Process for reducing heat treatment deformation of steel retainer and retainer

Abstract

The invention discloses a process for reducing heat treatment deformation of a steel retainer and the retainer, and relates to the technical field of retainer machining, high-temperature annealing treatment is firstly carried out between a punch forming procedure and a nitrocarburizing procedure, and then shaping and low-temperature annealing treatment are carried out, so that residual stress in the retainer is eliminated. Through the high-temperature annealing and nitrocarburizing processes, heat treatment deformation of the retainer with the outer diameter larger than or equal to 500 mm is reduced, and the percent of pass is increased.

Description

Technical Field

[0001] The invention relates to the technical field of cage processing, and in particular to a process for reducing heat treatment deformation of a steel cage and a cage. Background Art

[0002] For stamped steel retainers with an outer diameter of ≥500mm, due to their large size, there are large residual stresses during the stamping process, and large deformations are prone to occur during the nitrocarburizing process. The product qualification rate is less than 50%, which reduces the production efficiency of the product and increases the production cost. In addition, unqualified products cannot be reworked or reshaped (cracks will occur).

[0003] For controlling the deformation of nitrocarburized parts, the following solutions exist in the prior art: CN101805882A discloses a process for controlling the deformation of gas nitrocarburized parts, which includes the following steps: rough machining of parts; high temperature tempering treatment; pre-oxidation treatment; preheating treatment; nitrocarburizing treatment; pre-cooling treatment; quenching treatment. This solution adopts a high temperature tempering treatment method, that is, high temperature out of the furnace, fast cooling, and relatively greater deformation, which is not suitable for deformation treatment of steel cages. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a process and a cage for reducing heat treatment deformation of steel cages. Through high temperature annealing + nitrocarburizing process, heat treatment deformation of cages with an outer diameter ≥ 500 mm is reduced and the qualified rate is improved.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0006] In a first aspect, an embodiment of the present invention provides a process for reducing heat treatment deformation of a steel retainer, wherein a high temperature annealing treatment is first performed between the stamping and nitrocarburizing processes, and then shaping and low temperature annealing treatment are performed to eliminate residual stress inside the retainer.

[0007] As a further implementation, the annealing process parameters are: heating temperature is 640-660° C., and holding time is 4-5 hours.

[0008] As a further implementation method, the low-temperature annealing process parameters are: heating temperature is 540-560° C., and holding time is 4-5 hours.

[0009] As a further implementation method, furnace cooling is adopted during both high-temperature annealing and low-temperature annealing, and nitrogen is introduced for protection.

[0010] As a further implementation method, the nitrocarburizing process parameters are: temperature of 560-570° C. and holding time of 4-5 h.

[0011] As a further implementation method, 7-10 m3 / h of ammonia, 0.3-0.6 m3 / h of carbon dioxide and 3-5 m3 / h of nitrogen are introduced during the nitrocarburizing process.

[0012] As a further implementation method, the blanked steel plate is fed into a punching machine for forming.

[0013] As a further implementation method, the retaining frame after high temperature annealing is subjected to micro-shaping treatment.

[0014] In a second aspect, an embodiment of the present invention further provides a retaining frame, which is manufactured by using the above-mentioned process for reducing heat treatment deformation of a steel retaining frame.

[0015] As a further implementation, the surface hardness of the retaining frame is ≥400 HV0.1, and the depth of the white bright layer is 10-25 μm.

[0016] The beneficial effects of the present invention are as follows:

[0017] (1) The present invention adds a high temperature annealing treatment between nitrocarburizing and stamping to eliminate the residual stress inside the cage, reduce the deformation during nitrocarburizing, increase the qualified rate from 50% to 90%, improve the production efficiency of the product, and reduce the production cost. In addition, the cage processing is subjected to a two-step annealing treatment, and different annealing processes are performed after different processes; the use of furnace cooling has a slow cooling speed, small deformation, and better stress elimination.

[0018] (2) The present invention performs high-temperature annealing on the stamped steel plate, wherein the heating temperature is set to 640-660°C and the temperature is maintained for 4-5 hours to fully eliminate the stress inside the material and improve its organizational structure; the shaped retaining frame is subjected to low-temperature annealing, wherein the heating temperature during the low-temperature annealing process is set to 540-560°C and the temperature is maintained for 4-5 hours; low-temperature annealing can further eliminate the residual stress inside the material while maintaining its good mechanical properties and processing properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0020] Figure 1 is a process flow diagram according to one or more embodiments of the present invention. DETAILED DESCRIPTION

[0021] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0022] Embodiment 1:

[0023] For stamped steel retainers with an outer diameter ≥500mm, deformation is large during nitrocarburizing, resulting in a low pass rate (less than 50%), affecting production capacity and cost; this embodiment provides a process for reducing heat treatment deformation of steel retainers, based on the treatment process of stamping-high temperature annealing-shaping-low temperature annealing-nitrocarburizing, which reduces heat treatment deformation of retainers with an outer diameter ≥500mm and improves the pass rate.

