Machining process for preventing decarburization of bearing steel pipe

Abstract

The invention discloses a processing technology for preventing decarburization of a bearing steel pipe, which can effectively prevent the decarburization behavior of the bearing steel pipe in a furnace heating process, can effectively reduce the thickness of a decarburized layer of the bearing steel pipe, and further improves the surface performance of the bearing steel pipe. An anti-decarburization coating is prepared on the surface of the blank, so that an isolation protection layer can be effectively formed on the surface of the blank, and the decarburization reaction of the blank in the furnace heating process is avoided; it can be guaranteed that the coating is non-toxic and does not pollute the environment in the heating application process; according to the coating design, the complete sealing performance of self protection of the coating in the whole heating process can be guaranteed, and the coating design does not affect the internal quality of grains, structures and the like of the bearing steel pipe; the design of the coating can ensure that the coating can be basically completely peeled off after being discharged from a heating furnace and subjected to water descaling, so that the surface quality of the bearing steel pipe billet is prevented from being influenced.

Description

Technical Field

[0001] The present invention relates to the technical field of steel pipe production and processing, and more specifically, to a processing technology for preventing decarburization of a bearing steel pipe. Background Art

[0002] Bearing steel pipe refers to hot-rolled or cold-rolled (cold-drawn) seamless steel pipe for manufacturing common rolling bearing rings. Since bearings should have the characteristics of long life, high precision, high speed, low heat generation, high rigidity, high wear resistance, low noise, etc., bearing steel pipes are required to have: high hardness, high elastic limit, uniform hardness, high contact fatigue strength, necessary toughness, certain hardenability and corrosion resistance in atmospheric lubricants. In order to achieve the above performance requirements, strict requirements are imposed on the chemical composition uniformity, non-metallic inclusion content and type, carbide particle size and distribution, decarburization, etc. of bearing steel pipes, which is one of the most stringent steel grades in all steel production.

[0003] The decarburization layer is a chemical change caused by the so-called bridge-like structure change on the surface of the bearing steel material or the oxidation and precipitation of the main elements on the surface of the steel. The depth of the decarburization layer of the bearing steel is the external surface of the depth of this chemical change. The depth of the decarburization layer of the bearing steel is affected by many factors, mainly including the composition of the steel, the heat treatment method, the processing technology and other factors, among which the heat treatment is the most important influencing factor. International standards and industry standards have relevant regulations on the depth of the decarburization layer of bearing steel: according to ISO standards, the depth of the decarburization layer of ordinary steel cannot exceed 0.3mm, and the depth of the decarburization layer of precision steel cannot exceed 0.2mm. The depth of the decarburization layer of bearing steel is an important indicator of bearing quality. Reasonable control of the depth of the decarburization layer is conducive to improving the service life and stability of the bearing. In the production process, it is necessary to pay attention to the selection of suitable raw materials, control of heat treatment conditions and strengthening of quality management to ensure that the depth of the decarburization layer of the bearing steel is within the specified range.

[0004] Carbon is the main element in bearing steel besides iron (its content is generally between 0.95% and 1.10%), and is also the main strengthening element, which can enhance the strength, hardness and wear resistance of bearing steel. With the increase of carbon content, the strength limit, hardness and wear resistance of bearing steel increase rapidly. Due to the relatively high carbon content, the blank is prone to severe oxidation and decarburization during the heating process, which reduces the strength, hardness, wear resistance and fatigue strength of the bearing steel. Summary of the invention

[0005] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides a processing technology for preventing decarburization of a bearing steel pipe.

[0006] A processing technology for preventing decarburization of bearing steel pipe, the specific processing steps are as follows:

[0007] Step 1: before the billet of the bearing steel pipe enters the furnace, an online spraying treatment is performed to form a coating on the surface of the billet;

[0008] Step 2: After the coated billet is sent into a heating furnace for heating treatment for 3.5 to 4.5 hours, the steel is tapped;

[0009] Step 3: After steel is tapped, high-pressure water is used for dephosphorization. After dephosphorization, the steel billet is subjected to heat preservation treatment for 0.5 to 1.0 hours, the coating is removed, and the steel billet is cooled to obtain a bearing steel pipe billet.

