Thin-wall high-hardness sphere heat treatment deformation restraining tool and control method

Abstract

The invention discloses a thin-wall high-hardness ball heat treatment deformation restraining tool and a control method. The control method comprises the following steps that carbon cutting is conducted on a positive ball, turning is conducted on the positive ball except for the spherical surface position, the carburized surface of the positive ball is removed to form an outer seepage layer, and the inner diameter of the large end obtained after carbon cutting serves as a restraining reference; the constraint tool is assembled, the shape of the constraint tool and the inner machining cylindrical surface of the large end of the male ball are subjected to reserved gap assembly, the thickness of the tool and the expansion coefficient of a tool material need to be considered, the size of a matching surface is adjusted, and the constraint purpose is guaranteed; performing positive ball constraint heat treatment, namely performing high-temperature heating, heat preservation and cooling on the positive ball constrained in the step S2, enabling a tool to expand in the heating process to restrain deformation of the ball, enabling the tool to be large in thickness and slow in cooling in the cooling process to restrain deformation of the ball, and enabling the heating and cooling processes to achieve the constraint purpose; and after heat treatment, the tool is removed for ball jerk value detection. The quenching deformation problem which cannot be solved by conventional heat treatment is solved; the hardenability of the product is not affected after the tool is added, and the high hardness of the product is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment of metal positive balls, and in particular to a heat treatment deformation constraint tooling and a control method for a thin-walled high-hardness ball. Background Art

[0002] During the operation of the engine, the thrust size and direction are adjusted and controlled through the nozzle. Therefore, there is a key core supporting component in the engine manufacturing technology, the positive ball, which is responsible for the control and load-bearing of the nozzle during operation. According to the harsh environment requirements when the engine is working, the surface needs to have high hardness, high wear resistance, and good core toughness. The performance of general metal parts cannot meet the working requirements of the engine, so this product needs to be modified by chemical heat treatment to meet the special requirements of high surface hardness, high wear resistance and good core toughness. Due to the lightweight design of the supporting positive ball, the product structure is a thin-walled sphere, which is very easy to deform during the heat treatment process, resulting in product scrapping.

[0003] The forming process of the male ball of the nozzle accessories is: rough turning - carbonitriding - carbon cutting - quenching and tempering - fine turning of the spherical surface. At present, the male ball of the nozzle accessories adopts a controlled atmosphere multi-purpose furnace for carbonitriding. After carbonitriding, the non-diffused surface is carbonized, and the quenching and tempering process is performed after carbon cutting. Considering the design requirements of high surface hardness and small deformation after the product heat treatment. At present, the cutting reserve before the spherical surface heat treatment is (0.2-0.5) mm. The reserve is adjusted according to the different ball diameter sizes. The reserve for small ball products is small, and the reserve for large ball products is large. The existing reserve cannot be increased after considering the product turning size, hardness after turning and subsequent high hardness processing difficulties. After quenching and tempering in the existing process, the male ball has the problem of ball diameter shrinkage and deformation. According to the reserve, the spherical surface cannot be fully exposed to light after turning, resulting in scrapping. According to statistics, the qualified rate of male balls using the existing heat treatment method is less than 60%, and the qualified rate of products is low. Summary of the invention

[0004] The invention relates to a heat treatment method for a thin-wall high-hardness metal product, a positive ball, to solve the problems of quenching deformation size out-of-tolerance of the thin-wall positive ball after carbonitriding and low product qualification rate.

[0005] In order to solve the above technical problems, one of the purposes of the present invention is to provide a method for controlling the deformation of a thin-walled high-hardness sphere during heat treatment, comprising the following steps:

[0006] S1: Carburizing the male ball. The male ball is turned except for the spherical surface to remove the carburized layer outside the carburized surface of the male ball, and the inner diameter of the large end after carburizing is used as the constraint reference;

[0007] S2: Constraint tooling assembly, the constraint tooling shape is assembled with the cylindrical surface processed inside the male ball big end with a reserved gap, the tooling thickness and the expansion coefficient of the tooling material need to be considered, and the size of the mating surface is adjusted to ensure the purpose of the constraint;

[0008] S3: Constrained heat treatment of the positive ball, the positive ball constrained in S2 is subjected to high temperature heating, heat preservation and cooling. During the heating process, the tooling expands to constrain the ball deformation. During the cooling process, the tooling is thick and the cooling is slow to constrain the ball deformation. The heating and cooling processes both play a role in the constraint.

