structure similar to that obtained by accelerated cooling (quenching) after normalizing, achieving the effect of offline normalizing accelerated cooling.

[0022] In the tempering process, the tempering furnace temperature is between 752°C and 758°C, the total tempering time in the furnace is 3.5min / mm+20-30min, and the tempered billet is sent to the cooling bed to cool to room temperature; By increasing the tempering temperature, the surface hardness can be quickly reduced. The reduction in hardness is accompanied by an increase in plasticity and toughness, especially impact toughness. At the same time, the grain refinement and dislocation caused by the early controlled rolling achieve a reserve of strength, so that the strength after high-temperature tempering can still meet the standard requirements.

[0023] Through the implementation of the above measures, the Brinell hardness of the steel plate surface produced is between 165-182HB, the 0℃ impact average is ≥280J, the tensile properties are good, and the plate flatness is ≤3mm / 2m. The quenching process is effectively omitted, the heat treatment capacity is released, and the domestic advanced level is reached. This method is suitable for low-cost production methods with the thinnest thickness of 8mm and the maximum width of 4200mm, and has good market prospects.

[0024] The chemical composition of the steel billet production contains, by weight wt%, C: 0.08-0.16%, Si: 0.20-0.80%, Mn: 0.40-0.65%, Nb: <0.01%, V: <0.01%, Ti≤0.02%, Al: 0.03-0.06%, Ni<0.1%, Cu: <0.1%, Cr: 1.05-1.30%, Mo: 0.50-0.65%, B: <0.0007%, Ca: 0.0001-0.005%, P: ≤0.01%, S: ≤0.008%, O: <0.002%, N: ≤0.004%, H: ≤0.00015%, and the balance is Fe and unavoidable impurity elements.

[0025] The rolling process adopts controlled rolling in the austenite non-recrystallization zone.

[0026] The water cooling process adopts an ultra-fast cooling device to perform water cooling, so as to achieve the purpose of achieving the tissue transformation online and quickly.

[0027] In the water cooling process, the roller speed of the ultra-fast cooling device is 1.8±0.1 m / s. This is to enable the steel billet to quickly transform its structure online and improve its impact performance and strength.

[0028] The tempering process has a total furnace tempering time of not less than 120 minutes, ensuring that the surface hardness is reduced while the plastic toughness can be greatly improved.

[0029] The rolling in the austenite non-recrystallization zone is called finishing rolling.

[0030] By controlling the controlled rolling and controlled cooling processes at the front, on the basis of good performance of the steel plate in the rolled state, the normalizing and accelerated cooling (quenching) processes are omitted and tempering is carried out directly, thus relieving the production pressure of the heat treatment quenching furnace and releasing production capacity while ensuring that the steel plate meets the technical standards.

[0031] The present invention is further described below with reference to the examples. Example 1

[0032] The chemical composition of the steel plate and its mass percentage are shown in Table 1 below. The steel plate production process includes heating, rough rolling, finishing rolling, water cooling and tempering heat treatment processes. The steel plate is obtained by rolling the slab, and the slab is produced by various smelting processes. In the heating process, a step-beam heating furnace is used for heating. The slab specification is 220mm, the temperature of the billet heating section is 1280℃, the temperature of the soaking section is 1232℃, and the total furnace time is 208 minutes. The rough rolling process adopts a high-temperature and large-reduction process to minimize the number of reduction passes, and the single-pass reduction rate is allocated in a pass-increasing mode. The finishing rolling process adopts a large reduction system and is completed in 4 passes. In the water cooling process, an ultra-fast cooling mode is adopted to accelerate the cooling of the steel plate directly online. The starting rolling temperature of the rough rolling process, the final rolling temperature of the rough rolling process, the starting rolling temperature of the finishing rolling process, the final rolling temperature of the finishing rolling process, and the final cooling temperature of the water cooling process are shown in Table 2 below. In the tempering heat treatment process, the tempering temperature is 755℃ and the tempering time is 120min. Figure 1 The figure shows the metallographic structure after tempering, which is tempered bainite + ferrite. After the rough rolling process is completed, the intermediate billet has a thickness of 70 mm, and the finished steel plate has a thickness of 28 mm after rolling. Example 2