[0010] Furthermore, the raw materials of the coating include, by weight percentage, 26.5-28.5% aluminum oxide, 21.5-23.5% magnesium oxide, 19.0-21.0% silicon dioxide, 1.2-1.8% molybdenum powder, 1.2-1.8% aluminum powder, and the rest is borosilicate glass.

[0011] Furthermore, the raw materials of the coating include, by weight percentage, 27.0-28.0% of aluminum oxide, 22.0-23.0% of magnesium oxide, 19.5-20.5% of silicon dioxide, 1.4-1.6% of molybdenum powder, 1.4-1.6% of aluminum powder, and the rest is borosilicate glass.

[0012] Furthermore, the raw materials of the coating include, by weight percentage, 26.5% aluminum oxide, 21.5% magnesium oxide, 19.0% silicon dioxide, 1.2% molybdenum powder, 1.2% aluminum powder, and the rest is borosilicate glass.

[0013] Furthermore, the raw materials of the coating include, by weight percentage, 28.5% aluminum oxide, 23.5% magnesium oxide, 21.0% silicon dioxide, 1.8% molybdenum powder, 1.8% aluminum powder, and the rest is borosilicate glass.

[0014] The raw material processing steps of the coating are as follows:

[0015] Step S1: weighing aluminum oxide, magnesium oxide, silicon dioxide, molybdenum powder, aluminum powder, and borosilicate glass;

[0016] Step S2: firstly crush and grind the borosilicate glass, and then blend alumina, magnesium oxide, silicon dioxide, molybdenum powder, aluminum powder and the ground borosilicate glass to obtain the raw material of the coating.

[0017] Furthermore, in step S2, the particle size of the borosilicate glass after grinding is 8 to 15 μm, and the blending process is carried out in a mixer for 10 to 20 minutes at a stirring speed of 300 to 500 r / min.

[0018] Furthermore, in step one, an atmospheric plasma spraying process is used for online spraying treatment, with a spraying angle of 80 to 90 degrees, a spraying distance of 85 to 95 mm, a current of 600 to 700 A, a main gas flow rate of 60 to 70 L / min, an auxiliary gas flow rate of 25 to 35 L / min, a powder feeding amount of 20 to 30 g / min, a carrier gas flow rate of 10 to 15 L / min, the main gas and the carrier gas are both argon, and the auxiliary gas is helium; in step two, in a heating furnace, a heating rate of 9°C / min, and a steel-out temperature of 1230 to 1260°C; in step three, the insulation temperature of the billet after descaling is 950 to 1050°C.

[0019] Furthermore, in step one, an atmospheric plasma spraying process is used for online spraying treatment, with a spraying angle of 80 degrees, a spraying distance of 85 mm, a current of 600 A, a main gas flow rate of 60 L / min, an auxiliary gas flow rate of 25 L / min, a powder feeding amount of 20 g / min, a carrier gas flow rate of 10 L / min, the main gas and the carrier gas are both argon, and the auxiliary gas is helium; in step two, in the heating furnace, the heating rate is 9°C / min, and the steel tapping temperature is 1230°C; in step three, the insulation temperature of the billet after descaling is 950°C.

[0020] Furthermore, in step one, an atmospheric plasma spraying process is used for online spraying treatment, with a spraying angle of 85 degrees, a spraying distance of 90 mm, a current of 650 A, a main gas flow rate of 65 L / min, an auxiliary gas flow rate of 30 L / min, a powder feeding amount of 25 g / min, a carrier gas flow rate of 13 L / min, the main gas and the carrier gas are both argon, and the auxiliary gas is helium; in step two, in the heating furnace, the heating rate is 9°C / min, and the steel tapping temperature is 1245°C; in step three, the insulation temperature of the billet after descaling is 1000°C.

