Production method of high-density large-specification high-carbon chromium bearing steel GCr15 round steel

Abstract

The invention relates to the technical field of metallurgical materials, in particular to a production method of high-density large-specification high-carbon chromium bearing steel GCr15 round steel. During production of the high-density large-specification high-carbon chromium bearing steel GCr15 round steel, the steps of electric furnace smelting, LF furnace refining and VD vacuum degassing treatment, continuous casting, pit entering for slow cooling, rolling and slow cooling are sequentially carried out; during electric furnace smelting, carbon temperature dual control is conducted at the smelting end point, the C content ranges from 0.2% to 0.3%, and the tapping temperature ranges from 1600 DEG C to 1620 DEG C; during LF furnace refining and VD vacuum degassing treatment, the binary alkalinity in slag is 5-8, FeO + MnO is smaller than or equal to 0.5%, and the bottom blowing argon flow is controlled in a large-small-medium staged mode; during continuous casting, continuous casting operation is conducted at the constant pulling speed, the constant liquid level and the constant pouring temperature; during rolling, the compression ratio is greater than or equal to 15. The GCr15 round steel prepared through the production method is low in residual harmful element content and high in density.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgical materials, and in particular to a method for producing high-density, large-size, high-carbon chromium bearing steel GCr15 round steel. Background Art

[0002] Bearing steel is steel used to process and manufacture bearing products, and is widely used in the fields of electricity, metallurgical engineering, ships, vehicles, aerospace engineering, etc. Bearings, as basic parts of mechanical equipment, usually serve in extreme environments such as high temperature, high speed, high load, and high cycle frequency. They are subjected to the impact force of variable loads and contact stress, pulsating bending stress, friction and other forces for a long time. At the same time, they are also affected by various factors such as processing accuracy, assembly accuracy, and grinding of external hard particles. They are the most easily damaged parts among conventional parts. Therefore, bearing steel, especially large-size bearing steel, is required to have high toughness, fatigue strength and wear resistance.

[0003] Density is an important performance indicator of metal materials. It reflects the tightness of the bonding between atoms or molecules inside the material and directly affects the quality of the material. The density of steel depends on process factors such as chemical composition, structural morphology, organizational morphology, and heat treatment. It is directly related to the looseness, cracks, segregation, gas content, cleanliness, and grain structure of the steel. It has an important influence on the strength, toughness, wear resistance, homogenization level, and ability to withstand alternating impact loads of the steel. In the conventional process of preparing large-size bearing steel, various defects will inevitably occur inside the steel. Impurity elements, component segregation, internal pores, cracks, and looseness affect its density. Therefore, it is urgent to develop a high-density large-size high-carbon chromium bearing steel to meet the market demand for high-quality bearings. Summary of the invention

[0004] In view of the technical problem in the prior art that defects are easily present inside the material of large-sized high-carbon chromium bearing steel, resulting in low density, the present invention provides a production method for high-density large-sized high-carbon chromium bearing steel GCr15 round steel, and high-density large-sized high-carbon chromium bearing steel round steel is prepared through the design of quality system and the design of specific steps such as electric furnace smelting, LF furnace refining + VD vacuum degassing treatment and continuous casting.

[0005] The technical solution of the present invention is: A method for producing high-density, large-size, high-carbon chromium bearing steel GCr15 round steel, which comprises the steps of electric furnace smelting, LF furnace refining + VD vacuum degassing treatment, continuous casting, pit slow cooling, rolling and slow cooling in sequence; Among them, during electric furnace smelting, carbon and temperature dual control is carried out at the end of smelting, the C content is 0.2%-0.3%, the P content is ≤0.012%, and the steel tapping temperature is 1600-1620℃; aluminum ingots are used for precipitation deoxidation, and the addition amount is 0.8-0.9kg / t steel; During LF furnace refining + VD vacuum degassing treatment, the binary basicity in the slag is 5-8, FeO+MnO≤0.5%, and the bottom blowing argon flow rate is controlled in stages according to large-small-medium; the vacuum degree is kept below 67Pa for at least 15 minutes during the vacuum treatment process, and the soft blowing time is ≥30 minutes; oxygen in the steel is ≤8ppm, hydrogen is ≤1.5ppm, and Ds inclusions in the steel are ≤1.0 level; During continuous casting, the casting is protected throughout the whole process, and the three constant continuous casting operations of constant drawing speed, constant liquid level and constant pouring temperature are carried out; low drawing speed, secondary cooling, weak cooling and dynamic control technology are adopted, the drawing speed is 0.20-0.40m / min, and the total specific water volume is controlled at 0.10-0.25L / kg; the fluctuation range of the crystallizer liquid level is ±2mm; the superheat of the tundish is 20-25℃; the temperature of the round billet entering the straightening machine is ≥920℃; the continuous casting round billet center looseness is ≤1.5 level, and the shrinkage cavity is ≤0.5 level; when entering the pit for slow cooling, the pit entry temperature is ≥750℃, the pit exit temperature is 175-180℃, and the slow cooling time is ≥48 hours; During rolling, the compression ratio is ≥15; the two-fire rolling process or the one-fire rolling process is adopted according to the specifications of the round steel.

