Drawing method of small-size wire rod of bearing steel GCr15 for steel ball

Abstract

The application discloses a drawing method of small-size GCr15 bearing steel wire for steel ball, which comprises the following steps: sequentially performing pickling, spheroidizing annealing, shot blasting + sand blasting, twice drawing, intermediate annealing, one to two times of drawing and finished product annealing on a wire blank, controlling the partial decarburized layer of the pickling, annealing, sand blasting and drawing processes, so that the total decarburized layer depth (including the lamellar pearlite layer) of the finished product is less than or equal to 0.02 mm, the single-side decarburized layer depth of the steel wire is not more than 0.8% of the nominal diameter of the steel wire, the ball forming rate of the material is improved, and the use requirements of the continuous high-speed cold upsetting ball user are fully met.

Description

Technical Field

[0001] This invention relates to the manufacturing and processing technology of ferrous metal materials, and more specifically to a drawing method for small-diameter wire of GCr15 bearing steel for steel balls. Background Technology

[0002] GCr15 is a common type of high-carbon chromium bearing steel and one of the key materials used in the manufacture of bearing rolling elements. GCr15 steel is characterized by a carbon content of 0.95–1.05%, a silicon content of 0.15–0.35%, a manganese content of 0.25–0.45%, and a chromium content of 1.40–1.65%. Its wire-drawn products are mainly supplied to the steel ball industry for manufacturing bearing rolling elements. The environment in which it operates is on high-speed bearings, with extremely harsh working conditions. This requires the rolling elements to have high fatigue life, hardness, and wear resistance.

[0003] Currently, the development trend in the steel ball industry is to gradually replace general cold heading with high-speed cold heading. Due to the development of the domestic steel ball manufacturing industry, high-speed cold heading machines have been introduced, resulting in smaller ball rings and a corresponding reduction in grinding amount. This has placed new demands on the surface quality of bearing steel wire used in manufacturing rolling elements, especially the decarburization process.

[0004] Decarburization reduces the carbon content of the surface layer, preventing martensitic transformation after quenching or resulting in incomplete transformation and thus failing to achieve the required hardness. Decarburization of bearing steel surfaces can cause quenching soft spots, making it prone to contact fatigue damage during use. The decarburized layer after spheroidizing annealing includes a fully decarburized layer and a partially decarburized layer. The fully decarburized layer has a ferrite structure, while the partially decarburized layer has a lamellar pearlite structure.

[0005] Currently, steel manufacturers supply GCr15 bearing steel wire products with the following decarburization requirements: the depth of the decarburized layer on one side of the wire should not exceed 0.8% of the nominal diameter of the wire. Clearly, as the nominal diameter decreases, the decarburization requirements become increasingly stringent.

[0006] Commonly used technologies or methods for preventing decarburization, both domestically and internationally, typically include billet peeling, controlling furnace heating temperature and time, and using a protective atmosphere during spheroidizing annealing. These measures are effective in controlling the overall decarburized layer. However, partial decarburization, namely the aforementioned lamellar pearlite layer, cannot fully meet user requirements.

[0007] Patent application CN202310069683.5 discloses a full-process production method for controlling the decarburization layer depth of GCr15 bearing steel wire. This method controls the decarburization layer depth through surface treatment of the initial rolled billet, heating process in a heating furnace, controlled rolling and cooling, and spheroidizing annealing in a protective atmosphere. While this patent relates to steel wire, the method primarily focuses on the front end of the wire rod production process, and the decarburization layer, specifically the lamellar pearlite layer, is insufficient to meet high-end requirements.

[0008] The method for controlling the decarburization depth of bearing steel wire rod with patent application number CN201810894499.3 still controls decarburization through surface treatment of the initial rolled billet, heating process of the heating furnace, and atmosphere control of the heating furnace. It is mainly applied to hot-rolled bearing steel wire rod and is difficult to meet the decarburization requirements of bearing steel wire drawing.

[0009] A method for controlling decarburization of bearing steel, patent application number CN201911175679.7, reduces decarburization of bearing steel bars and controls the newly added decarburized layer of bearing steel bars to below 0.08 mm. This technology is mainly applied to bearing steel bars and is not applicable to bearing steel wire drawing.

[0010] In summary, existing technologies for controlling decarburization of bearing steel still have shortcomings:

[0011] In other words, controlling decarburization through methods such as surface treatment of the initial rolled billet, heating process in the heating furnace, and spheroidizing annealing with a protective atmosphere can effectively meet users' requirements for a fully decarburized layer. However, it cannot fully meet users' requirements for a partially decarburized layer (i.e., a lamellar pearlite layer), especially for small-sized wire drawing materials. The above methods also lack effective measures to prevent decarburization in the bright wire drawing process. Summary of the Invention

[0012] The purpose of this invention is to provide a drawing method for small-sized wire of GCr15 bearing steel for steel balls, which achieves high decarburization requirements through pickling, annealing, sand polishing, and drawing processes.