[0021] Technical effects and advantages of the present invention:

[0022] 1. The processing technology for preventing decarburization of bearing steel pipes in the present invention can effectively prevent decarburization of bearing steel pipes during heating in the furnace, effectively reduce the thickness of the decarburization layer of bearing steel pipes, and thus improve the surface performance of bearing steel pipes; firstly, the surface of the billet of the bearing steel pipe is sprayed to form an anti-decarburization coating on the surface of the billet, which can effectively form an isolation protective layer on the surface of the billet, thereby preventing the billet from undergoing decarburization reaction during heating in the furnace; the billet with the coating on the surface is sent into a heating furnace for heating treatment, and then steel is tapped; after steel is tapped, high-pressure water dephosphorization treatment is performed, and after dephosphorization, the billet is heat-insulated. During the heat-insulation process, due to the difference between the expansion coefficient of the bearing steel pipe billet and the expansion coefficient of the coating, the billet is heat-insulated. The coating of the bearing steel tube billet is relatively large, and the expansion coefficients of the two can be used to effectively remove the coating of the bearing steel tube billet, and then the bearing steel tube billet is obtained after cooling; the invention can ensure that the coating is non-toxic and will not pollute the environment during the heating application process; the coating design of the invention can ensure the complete sealing of the coating's own protection during the entire heating process; the coating design of the invention does not affect the thermal conductivity of the bearing steel tube billet during heating, and can avoid the coating affecting the heating temperature of the billet and increasing the rolling load; the coating design of the invention does not affect the internal quality of the bearing steel tube grain, organization, etc.; the coating design of the invention can ensure that the coating can be basically completely peeled off after leaving the heating furnace and being descaled by water, so as not to affect the surface quality of the bearing steel tube billet;

[0023] 2. In the present invention, the billet of the bearing steel pipe is heated in a heating furnace at a temperature of 1200-1280°C, which is the maximum temperature that the coating can withstand. Combined with its oxidation and decarburization characteristics, before reaching the phase transition temperature, a good seal is formed by the glass phase and filling. When the phase transition ends at a temperature of 1050°C, the glass phase is completely melted, and its viscosity decreases with the increase of temperature. In addition, there is O 2- The penetration behavior of the coating needs to balance the "C" balance between the coating and the steel substrate. When the temperature is above 1050℃ and the coating exists, the iron element in the steel substrate is gradually oxidized to form iron oxide and enter the coating. In the high temperature section of the heating furnace, the coating and the iron oxide scale and protective slag on the surface of the original steel billet form a dense sintered layer to isolate the diffusion of oxygen in the furnace gas and form a dense sintered layer, thereby blocking the deepening of oxidation; silicon dioxide and aluminum oxide are excellent refractory materials, but their thermal expansion coefficients are much lower than the expansion coefficient of the bearing steel pipe billet. Excessive use will cause the coating to crack and lose its protective effect. Metal elements (molybdenum and aluminum) that are easier to oxidize than iron at 750-950℃ and whose volume expansion after oxidation is 1-2 times greater than that of the bearing steel pipe billet are introduced to ensure the integrity of the coating closure; in order to eliminate the stress caused by the volume expansion caused by oxidation, an appropriate amount of low-temperature glass phase (borosilicate glass) is introduced for self-healing treatment. After the sintered layer is formed, the expansion coefficient of the coating is slightly greater than the expansion coefficient of the bearing steel pipe billet, which is convenient for falling off from the billet. DETAILED DESCRIPTION

[0024] The following will be described clearly and completely in conjunction with the technical solutions 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 are within the scope of protection of the present invention.

[0025] Embodiment 1:

[0026] The present invention provides a processing technology for preventing decarburization of a bearing steel pipe, and the specific processing steps are as follows:

[0027] Step 1: before the billet of the bearing steel pipe enters the furnace, an online spraying treatment is performed to form a coating on the surface of the billet;

[0028] The raw materials of the coating include, by weight percentage: 26.5% aluminum oxide, 21.5% magnesium oxide, 19.0% silicon dioxide, 1.2% molybdenum powder, 1.2% aluminum powder, and 30.6% borosilicate glass;

[0029] The raw material processing steps of the coating are as follows:

[0030] Step S1: weighing aluminum oxide, magnesium oxide, silicon dioxide, molybdenum powder, aluminum powder, and borosilicate glass;

[0031] Step S2: firstly crush and grind the borosilicate glass, and then blend aluminum oxide, magnesium oxide, silicon dioxide, molybdenum powder, aluminum powder and the ground borosilicate glass to obtain a raw material for the coating; the particle size of the borosilicate glass after grinding is 10 μm, and the blending is carried out in a blender for 15 minutes at a stirring speed of 400 r / min;

[0032] The atmospheric plasma spraying process is used for online spraying treatment, with a spraying angle of 80 degrees, a spraying distance of 85 mm, a current of 600 A, a main gas flow rate of 60 L / min, an auxiliary gas flow rate of 25 L / min, a powder delivery amount of 20 g / min, a carrier gas flow rate of 10 L / min, the main gas and the carrier gas are both argon, and the auxiliary gas is helium;

[0033] Step 2: After the coated billet is sent into a heating furnace for heating treatment for 4.0 hours, the steel is tapped; in the heating furnace, the heating rate is 9°C / min, and the tapping temperature is 1230°C;

[0034] Step 3: After steel is tapped, high-pressure water is used for dephosphorization. After dephosphorization, the billet is heat-insulated for 0.8 hours, the coating is removed, and the billet is cooled to obtain a bearing steel pipe billet. The insulation temperature of the billet after descaling is 950°C.

[0035] Alumina was purchased from Shanghai Yuanye Biotechnology Co., Ltd., item number: S24994; magnesium oxide was purchased from Shanghai Yuanye Biotechnology Co., Ltd., item number: S27399; silicon dioxide was purchased from Shanghai Yuanye Biotechnology Co., Ltd., item number: S30499; molybdenum powder was purchased from Qinghe County Tebo Metal Materials Co., Ltd., item number: 20230909; aluminum powder was purchased from Hebei Huazuan Alloy Welding Materials Co., Ltd., item number: HZ-Al-2; borosilicate glass was purchased from Jiangsu Qiuzheng New Materials Technology Co., Ltd. silicate glass powder (30% boron content glass powder).

[0036] Embodiment 2:

[0037] Different from Example 1, the raw materials of the coating include, by weight percentage, 28.5% aluminum oxide, 23.5% magnesium oxide, 21.0% silicon dioxide, 1.8% molybdenum powder, 1.8% aluminum powder, and 23.4% borosilicate glass.

[0038] Embodiment 3:

[0039] Different from Examples 1-2, the raw materials of the coating include, by weight percentage, 27.5% aluminum oxide, 22.5% magnesium oxide, 20.0% silicon dioxide, 1.5% molybdenum powder, 1.5% aluminum powder, and 27% borosilicate glass.

[0040] Embodiment 4:

[0041] Different from Example 3, a processing technology for preventing decarburization of a bearing steel pipe has the following specific processing steps:

[0042] Step 1: before the billet of the bearing steel pipe enters the furnace, an online spraying treatment is performed to form a coating on the surface of the billet;

[0043] The raw materials of the coating include, by weight percentage, 27.5% aluminum oxide, 22.5% magnesium oxide, 20.0% silicon dioxide, 1.5% molybdenum powder, 1.5% aluminum powder, and 27% borosilicate glass;

[0044] The raw material processing steps of the coating are as follows:

[0045] Step S1: weighing aluminum oxide, magnesium oxide, silicon dioxide, molybdenum powder, aluminum powder, and borosilicate glass;

[0046] Step S2: firstly crush and grind the borosilicate glass, and then blend aluminum oxide, magnesium oxide, silicon dioxide, molybdenum powder, aluminum powder and the ground borosilicate glass to obtain a raw material for the coating; the particle size of the borosilicate glass after grinding is 10 μm, and the blending is carried out in a blender for 15 minutes at a stirring speed of 400 r / min;

[0047] The atmospheric plasma spraying process is used for online spraying treatment, with a spraying angle of 85 degrees, a spraying distance of 90 mm, a current of 650 A, a main gas flow rate of 65 L / min, an auxiliary gas flow rate of 30 L / min, a powder delivery amount of 25 g / min, a carrier gas flow rate of 13 L / min, the main gas and the carrier gas are both argon, and the auxiliary gas is helium;

