High-manganese steel super-thick steel plate for mining machinery and production method of high-manganese steel super-thick steel plate

Abstract

The invention relates to a high manganese steel super-thick steel plate for mining machinery. The steel comprises the following element components in percentage by mass: 0.90%-1.20% of C, 0.15%-0.6% of Si, 14.5%-17.5% of Mn, 0.3%-0.6% of Cr, 0.025%-0.050% of Nb, greater than or equal to 0.015% of Als and the balance of Fe and impurities. The invention further relates to a production method of the steel plate, an LF + VD process is adopted to ensure the cleanliness of steel, a die casting material forming mode is used, a proper steel ingot heating system is adopted, the compression ratio in the rolling process is increased, it is ensured that the internal looseness and shrinkage cavity defects of a blank can be rolled, and the internal quality of the steel plate meets the flaw detection requirement; controlled rolling, DQ cooling and solution treatment are adopted, and the initial grain size of the steel plate is controlled before heat treatment, so that grains of the steel plate subjected to heat treatment are uniform and fine, and the steel plate can meet the flaw detection requirement of the level II of the acceptance level of NB / T47013.3-2023.

Description

Technical Field

[0001] The present invention relates to a production method of an extra-thick steel plate, in particular to an extra-thick high-manganese wear-resistant steel plate for mining machinery and equipment and a production method thereof. Background Art

[0002] High manganese steel plates for mining machinery are widely used in high-wear working environments such as crushing and grinding due to their excellent wear resistance, toughness and impact resistance. At present, domestic steel companies such as Liangang, Taiyuan Iron and Steel, Baosteel, etc. can produce Mn13 high manganese wear-resistant steel plates with specifications of 4-25mm, and they are widely used in shot blasting machines and crusher lining components on the market. However, for some mining machinery and equipment in extreme working environments, such as mining and ore crushing and transportation at high altitudes, low temperatures or extremely cold areas; large excavator shovel teeth, bulldozer buckets, etc., high manganese steel extra-thick plates with a thickness of ≥60mm are required. However, there is currently no production and supply on the market. Traditional cast steel materials are not easy to process and form, and there are many internal defects. The production cost is high and the efficiency is low, which cannot meet the use requirements. Therefore, developing a high-manganese steel extra-thick plate for mining machinery with uniform composition, dense structure, excellent mechanical properties and low production cost and its efficient production method to replace traditional medium and thick plates in extreme working conditions that are not suitable, significantly improving the service life of equipment and reducing maintenance costs, is of great significance for the upgrade of mining machinery and equipment. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an extra-thick plate of high-manganese wear-resistant steel for mining machinery and equipment and a production method thereof. Through precise control of the composition and reasonable production process, the steel plate has good internal quality and excellent mechanical properties, and still has good wear resistance under extreme working conditions of high load and high impact.

[0004] The technical solution of the present invention is: A high-manganese steel extra-thick steel plate for mining machinery, comprising the following element compositions and mass percentages: C: 0.90%-1.20%, Si 0.15%-0.6%, Mn: 14.5%-17.5%, Cr: 0.3%-0.6%, Nb: 0.025%-0.050%, Als ≥ 0.015%, and the remainder being Fe and unavoidable residual elements and impurities in the production process.

[0005] Preferably, the thickness specification is 60-120 mm.

