Method of hot forming a spring steel wire raceway main bearing for a CT machine

Abstract

The application discloses a hot forming method of a spring steel wire raceway main bearing for a CT machine, and comprises the following steps: step one: cutting a steel wire, winding the steel wire into a ring by using a coiling machine, machining a primary and secondary buckle at both ends, fixing and adjusting warping and roundness, and forming a steel wire ring; step two: rotating and heating the steel wire ring to austenite by using an induction heating device, and cooling to room temperature by spraying a quenching liquid; step three: tempering after quenching, and cooling to room temperature by spraying the quenching liquid again; step four: low-temperature heating for heat setting of the main bearing; and step five: raceway processing is conducted on the heat-set ring. The process controls deformation by rotating induction heating and clamping mold curvature tooling, reduces oil quenching pollution, avoids decarburization of the steel wire surface, and solves the problem of large forming deformation of the raceway main bearing.

Description

TECHNICAL FIELD

[0001] The application relates to a hot forming method of a spring steel wire raceway main bearing of a CT machine. BACKGROUND

[0002] Currently, high-end medical instruments begin to popularize the third generation CT machine, mainly adopts a steel wire raceway main bearing, has the advantages of high precision, low friction and long service life after precise machining. In order to respond to light weight and product shape diversification, Si-Cr spring steel gradually replaces Cr and Cr-V steel, and the prior art adopts oil quenched steel wire to replace cold-drawn steel wire after coiling and then separately quenches and tempering process. However, the main bearing of the CT machine is usually about 10000mm, and the heat treatment of the large part in the box type resistance furnace is difficult, and the deformation of the steel wire after oil quenching is difficult to control, surface decarburization cannot be avoided, quenching oil pollution is large, and the economic benefit is poor. SUMMARY

[0003] In view of the defects of the prior art, the application provides a hot forming method of a spring steel wire raceway main bearing of a CT machine, which reduces the environmental pollution and harm of oil quenching, avoids the decarburization of the surface of the steel wire, and effectively solves the problem of large deformation of the steel wire raceway main bearing in the forming process.

[0004] To achieve the above-mentioned purpose, the application provides a hot forming method of a spring steel wire raceway main bearing of a CT machine, comprising the following steps,

[0005] Step one: cutting the steel wire, coiling into a circular ring type through a coiling machine, machining a son and mother buckle at both ends of the steel wire, fixing forming and adjusting warping and roundness, and forming a steel wire circular ring;

[0006] Step two: rotating and heating the coiled steel wire circular ring through an induction heating device, heating to austenite, and then spraying quenching liquid to cool to room temperature;

[0007] Step three: quenching the steel wire circular ring, carrying out tempering treatment and spraying quenching liquid to cool to room temperature;

[0008] Step four: low-temperature heating the tempered steel wire circular ring to realize hot setting of the main bearing;

[0009] Step five: processing the raceway of the hot set steel wire circular ring.

[0010] As a further setting of the application, the steel wire in step one is selected as bright cold-drawn spring steel wire, the bright cold-drawn spring steel wire has a tensile strength of greater than or equal to 950MPa and a hardness of less than or equal to 35HRC.

[0011] As a further setting of the present application, the inductive heating device in step two carries out austenitizing heating, and the heating temperature is 920-960 DEG C for a steel wire with a diameter less than or equal to 9 mm, and the heating temperature is 940-960 DEG C for a steel wire with a diameter greater than 9 mm; the inductor heating device parameters are 20-60 kHz and 160-220 kW.

[0012] As a further setting of the present application, the quenching liquid medium in step two is a polymer quenching liquid with a mass fraction of 10-15%, and the polymer is one or more of polyethylene glycol, polyvinyl alcohol, polyethylene oxide or acrylic acid polymer.

[0013] As a further setting of the present application, the tempering temperature in step three is 350-500 DEG C; and the inductor heating device parameters are 140-180 kHz and 2-6 kW.

[0014] As a further setting of the present application, the low-temperature heating temperature in step four is lower than the tempering temperature setting, and the temperature difference between the low-temperature heating temperature and the tempering temperature is 30-50 DEG C.

[0015] The beneficial effects of such a setting are that, by using the inductive heating high-temperature rapid cooling method, the heat treatment defects of the surface decarburized layer are avoided, and excellent comprehensive mechanical properties are obtained; the inductive rotary heating steel wire raceway bearing and rotary clamp mold curvature tooling heat setting technology greatly avoids the difficulty of size control and deformation warping correction of the steel wire curling forming; the method optimizes the environmental pollution and potential hazards caused by the original oil quenching; and the technical problems of the processing cost of the difficulty of removing the surface decarburized layer and the difficulty of controlling the steel wire curling deformation after the original heat treatment are solved. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Fig. 1 is a schematic diagram of a spring steel wire sub-mother buckle interface in an embodiment of the present application;

[0017] Figure 2 Fig. 2 is a schematic diagram of the cross-sectional structure of AA in an embodiment of the present application; Figure 1