[0033] The chemical composition and mass percentage of the steel plate are shown in Table 1 below. The steel plate production process includes heating, rough rolling, finishing rolling, water cooling and tempering heat treatment processes. The steel plate is rolled from the slab, which is produced by various smelting processes. In the heating process, a step-beam heating furnace is used for heating. The slab specification is 220 mm, the heating section of the steel billet is 1278 ° C, the soaking section temperature is 1230 ° C, and the total furnace time is 221 minutes. The rough rolling process adopts a high-temperature large reduction process to minimize the number of reduction passes, and the single-pass reduction rate is allocated in a pass-increasing mode. The finishing rolling process adopts a large reduction system and is completed in 4 passes. In the water cooling process, an ultra-fast cooling mode is adopted to accelerate the cooling of the steel plate directly online. The starting rolling temperature of the rough rolling process, the final rolling temperature of the rough rolling process, the starting rolling temperature of the finishing rolling process, the final rolling temperature of the finishing rolling process, and the final cooling temperature of the water cooling process are shown in Table 2 below. In the tempering heat treatment process, the tempering temperature is 757 ° C and the tempering time is 128 min. After the rough rolling process is completed, the intermediate billet specification is 70mm thick, and after rolling is completed, the finished steel plate specification is 28mm thick. Example 3

[0034] The chemical composition and mass percentage of the steel plate are shown in Table 1 below. The steel plate production process includes heating, rough rolling, finishing rolling, water cooling and tempering heat treatment processes. The steel plate is rolled from the slab, which is produced by various smelting processes. In the heating process, a step-beam heating furnace is used for heating. The slab specification is 220 mm, the heating section of the steel billet is 1276 ° C, the soaking section temperature is 1228 ° C, and the total furnace time is 226 minutes. The rough rolling process adopts a high-temperature large reduction process to minimize the number of reduction passes, and the single-pass reduction rate is allocated in a pass-increasing mode. The finishing rolling process adopts a large reduction system and is completed in 4 passes. In the water cooling process, an ultra-fast cooling mode is adopted to accelerate the cooling of the steel plate directly online. The starting rolling temperature of the rough rolling process, the final rolling temperature of the rough rolling process, the starting rolling temperature of the finishing rolling process, the final rolling temperature of the finishing rolling process, and the final cooling temperature of the water cooling process are shown in Table 2 below. In the tempering heat treatment process, the tempering temperature is 753 ° C and the tempering time is 132 min. After the rough rolling process is completed, the intermediate billet specification is 70mm thick, and after rolling is completed, the finished steel plate specification is 28mm thick. Example 4

[0035] The chemical composition and mass percentage of the steel plate are shown in Table 1 below. The steel plate production process includes heating, rough rolling, finishing rolling, water cooling and tempering heat treatment processes. The steel plate is rolled from the slab, which is produced by various smelting processes. In the heating process, a step-beam heating furnace is used for heating. The slab specification is 220 mm, the heating section of the steel billet is 1275 ° C, the soaking section temperature is 1226 ° C, and the total furnace time is 215 minutes. The rough rolling process adopts a high-temperature large reduction process to minimize the number of reduction passes, and the single-pass reduction rate is allocated in a pass-increasing mode. The finishing rolling process adopts a large reduction system and is completed in 4 passes. In the water cooling process, an ultra-fast cooling mode is adopted to accelerate the cooling of the steel plate directly online. The starting rolling temperature of the rough rolling process, the final rolling temperature of the rough rolling process, the starting rolling temperature of the finishing rolling process, the final rolling temperature of the finishing rolling process, and the final cooling temperature of the water cooling process are shown in Table 2 below. In the tempering heat treatment process, the tempering temperature is 752 ° C and the tempering time is 130 min. After the rough rolling process is completed, the intermediate billet specification is 70mm thick, and after rolling is completed, the finished steel plate specification is 28mm thick. Example 5

[0036] The chemical composition of the steel plate and its mass percentage are shown in Table 1 below. The steel plate production process includes heating, rough rolling, finishing rolling, water cooling and tempering heat treatment processes. The steel plate is obtained by rolling the slab, and the slab is produced by various smelting processes. In the heating process, a step-beam heating furnace is used for heating. The slab specification is 220mm, the temperature of the steel billet heating section is 1272℃, the temperature of the soaking section is 1223℃, and the total furnace time is 206 minutes. The rough rolling process adopts a high-temperature and large-reduction process to minimize the number of reduction passes, and the single-pass reduction rate is allocated in a pass-increasing mode. The finishing rolling process adopts a large reduction system and is completed in 4 passes. In the water cooling process, an ultra-fast cooling mode is adopted to accelerate the cooling of the steel plate directly online. The starting rolling temperature of the rough rolling process, the final rolling temperature of the rough rolling process, the starting rolling temperature of the finishing rolling process, the final rolling temperature of the finishing rolling process, and the final cooling temperature of the water cooling process are shown in Table 2 below. In the tempering heat treatment process, the tempering temperature is 758℃ and the tempering time is 122min. Figure 2 As shown, it is the metallographic structure diagram after tempering, which is tempered bainite + ferrite. After the rough rolling process is completed, the intermediate billet specification is 70mm thick, and the finished steel plate specification after rolling is 28mm thick. Example 6

