Production method for producing green low-carbon bearing steel wire rod through one-time heating

Abstract

The production method comprises the steps of converter blowing, LF refining and RH refining, continuous casting, casting blank heating, dephosphorization and air cooling, in the casting blank heating step, high-temperature hot charging and hot delivery are adopted, the oxygen content of different sections is controlled through differential air-fuel ratios, the diffusion time of the high-temperature section is prolonged, and the oxygen content of the high-temperature section is controlled; meanwhile, in the air cooling step, the speed difference change of an air cooling roller way is controlled, the large-specification bearing steel wire rod one-fire material production method is achieved, the production cost is reduced, and the production efficiency is improved; the contradictory point that decarburization and carbide of a fire material cannot be met at the same time is solved, the carbide network of the wire rod is smaller than or equal to 2.5 grade, the banded structure is smaller than or equal to 2.0 grade, the diameter of a decarburized layer is smaller than or equal to 0.6%, and the performance requirement of a high-quality rolling body is met.

Description

Technical Field

[0001] The invention belongs to the technical field of high-speed wire rolling production, and in particular relates to a production method of green low-carbon bearing steel wire rod-fired material. Background Art

[0002] Bearings are an important component in mechanical equipment. They are subjected to very high alternating stress when rotating. In addition to requiring the material to have high compressive strength, contact fatigue strength and wear resistance, it must also have certain toughness, corrosion resistance, good dimensional stability and processability. Therefore, extremely strict requirements are placed on the uniformity of the chemical composition, non-metallic inclusions, carbide uniformity and surface decarburization of the bearing steel.

[0003] Traditional high-end bearing steels are all made by two-fire process. The mold or billet needs to undergo high-temperature diffusion annealing for more than ten hours or even longer to ensure the uniformity of carbides. At the same time, after the billet is opened, it is fully peeled and ground to ensure the decarburization layer and surface quality, and then it is heated again for production. Its production cycle is long, the production cost is high, and the production efficiency is low. If the traditional one-fire process is used to produce bearing steel, it is difficult to ensure the decarburization layer due to long-term high-temperature insulation and diffusion. The decarburization layer can be guaranteed by short-term high-temperature heating, but it is difficult to guarantee indicators such as carbide banding and liquid separation. It can be seen that it is difficult to control the balance between carbides and decarburization with the traditional one-fire process, and it is difficult to take both indicators into account. Summary of the invention

[0004] The present invention aims to solve the technical problems in the prior art of using a two-fired material process to prepare high-end bearing steel, such as long production cycle, high production cost and low production efficiency, and proposes a production method for low-carbon bearing steel wire rods using a one-fired material process, which saves energy and improves production efficiency.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for producing green low-carbon bearing steel wire rod-fired material comprises the following steps:

[0007] (1) Converter blowing: The raw materials are smelted through blast furnace molten iron, KR desulfurization, and 100-ton top and bottom double-blowing converter. The converter steel is blown by a double-blow method to reduce the content of impurity elements in the molten steel.

[0008] (2) LF refining + RH refining: After the steel is tapped from the converter, it is refined in the LF furnace and the RH furnace to obtain low-carbon bearing steel liquid;

[0009] (3) Continuous casting: A six-machine six-strand arc continuous casting machine is used for casting, and the light reduction technology is adopted with a reduction amount of 16 mm, and the segregation index of the continuous casting billet is controlled to be less than 1.08.

[0010] (4) Heating of ingot:

[0011] During the heating process of the bearing steel ingot, the heating rate needs to be controlled to prevent the ingot from cracking due to excessively fast heating rate. The specific operating process parameters are as follows.

[0012] The 620℃±10℃ ingot is conveyed to the loading platform of the high-speed heating furnace through a sealed steel conveying roller at a conveying speed of 1.5m / s within 20 minutes to ensure that the surface temperature of the ingot is ≥500℃ before entering the furnace, and the temperature can be quickly increased. After that, the heating furnace is used for segmented heating, wherein the temperature of the first heating stage is ≥1120℃, the air-fuel ratio is 0.5-1.0, and the residual oxygen content is ≤1%; the temperature of the second heating stage is 1180℃~1260℃, the air-fuel ratio is 0.5-1.0 during stepping, and the residual oxygen content is ≤1%; the air-fuel ratio during insulation is 1.5-3.5, and the residual oxygen content is 3%-8%; the temperature of the equalization stage is 1180℃~1270℃, the operation time is ≥60 minutes, the air-fuel ratio is 1.5-3.5, and the residual oxygen content is 3%-8%. The total diffusion time of the second heating stage and the soaking stage is ≥120 minutes, so that the carbides can be fully diffused; at the same time, the decarburized layer can be effectively controlled by controlling different residual oxygen contents.

[0013] (5) Phosphorus removal: After the billet is removed from the furnace, high-pressure water of 8MPa to 12MPa is used to remove phosphorus;

[0014] (6) High-speed wire rolling: the starting rolling temperature is 1120℃~1160℃. After rough rolling, intermediate rolling and pre-finishing rolling, the rolled piece temperature is 1100℃~1180℃. After that, the wire is cooled by water tank to make the wire entering the sizing temperature 850℃~900℃, and then cooled by water tank again to make the wire laying temperature 780℃~850℃.

[0015] (7) Air cooling:

[0016] After the rolling of bearing steel is completed, rapid cooling is required to inhibit the precipitation of carbides and control the carbide network and band levels. The rolled wire rod is evenly cooled through the Stelmor air-cooled roller, and the speed of the air-cooled roller increases first and then decreases.