[0006] Furthermore, during electric furnace smelting, the C content is 0.20%-0.30%, and the P content is ≤0.012%.

[0007] Furthermore, during LF furnace refining + VD vacuum degassing treatment, the upper steel temperature is 1510-1530℃.

[0008] Furthermore, during continuous casting, argon is blown into the tundish throughout the entire process; and the tundish cover is sealed.

[0009] Furthermore, a low-power microstructure inspection is performed on the continuous casting round billet after the continuous casting operation; The inspection standard is that there are no shrinkage cavities, bubbles, cracks, inclusions, delamination, peeling, white spots and intergranular cracks visible on the cross-section acid-etched low-magnification microstructure test piece of the continuous casting round billet.

[0010] Furthermore, when the rolling adopts a two-fire rolling process, the starting rolling temperature of the slab is ≥1050°C, and the finishing rolling temperature of the slab is ≥870°C; the intermediate billet heating temperature is 1150-1250°C, and the heating time is 3-10 hours; the starting rolling temperature of the finished product is ≥1030°C, and the finishing rolling temperature of the finished product is ≥850°C.

[0011] Furthermore, when the rolling adopts a one-fire material forming process, the slab opening and rolling temperature is ≥1050°C, the slab opening and final rolling temperature is 870-930°C, the slab is heated for ≥8 hours, and the soaking temperature is controlled at 1220-1250°C.

[0012] Furthermore, it also includes quality inspection of high-density, large-size, high-carbon chromium bearing steel GCr15 round steel after slow cooling.

[0013] Furthermore, quality testing includes grading according to Method A of GB / T 10561; Requirements for non-metallic inclusions in steel: Class A fine system is not greater than 1.0 level, Class A coarse system is not greater than 0.5 level; Class B fine system is not greater than 1.0 level, Class B coarse system is not greater than 0.5 level; Class C fine system is not greater than 0.5 level, Class C coarse system is 0 level; Class D fine system is not greater than 1.0 level, Class D coarse system is not greater than 0.5 level; Class Ds is not greater than 1.0 level; And meet the requirements of level 4 in SEP1527 standard: the test volume of water immersion ultrasonic inspection of rolled materials is ≤5.0dm 3 , the total amount of inclusions ≤ 5mm / dm 3 , the maximum length of a single inclusion is ≤2mm.

[0014] Furthermore, the quality inspection includes the use of in-situ statistical distribution analysis technology to measure the average apparent density, and the average apparent density is required to be ≥ 0.90.

[0015] The beneficial effects of the present invention are: The invention provides a production method of high-density and large-size high-carbon chromium bearing steel GCr15 round steel. The quality system requires reasonable design. After batching, a certain amount of aluminum ingots are added during electric furnace smelting for precipitation deoxidation, which can effectively control the oxygen content in the steel to ≤8ppm, thereby improving the quality of the GCr15 round steel. Compared with conventional large-medium-small stage control, large-small-medium stage control during LF furnace refining can ensure the stirring and mixing effect of molten steel and refined slag. Constant drawing speed, constant liquid level, and constant pouring temperature are used for continuous casting operations to improve the quality of continuous casting round billets, reduce defects such as segregation, looseness, and shrinkage cavities of continuous casting round billets, and further improve the quality of rolled materials based on tissue heredity. A large compression ratio (compression ratio ≥15) is used for rolling to improve the compaction effect of the internal structure of the billet, reduce the generation of welding holes and cracks, and evenly segregate components to make the steel performance consistent.