[0037] The chemical composition and mass percentage of the steel plate are shown in Table 1 below. The steel plate production process includes heating, rough rolling, finishing rolling, water cooling and tempering heat treatment. The steel plate is rolled from the slab, which is produced by various smelting processes. In the heating process, a step-beam heating furnace is used for heating. The slab specification is 220 mm, the heating section of the steel billet is 1270 ° C, the soaking section temperature is 1220 ° C, and the total furnace time is 209 minutes. The rough rolling process adopts a high-temperature large reduction process to minimize the number of reduction passes, and the single-pass reduction rate is allocated in a pass-increasing mode. The finishing rolling process adopts a large reduction system and is completed in 4 passes. In the water cooling process, an ultra-fast cooling mode is adopted to accelerate the cooling of the steel plate directly online. The starting rolling temperature of the rough rolling process, the final rolling temperature of the rough rolling process, the starting rolling temperature of the finishing rolling process, the final rolling temperature of the finishing rolling process, and the final cooling temperature of the water cooling process are shown in Table 2 below. In the tempering heat treatment process, the tempering temperature is 756 ° C and the tempering time is 128 min. After the rough rolling process is completed, the intermediate billet specification is 70mm thick, and after rolling is completed, the finished steel plate specification is 28mm thick.

[0038] Table 1

[0039] Table 2

[0040] The microstructures obtained by directly accelerating the cooling of the steel plates of Examples 1-6 are all bainite + ferrite structures, and the microstructures obtained after tempering are all tempered bainite + ferrite. The core of the steel plates of Examples 1-6 after tempering was tested for impact toughness and mechanical properties in the longitudinal direction. The test results are shown in Table 3 below. When testing the mechanical properties of the steel plates, the samples were processed into φ10mm standard tensile specimens and tensile tests were performed. When testing the mechanical properties in the longitudinal direction, the samples were stretched along the longitudinal direction of the steel plates. The impact toughness test item of the steel plates is 0℃ impact energy Akv, and the direction is transverse.

[0041] Table 3

[0042] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. However, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for producing a high-toughness SA387Gr11CL2 steel plate, comprising a heating process, a rolling process, a water cooling process and a tempering process, characterized in that: In the heating process, the temperature of the billet heating section is ≤1280°C, the temperature of the soaking section is between 1220°C and 1260°C, and the total heating time in the furnace is ≥0.9min / mm; In the rolling process, the starting temperature of rough rolling is ≥1000°C, the thickness of the intermediate billet is ≥2mm, the starting temperature of the austenite non-recrystallization zone is ≤920°C, and the final rolling temperature is ≤820°C; In the water cooling process, the steel billet is quickly water-cooled after rolling, and the steel billet is cooled to 620±20°C, and the water-cooled steel billet is sent to hot straightening for straightening, and then sent to a cooling bed for air cooling to room temperature; In the tempering process, the tempering furnace temperature is between 752°C and 758°C, the total tempering time in the furnace is 3.5min / mm+20-30min, and the tempered billet is sent to the cooling bed to cool to room temperature; The chemical composition of the steel billet production contains, by weight wt%, C: 0.08-0.16%, Si: 0.20-0.80%, Mn: 0.40-0.65%, Nb: <0.01%, V: <0.01%, Ti≤0.02%, Al: 0.03-0.06%, Ni<0.1%, Cu: <0.1%, Cr: 1.05-1.30%, Mo: 0.50-0.65%, B: <0.0007%, Ca: 0.0001-0.005%, P: ≤0.01%, S: ≤0.008%, O: <0.002%, N: ≤0.004%, H: ≤0.00015%, and the balance is Fe and unavoidable impurity elements.

2. The method for producing a high-toughness SA387Gr11CL2 steel plate according to claim 1, characterized in that: The rolling process adopts controlled rolling in the austenite non-recrystallization zone.

3. The method for producing a high-toughness SA387Gr11CL2 steel plate according to claim 1, characterized in that: The water cooling process uses an ultra-fast cooling device for water cooling.

4. The method for producing a high-toughness SA387Gr11CL2 steel plate according to claim 1, characterized in that: In the water cooling process, the roller speed of the ultra-fast cooling device is 1.8±0.1 m / s.

5. The method for producing a high-toughness SA387Gr11CL2 steel plate according to claim 1, characterized in that: The tempering process has a total tempering time in the furnace of not less than 120 minutes.

6. The method for producing a high-toughness SA387Gr11CL2 steel plate according to claim 1, characterized in that: The rolling in the austenite non-recrystallization zone is called finishing rolling.

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