[0024] Specifically, Figure 1 As shown, the following steps are included:

[0025] Step 1: Cutting steel plate:

[0026] According to the specific size requirements of the cage, the steel plate is accurately cut. This step ensures that the basic material size of the subsequent processing process is accurate.

[0027] Step 2: Stamping:

[0028] The blanked steel plate is sent to the stamping machine for forming. The stamping process is carried out strictly in accordance with the dimensional requirements of the product drawings to ensure that the shape and size of the finished cage meet the design requirements.

[0029] Step 3: High temperature annealing:

[0030] The stamped steel plate is subjected to high temperature annealing. The heating temperature is set to 640-660°C and maintained at this temperature for 4-5 hours to fully eliminate the stress inside the material and improve its organizational structure. The heating temperature of this embodiment is 650°C and kept at this temperature for 4 hours. During the annealing process, the furnace is cooled and nitrogen is introduced for protection to prevent the material from oxidation at high temperature.

[0031] Step 4: Shaping:

[0032] The cage after high temperature annealing is micro-shaped to ensure that its size and shape fully meet the design requirements. This step includes necessary finishing and grinding of the cage to improve its appearance quality and dimensional accuracy.

[0033] Step 5: Low temperature annealing:

[0034] The shaped retainer is subjected to low temperature annealing. The heating temperature during the low temperature annealing process is set to 540-560°C and maintained at this temperature for 4-5 hours. In this embodiment, the heating temperature of the low temperature annealing is 550°C and kept warm for 4 hours. Low temperature annealing can further eliminate the residual stress inside the material while maintaining its good mechanical properties and processing properties. The same furnace cooling method is adopted, and nitrogen is introduced for protection.

[0035] Step 6: Nitrocarburizing:

[0036] Finally, nitrocarburizing treatment is carried out to improve the surface hardness and wear resistance of the product. The treatment temperature is set between 560-570℃ and maintained at this temperature for 4-5 hours. During this process, 7-10m3 / h of ammonia, 0.3-0.6m3 / h of carbon dioxide and 3-5m3 / h of nitrogen are introduced to form a nitrogen-carbon compound layer with excellent performance on the surface of the cage. The surface hardness of the cage after treatment is ≥400HV0.1, and the depth of the white bright layer is between 10-25μm.

[0037] This embodiment adds high temperature annealing between nitrocarburizing and stamping to eliminate the residual stress inside the cage and reduce the deformation during nitrocarburizing. As shown in Table 1, this embodiment increases the qualified rate from 50% to 90%, improves the production efficiency of the product, and reduces the production cost. The cage processing of this embodiment is subjected to two-step annealing treatment, and different annealing processes are performed after different processes; the furnace cooling is used, which has a slow cooling speed, small deformation, and better stress elimination.

[0038] Table 1 Comparison of qualified rates of process validation

[0039] Serial number Process status Processing quantity Qualified quantity Pass rate 1 Original process 100 45 45％ 2 This process 100 91 91％ 3 This process 300 280 93.3％ 4 This process 500 475 90.5％

[0040] Embodiment 2:

[0041] This embodiment provides a retainer, which is processed by the process for reducing heat treatment deformation of a steel retainer as described in Embodiment 1. The surface hardness of the retainer is ≥400HV0.1, and the depth of the white bright layer is 10-25μm.

[0042] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A process for reducing heat treatment deformation of a steel cage, characterized in that: A high temperature annealing treatment is performed between the stamping and nitrocarburizing processes, followed by shaping and low temperature annealing treatments to eliminate residual stress inside the cage.

2. A process for reducing heat treatment deformation of a steel cage according to claim 1, characterized in that: The high temperature annealing process parameters are: heating temperature is 640-660° C., and holding time is 4-5 hours.

3. A process for reducing heat treatment deformation of a steel cage according to claim 2, characterized in that: The low temperature annealing process parameters are: heating temperature is 540-560° C., and holding time is 4-5 hours.

4. A process for reducing heat treatment deformation of a steel cage according to claim 3, characterized in that: During the high temperature annealing and low temperature annealing processes, furnace cooling is adopted, and nitrogen is introduced for protection.

5. A process for reducing heat treatment deformation of a steel cage according to any one of claims 1 to 4, characterized in that: The nitrocarburizing process parameters are: temperature of 560-570° C. and holding time of 4-5 h.

6. A process for reducing heat treatment deformation of a steel cage according to claim 5, characterized in that: During the nitrocarburizing process, 7-10m3 / h of ammonia, 0.3-0.6m3 / h of carbon dioxide and 3-5m3 / h of nitrogen are introduced.

7. The process for reducing heat treatment deformation of a steel cage according to claim 1, characterized in that: The blanked steel plate is fed into the punching machine for forming.

8. A process for reducing heat treatment deformation of a steel cage according to any one of claims 1 to 4, characterized in that: The cage is subjected to micro-shaping treatment after high temperature annealing.

9. A retainer, characterized in that: The steel retainer is manufactured by adopting the process for reducing heat treatment deformation of the steel retainer as described in any one of claims 1 to 8.

10. A retainer according to claim 9, characterized in that: The surface hardness of the retaining frame is ≥400HV0.1, and the depth of the white bright layer is 10-25μm.

Images