[0009] S4: After heat treatment, remove the tooling to test the ball runout.

[0010] Furthermore, the specific operation steps of the S2 tooling design are:

[0011] S21: Material selection should take into account repeated processing and reuse, and should have low through-hardening hardness, small quenching deformation, and easy processing performance;

[0012] S22: Structural selection: the newly designed tooling should not affect the fluidity of the quenching medium, hinder the rapid cooling and martensitic transformation of the product;

[0013] S23: Selection of size. The size of the constraint tooling directly affects the constraint effect of the product. If the size is large, the amount of turning will increase after constraint, and the spherical surface penetration layer and surface hardness will be unqualified. If the size is small, it will not play a restraining role. Therefore, for spheres of different specifications, it is necessary to pre-design the effective height and effective thickness of the constraint tooling, and carry out experimental verification. According to the experimental results, determine the size of the open end of the expanded product after quenching, and revise the final size of the sphere constraint tooling by comparing it with the pre-designed size.

[0014] Furthermore, the changeable position of the S2 male ball is the large opening end of the male ball body.

[0015] Based on the same inventive concept, the present invention also provides a constraint tooling for a method for controlling the deformation of a thin-walled, high-hardness sphere during heat treatment. The constraint tooling is integrally processed and formed, and its external shape structure constrains the position of the positive ball that is susceptible to deformation (thin wall and open end position). At the same time, the tooling must not affect the quenching and cooling transformation of the product to prevent insufficient hardness of the product after the constrained heat treatment.

[0016] Further, the restraining tooling is low carbon steel.

[0017] The above one or more technical solutions of the present invention have at least one or more of the following technical effects:

[0018] Through the improvement of the heat treatment process method, the problem of heat treatment deformation of thin-walled positive balls can be effectively solved. The constrained quenching method can be used to solve the heat treatment deformation problem caused by the combined action of processing stress, thermal stress and organizational stress when the workpiece is quenched in oil, meet the dimensional accuracy requirements of the product after turning, and improve the product qualification rate.

[0019] The present invention can solve the quenching deformation problem that cannot be solved by conventional heat treatment; the present invention can ensure the high hardness of the product without affecting the hardenability of the product after adding tooling; the present invention is suitable for constrained quenching of thin-walled spheres of different specifications, and has a simple device, low cost, easy operation and wide applicability; the present invention is suitable for batch parts production, and the product processing efficiency is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 : Schematic diagram of the positive ball;

[0021] Figure 2 : Schematic diagram of constraint tooling;

[0022] Figure 3 : Schematic diagram after constraint;

[0023] Among them: 1-support plane, 2-constraint cylinder, 3-quenching oil flow cylinder, 4-open end constraint reference plane. Specific implementation plan

[0024] The present invention proposes a heat treatment method to achieve constrained quenching of thin-walled high-hardness spheres, effectively control the quenching deformation problem of products, and meet the product use requirements after heat treatment. Through this heat treatment method, the deformation of the product during the heat treatment process is reduced, thereby meeting the machining allowance of such parts, and finally achieving the purpose of meeting the design dimensional accuracy requirements. The present invention is to improve the product qualification rate through the technical solution of tooling constrained quenching and controlling the heat treatment deformation. The main contents of the technical solution are as follows: design a constrained tooling, constrain the spherical open end according to the male ball structure, and quench the male ball after heating and heat preservation in a constrained state. During the cooling process, the male ball cools faster, and the structure changes and deformations occur. The slow cooling of the core tooling can prevent the male ball from shrinking and deforming, and play a restraining role. Constrained quenching, the male ball is placed on the constrained tooling, and the large mouth end is constrained and then quenched in the furnace.

[0025] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in combination with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the obtained embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0026] Combine the following Figure 1-Figure 3The present invention is described in detail in the following embodiments. The preferred embodiments of the present invention are described in detail below, but the protection scope of the present invention is not limited to the following.

[0027] The present invention improves the product qualification rate by means of a technical scheme of controlling the amount of heat treatment deformation through tool design and tool use. The heat treatment constrained quenching scheme mainly includes the following steps: positive ball carbon cutting, tool design, constrained quenching, measurement and tool repair. Specific implementation method:

[0029] Step 1: The positive ball is subjected to overall carbonitriding;

[0030] Step 2: Carburizing the male ball. Turn the male ball except the spherical surface to remove the carburized layer on the carburized surface of the male ball, and use the inner diameter of the large end after carburizing as the constraint reference.