[0048] Step 2: After the coated billet is sent into a heating furnace for heating treatment for 4.0 hours, the steel is tapped; in the heating furnace, the heating rate is 9°C / min, and the tapping temperature is 1245°C;

[0049] Step 3: After steel is tapped, high-pressure water is used for dephosphorization. After dephosphorization, the billet is heat-insulated for 0.8 hours, the coating is removed, and the billet is cooled to obtain a bearing steel pipe billet. The insulation temperature of the billet after descaling is 1000°C.

[0050] Comparative Example 1:

[0051] The difference from Example 4 is: a processing technology for preventing decarburization of a bearing steel pipe, and the specific processing steps are as follows:

[0052] Step 1: After the billet of the bearing steel pipe is sent into the heating furnace for heating treatment for 4.0 hours, the steel is tapped; in the heating furnace, the heating rate is 9°C / min, and the tapping temperature is 1245°C;

[0053] Step 2: After steel is tapped, high-pressure water is used for dephosphorization. After dephosphorization, the steel billet is subjected to insulation treatment for 0.8 hours, and then cooled to obtain a bearing steel pipe billet. The insulation temperature of the steel billet after descaling is 1000°C.

[0054] Comparative Example 2:

[0055] The difference from Example 4 is that the raw materials of the coating include, calculated by weight percentage, 27.5% aluminum oxide, 22.5% magnesium oxide, 20.0% silicon dioxide, and 30% borosilicate glass.

[0056] Comparative Example 3:

[0057] The difference from Example 4 is that the raw materials of the coating include, by weight percentage, 37.69% aluminum oxide, 30.82% magnesium oxide, 27.39% silicon dioxide, 2.05% molybdenum powder, and 2.05% aluminum powder.

[0058] The bearing steel pipes in the comparative examples and embodiments of the present invention were tested and processed:

[0059] Samples were taken from the head and tail of the billet and the thickness of the decarburized layer of the samples was measured microscopically;

[0060] The results are shown in Table 1:

[0061] Table 1:

[0062] Head decarburization layer thickness (mm) Thickness of tail decarburization layer (mm) Comparative Example 1 0.18 0.18 Comparative Example 2 0.11 0.10 Comparative Example 3 0.15 0.16 Example 1 0.02 0 Example 2 0.03 0.01 Example 3 0 0 Example 4 0 0

[0063] It can be seen from the above table that the processing technology for preventing decarburization of bearing steel pipes in the present invention can effectively prevent the decarburization of bearing steel pipes during the heating process in the furnace, and can effectively reduce the thickness of the decarburization layer of the bearing steel pipes, thereby improving the surface properties of the bearing steel pipes.

[0064] In the present invention, in step one, the surface of the blank of the bearing steel pipe is first sprayed to form an anti-decarburization coating on the surface of the blank, which can effectively form an isolation protective layer on the surface of the blank, thereby preventing the blank from undergoing a decarburization reaction during heating in the furnace; in step two, the blank with the coating on the surface is sent into a heating furnace for heating treatment, and then steel is tapped; in step three, high-pressure water dephosphorization treatment is performed after steel is tapped, and after dephosphorization, the steel billet is heat-insulated. During the heat-insulating process, since the expansion coefficient of the bearing steel pipe blank is significantly different from the expansion coefficient of the coating, the coating of the bearing steel pipe blank can be effectively removed by utilizing the expansion coefficients of the two, and then the bearing steel pipe blank is obtained by cooling;

