Heat treatment process method for thin-wall slender blind hole part

Abstract

The invention relates to a heat treatment process method for a thin-wall slender blind hole part, which comprises the following steps: firstly, designing an auxiliary hollow exhaust quenching device comprising a connecting cover and a hollow exhaust pipe, connecting the connecting cover with the open end of the thin-wall slender blind hole part through threads, and then connecting one end of the exhaust pipe with the center of the connecting cover through threads; secondly, after quenching, heating and heat preservation are conducted on the part, the part is discharged out of the furnace and air-cooled for 40-80 S; and then the part is vertically immersed in the oil until a part of the hollow exhaust pipe of the auxiliary hollow exhaust quenching device is immersed in the cooling medium, immersion is stopped, then the part is cooled in the medium for 40-50 min, and the part does not go out of the liquid level and is cooled in the medium in an up-and-down moving mode. The invention solves the safety problems of expansion and explosion of heating gas in closed heat treatment of the open end of the thin-wall slender blind hole type part, or high-temperature gasification and injection of an open quenching medium or oil cooling ignition and the like, and solves the quality problems of large deformation and the like caused by non-uniform cooling when a cooling medium does not flow into the blind hole.

Description

Technical Field

[0001] This invention belongs to the field of heat treatment of metallic materials, specifically relating to a heat treatment process for thin-walled, slender blind hole parts, and particularly to a quenching heat treatment process for finished thin-walled, slender blind hole parts, wherein the hardness, mechanical properties and dimensions after the final heat treatment meet the technical requirements of the parts. Background Technology

[0002] Thin-walled, slender blind hole parts are mostly used in the fields of weaponry, ships, pressure vessels, and automobile transportation, such as stress cavities and pressure vessels. They have strict requirements on the size, mechanical properties and other parameters of the parts.

[0003] The following problems exist in the heat treatment of thin-walled, slender blind hole parts: long length and thin wall thickness lead to large deformation during quenching; high strength and hardness after quenching, but the thin wall thickness makes deformation correction difficult; narrow dimensional tolerance range, easy for deformation to exceed tolerances, low pass rate, and high cost; and significant safety risks such as high-temperature vaporization jetting and ignition during the quenching cooling process. To solve the safety and quality problems of heat treatment for thin-walled, slender blind hole parts, improve the pass rate, reduce manufacturing costs, and meet the technical requirements of the parts, this study investigates heat treatment processes for such parts. Summary of the Invention

[0004] This invention provides a heat treatment process for thin-walled, slender blind hole parts, solving safety issues such as explosions due to gas expansion during heat treatment with closed openings, high-temperature vaporization and jetting of the quenching medium, or ignition due to oil cooling, as well as quality issues such as large deformation caused by uneven cooling due to different flow times of the cooling medium into the blind hole. This method achieves safe, uniform cooling, and minimal deformation in the quenching heat treatment of thin-walled, slender blind hole parts, ensuring that the hardness, mechanical properties, and dimensions meet the technical requirements of the parts after heat treatment.

[0005] To address the above technical problems, this invention provides a heat treatment process for thin-walled, elongated blind hole parts, characterized by the following steps:

[0006] First, design an auxiliary hollow exhaust quenching device, including a connecting cover 1 and a hollow exhaust pipe 2. Connect the connecting cover 1 to the open end of the thin-walled, slender blind hole part by thread, and then connect one end of the exhaust pipe 2 to the center of the connecting cover by thread.

[0007] Next, after the parts are quenched and heated to a certain temperature, they are air-cooled for 40 to 80 seconds after being taken out of the furnace.

[0008] Then, the parts are vertically immersed in the oil until a portion of the hollow exhaust pipe of the auxiliary hollow exhaust quenching device is immersed in the cooling medium. Immersion is then stopped, and the parts are cooled in the medium for another 40 to 50 minutes, with the parts moving up and down in the medium to cool without leaving the liquid surface.

[0009] Beneficial effects: This invention solves the safety problems of gas expansion and explosion during heat treatment of thin-walled, slender, blind-hole parts with closed openings, or high-temperature vaporization and spraying of quenching medium or oil cooling ignition, as well as the quality problems of large deformation caused by uneven cooling due to different flow of cooling medium into the blind hole. It realizes the quenching heat treatment of finished thin-walled, slender, blind-hole parts, achieving process safety, uniform cooling, and minimal or no distortion, and meeting the technical requirements of the parts in terms of hardness, mechanical properties, and dimensions after heat treatment.

[0010] By designing a dedicated auxiliary hollow exhaust quenching heat treatment fixture and its semi-immersion quenching process, a safe and minimally deformable heat treatment process for thin-walled, slender blind hole parts was achieved.