[0031] Step 3: Constrain tooling processing

[0032] When designing tooling, it is necessary to consider the material, structure and constraint dimensions (see Figure 2 ), thereby ensuring the heat treatment performance of the male ball and the dimensional accuracy requirements after heat treatment.

[0033] 1) Material selection

[0034] Considering multiple processing and repeated use, it is necessary to have low through-hardening hardness, small quenching deformation and easy processing properties.

[0035] 2) Structural selection

[0036] The newly designed tooling should not affect the fluidity of the quenching medium and hinder the rapid cooling and martensitic transformation of the product.

[0037] 3) Size selection

[0038] The size of the constraint tooling directly affects the constraint effect of the product. If the size is large, the turning amount will increase after the constraint, and the spherical surface penetration layer and surface hardness will be unqualified. If the size is small, it will not play a restraining role. Therefore, for spheres of different specifications, the effective height and effective thickness of the constraint tooling need to be designed in advance, and experimental verification should be carried out. According to the experimental results, the size of the open end of the expanded product after quenching is determined, and the final size of the sphere constraint tooling is revised by comparing with the pre-designed size.

[0039] Step 4: Install the restraint tooling in the opening reference of the inner diameter of the large end of the male ball after carbon cutting, and restrain the male ball at the deformable position before quenching.

[0040] The male ball is constrained and placed, and the outer shape of the constraint tooling is assembled with a reserved gap with the cylindrical surface processed inside the large end of the male ball. The thickness of the tooling and the expansion coefficient of the tooling material must be considered, and the size of the matching surface must be adjusted to ensure the purpose of the constraint.

[0041] Step 5: Constrained heat treatment of the positive ball, and quenching of the constrained positive ball under atmosphere protection, cold treatment after quenching, transforming the residual austenite into martensite structure, and timely tempering after cold treatment to eliminate the internal stress of the workpiece. During the heating process, the expansion of the tooling constrains the deformation of the ball, and during the cooling process, the tooling is thick and the cooling is slow, which constrains the deformation of the ball. The heating and cooling processes both play a role in the constraint.

[0042] Step 6: After heat treatment, remove the tooling and test the ball runout.

[0043] After the non-carbonitrided spherical surface of the male ball is carbonized, the carbonization treatment can reduce the difficulty of processing the high hardness of the non-working surface after the subsequent quenching of the male ball, eliminate the risk of slag and cracking during turning, and improve the processing quality and efficiency. Figure 3 As shown, the heating, quenching and tempering processes are carried out in the furnace. After the heat treatment of the sphere, the restraint effect and the size of the restraint tooling are measured. According to the frequency of use and size, the tooling is repaired and continued to be used.

[0044] The restraint tooling is formed by one-piece turning, and its appearance is a trapezoidal structure, which is composed of the male ball support plane, the male ball restraint cylinder and the male ball inner hole quenching oil flow cylinder. The material is low-carbon steel, which is not easy to deform during the oil quenching process. The appearance structure is mainly used to restrain the easily deformable position of the male ball (thin wall and open end position), and the reserve of the restraint tooling and the restraint benchmark is considered according to the inner and outer diameters and thickness of the restraint tooling. At the same time, the tooling must not affect the quenching and cooling transformation of the product to prevent the product from having insufficient hardness after the restraint heat treatment. The principle is that the tooling expands during the heating process to restrain the deformation of the ball, and the tooling is thick and the cooling is slow during the cooling process to restrain the deformation of the ball. Both the heating and cooling processes serve the purpose of restraint. According to the outer diameter of the male ball, the male ball support plane, the male ball constraint cylinder and the male ball inner hole quenching oil flow cylinder of the constraint tooling are adjusted in size, wherein the male ball support plane is consistent with the inner and outer diameters of the male ball opening end, the male ball constraint cylinder is (0.6-1.2) mm smaller than the diameter of the constraint reference plane at the male ball opening end, the constraint cylinder height is (5-10) mm, the difference between the diameter of the quenching oil flow cylinder and the outer diameter of the male ball opening end is (80-100) mm, and the total thickness of the constraint tooling is (40-60) mm.

[0045] The present invention has been tested and verified on various types of products of our company, including the range of male ball diameter Sφ(200-500)mm. The restraining tooling can play a restraining effect, the spherical surface size can meet the turning size, and the hardness of the male ball after turning meets the performance index requirements.