[0016] The GCr15 round steel with a diameter of 90-200 mm prepared by the production process of the present invention has low impurity elements and inclusions, reduces the porosity and dislocation of the steel matrix bonding parts, realizes the essential refinement of the steel matrix structure, and its density is greater than 0.9 as measured by in-situ analysis, with high density and good quality of high carbon chromium bearing steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 This is a schematic diagram of the two-fire material formation in Example 1.

[0019] Figure 2 This is a photo of the φ500mm continuously cast round billet in Example 1.

[0020] Figure 3 This is a low-magnification photograph of the φ110 mm rolled material in Example 1.

[0021] Figure 4 This is a screenshot of the density test results in Example 1.

[0022] Figure 5 This is a photo of the φ800mm continuously cast round billet in Example 2.

[0023] Figure 6 This is a low-magnification photograph of the φ180 mm rolled material in Example 2.

[0024] Figure 7 This is a screenshot of the density test results in Example 2.

[0025] Figure 8 This is a screenshot of the density test results in Example 1.

[0026] Fig. 9 This is a screenshot of the density test results in Example 2. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0028] Example 1 A production method of high-density, large-size, high-carbon chromium bearing steel GCr15 round steel is as follows: Batching → electric furnace smelting → LF furnace refining + VD vacuum degassing treatment → continuous casting (φ500mm) → slow cooling → rolling (two-fire product, φ110mm) → slow cooling → quality inspection.

[0029] The specific steps include: (1) Electric furnace smelting: After batching, the steel enters the electric furnace. The carbon and temperature are controlled at the end of smelting. The C content is 0.216%, the P content is 0.0107%, and the tapping temperature is 1612°C. Aluminum ingots are used for precipitation deoxidation. The addition amount is 0.9 kg / t steel. The aluminum content in the steel is 0.046%; The residual harmful elements in the steel are shown in Table 2. The gas content requirements in the steel are: [O] 6ppm, [N] 26ppm, [H] 1.2ppm; (2) LF furnace refining + VD vacuum degassing treatment: high basicity refining slag system is used, the binary basicity in the slag is controlled to 6.36, FeO+MnO is 0.35%, silicon carbide + aluminum particles are used for diffusion deoxidation, and the bottom blowing argon flow rate is controlled in stages according to large-small-medium (the large-small-medium here refers to the comparison and ranking of the argon blowing intensity during the LF furnace refining process); submerged arc operation is used to reduce nitrogen absorption by molten steel; the vacuum degree is maintained below 67Pa for 18 minutes during the vacuum treatment process; the ladle soft blowing time is 33 minutes; the upper steel temperature is 1523℃; the gas content requirements in the steel are: [O] ≤ 8ppm, [H] ≤ 1.5ppm, and the Ds inclusions in the steel are not greater than level 1.0; (3) Continuous casting: full protection of pouring, constant casting speed, constant liquid level, and constant pouring temperature; low casting speed, secondary cooling, weak cooling, and dynamic control technology are used, the casting speed is 0.36m / min, and the total specific water volume is controlled at 0.10-0.25L / kg; argon is blown throughout the tundish during the continuous casting process; the tundish cover is sealed; the crystallizer liquid level fluctuation range is ±2mm; the tundish superheat is 21℃; the round billet temperature entering the straightening machine is 936℃; (4) Slow cooling in the pit: The continuous casting round billet is slowly cooled off the line. The preheating temperature of the slow cooling pit is 500°C, the pit entry temperature is 760°C, the pit exit temperature is 175°C, and the slow cooling time is 96 hours; (5) Rolling: adopt a large compression ratio of 19.1; adopt a two-fire rolling process, the billet starting rolling temperature is 1155℃, the billet final rolling temperature is 920℃, the intermediate billet size is 265mm×265mm; the intermediate billet heating temperature is 1220℃, the heating time is 5.5 hours; the finished product starting rolling temperature is 1075℃, and the finished product final rolling temperature is 880℃; (6) Slow cooling: The temperature of the rolled material entering the slow cooling pit is 436°C, the slow cooling time is 36 hours, and the temperature out of the slow cooling pit is 85°C; the φ110mm GCr15 round steel is obtained, which is a high-density, large-size, high-carbon chromium bearing steel; (7) Quality inspection: The high-density, large-size, high-carbon chromium bearing steel is subjected to quality inspection. For details, see (2) inclusions and (4) density index in Experimental Example 1.