[0006] Furthermore, a production method of high manganese steel extra thick plate for mining machinery includes the following steps: electric furnace smelting, LF refining outside the furnace, VD vacuum degassing, die casting, controlled rolling and controlled cooling, and solution treatment; Electric furnace smelting process: The carbon content of the steel tapped from the electric furnace is ≥0.35%, and the manganese content is ≥4.0%, which reduces the burden of refining and alloying and ensures the deoxidation and inclusion removal effects; LF refining process: Control the sulfur content ≤ 0.0015% to reduce the formation of manganese sulfide inclusions; produce high basicity, reducing and high fluidity refining slag through the LF refining process; VD vacuum degassing process: the high vacuum holding time of the process is ≥25min, and the H content in the molten steel is ≤1.0ppm after the vacuum is completed; the "high vacuum holding time of the VD vacuum degassing process is ≥25min" means that the time interval from the start time to the end time when the vacuum degree is ≤40Pa detected by the Maxwell vacuum gauge during the vacuum process is ≥25min; In-mold casting process: The superheat of the molten steel is stably controlled at 40-50°C, the casting speed is controlled at 6.5-7 t / min, and the mold slag is added at a rate of 2.5-3.0 kg / t through hanging. The entire casting process is vacuum casting. The difference between the molten steel temperature and the liquidus line measured between the opening and closing of the water inlet of the ladle seat on the casting trolley is 40-50°C. The interval between the opening and closing of the water inlet of the ladle seat on the casting trolley and the inverse ratio of the weight of the molten steel is the casting speed, which is controlled at 6.5-7 t / min. The mold slag is hung with a self-made hook at a height of 150-200 mm on both sides of the ingot mold pouring port. The steel ingot should be demoulded and placed in a heating furnace at high temperature within 2-3 hours after the ladle nozzle is closed; the steel ingot should be demoulded and placed in a single-type soaking furnace at high temperature within 2-3 hours after the heating agent is added to the riser to avoid the precipitation of large amounts of carbides at the grain boundaries during the slow cooling process of the steel ingot, which will lead to poor plasticity and internal and surface defects during the subsequent rolling deformation process.

[0007] During the ingot heating process, the ingot is kept at a temperature of 1100-1160°C for 10-15 hours. The ingot is heated to 1100-1160°C along with the furnace, and kept in this temperature range for 10-15 hours. Controlled rolling and controlled cooling process: starting rolling temperature 1060-1080℃, finishing rolling temperature ≥850℃; after rolling, DQ+ACC cooling method is used to control cooling, and the cooling rate is controlled within the range of 10-30℃ / s. The surface temperature of the steel plate at the time of DQ is ≤600℃; In the controlled rolling process, the steel ingot is rolled in the range of 1060-1080℃ by a rough rolling mill with a reduction of 10-15mm per pass to a thickness of 300-350mm, and then rolled in a finishing mill with a reduction of 40mm per pass to a finished product thickness.

[0008] Solution treatment process: The solution temperature is 1060±10℃, and the holding time is 3.0±0.2min / mm. The holding time refers to the ratio of the total time from charging the steel plate from room temperature to the holding temperature until the end of the holding period to the thickness of the steel plate.

[0009] Preferably, in the electric furnace smelting process, 5-6 tons of manganese alloy are added to the ladle in advance and preheated to 600-800°C.

[0010] The "C content of electric furnace steel ≥0.35%, Mn content ≥4.0%" is achieved by adding 5-6 tons of manganese alloy into a ladle and preheating it to 600-800°C during the electric furnace smelting process. This facilitates electric furnace operation, reduces alloy loss, shortens the LF refining cycle to 90-120 minutes, and is beneficial to inclusion control and removal of harmful elements during the refining process.

[0011] Preferably, in the LF refining process, the amount of lime used in the LF refining process is 0.9-1.5 kg / t, and the amount of aluminum wire used is 4.8-5.5 m / t for deoxidation and slagging.

[0012] Preferably, in the VD vacuum degassing process, the vacuum degree of the vacuum process is ≤40Pa.

[0013] Preferably, the die casting process: a flat ingot mold is used during the die casting process, the ingot mold has a thickness of 450-600 mm, a width of 1200-1400 mm, a height of 2100-2400 mm, and a casting speed controlled at 6.5-7 t / min; a single-type soaking furnace is used for heating the steel ingot, and the total heating time is 16-22 h.

[0014] Preferably, the controlled rolling and controlled cooling process: the rolling process uses a four-roll roughing mill + a four-roll finishing mill.

[0015] Preferably, the solution treatment process: the solution treatment is heated by a car bottom furnace and cooled by a water cooling pool, and the circulating water temperature is 20-28°C.