[0017] In order to ensure uniform cooling of the loose coils on the Stelmor air-cooled roller after spinning, it is necessary to pull the contact points of the thick edges apart when running on the air-cooled roller. The traditional roller speed adopts an increasing control method to displace the thick edge accumulation parts, so that the cooling tends to be uniform, but this method has high requirements on the length of the air-cooled roller; and the large-sized bearing steel loose coils will be difficult to roll after cooling due to the roller speed being too high, the circle spacing of each circle of the loose coil is too large, and the bearing steel has a large rigidity, which makes it difficult to roll. When bundling, it is easy to have staggered layers and warping, resulting in problems such as squeezing, abrasions and loose coils during transportation. The present invention adopts a roller speed control method that first increases and then decreases. Before rolling, the roller speed is reduced as the specifications increase, and the length between circles is shortened to facilitate collection.

[0018] Preferably, the weight percentage content of the low-carbon bearing steel molten steel composition is C0.97%, Si 0.26%, Mn 0.30%, P 0.015%, S 0.006%, Ni 0.01%, Cr 1.47%, Cu 0.02%, Al 0.012%, Ti0.0020%, and the remainder Fe and inevitable impurities.

[0019] Preferably, in step (3), during the conveying process of the ingot, the conveying speed and conveying time are controlled to ensure that the surface temperature of the ingot when entering the furnace is ≥500°C.

[0020] Preferably, the surface temperature of the ingot when entering the furnace is 540-585°C.

[0021] Preferably, the air-cooling roller speed control strategy in step (7) is as follows: when the wire rod diameter is 8.0 mm to 16.0 mm, the roller speed in the air-cooling roller fan area is 0.42 m / s in the first section, 0.44 m / s in the second section, 0.56 m / s in the third section, and 0.70 m / s in the fourth section; the roller speed entering the slow cooling area of ​​the heat preservation cover is 0.58 m / s in the fifth section, 0.48 m / s in the sixth section, 0.34 m / s in the seventh to twelfth sections, and the 13th to 15th sections are controlled automatically;

[0022] When the wire rod diameter is 17mm-23mm, the roller speed in the air-cooling roller fan area is 0.38m / s in the first section, 0.40m / s in the second section, 0.52m / s in the third section, and 0.64m / s in the fourth section. The roller speed entering the slow cooling area of ​​the heat preservation cover is 0.52m / s in the fifth section, 0.42m / s in the sixth section, 0.32m / s in the seventh to twelfth sections, and the 13th to 15th sections are automatically controlled.

[0023] When the wire rod diameter is 24mm~26mm, the roller speed in the air-cooling roller fan area is 0.30m / s in the first section, 0.32m / s in the second section, 0.44m / s in the third section, and 0.56m / s in the fourth section. The roller speed entering the slow cooling area of ​​the insulation cover is 0.44m / s in the fifth section, 0.34m / s in the sixth section, 0.28m / s in the seventh to twelfth sections, and 0.13 to 15 sections, which are automatically controlled.

[0024] Preferably, the cross-sectional size of the ingot obtained in the continuous casting step is 164*240 mm.

[0025] Preferably, in step (7), when the wire rod runs on the air-cooled roller, the contact points of the thick edges are pulled apart and misaligned.

[0026] Preferably, the weight percentage content of the low-carbon bearing steel molten steel composition is C0.96%, Si 0.24%, Mn0.28%, P 0.020%, S 0.008%, Ni 0.02%, Cr 1.45%, Cu 0.03%, Al 0.015%, Ti0.0023%, and the remainder Fe and inevitable impurities.

[0027] Preferably, the weight percentage content of the low carbon bearing steel molten steel composition is C0.98%, Si 0.22%, Mn0.28%, P 0.015%, S 0.005%, Ni 0.02%, Cr 1.45%, Cu 0.03%, Al 0.015%, Ti0.0017%, and the balance Fe and inevitable impurities.

[0028] Preferably, in step (4), the temperature of the first heating stage is 1130°C to 1180°C, the air-fuel ratio is 0.5 to 0.6, and the residual oxygen content is ≤0.4%; the temperature of the second heating stage is 1220°C to 1260°C, the air-fuel ratio during stepping is 0.5 to 0.6, and the residual oxygen content is 0.4% to 0.5%; the air-fuel ratio during insulation is 1.9 to 2.0, and the residual oxygen content is 5.0% to 5.2%; the temperature of the equalizing stage is 1230 to 1260°C, the operating time is 75 to 85 minutes, the air-fuel ratio is 1.9 to 2.0, and the residual oxygen content is 5.2% to 5.6%.

[0029] Compared with the prior art, the advantages and positive effects of the present invention are:

[0030] The present invention adopts high-temperature hot delivery and hot loading of continuous casting billets, which can effectively avoid the temperature of the brittle sensitive zone in the preheating section of the heating furnace, so that the bearing steel billet can be quickly heated in the heating furnace; the temperature of the heating section is increased, and the diffusion time of the carbide in the high temperature section is extended under the same furnace time. At the same time, different air-fuel ratios are used in different temperature sections to control the residual oxygen content, control the depth of the decarburization layer, adjust decarburization and burning loss, balance the contradiction between decarburization and carbide diffusion, and achieve one-fire material production. Compared with the "two-fire material production" process, it can save 54.56kg of standard coal / ton of steel and reduce carbon dioxide emissions by 64.30m3 / ton of steel, which is of great economic and environmental significance.

