Heat treatment method for guaranteeing quality of contact position of hot coiling spring and mandrel

Abstract

The invention discloses a heat treatment method for ensuring the quality of a contact part of a hot coiling spring and a mandrel, a spring bar is coiled on the mandrel after being heated to obtain the spring, and the heat treatment method is characterized in that the mandrel is preheated to 300-400 DEG C before the spring is coiled, the spring bar is heated to 950-1000 DEG C, then the spring bar is coiled on the mandrel, and meanwhile, the mandrel is subjected to air cooling; the temperature of the mandrel is kept at 300-400 DEG C; after improvement according to the technology, the structure of the contact position of the spring and the mandrel is obviously improved, the structure is finer and more uniform, and obvious ferrite and pearlite aggregation is avoided. The Rockwell hardness difference between the hardness of the spring inner ring contact mandrel part and the spring 1 / 2 radius part and the core part is not larger than 2, and the quality requirement of the spring is met.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment of hot coil springs, in particular to a heat treatment method for ensuring the quality of the contact between a hot coil spring and a core shaft. Background Art

[0002] Cylindrical helical springs are usually wound around a mandrel. Depending on the size of the spring, the winding process usually takes 30 to 60 seconds, and the contact time between the spring bar and the mandrel is basically the same. To ensure that the mandrel will not deform during continuous production, the mandrel is usually a hollow internally cooled mandrel, and the mandrel is cooled by circulating water. Therefore, the temperature of the mandrel is basically maintained at around 100°C during continuous production. The cross-sectional diagram of the contact between the spring bar and the mandrel during the coiling process is shown in the figure below. Figure 1 As shown. The spring bar and the mandrel come into contact and heat exchange occurs. After the spring is rolled, the inner ring and the mandrel contact area ( Figure 1 The temperature of the A zone in the spring (hereinafter referred to as the "contact zone") is reduced to below 700℃, resulting in the quenching temperature of the spring contact zone being unable to meet the process requirements of 830~870℃. Figure 2 The metallographic structure and hardness of the spring surface area B (area B, the depth of area B is about 3mm) were tested. The contact area contains a small amount of ferrite and pearlite, and the Rockwell hardness of the contact area is 3~5 lower than that of the spring core and 1 / 2 radius (area C on the spring surface). Therefore, the metallographic structure and hardness of the contact area do not meet the technical requirements of the spring (see the metallographic structure diagram Figure 3 ), resulting in unqualified spring product quality. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a heat treatment method for ensuring the quality of the contact between the hot-rolled spring and the mandrel, aiming to solve the problem that the contact area between the spring bar and the mandrel does not meet the structure and hardness requirements of the spring.

[0004] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a heat treatment method for ensuring the quality of the contact between the hot-rolled spring and the mandrel, the spring bar is heated and then rolled on the mandrel to obtain a spring, the mandrel is preheated to 300-400°C before the spring is rolled, the spring bar is heated to 950-1000°C, and then the spring bar is rolled on the mandrel, and the mandrel is air-cooled at the same time, so that the mandrel is kept at 300-400°C.

[0005] Increase the speed of spring bar rolling, so that the time the spring bar is rolled on the mandrel is shortened by 5-10%.

[0006] After the spring is rolled, remove the spring from the mandrel and leave it for 8 to 10 seconds before quenching.

[0007] The core shaft is made of heat-resistant alloy steel and is integrally quenched.

[0008] Before spring rolling, preheat the mandrel to 330-370℃, heat the spring bar to 970~1000℃, and then roll the spring bar on the mandrel. At the same time, air-cool the mandrel to keep the mandrel at 330-370℃ and increase the speed of spring bar rolling, so that the time of spring bar rolling on the mandrel is shortened by 6-8%. After the spring is rolled, take the spring out of the mandrel, stay for 9s before quenching, and then quench.

[0009] The beneficial effects of the present invention are as follows: the mandrel of the present invention is made of heat-resistant alloy steel and is cooled by air, so that the contact between the inner ring of the spring and the mandrel is kept at a high temperature during the rolling process; the mandrel is preheated to reduce the temperature drop of the inner ring of the spring; the spring is stopped for a short time after rolling and before quenching to allow the heat of the core to diffuse outward through the surface of the inner ring of the spring. After the technical improvement of the present invention, the structure of the contact between the spring and the mandrel is significantly improved (see Figure 4 ), the structure is more delicate and uniform, and there is no obvious ferrite and pearlite aggregation. The hardness of the inner ring of the spring in contact with the mandrel is not more than 2 points higher than the Rockwell hardness at the 1 / 2 radius of the spring and the core, which meets the quality requirements of the spring. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will be further described below in conjunction with the accompanying drawings: Figure 1 It is a schematic diagram of the contact between the mandrel and the spring bar; Figure 2 This is an enlarged schematic diagram of the contact area between the spring bar and the mandrel; Figure 3 This is the metallographic structure diagram of the contact area of ​​the prior art; Figure 4 This is the metallographic structure diagram of the surface layer of the inner ring of the spring after improvement according to the present invention. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Example