[0016] The beneficial effects of adopting the above technical solution are: The steel plate produced by the production method of the present invention has good internal quality and excellent mechanical properties, and still has good wear resistance under extreme working conditions of high load and high impact, and can meet the nondestructive testing requirements of NB / T47013.3-2023 acceptance grade Level II and the performance requirements of yield strength ≥400MPa, tensile strength ≥1000MPa, elongation ≥50%, -20℃ impact energy ≥150J, and surface hardness ≤240HBW. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a 200x image of the metallographic structure of Example 1 of the present invention.

[0018] Figure 2 This is a 200x image of the metallographic structure of Example 2 of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Example 1

[0020] The chemical composition and weight percentages of the steel plate are shown in Table 1. The remainder consists of Fe and unavoidable impurities. The steel plate thickness is 60 mm. The production process includes the following steps: 5 tons of manganese alloy were preheated to 600°C in a ladle. The carbon content of the ladle sample tapped from the electric furnace was 0.35% and the manganese content was 4.5%. The total ash content of the LF furnace refining process was 0.9 kg / t, and the aluminum wire was 4.8 m / t. The sulfur content before the ladle was lifted was 0.0012%. The high vacuum was maintained for 26 minutes during the VD vacuum degassing process. The vacuum was measured at 40 Pa using a McLaurel vacuum gauge. After the degassing process, the hydrogen content in the molten steel was 1.00 ppm. The casting process uses a flat ingot mold with a thickness of 450-600mm, a width of 1200-1400mm, and a height of 2100-2400mm. The molten steel superheat is maintained at 46°C during casting, with a casting rate of 6.8t / min. Mold slag is added in a single pass at a rate of 2.6kg / t, with a hanging height of 150mm. Vacuum casting is performed throughout. After the ladle nozzle is closed for 160 minutes, the ingot is demoulded and placed in a high-temperature heating furnace. The ingot is held at 1150°C for 10 hours, for a total furnace time of 16 hours. Rolling is performed using a four-roll roughing mill and a four-roll finishing mill. The roughing mill has an opening temperature of 1080°C, with a 10mm per pass ratio, resulting in an intermediate billet thickness of 300mm. The ingot is then rolled to the finishing mill at a reduction of 40mm per pass to the finished product thickness. The final rolling temperature is 910°C. After rolling, the DQ+ACC cooling method is used to control cooling, and the cooling rate is controlled within the range of 30℃ / s. The temperature when DQ is released is 520℃; the solution temperature is 1070℃, the holding time is 2.8min / mm, and the circulating water temperature is 20℃. Figure 1 . Example 2

[0021] The chemical composition and weight percentages of the steel plate are shown in Table 1. The remainder consists of Fe and unavoidable impurities. The steel plate thickness is 70 mm. The production process includes the following steps: 5.1 tons of manganese alloy was preheated to 630°C in a ladle. The carbon content of the ladle sample tapped from the electric furnace was 0.41% and the manganese content was 4.3%. The LF furnace refining process contained 0.95 kg / t of total ash, 5 m / t of aluminum wire, and a sulfur content of 0.0013% before the ladle was lifted. The VD vacuum degassing process maintained a high vacuum for 26 minutes, with a vacuum of 40 Pa using a McLaurel vacuum gauge. After the degassing, the hydrogen content in the molten steel was measured to be 0.92 ppm. The casting process uses a flat ingot mold with a thickness of 450-600mm, a width of 1200-1400mm, and a height of 2100-2400mm. During casting, the molten steel superheat is 40°C, the casting speed is controlled at 7.0t / min, and mold slag is added in one go via a hanging system at a rate of 2.5kg / t, with a hanging height of 150mm. Vacuum casting is performed throughout. After the ladle nozzle is closed for 160 minutes, the ingot is demoulded and placed in a high-temperature heating furnace. The ingot is held at 1150°C for 12 hours, for a total furnace time of 17 hours. Rolling is performed using a four-roll roughing mill and a four-roll finishing mill. The roughing mill starts at 1060°C, with a 10mm per pass ratio, resulting in an intermediate billet thickness of 310mm. The ingot is then rolled to the finishing mill at a reduction of 40mm per pass to the finished product thickness, with a final rolling temperature of 850°C. After rolling, the DQ+ACC cooling method is used to control cooling, and the cooling rate is controlled within the range of 25℃ / s. The temperature when DQ is released is 522℃; the solution temperature is 1070℃, the holding time is 2.8min / mm, and the circulating water temperature is 22℃. See the 200x metallographic structure diagram Figure 2 . Example 3