[0031] In the air cooling step of the present invention, a roller speed control method of first increasing and then decreasing is adopted to ensure uniform cooling of the loose coils without increasing the rolling length, thereby achieving carbide homogeneity control; before rolling, the roller speed is reduced as the specifications increase, and the length between the coils is shortened to facilitate collection. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 (a) and Figure 1 (b) are microscope metallographic organization diagrams of the hot-rolled wire rod samples prepared in Example 1 of the present invention and Comparative Example 1 respectively;

[0033] Figure 2 The microscopic metallographic structure diagram of the samples after heat treatment of the hot-rolled wire rods prepared in Example 1 of the present invention and Comparative Example 1, wherein: Figure 2 (a) and Figure 2 (d) Carbide network, Figure 2 (b) and Figure 2 (e) Carbide bands, Figure 2 (c) and Figure 2 (f) Carbide precipitation; DETAILED DESCRIPTION

[0034] In order to better understand the present invention, a detailed description is given below in conjunction with the accompanying drawings and embodiments.

[0035] Example 1

[0036] The production method of green low-carbon bearing steel wire rod-fired material is used to produce a batch of bearing steel GCr15 with a wire rod diameter of 17mm, and specifically includes the following steps:

[0037] (1) Converter blowing: The raw materials are smelted through blast furnace molten iron-KR desulfurization-100-ton top and bottom double-blowing converter. The converter steel is blown by double-blow method to reduce the content of impurity elements in the molten steel. The P element content at the converter end point is ≤0.015%, and the S element content is ≤0.006%.

[0038] (2) LF refining + RH refining: After the steel is tapped from the converter, it is refined in an LF furnace-RH furnace to obtain bearing steel molten steel, wherein the weight percentage composition of the molten steel is C 0.97%, Si 0.26%, Mn 0.30%, P 0.015%, S 0.006%, Ni 0.01%, Cr 1.47%, Cu 0.02%, Al 0.012%, Ti 0.0020%, and the balance is Fe and inevitable impurities.

[0039] (3) Continuous casting: A six-machine, six-stream 180*240mm arc continuous casting machine is used for casting. The light reduction technology is adopted with a reduction of 16mm. The segregation index of the continuous casting billet is controlled at 1.04-1.08. The cross-sectional size of the qualified billet is 164*240mm.

[0040] (4) Heating of ingot:

[0041] During the heating process of the bearing steel ingot, the heating rate needs to be controlled to prevent the ingot from cracking due to too fast a heating rate. The specific operating process parameters are as follows:

[0042] The ingot at 615℃~622℃ is conveyed through a sealed steel conveying roller at a speed of 1.5m / s. The time from the cooling bed to the furnace is 10 minutes to 18 minutes. When entering the furnace, the surface temperature of the ingot is 545~585℃, and it can be heated up quickly.

[0043] After that, a heating furnace is used for segmented heating, wherein the temperature of the first heating stage is 1130℃~1180℃, the air-fuel ratio is 0.5~0.6, and the residual oxygen content is ≤0.4%; the temperature of the second heating stage is 1220℃~1260℃, the air-fuel ratio is 0.5~0.6 during stepping, and the residual oxygen content is 0.4%~0.5%; the air-fuel ratio is 1.9~2.0 during insulation, and the residual oxygen content is 5.0%~5.2%; the temperature of the soaking stage is 1230~1260℃, the operation time is 75~85 minutes, the air-fuel ratio is 1.9~2.0, and the residual oxygen content is 5.2%~5.6%. The diffusion time of the second heating stage and the soaking stage is accumulated to 160 minutes~180 minutes, so that the carbides are fully diffused; at the same time, the decarburized layer is effectively controlled by controlling different residual oxygen contents.

[0044] (5) Phosphorus removal: After the billet is removed from the furnace, high-pressure water of 8MPa to 12MPa is used to remove phosphorus;

[0045] (6) High-speed wire rolling: the starting rolling temperature is 1120℃~1160℃. After rough rolling, intermediate rolling and pre-finishing rolling, the rolled piece temperature is 1100℃~1180℃. After that, the wire is cooled by water tank to make the wire entering the sizing temperature 850℃~900℃, and then cooled by water tank again to make the wire laying temperature 780℃~850℃.

[0046] (7) Air cooling:

[0047] After the rolling of the bearing steel is completed, rapid cooling is required to inhibit the precipitation of carbides and control the network and band levels of carbides. The rolled wire rod is evenly cooled by the Stelmor air-cooled roller, and the speed of the air-cooled roller increases first and then decreases. In this embodiment, the speed of the first section is 0.42m / s, the second section is 0.44m / s, the third section is 0.56m / s, and the fourth section is 0.70m / s; the roller speed entering the slow cooling area of ​​the insulation cover: the fifth section is 0.58m / s, the sixth section is 0.48m / s, the seventh to twelfth sections are 0.34m / s; the thirteenth section is 0.31m / s; the 14th section is 0.30m / s; the 15th section is 0.30m / s. The fan cooling speed before the phase change is 8.0~12.0℃ / s, the temperature entering the cover is 640℃~680℃, the insulation cover is slowly cooled, and the temperature out of the insulation cover is 450~540℃.

[0048] (8) Collect and roll the finished wires.