[0030] Its chemical composition, excluding Fe and inevitable impurities, is shown in Table 1.

[0031] Table 1 Chemical composition (wt%)

[0032] Example 2 A production method of high-density, large-size, high-carbon chromium bearing steel GCr15 round steel is as follows: Batching → electric furnace smelting → LF furnace refining + VD vacuum degassing treatment → continuous casting (φ800mm) → slow cooling → rolling (one-fire product, φ180mm) → slow cooling → quality inspection.

[0033] The specific steps include: (1) Electric furnace smelting: After batching, the steel enters the electric furnace. The carbon and temperature are controlled at the end of smelting. The C content is 0.237%, the P content is 0.0116%, and the tapping temperature is 1618°C. Aluminum ingots are used for precipitation deoxidation. The addition amount is 0.8kg / t steel. The aluminum content in the steel is 0.056%; The residual element content in the steel is shown in Table 2. The gas content requirements in the steel are: [O] 7ppm, [N] 31ppm, [H] 1.4ppm; (2) LF furnace refining + VD vacuum degassing treatment: high basicity refining slag system is used, the binary basicity in the slag is controlled to 5.96, FeO+MnO is 0.32%, silicon carbide + aluminum particles are used for diffusion deoxidation, and the bottom blowing argon flow rate is controlled in stages according to large-small-medium; submerged arc operation is used to reduce nitrogen absorption by molten steel; the vacuum degree is maintained below 67Pa for 18 minutes during the vacuum treatment process; the ladle soft blowing time is 31 minutes; the upper steel temperature is 1518℃; the gas content requirements in the steel are: [O] ≤ 8ppm, [H] ≤ 1.5ppm, and the Ds inclusions in the steel are not greater than level 1.0; (3) Continuous casting: full protection of pouring, constant casting speed, constant liquid level, constant pouring temperature three constant continuous casting operation; low casting speed, secondary cooling weak cooling and dynamic control technology are adopted, the casting speed is 0.23m / min, and the total specific water volume is controlled at 0.10-0.25L / kg; argon is blown in the tundish throughout the continuous casting process; the tundish cover is sealed; the crystallizer liquid level fluctuation range is ±2mm; the tundish superheat is 22℃; the round billet feeding temperature of the straightening machine is 933℃; (4) Slow cooling in the pit: The continuous casting round billet is slowly cooled off the line. The preheating temperature of the slow cooling pit is 500°C, the pit entry temperature is 772°C, the pit exit temperature is 180°C, and the slow cooling time is 96 hours; (5) Rolling: adopt a large compression ratio of 18.9; adopt a one-fire material forming process, the billet opening and rolling temperature is 1160℃, the billet opening and final rolling temperature is 956℃, the billet is heated for 8 hours, and the soaking temperature is controlled at 1220-1250℃; (6) Slow cooling: The upper cooling bed temperature is 670°C, and the slow cooling time after rolling is 24 hours. The φ180mm GCr15 round steel is obtained, which is a high-density, large-size, high-carbon chromium bearing steel. (7) Quality inspection: The high-density, large-size, high-carbon chromium bearing steel is subjected to quality inspection. For details, see (2) inclusions and (4) density index in Experimental Example 1.

[0034] Its chemical composition, excluding Fe and inevitable impurities, is shown in Table 1.

[0035] Comparative Example 1 A production method of high-density, large-size, high-carbon chromium bearing steel is as follows: Batching → electric furnace smelting → LF furnace refining + VD vacuum degassing treatment → continuous casting (φ500mm) → slow cooling → rolling (one-fire product, φ180mm) → slow cooling → quality inspection.