[0022] The chemical composition and weight percentages of the steel plate are shown in Table 1. The remainder consists of Fe and unavoidable impurities. The steel plate thickness is 80 mm. The production process includes the following steps: 5.2 tons of manganese alloy were preheated to 780°C in a ladle. The carbon content of the ladle sample tapped from the electric furnace was 0.44% and the manganese content was 4.0%. The LF furnace refining process contained 1.3 kg / t of total ash, 5.2 m / t of aluminum wire, and a sulfur content of 0.0009% before the ladle was lifted. The VD vacuum degassing process maintained a high vacuum for 26 minutes, with a vacuum of 40 Pa using a McLaurel vacuum gauge. After the degassing, the hydrogen content in the molten steel was measured to be 0.93 ppm. The casting process uses a flat ingot mold with a thickness of 450-600mm, a width of 1200-1400mm, and a height of 2100-2400mm. During casting, the molten steel superheat is 50°C, the casting rate is controlled at 6.5t / min, and mold slag is added in one go via a hanging system at a rate of 2.7kg / t, with a hanging height of 180mm. Vacuum casting is performed throughout. After the ladle nozzle is closed for 120 minutes, the ingot is demoulded and placed in a high-temperature heating furnace. The ingot is held at 1100°C for 13 hours, for a total furnace time of 18 hours. Rolling is performed using a four-high roughing mill and a four-high finishing mill. The roughing mill has an opening temperature of 1070°C, with each roughing pass of 12mm. The intermediate billet is 310mm thick. The finishing mill then rolls the ingot to the finished thickness at a reduction of 40mm per pass. The final rolling temperature is 890°C. After rolling, the DQ+ACC cooling method is used to control cooling, the cooling rate is controlled within the range of 25℃ / s, the temperature when out of DQ is 540℃; the solid solution temperature is 1065℃, the holding time is 2.9min / mm, and the circulating water temperature is 26℃. Example 4

[0023] The chemical composition and weight percentages of the steel plate are shown in Table 1. The remainder consists of Fe and unavoidable impurities. The steel plate thickness is 90 mm. The production process includes the following steps: 5.8 tons of manganese alloy were preheated to 750°C in a ladle. The carbon content of the ladle sample tapped from the electric furnace was 0.41% and the manganese content was 4.6%. The LF furnace refining process contained 1.5 kg / t of total ash, 5.5 m / t of aluminum wire, and a sulfur content of 0.0015% before the ladle was lifted. The high vacuum during the VD vacuum degassing process was maintained for 27 minutes, and the vacuum level was 30 Pa using a McLaurel vacuum gauge. After the degassing process, the hydrogen content in the molten steel was measured to be 0.98 ppm. The casting process uses a flat ingot mold with a thickness of 450-600mm, a width of 1200-1400mm, and a height of 2100-2400mm. The molten steel superheat is maintained at 42°C during casting, and the casting rate is controlled at 6.9t / min. 3.0kg / t of mold slag is added in one go via a hanging system at a height of 200mm. Vacuum casting is performed throughout. After the ladle nozzle is closed for 180 minutes, the mold is removed and placed in a high-temperature heating furnace. The ingot is held at 1150°C for 15 hours, with a total furnace time of 22 hours. Rolling is performed using a four-high roughing mill and a four-high finishing mill. The roughing mill has an opening temperature of 1060°C, with each roughing pass increasing to 10mm. The intermediate billet thickness is 350mm, and the final rolling temperature is 870°C. The steel is turned to the finishing mill and rolled to the finished product thickness with a reduction of 40mm per pass. After rolling, the DQ+ACC cooling method is used to control cooling. The cooling rate is controlled within the range of 25℃ / s. The temperature at DQ is 580℃; the solution temperature is 1050℃, the holding time is 3.2min / mm, and the circulating water temperature is 28℃. Example 5

