Thin-wall hemispherical structure part and heat treatment method for effectively controlling deformation

Abstract

The invention discloses a thin-wall hemispherical structure part and a heat treatment method for effectively controlling deformation, and relates to the field of deformation control in the quenching process, and the heat treatment method comprises the steps that the thin-wall hemispherical structure part is heated to 906 DEG C in heating equipment, the heat preservation time is 30-35 min, and the heated thin-wall hemispherical structure part is obtained; and the heated thin-wall hemisphere structure part is taken out of the heating equipment, so that the heated thin-wall hemisphere structure part keeps the hemisphere opening face to be perpendicular to the water surface to enter the water vertically, and stays in the water for 20-26 seconds. And the qualified rate of parts is greatly improved, the production period is shortened, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to a heat treatment method for controlling deformation during a quenching process, in particular to a heat treatment technology for the problem of excessive deformation of a thin-walled hemispherical structure after quenching. Background Art

[0002] The titanium alloy hemisphere is a thin-walled complex structural part that needs to be quenched to improve its strength. However, in actual production, the quenching process of the titanium alloy hemisphere often causes the inner hole and end face to deform by 3 to 4 mm due to too fast stress release, which exceeds the standard deformation requirement of no more than 0.25 mm. It is difficult to correct the deformation, which makes it impossible to fine-process qualified products in the future, resulting in scrapping, which greatly increases production costs. The excessive deformation of the titanium alloy hemisphere after quenching has become a major obstacle to product quality and pass rate. Summary of the invention

[0003] The technical problem solved by the present application is: to overcome the deficiencies of the prior art, to provide a heat treatment method for effectively controlling the deformation of thin-walled hemispherical structural parts, to significantly improve the qualified product rate of parts, to shorten the production cycle, and to reduce production costs.

[0004] In order to ensure the product development and production cycle and reduce production costs, a large number of process technology research and development have been carried out. By refining and quantifying the heat treatment quenching process, the problem of excessive deformation of the inner hole and end surface caused by stress release during the water cooling process of the titanium alloy hemisphere has been solved. It has been successfully applied to the quenching process of multiple batches of titanium alloy hemisphere parts. The deformation meets the requirements of the process documents and design documents, ensuring the production progress of aerospace products, and can be promoted and applied to the quenching heat treatment process of related thin-walled complex structure parts.

[0005] The technical solutions provided by this application are as follows:

[0006] A heat treatment method for effectively controlling the deformation of thin-walled hemispherical structural parts, comprising:

[0007] The thin-walled hemispherical structure parts are heated to 906°C in a heating device for 30 to 35 minutes to obtain the heated thin-walled hemispherical structure parts;

[0008] The heated thin-walled hemispherical structure part is taken out from the heating device, and the heated thin-walled hemispherical structure part is vertically put into the water with the hemispherical opening surface perpendicular to the water surface, and stays in the water for 20 to 26 seconds.

[0009] Optionally, after the heating after entering the water, the cooling rate of the thin-walled hemispherical structure part in the water is 220°C to 240°C / s.

[0010] Optionally, removing the heated thin-walled hemispherical structure part from the heating device comprises: using a straight holding pliers with optional jaws to remove the heated thin-walled hemispherical structure part from the heating device.

[0011] The method allows the heated thin-walled hemispherical structure part to enter the water vertically with the hemispherical opening surface perpendicular to the water surface and stay in the water for 20 to 26 seconds, including: driving the heated thin-walled hemispherical structure part to enter the water of the water tank vertically by clamping and keeping the hemispherical opening surface perpendicular to the water surface, and maintaining the clamping state so that the heated thin-walled hemispherical structure part does not touch the bottom of the water tank and stays for 20 to 26 seconds.

[0012] Optionally, the heating equipment is an air resistance furnace with a flat and smooth furnace bottom, and thin-walled hemispherical structure parts are placed in the effective heating zone of the air resistance furnace, and the parts are placed at intervals greater than 28 mm.

[0013] Optionally, the water tank is continuously filled with cold water.

[0014] Optionally, the cooling water inlet of the water trough is located at an upper position of the water trough, an outlet is arranged at a bottom position of the water trough, and the inlet and the outlet are located at opposite sides of the water trough.

[0015] Optionally, when the thin-walled hemispherical structure component stays in water, the opening of the thin-walled hemispherical structure component faces the direction of the cooling water inlet.

[0016] Optionally, after the heated thin-walled hemispherical structure parts stay in water for 20 to 26 seconds, they are slowly placed at the bottom of the water tank, and the parts are placed at a uniform distance at the bottom of the water tank without accumulation.

[0017] A thin-walled hemispherical structural part is obtained by any of the above-mentioned heat treatment methods for effectively controlling the deformation of the thin-walled hemispherical structural part, and the flatness of the obtained thin-walled hemispherical structural part is ≤0.5mm and the ovality is ≤0.3mm.