[0049] Example 2

[0050] The production method of green low-carbon bearing steel wire rod-fired material is used to produce a batch of bearing steel GCr15 with a wire rod diameter of 17mm, and specifically includes the following steps:

[0051] (1) Converter blowing: The raw materials are smelted through blast furnace molten iron-KR desulfurization-100-ton top and bottom double-blowing converter. The converter steel is blown by double-blow method to reduce the content of impurity elements in the molten steel. The P element content at the converter end is ≤0.02%, and the S element content is ≤0.008%.

[0052] (2) LF refining + RH refining: After the steel is tapped from the converter, it is refined in an LF furnace-RH furnace to obtain molten steel of bearing steel, wherein the weight percentage composition of the molten steel is: C 0.96%, Si 0.24%, Mn 0.28%, P 0.020%, S 0.008%, Ni 0.02%, Cr 1.45%, Cu 0.03%, Al 0.015%, Ti 0.0023%, and the balance is Fe and inevitable impurities.

[0053] (3) Continuous casting: A six-machine, six-stream 180*240mm arc continuous casting machine is used for casting. The light reduction technology is adopted with a reduction of 16mm. The segregation index of the continuous casting billet is controlled at 1.04-1.08. The cross-sectional size of the qualified billet is 164*240mm.

[0054] (4) Heating of ingot:

[0055] During the heating process of the bearing steel ingot, the heating rate needs to be controlled to prevent the ingot from cracking due to excessively fast heating rate. The specific operating process parameters are as follows.

[0056] The ingot at 620℃~625℃ is conveyed through a sealed steel conveying roller at a speed of 1.5m / s. The time from the cooling bed to the furnace is 10 minutes to 18 minutes. When entering the furnace, the surface temperature of the ingot is 540~580℃, and it can be heated up quickly.

[0057] After that, a heating furnace is used for segmented heating, wherein the temperature of the first heating stage is 1130℃~1180℃, the air-fuel ratio is 0.5~0.6, and the residual oxygen content is ≤0.4%; the temperature of the second heating stage is 1220℃~1260℃, the air-fuel ratio is 0.5~0.6 during stepping, and the residual oxygen content is 0.4%~0.5%; the air-fuel ratio is 1.9~2.0 during insulation, and the residual oxygen content is 5.0%~5.2%; the temperature of the soaking stage is 1230~1260℃, the operation time is 75~85 minutes, the air-fuel ratio is 1.9~2.0, and the residual oxygen content is 5.2%~5.6%. The diffusion time of the second heating stage and the soaking stage is 155 minutes~180 minutes in total, so that the carbides are fully diffused; at the same time, the decarburized layer is effectively controlled by controlling different residual oxygen contents.

[0058] (5) Phosphorus removal: After the billet is removed from the furnace, high-pressure water of 8MPa to 12MPa is used to remove phosphorus;

[0059] (6) High-speed wire rolling: the starting rolling temperature is 1120℃~1160℃. After rough rolling, intermediate rolling and pre-finishing rolling, the rolled piece temperature is 1100℃~1180℃. After that, the wire is cooled by water tank to make the wire entering the sizing temperature 850℃~900℃, and then cooled by water tank again to make the wire laying temperature 780℃~850℃.

[0060] (7) Air cooling:

[0061] After the rolling of the bearing steel is completed, rapid cooling is required to inhibit the precipitation of carbides and control the network and band levels of carbides. The rolled wire rod is evenly cooled by the Stelmor air-cooled roller, and the speed of the air-cooled roller increases first and then decreases. In this embodiment, the speed of the first section is 0.38m / s, the second section is 0.40m / s, the third section is 0.52m / s, and the fourth section is 0.64m / s; the roller speed entering the slow cooling area of ​​the insulation cover: the fifth section is 0.52m / s, the sixth section is 0.42m / s, the seventh to 12th sections are 0.32m / s; the 13th section is 0.31m / s; the 14th section is 0.30m / s; the 15th section is 0.30m / s. The fan cooling speed before the phase change is 7.0~11.0℃ / s, the temperature entering the cover is 645℃~685℃, the insulation cover is slowly cooled, and the temperature out of the insulation cover is 480~560℃.

[0062] (8) Collect and roll the finished wires.

[0063] Example 3

[0064] The production method of green low-carbon bearing steel wire rod-fired material is used to produce a batch of bearing steel GCr15 with a wire rod diameter of 26mm, which specifically includes the following steps:

[0065] (1) Converter blowing: The raw materials are smelted through blast furnace molten iron-KR desulfurization-100-ton top and bottom double-blowing converter. The converter steel is blown by double-blow method to reduce the content of impurity elements in the molten steel. The P element content at the converter end is ≤0.015%, and the S element content is ≤0.005%.

[0066] (2) LF refining + RH refining: After the steel is tapped from the converter, it is refined in an LF furnace-RH furnace to obtain bearing steel molten steel, wherein the weight percentage composition of the molten steel is C 0.98%, Si 0.22%, Mn 0.28%, P 0.015%, S 0.005%, Ni 0.02%, Cr 1.45%, Cu 0.03%, Al 0.015%, Ti 0.0017%, and the balance is Fe and inevitable impurities.

[0067] (3) Continuous casting: A six-machine, six-stream 180*240mm arc continuous casting machine is used for casting. The light reduction technology is adopted with a reduction of 16mm. The segregation index of the continuous casting billet is controlled at 1.04-1.08. The cross-sectional size of the qualified billet is 164*240mm.

[0068] (4) Heating of ingot:

[0069] During the heating process of the bearing steel ingot, the heating rate needs to be controlled to prevent the ingot from cracking due to excessively fast heating rate. The specific operating process parameters are as follows.