[0036] The specific steps include: (1) Electric furnace smelting: After batching, the steel enters the electric furnace. The carbon and temperature are controlled at the end of smelting. The C content is 0.207%, the P content is 0.0126%, and the tapping temperature is 1622°C. Aluminum ingots are used for precipitation deoxidation, and the addition amount is 0.72kg / t steel. (2) LF furnace refining + VD vacuum degassing treatment: high basicity refining slag system is used, the binary basicity in the slag is controlled to 4.36, FeO+MnO is 0.78%, silicon carbide + aluminum particles are used for diffusion deoxidation, and the bottom blowing argon flow rate is controlled in stages according to large-small-medium; submerged arc operation is used to reduce nitrogen absorption by molten steel; the vacuum degree is maintained below 67Pa for 17 minutes during the vacuum treatment process; the ladle soft blowing time is 30 minutes; the upper steel temperature is 1520℃; (3) Continuous casting: full protection of pouring, constant casting speed, constant liquid level, constant pouring temperature three constant continuous casting operation; low casting speed, secondary cooling weak cooling and dynamic control technology are adopted, the casting speed is 0.42m / min, and the total specific water volume is controlled at 0.10-0.25L / kg; argon is blown in the tundish throughout the continuous casting process; the tundish cover is sealed; the crystallizer liquid level fluctuation range is ±2mm; the tundish superheat is 23℃; the temperature of the round billet entering the straightening machine is 935℃; (4) Slow cooling in the pit: The continuous casting round billet is slowly cooled off the line. The preheating temperature of the slow cooling pit is 500°C, the pit entry temperature is 776°C, the pit exit temperature is 180°C, and the slow cooling time is 96 hours; (5) Rolling: The compression ratio during rolling is 7.71; the ingot is heated for 8 hours, the soaking temperature is controlled at 1220-1250°C, and the one-fire process is adopted. The starting rolling temperature is 1160°C and the final rolling temperature is 966°C; (6) Slow cooling: The upper cooling bed temperature is 680°C, and the slow cooling time of the stacking after rolling is 24 hours; GCr15 round steel with a diameter of 180 mm is obtained; (7) Quality inspection: The high-density, large-size, high-carbon chromium bearing steel is subjected to quality inspection. For details, see (2) inclusions and (4) density index in Experimental Example 1.

[0037] Its chemical composition, excluding Fe and inevitable impurities, is shown in Table 1.

[0038] Comparative Example 2 A production method of high-density, large-size, high-carbon chromium bearing steel is as follows: Batching → electric furnace smelting → LF furnace refining + VD vacuum degassing treatment → continuous casting (φ650mm) → slow cooling → rolling (one-fire product, φ200mm) → slow cooling → quality inspection.

[0039] The production process includes the following steps: (1) Electric furnace smelting: After batching, the steel enters the electric furnace. The carbon and temperature are controlled at the end of smelting. The C content is 0.155%, the P content is 0.0122%, and the tapping temperature is 1625°C. Aluminum ingots are used for precipitation deoxidation, and the addition amount is 0.75kg / t steel. (2) LF furnace refining + VD vacuum degassing treatment: high basicity refining slag system is used, the binary basicity in the slag is controlled to 5.02, FeO+MnO is 0.82%, silicon carbide + aluminum particles are used for diffusion deoxidation, and the bottom blowing argon flow rate is controlled in stages according to large-small-medium; submerged arc operation is used to reduce nitrogen absorption by molten steel; the vacuum degree is maintained below 67Pa for 18 minutes during the vacuum treatment process; the ladle soft blowing time is 28 minutes; the upper steel temperature is 1523℃; (3) Continuous casting: full protection of pouring, constant casting speed, constant liquid level, and constant pouring temperature; low casting speed, secondary cooling, weak cooling, and dynamic control technology are used, the casting speed is 0.35m / min, and the total specific water volume is controlled at 0.10-0.25L / kg; argon is blown throughout the tundish during the continuous casting process; the tundish cover is sealed; the crystallizer liquid level fluctuation range is ±2mm; the tundish superheat is 24℃; the round billet feeding temperature of the straightening machine is 940℃; (4) Slow cooling in the pit: The continuous casting round billet is slowly cooled off the line. The preheating temperature of the slow cooling pit is 500°C, the pit entry temperature is 780°C, the pit exit temperature is 180°C, and the slow cooling time is 96 hours; (5) Rolling: The compression ratio during rolling is 10.56; the one-fire material forming process is adopted, the billet opening and rolling temperature is 1180℃, the billet opening and final rolling temperature is 977℃, the billet is heated for 8 hours, and the soaking temperature is controlled at 1220-1250℃; (6) Slow cooling: The upper cooling bed temperature is 680°C, and the slow cooling time of the stacking after rolling is 24 hours; GCr15 round steel with a diameter of 200 mm is obtained; (7) Quality inspection: The high-density, large-size, high-carbon chromium bearing steel is subjected to quality inspection. For details, see (2) inclusions and (4) density index in Experimental Example 1.