[0013] To achieve the above objectives, the present invention adopts the following technical solution.

[0014] A method for drawing small-diameter wire of GCr15 bearing steel for steel balls, comprising:

[0015] The wire blank is subjected to pickling, spheroidizing annealing, shot blasting and sand blasting, two drawing operations, intermediate annealing, one or two drawing operations, and finished product annealing in sequence.

[0016] The pickling is sulfuric acid pickling, with a sulfuric acid concentration of 10-20%, wherein the ferrous sulfate content is not greater than 55g / L; the pickling temperature is controlled at 60-80℃, and the pickling time is 5-8 minutes.

[0017] The spheroidizing annealing temperature is 785℃.

[0018] The intermediate annealing temperature is 680°C.

[0019] The annealing temperature of the finished product is 680℃.

[0020] The annealing process is performed under nitrogen protection, with a purging flow rate of 30-50 m³ / h initially. 3 Purge the inner shroud at a flow rate of / h for 5–7 hours, then use 10–20m 3 Maintain a flow rate of / h for purging for 5 to 7 hours, and control the oxygen content in the furnace after purging to ≤1%.

[0021] Before phosphating, shot blasting and sand blasting are used to remove iron oxide scale, with a removal amount of 0.03 mm per side. The sand blasting process is as follows: two groups of 60 mesh, one group of 80 mesh, and one group of 120 mesh are used, with two sand belts in each group.

[0022] The total compression ratio of all drawing operations shall not exceed 55%, and the compression ratio of each pass shall not exceed 36%.

[0023] The GCr15 bearing steel high-requirement small-size drawing material produced by this invention has a total decarburization layer depth (including lamellar pearlite layer) ≤0.02mm, while meeting the requirement that the single-sided decarburization layer depth of the steel wire should not exceed 0.8% of the nominal diameter of the steel wire, thus improving the balling rate of the material and fully meeting the usage requirements of users of continuous high-speed cold heading ball production. Detailed Implementation

[0024] The present invention provides a method for drawing small-diameter wire rods of GCr15 bearing steel for steel balls, comprising: sequentially performing pickling, spheroidizing annealing, shot blasting + sand blasting, two drawing operations, intermediate annealing, one to two finishing annealing operations, and final annealing on the wire rod blank, wherein...

[0025] Because the hot-rolled wire rod has oxide scale on its surface, the pickling process uses sulfuric acid to remove the oxide scale and clean the steel surface. The sulfuric acid concentration is 10-20%, with a ferrous sulfate content not exceeding 55 g / L; the pickling temperature is controlled at 60-80℃, and the pickling time is 5-8 minutes.

[0026] The spheroidizing annealing temperature is 785℃.

[0027] The intermediate annealing is performed at a low temperature of 680°C.

[0028] The finished product is also annealed at a low temperature of 680℃.

[0029] The annealing process is performed under nitrogen protection, with a purging flow rate of 30-50 m³ / h initially. 3 Purge the inner shroud at a flow rate of / h for 5–7 hours, then use 10–20m 3Maintain a flow rate of / h for purging for 5 to 7 hours, and control the oxygen content in the furnace after purging to ≤1%.

[0030] Before phosphating, shot blasting and sand blasting are used to remove iron oxide scale, with a removal amount of 0.03 mm per side. The sand blasting process is as follows: two groups of 60 mesh, one group of 80 mesh, and one group of 120 mesh are used, with two sand belts in each group.

[0031] The total compression ratio of all drawing operations shall not exceed 55%, and the compression ratio of each pass shall not exceed 36%.

[0032] Example 1

[0033] 1) Production number: 2K01576, furnace number: 261A0365, specification: Φ2.8mm, its main chemical composition is as follows:

[0034] Main chemical components of GCr15 steel

[0035]

[0036] 2) Improve the main process flow for decarburization of small-diameter GCr15 bearing steel wire rods:

[0037] Steel billet fully peeled + coating → wire rod rolled into Φ5.5 wire rod at wire rod mill → pickling → spheroidizing annealing → shot blasting + sand blasting → coiled Φ4.5, coiled Φ3.7 wire rod → intermediate annealing → coiled Φ3.2, coiled Φ2.8 wire rod → finished product annealing → inspection → packaging.