[0070] The ingot at 615℃~620℃ is conveyed through a sealed steel conveying roller at a speed of 1.5m / s. The time from the cooling bed to the furnace is 15 minutes to 20 minutes. When entering the furnace, the surface temperature of the ingot is 545~580℃, and it can be heated up quickly.

[0071] After that, a heating furnace is used for segmented heating, wherein the temperature of the first heating stage is 1130℃~1180℃, the air-fuel ratio is 0.5~0.6, and the residual oxygen content is ≤0.4%; the temperature of the second heating stage is 1230℃~1270℃, the air-fuel ratio is 0.5~0.6 during stepping, and the residual oxygen content is 0.4%~0.5%; the air-fuel ratio is 1.9~2.0 during insulation, and the residual oxygen content is 5.0%~5.2%; the temperature of the soaking stage is 1240~1260℃, the operation time is 100~120 minutes, the air-fuel ratio is 1.9~2.0, and the residual oxygen content is 5.2%~5.6%. The diffusion time of the second heating stage and the soaking stage is accumulated to 180 minutes to 240 minutes, so that the carbides are fully diffused; at the same time, the decarburized layer is effectively controlled by controlling different residual oxygen contents.

[0072] (5) Phosphorus removal: After the billet is removed from the furnace, high-pressure water of 8MPa to 12MPa is used to remove phosphorus;

[0073] (6) High-speed wire rolling: the starting rolling temperature is 1120℃~1160℃. After rough rolling, intermediate rolling and pre-finishing rolling, the rolled piece temperature is 1100℃~1180℃. After that, the wire is cooled by water tank to make the wire entering the sizing temperature 850℃~900℃, and then cooled by water tank again to make the wire laying temperature 780℃~850℃.

[0074] (7) Air cooling:

[0075] After the rolling of the bearing steel is completed, rapid cooling is required to inhibit the precipitation of carbides and control the network and band levels of carbides. The rolled wire rod is evenly cooled by the Stelmor air-cooled roller, and the speed of the air-cooled roller increases first and then decreases. In this embodiment, the speed of the first section is 0.38m / s, the second section is 0.40m / s, the third section is 0.52m / s, and the fourth section is 0.64m / s; the roller speed entering the slow cooling area of ​​the insulation cover: the fifth section is 0.52m / s, the sixth section is 0.42m / s, the seventh to 12th sections are 0.32m / s; the 13th section is 0.31m / s; the fourth section is 0.30m / s; the 15th section is 0.30m / s. The fan cooling speed before the phase change is 7.0~10.0℃ / s, the temperature entering the cover is 650℃~690℃, the insulation cover is slowly cooled, and the temperature out of the insulation cover is 490~565℃.

[0076] (8) Collect and roll the finished wires.

[0077] Comparative Example 1

[0078] A batch of bearing steel GCr15 with a wire rod diameter of 12mm is produced using traditional technology. The specific steps are as follows:

[0079] (1) Converter blowing: The raw materials are smelted through blast furnace molten iron-KR desulfurization-100-ton top and bottom double-blowing converter. The converter steel is blown by double-blow method to reduce the content of impurity elements in the molten steel. The P element content at the converter end point is ≤0.015%, and the S element content is ≤0.006%.

[0080] (2) LF refining + RH refining: After the steel is tapped from the converter, it is refined in an LF furnace-RH furnace to obtain bearing steel molten steel, wherein the weight percentage composition of the molten steel is C 0.97%, Si 0.26%, Mn 0.30%, P 0.015%, S 0.006%, Ni 0.01%, Cr 1.47%, Cu 0.02%, Al 0.012%, Ti 0.0020%, and the balance is Fe and inevitable impurities.

[0081] (3) Continuous casting: A six-machine, six-stream 180*240mm arc continuous casting machine is used for casting. The light reduction technology is adopted with a reduction of 16mm. The segregation index of the continuous casting billet is controlled at 1.04-1.08. The cross-sectional size of the qualified billet is 164*240mm.

[0082] (4) Heating of ingot:

[0083] The continuous casting billet is cold charged, the preheating section temperature is ≤750°C, the first heating section temperature is 850°C ~ 1180°C, the second heating section temperature is 1180°C ~ 1240°C, the soaking section temperature is 1200 ~ 1260°C, the air-fuel ratio control range in the furnace is 0.5 ~ 1.0, the oxygen content is ≤2.0%, and the soaking section holding time is 40 minutes ~ 80 minutes.

[0084] (5) Phosphorus removal: After the billet is removed from the furnace, high-pressure water of 8MPa to 12MPa is used to remove phosphorus;

[0085] (6) High-speed wire rolling: the starting rolling temperature is 1120℃~1160℃. After rough rolling, intermediate rolling and pre-finishing rolling, the rolled piece temperature is 1100℃~1180℃. After that, the wire is cooled by water tank to make the wire entering the sizing temperature 850℃~900℃, and then cooled by water tank again to make the wire laying temperature 780℃~850℃.

[0086] (7) Air cooling:

[0087] The roller speed in the air-cooling roller fan area is: 0.38m / s in the first section, 0.40m / s in the second section, 0.42m / s in the third section, and 0.44m / s in the fourth section; the roller speed in the slow cooling area of ​​the heat preservation cover is: 0.44m / s in the fifth section, 0.44m / s in the sixth section, 0.44m / s in the seventh to twelfth sections, 0.40m / s in the thirteenth section, 0.34m / s in the fourteenth section, and 0.30m / s in the fifteenth section. After the temperature entering the cover is 640℃~690℃, the temperature exiting the heat preservation cover is 520℃~580℃, and the rolls are collected.