[0040] Its chemical composition, excluding Fe and inevitable impurities, is shown in Table 1.

[0041] Experimental Example 1 Quality System Design (1) Impurity element content Table 2 Residual harmful elements (wt%)

[0042] As shown in Table 2, after testing, the residual harmful element content in the GCr15 round steel of Example 1 and Example 2 meets the specified requirements.

[0043] (2) Inclusions The GCr15 round steels of Example 1-2 and Comparative Example 1-2 were rated according to Method A in GB / T 10561. The results are shown in Table 3.

[0044] Table 3 Inspection details (level)

[0045] As shown in Table 3, the GCr15 round steel prepared in Example 1 and Example 2 meets the specified standard for inclusions, while the inclusion content of the GCr15 round steel prepared in Comparative Example 1 and Comparative Example 2 does not meet the specified standard. Moreover, the water immersion ultrasonic test volume of the GCr15 round steel prepared in Example 1 and Example 2 is ≤5.0dm 3 , the total amount of inclusions ≤ 5mm / dm 3 The maximum length of a single inclusion is ≤2mm, meeting the level 4 requirements of the SEP1527 standard.

[0046] (3) Product internal quality In Example 1 and Example 2, after the continuous casting operation (3), a low-power microstructure inspection is performed on the continuously cast round billet, which meets the requirements of central porosity ≤1.5 level, shrinkage cavity ≤0.5 level and defects. Specifically, the central porosity of the continuously cast round billet of Example 1 is 1.0 level, the shrinkage cavity is 0.5 level, and there are no defects such as central cracks, middle cracks, subcutaneous bubbles and subcutaneous cracks; the central porosity of the continuously cast round billet of Example 2 is 1.0 level, the shrinkage cavity is 0.5 level, and there are no defects such as central cracks, middle cracks, subcutaneous bubbles and subcutaneous cracks.

[0047] The macrostructures of the rolled products obtained in Example 1 and Example 2 after rolling in (5) were inspected according to GB / T 1979 standard. There were no shrinkage cavities, bubbles, cracks, inclusions, delamination, peeling, white spots and intergranular cracks visible on the cross-sectional acid-etched macrostructure test pieces, and the products met the requirements of Table 4.

[0048] Table 4 Requirements for macrostructure of round steel

[0049] (4) Density index The average apparent density and porosity were determined by in-situ statistical distribution analysis (OPA, in-situ analysis). Figure 4 , Figure 7 , Figure 8 and Fig. 9 As shown, the average apparent density of Example 1 is 0.9165, the average apparent density of Example 2 is 0.9047, the average apparent density of Comparative Example 1 is 0.8870, and the average apparent density of Comparative Example 2 is 0.8512. The density of the GCr15 round steel obtained in Example 1 and Example 2 is greater than 0.9, which is higher, indicating that its hardness, anisotropy and thermoelectric performance are better.

[0050] Although the present invention has been described in detail with reference to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention.

Claims

1. A method for producing high-density, large-size, high-carbon chromium bearing steel GCr15 round steel, characterized in that: The steps of electric furnace smelting, LF furnace refining + VD vacuum degassing treatment, continuous casting, slow cooling in the pit, rolling and slow cooling are carried out in sequence; Among them, during electric furnace smelting, carbon and temperature dual control is carried out at the end of smelting, the C content is 0.2%-0.3%, the P content is ≤0.012%, and the steel tapping temperature is 1600-1620℃; aluminum ingots are used for precipitation deoxidation, and the addition amount is 0.8-0.9kg / t steel; During LF furnace refining + VD vacuum degassing treatment, the binary basicity in the slag is 5-8, FeO+MnO≤0.5%, and the bottom blowing argon flow rate is controlled in stages according to large-small-medium; the vacuum degree is kept below 67Pa for at least 15 minutes during the vacuum treatment process, and the soft blowing time is ≥30 minutes; oxygen in the steel is ≤8ppm, hydrogen is ≤1.5ppm, and Ds inclusions in the steel are ≤1.0 level; During continuous casting, the casting is protected throughout the whole process, and the three constant continuous casting operations of constant drawing speed, constant liquid level and constant pouring temperature are carried out; low drawing speed, secondary cooling, weak cooling and dynamic control technology are adopted, the drawing speed is 0.20-0.40m / min, and the total specific water volume is controlled at 0.10-0.25L / kg; the fluctuation range of the crystallizer liquid level is ±2mm; the superheat of the tundish is 20-25℃; the temperature of the round billet entering the straightening machine is ≥920℃; the continuous casting round billet center looseness is ≤1.5 level, and the shrinkage cavity is ≤0.5 level; when entering the pit for slow cooling, the pit entry temperature is ≥750℃, the pit exit temperature is 175-180℃, and the slow cooling time is ≥48 hours; During rolling, the compression ratio is ≥15; two-fire rolling process or one-fire rolling process is adopted according to the specifications of the round steel.