[0011] To address the aforementioned auxiliary hollow exhaust quenching heat treatment process device for thin-walled, slender blind hole parts, a heat treatment process method for these parts is proposed. This method enables the finished thin-walled, slender blind hole parts to undergo quenching heat treatment, achieving process safety, uniform cooling, minimal or no deformation, and ensuring that the hardness, mechanical properties, and dimensions of the heat-treated parts meet the technical requirements. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a thin-walled, slender blind hole component.

[0013] Figure 2 Schematic diagram of the auxiliary hollow exhaust quenching device;

[0014] Figure 3 This is a schematic diagram showing the location of the quenching process for blind hole parts. Detailed Implementation

[0015] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below.

[0016] The present invention proposes an auxiliary hollow exhaust quenching device for the open end of a thin-walled, slender blind hole part, comprising a connecting cover 1, a hollow exhaust pipe 2, and a torsion bar 3. Under the force of the torsion bar 3, the open end of the blind hole part is connected to the connecting cover 1 by a thread, and then one end of the hollow exhaust pipe 2 is connected to the through hole in the center of the connecting cover 1 by a thread.

[0017] The process of quenching by partially immersing a hollow exhaust pipe in the cooling medium is adopted to achieve heat treatment (quenching + low temperature tempering) of thin-walled, slender blind hole finished parts, so as to achieve uniform quenching and cooling, small deformation, and hardness, mechanical properties and dimensions that meet the technical requirements of the parts.

[0018] A heat treatment process for thin-walled, elongated blind hole parts, the specific process of which is as follows:

[0019] (1) Select a pit-type electric furnace (furnace temperature uniformity ≤ ±10℃) for heat treatment of parts.

[0020] (2) Design and manufacture an auxiliary hollow exhaust quenching device that connects to the open end of blind hole parts (see details). Figure 1 The assembly includes a connecting cover 1, a hollow exhaust pipe 2, and a torque bar 3. The connecting cover 1 mainly serves to connect and seal the thin-walled, slender, blind hole part. The hollow exhaust pipe 2 mainly discharges the expanding gas during the heat treatment heating process and prevents the quenching medium from flowing into the blind hole of the part during quenching. The torque bar 3 is a tool used to tighten the threaded connection between the connecting cover and the blind hole part, ensuring a reliable seal between the connecting cover and the thin-walled, slender, blind hole part.

[0021] (3) Assemble and connect the auxiliary hollow exhaust quenching device with the blind hole part. Under the force of the torsion bar 3, connect the open end of the blind hole part to the connecting cover 1 by thread, and then connect one end of the exhaust pipe 2 to the center of the connecting cover by thread.

[0022] (4) When mounting the heat treatment device, the open exhaust pipe end of the blind hole part of the auxiliary hollow exhaust quenching device should be facing upward and vertically fixed to ensure that it is firm and reliable.

[0023] (5) During heat treatment, charcoal is added to the furnace to slow down oxidation and decarburization, ensuring that the oxygen layer depth on one side is ≤0.1mm.

[0024] (6) Quenching heating temperature: 880±10℃, holding time: 30min~50min.

[0025] (7) After heating and holding the blind hole parts (including the auxiliary hollow exhaust quenching device) at a certain temperature, air cool them for 40-80 seconds after removing them from the furnace. Then, vertically immerse the parts in oil until half of the hollow exhaust pipe of the device (about 300mm) is submerged. Stop immersing them and then cooling them (initially at an oil temperature of 30℃-80℃) for 40-50 minutes, ensuring the parts do not leave the oil surface but move up and down within the oil. See the quenching process... Figure 3 .

[0026] (8) Tempering temperature: 210℃~240℃, holding time: 60min~90min, air cooling or water cooling after removal from the furnace.

[0027] (9) Sandblasting of parts to remove oxide scale.

[0028] (10) Hardness, mechanical properties testing, and dimensional inspection.

[0029] Example:

[0030] A thin-walled, slender blind hole part (structural diagram) Figure 2Material: 35CrMnSiA, Length: 1840mm, Maximum outer diameter: φ356±0.5, Minimum wall thickness: 13mm; Overall heat treatment tensile strength Rm≥1620MPa, room temperature impact energy AKV≥36J, hardness 45HRC~55HRC; Finished parts must have uniform wall thickness (no wall thickness difference).

[0031] (1) Select a pit-type electric furnace (furnace temperature uniformity ≤ ±10℃) for heat treatment of parts.

[0032] (2) Design and manufacture an auxiliary hollow exhaust quenching device that connects to the open end of blind hole parts (see details). Figure 1 ), including connecting cover 1, hollow exhaust pipe 2, and torsion bar 3.