[0038] 3) Improve the main decarburization process of small-diameter drawn GCr15 bearing steel wire:

[0039] Pickling + spheroidizing annealing: sulfuric acid concentration 10%, ferrous sulfate content not exceeding 55 g / L, temperature controlled at 60℃, pickling time 5 min, spheroidizing annealing temperature 785℃, holding time 7 hours, nitrogen protection used, purging flow rate initially 30 m³ / h. 3 The inner cover was purged with a high flow rate of / h for 5 hours, followed by 10m 3 Maintain a flow rate of / h for purging for 5 hours, and the oxygen content in the furnace after purging should be ≤1%.

[0040] Shot blasting + sand blasting: Shot blasting removes iron oxide scale, and sand blasting uses 2 groups of 60 mesh + 1 group of 80 mesh + 1 group of 120 mesh (a total of 4 groups, 1 group has 2 sand belts), with a removal amount of 0.03mm on one side.

[0041] Drawing process: Multiple drawing passes with large drawing volume are adopted, with a total drawing compression rate not exceeding 55%, and the partial compression rate of each pass not exceeding 36%. That is, the process is changed from one drawing and one annealing to two drawing and one annealing, reducing the number of intermediate annealing times.

[0042] Intermediate annealing and finished annealing were performed at a low temperature of 680℃ for 7 hours under nitrogen protection, with a purging flow rate of 30m³ / h. 3 The inner cover was purged with a high flow rate of / h for 5 hours, followed by 10m 3 Maintain a flow rate of / h for purging for 5 hours, and the oxygen content in the furnace after purging should be ≤1%.

[0043] 4) Performance of GCr15 decarburized high-requirement small-gauge wire drawing material: After inspection, the total decarburized layer depth of the finished product (including the lamellar pearlite layer) is 0 to 0.01 mm, with a maximum value of 0.36% of the nominal diameter, which meets the delivery standard requirements.

[0044] Example 2

[0045] 1) Production number: 2K01576, furnace number: 261A0365, specification: Φ3.1mm, its main chemical composition is as follows:

[0046] Main chemical components of GCr15 steel

[0047]

[0048] 2) Improve the main process flow for decarburization of small-diameter GCr15 bearing steel wire rods:

[0049] Steel billet fully peeled + coating → wire rod rolled into Φ5.5 wire rod at wire rod mill → pickling → spheroidizing annealing → shot blasting + sand blasting → coiled Φ4.7, coiled Φ4.0 → intermediate annealing → coiled Φ3.5, coiled Φ3.1 → finished product annealing → inspection → packaging.

[0050] 3) Improve the main decarburization process of small-diameter drawn GCr15 bearing steel wire:

[0051] Pickling + spheroidizing annealing: sulfuric acid concentration is 15%, ferrous sulfate content is not greater than 55 g / L, temperature is controlled at 70℃, pickling time is 6.5 min, spheroidizing annealing temperature is 785℃, holding time is 7 hours, nitrogen protection is used, and the purging flow rate is initially 40 m³ / h. 3 The inner cover was purged with a high flow rate of / h for 6 hours, followed by 15m 3 Maintain a flow rate of / h for 6 hours of purging, and the oxygen content in the furnace after purging should be ≤1%.

[0052] Shot blasting + sand blasting: Shot blasting removes iron oxide scale, and sand blasting uses 2 groups of 60 mesh + 1 group of 80 mesh + 1 group of 120 mesh (a total of 4 groups, 1 group has 2 sand belts), with a removal amount of 0.03mm on one side.

[0053] Drawing process: Multiple drawing passes with large drawing volume are adopted, with a total drawing compression rate not exceeding 55%, and the partial compression rate of each pass not exceeding 36%. That is, the process is changed from one drawing and one annealing to two drawing and one annealing, reducing the number of intermediate annealing times.

[0054] Intermediate annealing and finished annealing were performed at a low temperature of 680℃ for 7 hours under nitrogen protection, with a purging flow rate of 40m³ / h. 3 The inner cover was purged with a high flow rate of / h for 6 hours, followed by 15m 3 Maintain a flow rate of / h for 6 hours of purging, and the oxygen content in the furnace after purging should be ≤1%.

[0055] 4) Performance of GCr15 decarburized high-requirement small-gauge wire drawing material: The total decarburization layer depth (including the lamellar pearlite layer) is 0 to 0.01 mm, with a maximum value of 0.32% of the nominal diameter, which meets the delivery standard requirements.