[0046] Obviously, those skilled in the art can make various changes and modifications to the embodiments of the present invention without departing from the spirit and scope of the embodiments of the present invention. Thus, if these modifications and variations of the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for controlling deformation of a thin-walled high-hardness sphere during heat treatment, characterized in that: The steps include: S1: The positive ball is subjected to overall carbonitriding; S2: Carburizing the male ball. The male ball is turned except for the spherical surface to remove the carburized layer outside the carburized surface of the male ball, and the inner diameter of the large end after carburizing is used as the constraint reference; S3: Constraint tooling processing, the constraint tooling shape is assembled with the cylindrical surface processed inside the big end of the male ball with a reserved gap. The thickness of the tooling and the expansion coefficient of the tooling material need to be considered, and the size of the mating surface is adjusted to ensure the purpose of the constraint; S4: Constrain the male ball before quenching, install the constraint tooling in the opening reference of the inner diameter of the large end of the male ball after carbon cutting, and constrain the position of the male ball that is easy to change; S5: Yang ball restraint heat treatment, the Yang ball restrained in S2 is subjected to high temperature heating, heat preservation and cooling. During the heating process, the tooling expands to restrain the ball deformation. During the cooling process, the tooling is thick and the cooling is slow to restrain the ball deformation. The heating and cooling processes both play a restraining role. S6: After heat treatment, remove the tooling to test the ball runout.

2. The method for controlling deformation of a thin-walled high-hardness sphere during heat treatment according to claim 1, characterized in that: The specific operation steps of the S2 tooling design are: S21: Material selection, considering the base material, multiple processing and repeated use, needs to have low hardening hardness, small quenching deformation and easy processing performance; S22: Structural selection: the newly designed tooling should be easy to install without affecting the fluidity of the quenching medium and hindering the rapid cooling and martensitic transformation of the product; S23: Selection of size. The size of the constraint tooling directly affects the constraint effect of the product. If the size is large, the amount of turning will increase after constraint, and the spherical surface penetration layer and surface hardness will be unqualified. If the size is small, it will not play a restraining role. Therefore, for spheres of different specifications, it is necessary to pre-design the effective height and effective thickness of the constraint tooling, and carry out experimental verification. According to the experimental results, determine the size of the open end of the expanded product after quenching, and compare it with the pre-designed size to correct the final size of the sphere constraint tooling.

3. The method for controlling deformation of a thin-walled high-hardness sphere during heat treatment according to claim 1, characterized in that: The easily changeable position of the S2 male ball is the large opening end of the male ball body.

4. The constraint tooling for the thin-walled high-hardness sphere heat treatment deformation control method according to any one of claims 1 or 2, characterized in that: The constraint tooling is formed by one-piece turning, and its external shape structure constrains the flexible position of the male ball. The reserved amount between the constraint tooling and the constraint datum is considered according to the inner and outer diameters and thickness of the constraint tooling. At the same time, the tooling must not affect the quenching and cooling transformation of the product to prevent insufficient hardness of the product after the constraint heat treatment.

5. The thin-walled high-hardness sphere heat treatment deformation restraint tooling according to claim 4 is characterized in that: The restraint fixture is made of low carbon steel and is not easily deformed during the oil quenching process.

6. The thin-walled high-hardness sphere heat treatment deformation restraint tooling according to claim 4 is characterized in that: The deformable position of the male ball is constrained to be the thin wall and the open end position.

7. The thin-walled high-hardness sphere heat treatment deformation restraint tooling according to claim 4 is characterized in that: The restraint fixture has a trapezoidal structure, which is composed of a male ball supporting plane, a male ball restraining cylinder and a male ball inner hole quenching oil flow cylinder.

8. The thin-walled high-hardness sphere heat treatment deformation restraint tooling according to claim 4 is characterized by: According to the outer diameter of the male ball, the male ball support plane, the male ball constraint cylinder and the male ball inner hole quenching oil flow cylinder of the constraint tooling are adjusted in size, wherein the male ball support plane is consistent with the inner and outer diameters of the male ball opening end, the male ball constraint cylinder is (0.6-1.2) mm smaller than the diameter of the constraint reference plane at the male ball opening end, the constraint cylinder height is (5-10) mm, the difference between the diameter of the quenching oil flow cylinder and the outer diameter of the male ball opening end is (80-100) mm, and the total thickness of the constraint tooling is (40-60) mm.

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