[0024] The chemical composition and weight percentages of the steel plate are shown in Table 1. The remainder consists of Fe and unavoidable impurities. The steel plate thickness is 100 mm. The production process includes the following steps: 5.5 tons of manganese alloy were preheated to 700°C in a ladle. The carbon content of the ladle sample tapped from the electric furnace was 0.38% and the manganese content was 4.2%. The LF furnace refining process contained 1.3 kg / t of total ash, 5.2 m / t of aluminum wire, and a sulfur content of 0.0013% before the ladle was lifted. The VD vacuum degassing process maintained a high vacuum for 26 minutes, with a vacuum level of 30 Pa using a McLaurel vacuum gauge. After the degassing, the hydrogen content in the molten steel was measured to be 0.93 ppm. The casting process uses a flat ingot mold with a thickness of 450-600mm, a width of 1200-1400mm, and a height of 2100-2400mm. The molten steel superheat is maintained at 44°C during casting, with a casting rate of 6.6t / min. Mold slag is added in a single pass at a rate of 2.9kg / t from a hanging hopper at a height of 200mm. Vacuum casting is performed throughout. After the ladle nozzle is closed for 150 minutes, the ingot is demoulded and placed in a heated heating furnace. The ingot is held at 1150°C for 15 hours, with a total furnace time of 22 hours. Rolling is performed using a four-roll roughing mill and a four-roll finishing mill. The roughing mill has an opening temperature of 1080°C, with a 15mm per pass ratio. The intermediate billet is 350mm thick. The finishing mill then rolls the ingot to the finished thickness at a reduction of 40mm per pass. The final rolling temperature is 860°C. After rolling, the DQ+ACC cooling method is used to control cooling, the cooling rate is controlled within the range of 25℃ / s, the temperature when out of DQ is 598℃; the solid solution temperature is 1050℃, the holding time is 3.1min / mm, and the circulating water temperature is 27℃. Example 6

[0025] The chemical composition and weight percentages of the steel plate are shown in Table 1. The remainder consists of Fe and unavoidable impurities. The steel plate thickness is 120 mm. The production process includes the following steps: 6 tons of manganese alloy were preheated to 800°C in a ladle. The carbon content of the ladle sample tapped from the electric furnace was 0.43% and the manganese content was 4.6%. The total ash content of the LF furnace refining process was 1.3 kg / t, and the aluminum wire was 4.9 m / t. The sulfur content before the ladle was lifted was 0.0008%. The high vacuum was maintained for 25 minutes during the VD vacuum degassing process. The vacuum level was 30 Pa using a McLaurel vacuum gauge. After the degassing process, the hydrogen content in the molten steel was measured to be 0.91 ppm. The casting process uses a flat ingot mold with a thickness of 450-600mm, a width of 1200-1400mm, and a height of 2100-2400mm. During casting, the molten steel superheat is maintained at 40°C, the casting rate is controlled at 6.9t / min, and mold slag is added in one go via a hanging system at a rate of 3.0kg / t, with a hanging height of 200mm. Vacuum casting is performed throughout. After the ladle nozzle is closed for 180 minutes, the ingot is demoulded and placed in a high-temperature heating furnace. The ingot is held at 1150°C for 15 hours, for a total furnace time of 22 hours. Rolling is performed using a four-high roughing mill and a four-high finishing mill. The roughing mill has an opening temperature of 1079°C, with a 15mm per pass. The intermediate billet is 350mm thick, and then the finishing mill rolls the ingot at a reduction of 40mm per pass to the finished product thickness. The final rolling temperature is 890°C. After rolling, the DQ+ACC cooling method is used to control cooling, the cooling rate is controlled within the range of 10℃ / s, the temperature when exiting DQ is 600℃; the solid solution temperature is 1060℃, the holding time is 3.0min / mm, and the circulating water temperature is 25℃.

[0026] Table 1

[0027] Ultrasonic testing was performed on the steel plates produced in Examples 1-6. The testing results are shown in Table 2.

[0028] Table 2

[0029] The steel plates produced in Examples 1-6 were subjected to test results of yield strength, tensile strength, elongation, AKV impact energy at -20°C, and hardness 2 mm below the surface, as shown in Table 3.