[0012] A heat treatment method for ensuring the quality of the contact between a hot-rolled spring and a mandrel, wherein a spring bar is heated and then rolled on a mandrel to obtain a spring, the mandrel is preheated to 300-400°C before the spring is rolled, the spring bar is heated to 950-1000°C, and then the spring bar is rolled on the mandrel, while the mandrel is air-cooled to keep the mandrel at 300-400°C.

[0013] The core shaft is kept at 300-400℃, which can reduce the contact heat dissipation of the inner ring of the spring, and the spring bar is heated to 950~1000℃, which increases the residual temperature of the rolled spring. Increase the speed of spring bar rolling, shorten the time the spring bar is rolled on the mandrel by 5-10%, and reduce the temperature drop of the inner ring of the spring.

[0014] After the spring is rolled, take it out from the mandrel, leave it for 8-10 seconds before quenching, and then quench it, so that the heat in the core of the spring bar can dissipate and re-penetrate and heat the surface of the inner ring of the spring bar, so that the contact area can reach the quenching temperature requirement again.

[0015] The core shaft is made of heat-resistant alloy steel and is integrally quenched to improve the strength of the core shaft. Example

[0016] The specific process is as follows: before spring rolling, the mandrel is preheated to 330-370℃, the spring bar is heated to 970~1000℃, and then the spring bar is rolled on the mandrel. At the same time, the mandrel is air-cooled to keep the mandrel at 330-370℃ and increase the speed of spring bar rolling, so that the time of spring bar rolling on the mandrel is shortened by 6-8%. After the spring is rolled, the spring is taken out from the mandrel, and stays for 9s before quenching, and then quenched. Example

[0017] The specific process is as follows: before spring rolling, the mandrel is preheated to 350℃, the spring bar is heated to 980℃, and then the spring bar is rolled on the mandrel. At the same time, the mandrel is air-cooled to keep the mandrel at 350℃ and increase the speed of spring bar rolling, so that the time of spring bar rolling on the mandrel is shortened by 7%. After the spring is rolled, the spring is taken out from the mandrel and stays for 9s before quenching, so that the surface temperature of the inner ring of the spring is raised to 850℃, and then quenched.

[0018] In addition to the above-mentioned preferred embodiments, the present invention also has other implementation modes. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection requested by the present invention.

Claims

1. A heat treatment method for ensuring the quality of the contact between a hot-rolled spring and a mandrel, wherein a spring bar is heated and rolled on a mandrel to obtain a spring, characterized in that: Before spring coiling, the mandrel is preheated to 300-400℃, the spring bar is heated to 950~1000℃, and then the spring bar is coiled on the mandrel. At the same time, the mandrel is air-cooled to keep the mandrel at 300-400℃.

2. A heat treatment method for ensuring the quality of the contact between the hot coil spring and the mandrel according to claim 1, characterized in that: Increase the speed of spring bar rolling, so that the time the spring bar is rolled on the mandrel is shortened by 5-10%.

3. A heat treatment method for ensuring the quality of the contact between the hot coil spring and the mandrel according to claim 1, characterized in that: After the spring is rolled, remove the spring from the mandrel and leave it for 8 to 10 seconds before quenching.

4. A heat treatment method for ensuring the quality of the contact between the hot coil spring and the mandrel according to claim 1, characterized in that: The core shaft is made of heat-resistant alloy steel and is integrally quenched.

5. A heat treatment method for ensuring the quality of the contact between the hot coil spring and the mandrel according to any one of claims 1 to 4, characterized in that: Before spring rolling, preheat the mandrel to 330-370℃, heat the spring bar to 970~1000℃, and then roll the spring bar on the mandrel. At the same time, air-cool the mandrel to keep the mandrel at 330-370℃ and increase the speed of spring bar rolling, so that the time of spring bar rolling on the mandrel is shortened by 6-8%. After the spring is rolled, take the spring out of the mandrel, stay for 9s before quenching, and then quench.

Images