2. The method for producing high-density, large-size, high-carbon chromium bearing steel GCr15 round steel according to claim 1, characterized in that: During electric furnace smelting, the C content is 0.20%-0.30%, and the P content is ≤0.012%.

3. The method for producing high-density, large-size, high-carbon chromium bearing steel GCr15 round steel according to claim 1, characterized in that: During LF furnace refining + VD vacuum degassing treatment, the upper steel temperature is 1510-1530℃.

4. The method for producing high-density, large-size, high-carbon chromium bearing steel GCr15 round steel according to claim 1, characterized in that: During continuous casting, argon is blown into the tundish throughout the entire process; the tundish cover is sealed.

5. The method for producing high-density, large-size, high-carbon chromium bearing steel GCr15 round steel according to claim 1, characterized in that: Conduct macroscopic inspection on the continuous casting round billet after continuous casting operation; The inspection standard is that there are no shrinkage cavities, bubbles, cracks, inclusions, delamination, peeling, white spots and intergranular cracks visible on the cross-section acid-etched low-magnification microstructure test piece of the continuous casting round billet.

6. The method for producing high-density, large-size, high-carbon chromium bearing steel GCr15 round steel according to claim 1, characterized in that: When the rolling adopts the two-fire rolling process, the starting rolling temperature of the slab is ≥1050℃, and the finishing rolling temperature of the slab is ≥870℃; the intermediate billet heating temperature is 1150-1250℃, and the heating time is 3-10 hours; the starting rolling temperature of the finished product is ≥1030℃, and the finishing rolling temperature of the finished product is ≥850℃.

7. The method for producing high-density, large-size, high-carbon chromium bearing steel GCr15 round steel as claimed in claim 1, characterized in that: When the rolling adopts the one-fire material forming process, the starting rolling temperature is ≥1050℃, the final rolling temperature is 870-930℃, the ingot is heated for ≥8 hours, and the soaking temperature is controlled at 1220-1250℃.

8. The method for producing high-density, large-size, high-carbon chromium bearing steel GCr15 round steel as claimed in claim 1, characterized in that: It also includes quality inspection of high-density, large-size, high-carbon chromium bearing steel GCr15 round steel after slow cooling.

9. The method for producing high-density, large-size, high-carbon chromium bearing steel GCr15 round steel according to claim 8, characterized in that: Quality testing includes grading according to Method A of GB / T 10561; Requirements for non-metallic inclusions in steel: Class A fine system is not greater than 1.0 level, Class A coarse system is not greater than 0.5 level; Class B fine system is not greater than 1.0 level, Class B coarse system is not greater than 0.5 level; Class C fine system is not greater than 0.5 level, Class C coarse system is 0 level; Class D fine system is not greater than 1.0 level, Class D coarse system is not greater than 0.5 level; Class Ds is not greater than 1.0 level; And meet the requirements of level 4 in SEP1527 standard: the test volume of water immersion ultrasonic inspection of rolled materials is ≤5.0dm 3 , the total amount of inclusions ≤ 5mm / dm 3 , the maximum length of a single inclusion is ≤2mm.

10. The method for producing high-density, large-size, high-carbon chromium bearing steel GCr15 round steel as claimed in claim 8, characterized in that: Quality testing includes the use of in-situ statistical distribution analysis technology to measure the average apparent density, and the average apparent density is required to be ≥0.90.

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