[0030] Table 3

[0031] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A high manganese steel extra thick steel plate for mining machinery, characterized in that: The composition and mass percentage of each element are: C: 0.90%~1.20%, Si 0.15%-0.6%, Mn: 14.5%~17.5%, Cr: 0.3%~0.6%, Nb: 0.025%~0.050%, Als≥0.015%, and the balance is Fe and inevitable residual elements and impurities in the production process.

2. The high manganese steel extra thick steel plate for mining machinery according to claim 1, characterized in that: The thickness specification is 60-120mm.

3. A method for producing a high manganese steel extra thick plate for mining machinery, comprising producing the high manganese steel extra thick plate for mining machinery according to any one of claims 1 to 2, characterized in that: It includes the following processes: electric furnace smelting, LF refining outside the furnace, VD vacuum degassing, die casting, ingot heating, controlled rolling and controlled cooling, and solution treatment; Electric furnace smelting process: The carbon content of the steel tapped from the electric furnace is ≥0.35%, and the manganese content is ≥4.0%; LF refining process outside the furnace: control the S content ≤ 0.0015%; VD vacuum degassing process: the high vacuum holding time is ≥25min, and the H content in the molten steel is ≤1.0ppm after the vacuum is completed; In-mold casting process: The superheat of molten steel is stably controlled at 40-50℃, the casting speed is controlled at 6.5-7t / min, the protective slag is added at 2.5-3.0kg / t at one time through hanging, and the whole process is vacuum casting; the ladle nozzle is closed and the mold is removed within 2-3 hours and the high-temperature heating furnace is placed; In the ingot heating process, the ingot holding temperature is 1100-1160℃ and the holding time is 10-15h; Controlled rolling and controlled cooling process: starting rolling temperature 1060-1080℃, finishing rolling temperature ≥850℃; after rolling, DQ+ACC cooling method is used to control cooling, and the cooling rate is controlled within the range of 10-30℃ / s. The surface temperature of the steel plate at the time of DQ is ≤600℃; Solution treatment process: solution temperature is 1060±10℃, and holding time is 3.0±0.2min / mm.

4. The method for producing a high manganese steel extra thick plate for mining machinery according to claim 3, characterized in that: Electric furnace smelting process: During the electric furnace smelting process, 5-6 tons of manganese alloy are added into the ladle in advance and preheated to 600-800℃.

5. The method for producing a high manganese steel extra thick plate for mining machinery according to claim 3, characterized in that: LF refining process: During the LF refining process, the amount of lime used is 0.9-1.5kg / t, and the amount of aluminum wire used is 4.8-5.5m / t for deoxidation and slagging.

6. The method for producing a high manganese steel extra thick plate for mining machinery according to claim 3, characterized in that: VD vacuum degassing process: vacuum degree of the vacuum process ≤40Pa.

7. The method for producing a high manganese steel extra thick plate for mining machinery according to claim 3, characterized in that: Mold casting process: A flat ingot mold is used during the mold casting process. The ingot mold has a thickness of 450-600mm, a width of 1200-1400mm, and a height of 2100-2400mm. The casting speed is controlled at 6.5-7.0t / min. A single-type soaking furnace is used for heating the steel ingot, and the total heating time is 16-22h.

8. The method for producing a high manganese steel extra thick plate for mining machinery according to claim 3, characterized in that: Controlled rolling and controlled cooling process: The rolling process uses a four-roll roughing mill + a four-roll finishing mill.

9. The method for producing a high manganese steel extra thick plate for mining machinery according to claim 3, characterized in that: The controlled rolling process is as follows: the rough rolling mill rolls the steel to a thickness of 300-350 mm with a reduction of 10-15 mm per pass, and then the finishing rolling mill rolls the steel to a finished product thickness with a reduction of 40 mm per pass.

10. The method for producing a high manganese steel extra thick plate for mining machinery according to claim 3, characterized in that: Solution treatment process: Solution treatment uses a car bottom furnace for heating and a water cooling pool for cooling, with the circulating water temperature at 20-28°C.

Images