[0088] Comparative Example 2

[0089] A batch of bearing steel GCr15 with a wire rod diameter of 17mm is produced using traditional technology. The specific steps are as follows:

[0090] (1) Converter blowing: The raw materials are smelted through blast furnace molten iron-KR desulfurization-100-ton top and bottom double-blowing converter. The converter steel is blown by double-blow method to reduce the content of impurity elements in the molten steel. The P element content at the converter end is ≤0.02%, and the S element content is ≤0.008%.

[0091] (2) LF refining + RH refining: After the steel is tapped from the converter, it is refined in an LF furnace-RH furnace to obtain molten steel of bearing steel, wherein the weight percentage composition of the molten steel is: C 0.96%, Si 0.24%, Mn 0.28%, P 0.020%, S 0.008%, Ni 0.02%, Cr 1.45%, Cu 0.03%, Al 0.015%, Ti 0.0023%, and the balance is Fe and inevitable impurities.

[0092] (3) Continuous casting: A six-machine, six-stream 180*240mm arc continuous casting machine is used for casting. The light reduction technology is adopted with a reduction of 16mm. The segregation index of the continuous casting billet is controlled at 1.04-1.08. The cross-sectional size of the qualified billet is 164*240mm.

[0093] (4) Heating of ingot:

[0094] The continuous casting billet is cold charged, the preheating temperature is ≤750℃, the heating temperature is controlled at 850℃~1180℃, the second heating temperature is controlled at 1180℃~1240℃, the soaking temperature is controlled at 1200~1260℃, the air-fuel ratio in the furnace is 0.5~1.0, the oxygen content is ≤2.0%, and the soaking time is 40 minutes~80 minutes

[0095] (5) Phosphorus removal: After the billet is removed from the furnace, high-pressure water of 8MPa to 12MPa is used to remove phosphorus;

[0096] (6) High-speed wire rolling: the starting rolling temperature is 1120℃~1160℃. After rough rolling, intermediate rolling and pre-finishing rolling, the rolled piece temperature is 1100℃~1180℃. After cooling by water tank, the sizing temperature is 850℃~900℃. After cooling by water tank again, the wire drawing temperature is controlled at 780℃~850℃.

[0097] (7) Air cooling:

[0098] After the rolling of the bearing steel is completed, rapid cooling is required to inhibit the precipitation of carbides and control the network and band levels of carbides. The rolled wire rod is evenly cooled by the Stelmor air-cooled roller, and the speed of the air-cooled roller increases first and then decreases. In this embodiment, the speed of the first section is 0.38m / s, the second section is 0.40m / s, the third section is 0.42m / s, and the fourth section is 0.44m / s; the roller speed entering the slow cooling area of ​​the insulation cover: the fifth section is 0.44m / s, the sixth section is 0.44m / s, the seventh to 12 sections are 0.44m / s; the 13th section is 0.40m / s; the 14th section is 0.34m / s; the 15th section is 0.30m / s. After the temperature entering the cover is 660℃~700℃, it is 530℃~590℃ out of the insulation cover.

[0099] (8) The finished wire is collected and rolled.

[0100] Comparative Example 3

[0101] A batch of bearing steel GCr15 with a wire rod diameter of 26mm is produced using traditional technology. The specific steps are as follows:

[0102] (1) Converter blowing: The raw materials are smelted through blast furnace molten iron-KR desulfurization-100-ton top and bottom double-blowing converter. The converter steel is blown by double-blow method to reduce the content of impurity elements in the molten steel. The P element content at the converter end is ≤0.015%, and the S element content is ≤0.005%.

[0103] (2) LF refining + RH refining: After the steel is tapped from the converter, it is refined in an LF furnace-RH furnace to obtain bearing steel molten steel, wherein the weight percentage composition of the molten steel is C 0.98%, Si 0.22%, Mn 0.28%, P 0.015%, S 0.005%, Ni 0.02%, Cr 1.45%, Cu 0.03%, Al 0.015%, Ti 0.0017%, and the balance is Fe and inevitable impurities.

[0104] (3) Continuous casting: A six-machine, six-stream 180*240mm arc continuous casting machine is used for casting. The light reduction technology is adopted with a reduction of 16mm. The segregation index of the continuous casting billet is controlled at 1.04-1.08. The cross-sectional size of the qualified billet is 164*240mm.

[0105] (4) Ingot heating: The temperature of the preheating section of the continuous casting ingot is controlled at ≤750°C, the temperature of the first heating section is controlled at 850°C to 1180°C, the temperature of the second heating section is controlled at 1180°C to 1240°C, the temperature of the soaking section is controlled at 1200°C to 1260°C, the air-fuel ratio in the furnace is 0.5 to 1.0, the oxygen content is ≤2.0%, and the holding time of the soaking section is 40 minutes to 80 minutes.