[0018] The heat treatment method of this patent is a quenching method. Quenching includes heating and water entering steps. The process of heating in the furnace, taking out of the furnace, and cooling the medium is refined and quantified to achieve precise control of the quenching deformation of the titanium alloy hemisphere. The deformation of the inner hole and end face of the product after quenching is greatly reduced, so that the deformation of the titanium alloy hemisphere after quenching can be controlled within 0.25mm, meeting the product performance requirements, achieving the consistency and stability of the titanium alloy hemisphere product after quenching, and reducing the product scrap rate. It is easy to operate and has significant effects, and can be promoted and applied to the quenching heat treatment process of titanium alloy hemisphere parts.

[0019] In summary, the present application includes at least the following beneficial technical effects: a method for controlling deformation of thin-walled hemispherical structure parts during heat treatment is invented. The problem of deformation of thin-walled hemispherical parts after heat treatment and quenching in the field of heat treatment is solved, the qualified rate of parts is greatly improved, and the manufacturing cost of heat treatment and quenching of high-value thin-walled hemispherical structures is saved. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments disclosed in the present invention are described in further detail.

[0021] Example 1

[0022] Through a large number of tests and verifications, including refinement and quantification of the quenching process from the furnace loading, furnace unloading, cooling process, etc., the precise control of the quenching deformation of the titanium alloy hemisphere is achieved. The specific measures are as follows:

[0023] (1) Equipment selection: Heat treatment equipment must use an air resistance furnace with a flat and smooth bottom. Avoid quality problems such as bumps and scratches on the product during loading and unloading due to uneven furnace bottom surface. At the same time, the holding temperature of titanium alloy hemisphere quenching is 906℃, and the holding time is 30min. The strength of the parts decreases at high temperatures. If the furnace bottom surface is uneven, it will directly lead to increased resistance during the quenching process of the parts, thereby increasing the deformation of the parts.

[0024] (2) Parts placement: The placement of parts during heat treatment is also very important. Combined with the characteristics of heat treatment equipment, all parts must be placed in the effective heating zone of the air resistance furnace. At the same time, the flash interval of the parts should be greater than 28mm to prevent the parts from being squeezed and deformed due to excessive furnace loading.

[0025] (3) Parts out of the furnace: When quenching the titanium alloy hemisphere, the tooling needs to select a clamp with straight jaws to avoid quality problems such as bumps, deformation, etc. caused by loose clamping and falling off. At the same time, in order to make the product evenly contact the cooling medium to ensure the cooling speed of quenching, the cooling rate in this patent is 220℃~240℃ / s. The quenching water tank should be placed in a position close to the heat treatment furnace first. During the quenching process, uninterrupted cold water injection should be ensured to ensure uniform cooling of the parts. At the same time, in order to minimize the external force on the parts during quenching, choose the direction with less resistance to enter the water (that is, vertically enter the water along the opening direction of the titanium alloy hemisphere). After entering the water, the parts cannot touch the bottom of the water tank. After staying in the water for 20 to 26 seconds, slowly place them at the bottom of the water tank. When cooling in the water tank, the parts should be placed evenly and not piled up to avoid affecting the quenching process of the next titanium alloy product. After following this operation method, the deformation of the parts was measured. The flatness of the thin-walled hemisphere was 0.3mm and the ellipticity was 0.2mm, which met the requirements.

[0026] Comparative Example 1

[0027] The heating process is the same as in Example 1.

[0028] During the quenching process, only the traditional static water plus stirring method is used as a cooling device. At this time, the cooling rate is 170℃~180℃ / s. At the same time, in order to minimize the external force on the parts during quenching, the parts are placed vertically into the water along the opening direction of the titanium alloy hemisphere. The parts cannot touch the bottom of the water tank after entering the water. They stay in the water for 20 to 26 seconds and then slowly placed at the bottom of the water tank. When the parts are cooled in the water tank, they should be placed evenly and not piled up to avoid affecting the quenching process of the next titanium alloy product. After measuring the deformation of the parts according to this operation method, the flatness of the thin-walled hemisphere is 0.7mm and the ellipticity is 0.9mm, which does not meet the requirements.

[0029] This is because, when the metal is heat treated, the structure of the metal changes from hot to cold, and the specific volume change of each part of the structure is different. In this case, the product will also deform, which is manifested as contraction or expansion. The force generated in this process is the tissue stress. When the yield strength is exceeded, the parts will deform. When the product is heat treated, temperature differences will occur due to various factors. The phase change part starts from the surface. The surface that has undergone phase change will affect the part that has not undergone phase change, and the center part that has not undergone phase change will undergo plastic deformation. During quenching and cooling, the supercooled austenite will undergo phase change. If the cooling rate of the thin-walled hemisphere is controlled so that the time difference between the inner and outer surfaces of the hemisphere undergoes the transformation of the structure is smaller, the deformation caused by the phase change of the structure will be smaller, thereby better controlling the deformation.