[0033] (3) Assemble and connect the auxiliary hollow exhaust quenching device with the blind hole part. Under the force of the torsion bar 3, connect the open end of the blind hole part to the connecting cover 1 by thread, and then connect one end of the exhaust pipe 2 to the center of the connecting cover by thread.

[0034] (4) When mounting the heat treatment device, the open exhaust pipe end of the blind hole part of the auxiliary hollow exhaust quenching device should be facing upward and vertically fixed to ensure that it is firm and reliable.

[0035] (5) During heat treatment, charcoal is added to the furnace to slow down oxidation and decarburization, ensuring that the oxygen layer depth on one side is ≤0.1mm.

[0036] (6) Quenching heating temperature: 880℃, holding time: 40min.

[0037] (7) After removing the heated blind hole parts (including the auxiliary hollow exhaust quenching device) from the furnace, air cool them for 60 seconds. Then, vertically immerse the parts in oil until they reach halfway through the hollow exhaust pipe of the device (approximately 300 mm). Stop immersion and then cool them in oil (initially at 40°C) for 45 minutes, ensuring the parts do not leave the oil surface and move up and down within ±100 mm. See the quenching process below. Figure 3 .

[0038] (8) Tempering temperature: 220℃, holding time: 80min, air cooling after removal from the furnace.

[0039] (9) Sandblasting of parts to remove surface oxide scale and other contaminants.

[0040] (10) Hardness, mechanical properties testing, and dimensional inspection.

[0041] Trial production and testing results: Hardness is 50HRC~51HRC, tensile strength Rm is 1750MPa, room temperature impact energy AKV is 45J, and the mechanical property test results meet the technical requirements; dimensional test results are φ355.7mm~φ356.5mm, with uniform wall thickness (no wall thickness difference), meeting the part size requirements. The quenching heat treatment achieved safe operation, uniform cooling, and minimal deformation.

[0042] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A heat treatment process for thin-walled, slender blind hole parts, characterized in that, Includes the following steps: First, design an auxiliary hollow exhaust quenching device, including a connecting cover 1 and a hollow exhaust pipe 2. Connect the connecting cover 1 to the open end of the thin-walled, slender blind hole part by thread, and then connect one end of the exhaust pipe 2 to the center of the connecting cover by thread. Next, after the parts are quenched and heated to a certain temperature, they are air-cooled for 40 to 80 seconds after being taken out of the furnace. Then, the parts are vertically immersed in the oil until a portion of the hollow exhaust pipe of the auxiliary hollow exhaust quenching device is immersed in the cooling medium. Immersion is then stopped, and the parts are cooled in the medium for another 40 to 50 minutes, with the parts moving up and down in the medium to cool without leaving the liquid surface.

2. The heat treatment process for a thin-walled, slender blind hole part according to claim 1, characterized in that, Tighten the connecting cover to the blind hole part using the torsion bar 3.

3. The heat treatment process for a thin-walled, slender blind hole part according to claim 1, characterized in that, The parts are heat-treated using a pit-type electric furnace.

4. The heat treatment process for a thin-walled, slender blind hole part according to claim 1, characterized in that, Furnace temperature uniformity ≤ ±10℃.

5. The heat treatment process for a thin-walled, slender blind hole part according to claim 1, characterized in that, When mounting the heat treatment unit, the open exhaust pipe end of the blind hole part connected to the auxiliary hollow exhaust quenching device should be facing upwards and fixed vertically.

6. The heat treatment process for a thin-walled, slender blind hole part according to claim 1, characterized in that, During heat treatment, charcoal is added to the furnace to slow down oxidation and decarburization, ensuring that the oxygen layer depth on one side is ≤0.1mm.

7. The heat treatment process for a thin-walled, slender blind hole part according to claim 1, characterized in that, Quenching temperature: 880±10℃, holding time: 30min~50min.

8. The heat treatment process for a thin-walled, slender blind hole part according to claim 1, characterized in that, When cooled in a medium, the oil temperature of the medium is 30℃~80℃.

9. The heat treatment process for a thin-walled, slender blind hole part according to claim 1, characterized in that, Tempering temperature: 210℃~240℃, holding time: 60min~90min, air cooling or water cooling after removal from the furnace.

10. The heat treatment process for a thin-walled, slender blind hole part according to claim 1, characterized in that, The part is made of 35CrMnSiA material, with a maximum outer diameter of φ356±0.5mm and a minimum wall thickness of 13mm. The overall heat treatment tensile strength Rm≥1620MPa, room temperature impact energy AKV≥36J, and hardness of 45HRC~55HRC.

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