[0106] (5) Phosphorus removal: After the billet is removed from the furnace, high-pressure water of 8MPa to 12MPa is used to remove phosphorus;

[0107] (6) High-speed wire rolling: After the billet is taken out of the furnace, it is dephosphorized by high-pressure water at a water pressure of 8MPa to 12MPa; the starting rolling temperature is 1120℃ to 1160℃, and after rough rolling, intermediate rolling, and pre-finishing rolling, the rolled piece temperature is 1100℃ to 1180℃; it is cooled by a water tank, and the sizing temperature is 850℃ to 900℃; it is cooled by a water tank again, and the wire drawing temperature is controlled at 780℃ to 850℃

[0108] (7) Air cooling:

[0109] After the rolling of the bearing steel is completed, rapid cooling is required to inhibit the precipitation of carbides and control the network and band levels of carbides. The rolled wire rod is evenly cooled through the Stelmor air-cooled roller, and the speed of the air-cooled roller first increases and then decreases. In this embodiment, the speed of the first section is 0.38m / s, the second section is 0.40m / s, the third section is 0.42m / s, and the fourth section is 0.44m / s; the roller speed entering the slow cooling area of ​​the insulation cover: the fifth section is 0.44m / s, the sixth section is 0.44m / s, the seventh to 12 sections are 0.44m / s; the 13th section is 0.40m / s; the 14th section is 0.34m / s; the 15th section is 0.30m / s. After the temperature entering the cover is 680℃~710℃, the temperature out of the insulation cover is 545℃~600℃,

[0110] (8) The finished wire is collected and rolled.

[0111] Samples were taken from the hot-rolled wire rods prepared in Example 1-3 and Comparative Example 1-3, and the samples were cut transversely to prepare samples. The decarburization layer depth was tested according to the provisions of GB / T 224-2019 Determination of Decarburization Layer Depth of Steel. The results of the optical microscope test are shown in Table 1. The microscopic metallographic structure diagram of the hot-rolled wire rod sample prepared in Example 1 is shown in Table 1. Figure 1 (a), the microscopic metallographic structure of the hot-rolled wire rod sample prepared in Comparative Example 1 is shown in Figure 1 (b) Combined Figure 1 It can be seen from Table 1 that the decarburization layer depth of the wire rod prepared by the production method of the present invention is significantly reduced, and the decarburization layer is ≤0.6% of the diameter, which meets the requirements for high-quality rolling element use.

[0112] Table 1 Statistical table of wire rod decarburization depth for examples 1-3 and comparative examples 1-3

[0113] Classification Wire rod diameter / mm Average value of total decarburized layer on one side / mm Decarburized layer percentage Example 1 12 0.03 0.25％ Example 2 17 0.06 0.35％ Example 3 26 0.10 0.38％ Comparative Example 1 12 0.08 0.67％ Comparative Example 2 17 0.12 0.71％ Comparative Example 3 26 0.20 0.77％

[0114] Samples were taken from the hot-rolled wire rods prepared in Implementation Examples 1-3 and Comparative Examples 1-3, and the samples were heat treated and inspected for carbide heterogeneity in accordance with "GB / T18254-2016 High Carbon Chromium Bearing Steel". The heat treatment process is as follows: (1) Spheroidizing annealing: heat the sample to 800°C, keep warm for 4 hours, then cool to 740°C in 1 hour, keep warm for 6 hours, turn off the power and cool to 300°C before taking out of the furnace; (2) Quenching and tempering: heat the sample to 840°C, keep warm for 35-60 minutes, then quench in 70°C oil, then place in a 150°C muffle furnace, keep warm for 2 hours, and air cool to room temperature. The carbides of the heat-treated samples were inspected using an optical microscope. The microscopic metallographic structure of the heat-treated sample of the wire rod prepared in Example 1 is shown in the figure. Figure 2 (a) (b) (c) shows the microscopic metallographic structure of the sample after heat treatment of the wire rod prepared in Comparative Example 1. Figure 2 (d)(e)(f), the test results are shown in Table 2, combined with Figure 2 It can be seen from Table 2 that the carbide network of the wire rod prepared by the production method of the present invention is controlled at level 1.0-1.5, the banded structure is controlled at level 1.0-1.5, and the carbide liquid separation is controlled at level 0, which is significantly improved compared with the traditional method.

[0115] Table 2 Statistical table of the inhomogeneity of wire rod carbides in Examples 1-3 and Comparative Examples 1-3

[0116] Classification Carbide network / grade Carbide bands / grades Carbide liquid separation / grade Example 1 1.0 1.0 0 Example 2 1.5 1.0 0 Example 3 1.5 1.5 0 Comparative Example 1 2.5 2.0 0.5 Comparative Example 2 3.0 2.5 1.0 Comparative Example 3 3.0 2.5 1.0

[0117] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for producing green low-carbon bearing steel wire rod-fired material, characterized in that: The following steps are included: (1) Converter blowing: The raw materials are smelted through blast furnace molten iron, KR desulfurization, and 100-ton top and bottom double-blowing converter. The converter steel is blown by a double-blow method to reduce the content of impurity elements in the molten steel. (2) LF refining + RH refining: After the steel is tapped from the converter, it is refined in the LF furnace and the RH furnace to obtain molten steel for bearing steel; (3) Continuous casting: A six-machine six-strand arc continuous casting machine is used for casting, and the light reduction technology is adopted with a reduction amount of 16 mm, and the segregation index of the continuous casting billet is controlled to be less than 1.