[0030] Comparative Example 2

[0031] The heating process is the same as in Example 1.

[0032] During the quenching process, uninterrupted cold water injection should be ensured. At this time, the cooling rate can reach 220℃~240℃ / s to ensure that the parts are cooled quickly and evenly. The water entry angle along the opening direction of the titanium alloy hemisphere is selected to be 45°. The parts cannot touch the bottom of the water tank after entering the water. They should stay in the water for 20 to 26 seconds and then be slowly placed on the bottom of the water tank. When the parts are cooled in the water tank, they should be placed evenly and without accumulation to avoid affecting the quenching process of the next titanium alloy product. After measuring the deformation of the parts according to this operation method, the flatness of the thin-walled hemisphere is 0.6mm and the ellipticity is 0.7mm, which does not meet the requirements.

[0033] This is because, although the cooling speed of the parts is guaranteed to be sufficient, due to the water entry angle of 45° during quenching cooling, there is a long time difference in the phase change time between the inside and outside of the hemisphere. When phase change occurs on one side of the opposite sides of the hemisphere and not on the other side, the deformation difference between the two sides cannot be offset, resulting in a larger deformation.

[0034] The contents not described in detail in this application specification belong to the common knowledge of those skilled in the art.

[0035] The present application is described in detail above in conjunction with specific implementation methods and exemplary examples, but these descriptions cannot be understood as limiting the present application. Those skilled in the art understand that, without departing from the spirit and scope of the present application, a variety of equivalent replacements, modifications or improvements can be made to the technical solution of the present application and its implementation methods, all of which fall within the scope of the present application. The scope of protection of the present application shall be subject to the attached claims.

Claims

1. A heat treatment method for effectively controlling the deformation of thin-walled hemispherical structural parts, characterized in that: include: The thin-walled hemispherical structure parts are heated to 906°C in a heating device for 30 to 35 minutes to obtain the heated thin-walled hemispherical structure parts; The heated thin-walled hemispherical structure part is taken out from the heating device, and the heated thin-walled hemispherical structure part is vertically put into the water with the hemispherical opening surface perpendicular to the water surface, and stays in the water for 20 to 26 seconds.

2. A heat treatment method for effectively controlling the deformation of thin-walled hemispherical structural parts according to claim 1, characterized in that: After being heated in water, the cooling rate of the thin-walled hemispherical structure parts in water is 220°C to 240°C / s.

3. A heat treatment method for effectively controlling the deformation of thin-walled hemispherical structural parts according to claim 1, characterized in that: The method of taking out the heated thin-walled hemispherical structure part from the heating device comprises: taking out the heated thin-walled hemispherical structure part from the heating device by using a holding pliers with straight jaws.

4. A heat treatment method for effectively controlling the deformation of thin-walled hemispherical structural parts according to claim 3, characterized in that: The method allows the heated thin-walled hemispherical structure part to enter the water vertically with the hemispherical opening surface perpendicular to the water surface and stay in the water for 20 to 26 seconds, including: driving the heated thin-walled hemispherical structure part to enter the water of the water tank vertically by clamping and keeping the hemispherical opening surface perpendicular to the water surface, and maintaining the clamping state so that the heated thin-walled hemispherical structure part does not touch the bottom of the water tank and stays for 20 to 26 seconds.

5. A heat treatment method for effectively controlling the deformation of thin-walled hemispherical structural parts according to claim 1, characterized in that: The heating equipment is an air resistance furnace with a flat and smooth furnace bottom. Thin-walled hemispherical structure parts are placed in the effective heating area of ​​the air resistance furnace, and the parts are placed at a spacing greater than 28 mm.

6. A heat treatment method for effectively controlling the deformation of thin-walled hemispherical structural parts according to claim 4, characterized in that: The water tank is continuously supplied with cold water.

7. A heat treatment method for effectively controlling the deformation of thin-walled hemispherical structural parts according to claim 6, characterized in that: The cooling water inlet of the water tank is located at the upper position of the water tank, the outlet is arranged at the bottom position of the water tank, and the inlet and the outlet are located at the opposite sides of the water tank.

8. A heat treatment method for effectively controlling the deformation of thin-walled hemispherical structural parts according to claim 4, characterized in that: After the heated thin-walled hemispherical structure parts stay in the water for 20 to 26 seconds, they are slowly placed at the bottom of the water tank. The parts are placed at a uniform distance at the bottom of the water tank without accumulation.

9. A thin-walled hemispherical structural part, characterized in that: The thin-walled hemispherical structure part is obtained by a heat treatment method for effectively controlling the deformation of the thin-walled hemispherical structure part according to any one of claims 1 to 8, wherein the flatness of the obtained thin-walled hemispherical structure part is ≤0.5mm and the ovality is ≤0.3mm.