[0065] The billet of bearing steel pipe is heated in the heating furnace at 1200-1280℃, which is the highest temperature that the coating can withstand. Combined with its oxidation and decarburization characteristics, before reaching the phase transition temperature, it forms a good seal by glass phase and filling. When the phase transition ends at 1050℃, the glass phase is completely melted, and its viscosity decreases with the increase of temperature. 2-The penetration behavior of the coating requires a balance between the "C" of the coating and the steel substrate. Above 1050°C and in the presence of the coating, the iron in the steel substrate is gradually oxidized to form iron oxide and enters the coating. In the high-temperature section of the heating furnace, the coating and the iron oxide scale and protective slag residue on the surface of the original steel billet form a dense sintered layer to isolate the diffusion of oxygen in the furnace gas and form a dense sintered layer, thereby blocking the penetration of oxidation. In order to ensure the integrity and sealing of the coating throughout the heating process, as well as the heating efficiency and the ease of peeling after being fired, the composition needs to be adjusted according to the thermal expansion coefficient of the steel and the thermal conductivity of the coating. Among the commonly used inorganic high-temperature resistant materials, only magnesium oxide is inert to steel and has an expansion coefficient close to that of bearing steel billets. However, magnesium oxide is in an unsintered state below 750°C and cannot form a complete protection for the billet. Silica and alumina are excellent refractory materials, but their thermal expansion coefficient is close to that of bearing steel billets. The coefficient is much lower than the expansion coefficient of the bearing steel pipe billet. Excessive use will cause the coating to crack, thus losing its protective effect. Metal elements (molybdenum and aluminum) that are easier to oxidize than iron at 750-950°C and whose volume expansion after oxidation is 1-2 times greater than that of the bearing steel pipe billet are introduced to ensure the integrity of the coating seal. In order to eliminate the stress caused by the volume expansion caused by oxidation, an appropriate amount of low-temperature glass phase (borosilicate glass) is introduced for self-healing treatment. Borosilicate glass has a lower firing and glass transition temperature, and a wider softening sealing band. It forms a film phase at low temperature. The treated glass powder begins to melt at 490°C and self-heals and seals at 660-900°C. The elements in the coating can realize the compensation of reaction heat for heat transfer in the early stage of temperature rise. After the sintered layer is formed, its thermal conductivity is 45-50W / (m·℃). After the sintered layer is formed, the expansion coefficient of the coating is (8-10)×10 -6 K -1 , which is slightly larger than the expansion coefficient of the bearing steel pipe billet, so it is easy to fall off from the billet; during the heating process, the glass phase in the coating has begun to soften below 500°C, has completely melted at 640°C, and a new crystal phase appears at about 1000°C, and a dense sintered layer is formed at about 1230°C. The addition of magnesium oxide makes the coating finally coexist in multiple phases such as cordierite phase, iron-aluminum spinel phase, and ferrosilicon olivine phase; the present invention can ensure that the coating is non-toxic and will not pollute the environment during the heating application process; the coating design of the present invention can ensure the complete sealing of the coating's own protection during the entire heating process; the coating design of the present invention does not affect the thermal conductivity of the bearing steel pipe billet during heating, and can avoid the coating affecting the heating temperature of the billet and increasing the rolling load; the coating design of the present invention does not affect the internal quality of the bearing steel pipe such as grains and organization; the coating design of the present invention can ensure that the coating can be basically completely peeled off after leaving the heating furnace and being descaled by water, so as not to affect the surface quality of the bearing steel pipe billet.

[0066] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A processing technology for preventing decarburization of bearing steel pipe, characterized in that: The specific processing steps are as follows: Step 1: before the billet of the bearing steel pipe enters the furnace, an online spraying treatment is performed to form a coating on the surface of the billet; Step 2: After the coated billet is sent into a heating furnace for heating treatment for 3.5 to 4.5 hours, the steel is tapped; Step 3: After steel is tapped, high-pressure water is used for dephosphorization. After dephosphorization, the steel billet is subjected to heat preservation treatment for 0.5 to 1.0 hours, the coating is removed, and the steel billet is cooled to obtain a bearing steel pipe billet.

2. A processing technology for preventing decarburization of a bearing steel pipe according to claim 1, characterized in that: The raw materials of the coating include, by weight percentage, 26.5-28.5% of aluminum oxide, 21.5-23.5% of magnesium oxide, 19.0-21.0% of silicon dioxide, 1.2-1.8% of molybdenum powder, 1.2-1.8% of aluminum powder, and the rest is borosilicate glass.