08. (4) Heating of the ingot: The ingot is transported to a heating furnace for staged heating, wherein the temperature of the first stage is ≥1120°C, the air-fuel ratio is 0.5-1.0, and the residual oxygen content is ≤1%; the temperature of the second stage is 1180°C-1260°C, the air-fuel ratio is 0.5-1.0 during stepping, and the residual oxygen content is ≤1%; The air-fuel ratio of the holding section is 1.5-3.5, and the residual oxygen content is 3%-8%; the temperature of the soaking section is 1180℃-1270℃, the operation time is ≥60 minutes, the air-fuel ratio is 1.5-3.5, and the residual oxygen content is 3%-8%; the diffusion time of the second heating section and the soaking section is ≥120 minutes in total, so that the carbides can be fully diffused. (5) Phosphorus removal: After the billet is removed from the furnace, high-pressure water of 8MPa to 12MPa is used to remove phosphorus; (6) High-speed wire rolling: the starting rolling temperature is 1120℃~1160℃. After rough rolling, intermediate rolling and pre-finishing rolling, the rolled piece temperature is 1100℃~1180℃. After that, the wire is cooled by water tank to make the wire entering the sizing temperature 850℃~900℃, and then cooled by water tank again to make the wire laying temperature 780℃~850℃. (7) Air cooling: The rolled wire rod is evenly cooled by passing it through a Stelmor air-cooling roller, and the speed of the air-cooling roller increases first and then decreases.

2. The method for producing green low-carbon bearing steel wire rod-pyrotechnical material according to claim 1, characterized in that: The weight percentage content of the bearing steel molten steel composition is C 0.97%, Si 0.26%, Mn 0.30%, P 0.015%, S 0.006%, Ni 0.01%, Cr 1.47%, Cu 0.02%, Al 0.012%, Ti 0.0020%, and the balance is Fe and inevitable impurities.

3. The method for producing green low-carbon bearing steel wire rod-pyrotechnical material according to claim 1, characterized in that: In step (3), the conveying speed and conveying time are controlled during the conveying process of the cast billet to ensure that the surface temperature of the cast billet is ≥500°C when entering the furnace.

4. The method for producing green low-carbon bearing steel wire rod-pyrotechnical material according to claim 1, characterized in that: The surface temperature of the ingot when entering the furnace is 540-585°C.

5. The method for producing green low-carbon bearing steel wire rod-pyrotechnical material according to claim 1, characterized in that: The air-cooling roller speed control strategy in step (7) is as follows: when the wire rod diameter is 8 mm to 16 mm, the roller speed in the air-cooling roller fan area is 0.42 m / s in the first section, 0.44 m / s in the second section, 0.56 m / s in the third section, and 0.70 m / s in the fourth section; the roller speed entering the slow cooling area of ​​the heat preservation cover is 0.58 m / s in the fifth section, 0.48 m / s in the sixth section, 0.34 m / s in the seventh to twelfth sections, and the 13th to 15th sections are controlled automatically; When the wire rod diameter is 17mm-23mm, the roller speed in the air-cooling roller fan area is 0.38m / s in the first section, 0.40m / s in the second section, 0.52m / s in the third section, and 0.64m / s in the fourth section. The roller speed entering the slow cooling area of ​​the heat preservation cover is 0.52m / s in the fifth section, 0.42m / s in the sixth section, 0.32m / s in the seventh to twelfth sections, and the 13th to 15th sections are automatically controlled. When the wire rod diameter is 24mm~26mm, the roller speed in the air-cooling roller fan area is 0.30m / s in the first section, 0.32m / s in the second section, 0.44m / s in the third section, and 0.56m / s in the fourth section. The roller speed entering the slow cooling area of ​​the insulation cover is 0.44m / s in the fifth section, 0.34m / s in the sixth section, 0.28m / s in the seventh to twelfth sections, and the 13th to 15th sections are automatically controlled.

6. The method for producing green low-carbon bearing steel wire rod-pyrotechnical material according to claim 1, characterized in that: The cross-sectional size of the ingot obtained by the continuous casting step is 164*240mm.

7. The method for producing green low-carbon bearing steel wire rod-pyrotechnical material according to claim 1, characterized in that: In step (7), when the wire rod runs on the air-cooled roller, the contact points of the thick edges of the accumulation are pulled apart and misaligned.

8. The method for producing green low-carbon bearing steel wire rod-pyrotechnical material according to claim 1, characterized in that: The weight percentage content of the bearing steel molten steel composition is C 0.96%, Si 0.24%, Mn 0.28%, P 0.020%, S 0.008%, Ni 0.02%, Cr 1.45%, Cu 0.03%, Al 0.015%, Ti 0.0023%, and the balance is Fe and inevitable impurities.

9. The method for producing green low-carbon bearing steel wire rod-pyrotechnical material according to claim 1, characterized in that: The weight percentage content of the bearing steel molten steel composition is C 0.98%, Si 0.22%, Mn 0.28%, P 0.015%, S 0.005%, Ni 0.02%, Cr 1.45%, Cu 0.03%, Al 0.015%, Ti 0.0017%, and the balance is Fe and inevitable impurities.

10. The method for producing green low-carbon bearing steel wire rod-pyrotechnical material according to claim 1, characterized in that: In step (4), the temperature of the first heating stage is 1130° C. to 1180° C., the air-fuel ratio is 0.5 to 0.6, and the residual oxygen content is ≤0.4%; the temperature of the second heating stage is 1220° C. to 1260° C., the air-fuel ratio during stepping is 0.5 to 0.6, and the residual oxygen content is 0.4% to 0.5%; the air-fuel ratio during insulation is 1.9 to 2.0, and the residual oxygen content is 5.0% to 5.2%; the temperature of the soaking stage is 1230 to 1260° C., the operating time is 75 to 85 minutes, the air-fuel ratio is 1.9 to 2.0, and the residual oxygen content is 5.2% to 5.6%.

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