[0018] Figure 3 Fig. 3 is a schematic diagram of inductive rotary heating of a spring steel wire in an embodiment of the present application;

[0019] Figure 4 Fig. 4 is a schematic diagram of rotary clamp mold curvature tooling heat setting in an embodiment of the present application;

[0020] Figure 5 Fig. 5 is a schematic diagram of the cross-sectional structure of a heat setting processing position in an embodiment of the present application;

[0021] Figure 6 Fig. 6 is a microstructure diagram of a spring steel wire main bearing after processing and forming in an embodiment of the present application.​ DETAILED DESCRIPTION

[0022] The embodiment of the hot forming method of the spring steel wire raceway main bearing for CT machine of the present application is shown as follows: Figures 1 to 5 Step one: cut the bright cold-drawn spring steel wire, and roll it into a circular ring through a coiling machine, and machine a male and female buckle at both ends of the steel wire to fix the shape and adjust the warping and roundness;

[0023] Step two: rotate and heat the coiled spring steel wire circular ring to austenite through an induction heating device, and then spray quenching liquid to cool it to room temperature;

[0024] Step three: adjust the induction quenching parameters to perform induction tempering treatment on the quenched steel wire circular ring, and spray quenching liquid to cool it to room temperature;

[0025] Step four: heat the steel wire circular ring after induction tempering at a low temperature, and use the residual heat to perform hot setting of the main bearing;

[0026] Step five: perform raceway processing on the steel wire circular ring after hot setting to the precision of the main bearing;

[0027] The bright cold-drawn spring steel wire in step one is made of 54SiCr6, has a tensile strength of 1120 MPa, a hardness of 33 HRC, and is coiled into a circular ring with a diameter of 900 mm. In step two, the heating temperature for austenitization by induction heating is 920-960℃ for steel wires with a diameter of not more than 9 mm, and is 940-960℃ for steel wires with a diameter of more than 9 mm. In this case, the steel wire has a diameter of 7 mm, the heating temperature is 950℃, the holding time is 2 min, and the induction heater parameters are 35 kHz and 200 kW. In step two, the quenching liquid medium is a polymer quenching liquid with a mass fraction of 10-15%. In step three, the tempering temperature is 450℃, the holding time is 30 s, the induction heater parameters are 160 kHz and 4 kW. In step four, the low-temperature heating temperature is 50℃ lower than the induction tempering temperature, the heating temperature is 400℃, the hot setting adopts a specified rotary clamp mold curvature quenching, the warping and roundness are controlled, and the stress is eliminated at the same time. In step five, the steel wire raceway main bearing after processing and forming is coated with rust-proof oil for protection.

[0028] After the CT machine steel wire raceway main bearing is formed according to the above operation steps, the results are detected. The roundness difference of the steel wire raceway bearing is less than 0.006 mm, the hardness is 55.3 HRC, the tensile strength is 1982 MPa, the reduction of area is 49%, the microstructure is fine troostite, as shown in Figure 6 , and there is no decarburized layer on the surface.

[0029] The above examples are only preferred specific examples of the present application, and all the common changes and replacements made by those skilled in the art within the technical scheme of the present application are included in the protection scope of the present application.

Claims

1. A hot forming method for a spring steel wire raceway main bearing for a CT machine, characterized by: The following steps are included: Step 1: Cut the steel wire and curl it into a ring shape through a coiling machine. Machine snap fasteners on both ends of the steel wire, fix the shape and adjust the warping and roundness to form a steel wire ring. The steel wire is made of bright cold-drawn spring steel wire with a tensile strength of ≥950MPa and a hardness of ≤35HRC. Step 2: The coiled steel wire ring is heated by rotation through an induction heating device. After being heated to austenite, the quenching liquid is sprayed and cooled to room temperature. When the induction heating device is austenitizing, the heating temperature for steel wire with a diameter less than or equal to 9mm is 920~960℃; for steel wire with a diameter greater than 9mm, the heating temperature is 940~960℃; the parameters of the induction heating device are 20~60kHz, 160~220kW; Step 3: After quenching, the steel wire ring is tempered and sprayed with quenching liquid to cool to room temperature; Step 4: The tempered steel wire ring is subjected to low-temperature heating to achieve heat setting processing of the main bearing, wherein the low-temperature heating temperature is lower than the tempering temperature setting; Step 5: Perform raceway processing on the heat-set steel wire ring.

2. The hot forming method of the spring steel wire raceway main bearing for CT machine according to claim 1, characterized in that: The quenching liquid medium in step 2 is a polymer quenching liquid with a mass fraction of 10-15%, and the polymer is one or more of polyethylene glycol, polyvinyl alcohol, polyethylene oxide or acrylic acid polymer.

3. The hot forming method of the spring steel wire raceway main bearing for CT machine according to claim 1, characterized in that: The tempering temperature in step 3 is 350-500° C.; the parameters of the inductor heating device are 140-180 kHz and 2-6 kW.

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