3. A processing technology for preventing decarburization of a bearing steel pipe according to claim 2, characterized in that: The raw materials of the coating include, by weight percentage, 27.0-28.0% of aluminum oxide, 22.0-23.0% of magnesium oxide, 19.5-20.5% of silicon dioxide, 1.4-1.6% of molybdenum powder, 1.4-1.6% of aluminum powder, and the rest is borosilicate glass.

4. A processing technology for preventing decarburization of a bearing steel pipe according to claim 2, characterized in that: The raw materials of the coating include, by weight percentage, 26.5% aluminum oxide, 21.5% magnesium oxide, 19.0% silicon dioxide, 1.2% molybdenum powder, 1.2% aluminum powder, and the rest is borosilicate glass.

5. The processing technology for preventing decarburization of bearing steel pipe according to claim 2 is characterized in that: The raw materials of the coating include, by weight percentage, 27.5% aluminum oxide, 22.5% magnesium oxide, 20.0% silicon dioxide, 1.5% molybdenum powder, 1.5% aluminum powder, and the rest is borosilicate glass.

6. A processing technology for preventing decarburization of a bearing steel pipe according to claim 2, characterized in that: The raw material processing steps of the coating are as follows: Step S1: weighing aluminum oxide, magnesium oxide, silicon dioxide, molybdenum powder, aluminum powder, and borosilicate glass; Step S2: firstly crush and grind the borosilicate glass, and then blend alumina, magnesium oxide, silicon dioxide, molybdenum powder, aluminum powder and the ground borosilicate glass to obtain the raw material of the coating.

7. A processing technology for preventing decarburization of a bearing steel pipe according to claim 6, characterized in that: In step S2, the particle size of the borosilicate glass after grinding is 8 to 15 μm, and the blending process is carried out in a mixer for 10 to 20 minutes at a stirring speed of 300 to 500 r / min.

8. A processing technology for preventing decarburization of a bearing steel pipe according to claim 1, characterized in that: In step one, an atmospheric plasma spraying process is used for online spraying treatment, with a spraying angle of 80 to 90 degrees, a spraying distance of 85 to 95 mm, a current of 600 to 700 A, a main gas flow rate of 60 to 70 L / min, an auxiliary gas flow rate of 25 to 35 L / min, a powder feeding amount of 20 to 30 g / min, a carrier gas flow rate of 10 to 15 L / min, the main gas and the carrier gas are both argon, and the auxiliary gas is helium; in step two, in a heating furnace, a heating rate of 9°C / min, and a steel-out temperature of 1230 to 1260°C; in step three, the insulation temperature of the billet after descaling is 950 to 1050°C.

9. A processing technology for preventing decarburization of a bearing steel pipe according to claim 8, characterized in that: In step one, an atmospheric plasma spraying process is used for online spraying treatment, with a spraying angle of 80 degrees, a spraying distance of 85 mm, a current of 600 A, a main gas flow rate of 60 L / min, an auxiliary gas flow rate of 25 L / min, a powder feeding amount of 20 g / min, a carrier gas flow rate of 10 L / min, the main gas and the carrier gas are both argon, and the auxiliary gas is helium; in step two, in the heating furnace, the heating rate is 9°C / min, and the steel-out temperature is 1230°C; in step three, the insulation temperature of the billet after descaling is 950°C.

10. A processing technology for preventing decarburization of a bearing steel pipe according to claim 8, characterized in that: In step one, an atmospheric plasma spraying process is used for online spraying treatment, with a spraying angle of 85 degrees, a spraying distance of 90 mm, a current of 650 A, a main gas flow rate of 65 L / min, an auxiliary gas flow rate of 30 L / min, a powder feeding amount of 25 g / min, a carrier gas flow rate of 13 L / min, the main gas and the carrier gas are both argon, and the auxiliary gas is helium; in step two, in the heating furnace, the heating rate is 9 ° C / min, and the steel tapping temperature is 1245 ° C; in step three, the insulation temperature of the billet after descaling is 1000 ° C.