[0056] Example 3

[0057] 1) Production number: 2K01307, furnace number: 261A0218, specification: Φ3.6mm, its main chemical composition is as follows:

[0058] Main chemical components of GCr15 steel

[0059]

[0060]

[0061] 2) Improve the main process flow for decarburization of small-diameter GCr15 bearing steel wire rods:

[0062] Steel billet fully peeled + coating → wire rod mill rolls Φ5.5 wire → pickling → spheroidizing annealing → shot blasting + sand blasting → coil drawing Φ4.5, coil drawing Φ3.7 → intermediate annealing → coil drawing Φ3.6 → inspection → packaging.

[0063] 3) Improve the main decarburization process of small-diameter drawn GCr15 bearing steel wire:

[0064] Pickling + spheroidizing annealing: sulfuric acid concentration 20%, ferrous sulfate content not exceeding 55 g / L, temperature controlled at 80℃, pickling time 8 min, spheroidizing annealing temperature 785℃, holding time 7 hours, nitrogen protection used, purging flow rate initially 50 m³ / h. 3 The inner cover was purged with a high flow rate of / h for 7 hours, followed by 20m 3 Maintain a flow rate of / h for 7 hours of purging, and the oxygen content in the furnace after purging should be ≤1%.

[0065] Shot blasting + sand blasting: Shot blasting removes iron oxide scale, and sand blasting uses 2 groups of 60 mesh + 1 group of 80 mesh + 1 group of 120 mesh (a total of 4 groups, 1 group has 2 sand belts), with a removal amount of 0.03mm on one side.

[0066] Drawing process: Multiple drawing passes with large drawing volume are adopted, with a total drawing compression rate not exceeding 55%, and the partial compression rate of each pass not exceeding 36%. That is, the process is changed from one drawing and one annealing to two drawing and one annealing, reducing the number of intermediate annealing times.

[0067] Intermediate annealing was performed at a low temperature of 680℃ for 7 hours under nitrogen protection, with a purging flow rate of 50 m³ / h. 3 The inner cover was purged with a high flow rate of / h for 7 hours, followed by 20m 3 Maintain a flow rate of / h for 7 hours of purging, and the oxygen content in the furnace after purging should be ≤1%.

[0068] 4) Performance of GCr15 decarburized high-requirement small-gauge wire drawing material: After inspection, the total decarburization layer depth of the finished product (including the lamellar pearlite layer) is 0 to 0.01 mm, with a maximum value of 0.28% of the nominal diameter, which meets the delivery standard requirements.

[0069] In summary, the drawing method for small-diameter GCr15 bearing steel wire for steel balls according to the present invention achieves a total decarburized layer depth (including the lamellar pearlite layer) of ≤0.02mm for the finished product, while simultaneously satisfying that the single-sided decarburized layer depth of the steel wire should not exceed 0.8% of the nominal diameter of the steel wire (the maximum values ​​for the three embodiments above are 0.36%, 0.32%, and 0.28% of the nominal diameter, respectively). This effectively meets the needs of mass production of continuous high-speed cold heading ball-making materials with high decarburization requirements.

[0070] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A method for drawing small-diameter wire of GCr15 bearing steel for steel balls, characterized in that, include: The wire blank is subjected to pickling, spheroidizing annealing, shot blasting and sand blasting, two drawing operations, intermediate annealing, one or two drawing operations, and finished product annealing in sequence. The pickling is sulfuric acid pickling, with a sulfuric acid concentration of 10-20%, wherein the ferrous sulfate content is not greater than 55g / L; the pickling temperature is controlled at 60-80℃, and the pickling time is 5-8 minutes; Before phosphating, shot blasting and sand blasting are used to remove iron oxide scale, with a removal amount of 0.03 mm per side. The sand blasting process is as follows: two groups of 60 mesh, one group of 80 mesh, and one group of 120 mesh are used, with two sand belts in each group.

2. The drawing method as described in claim 1, characterized in that: The spheroidizing annealing temperature is 785℃.

3. The drawing method as described in claim 1, characterized in that: The intermediate annealing temperature is 680°C.

4. The drawing method as described in claim 1, characterized in that: The annealing temperature of the finished product is 680℃.

5. The drawing method according to any one of claims 2-4, characterized in that: The annealing process is performed under nitrogen protection, with a purging flow rate of 30-50 m³ / h initially. 3 Purge the inner shroud at a flow rate of / h for 5-7 hours, then purge with 10-20 m 3 Maintain a flow rate of / h for purging for 5-7 hours, and control the oxygen content in the furnace after purging to ≤1%.

6. The drawing method as described in claim 1, characterized in that: The total compression ratio of all drawing operations shall not exceed 55%, with the compression ratio of each individual pass not exceeding 36%.

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