Hot forming method of spring steel wire raceway main bearing for CT (Computed Tomography) machine

Abstract

The invention discloses a hot forming method of a spring steel wire raceway main bearing for a CT machine. The hot forming method comprises the following steps that firstly, a steel wire is cut and rolled into a circular ring through a crimping machine, snap fasteners are machined at the two ends, fixing and warping and roundness adjusting are conducted, and a steel wire circular ring is formed; secondly, the steel wire ring is rotationally heated to austenite through an induction heating device, quenching liquid is sprayed, and the steel wire ring is cooled to the room temperature; thirdly, tempering is conducted after quenching, quenching liquid is sprayed, and cooling is conducted to the room temperature; 4, performing low-temperature heating to perform heat setting on the main bearing; and fifthly, the ring subjected to heat setting is subjected to raceway machining. According to the process, deformation is controlled through rotary induction heating and a clamping die curvature tool, oil quenching pollution is reduced, decarburization of the surface of a steel wire is avoided, and the problem of large forming deformation of the raceway main bearing is solved.

Description

Technical Field

[0001] The invention relates to a hot forming method for a spring steel wire raceway main bearing for a CT machine. Background Art

[0002] Currently, third-generation CT machines are becoming increasingly common in high-end medical devices. These primarily utilize steel wire raceway main bearings, which, through precision machining, exhibit high precision, low friction, high speed, and long life. To address lightweighting and product diversification, Si-Cr spring steel has gradually replaced Cr and Cr-V steels. my country is increasingly adopting oil-quenched steel wire, replacing cold-drawn wire coiling followed by individual quenching and tempering. However, CT machine main bearings are typically around 10,000 mm, making heat treatment of large parts in box-type resistance furnaces difficult. Furthermore, deformation control is difficult after oil quenching, surface decarburization is unavoidable, and quenching oil is highly contaminated. This, coupled with poor economic returns, has become an increasingly prominent problem, creating certain technical barriers to the localization of CT machines. Summary of the Invention

[0003] In response to the shortcomings of the existing technology, the present invention provides a hot forming method for a spring steel wire raceway main bearing for a CT machine. By using rotary induction heating treatment and a rotary clamping curvature tooling to control deformation technology, the environmental pollution and harm caused by oil quenching are reduced, decarburization of the steel wire surface is avoided, and the problem of large deformation during the forming process of the steel wire raceway main bearing is effectively solved.

[0004] To achieve the above object, the present invention provides a method for hot forming a spring steel wire raceway main bearing for a CT machine, comprising the following steps: Step 1: Cut the steel wire and curl it into a ring shape through a crimping 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. Step 2: The coiled steel wire ring is heated by rotation through an induction heating device until it reaches austenite and then sprayed with quenching liquid to cool to room temperature; 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; Step 5: Perform raceway processing on the heat-set steel wire ring.

[0005] As a further configuration of the present invention, the steel wire in step one is bright cold-drawn spring steel wire, and the bright cold-drawn spring steel wire has a tensile strength of ≥950 MPa and a hardness of ≤35 HRC.

[0006] As a further configuration of the present invention, when the induction heating device in step 2 performs austenitizing heating, the heating temperature for steel wire with a diameter less than or equal to 9 mm is 920~960°C; for steel wire with a diameter greater than 9 mm, the heating temperature is 940~960°C; the parameters of the inductor heating device are 20~60kHz, 160~220kW.

[0007] As a further configuration of the present invention, 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 polymer.

[0008] As a further configuration of the present invention, the tempering temperature in step three is 350-500° C.; the parameters of the inductor heating device are 140-180 kHz, 2-6 kW.

[0009] As a further configuration of the present invention, the low-temperature heating temperature in step 4 is lower than the tempering temperature setting, and the temperature difference between the low-temperature heating temperature and the tempering temperature is 30-50°C.

[0010] The beneficial effects of this arrangement are: by using the induction heating high-temperature rapid cooling method, the heat treatment defects of the surface decarburization layer are avoided, and excellent comprehensive mechanical properties are obtained; the induction rotary heating wire raceway bearing and the rotary clamping curvature tooling heat setting technology greatly avoid the difficulty of size control and deformation warping correction of the wire curling; this method optimizes the environmental pollution and potential hazards caused by the original oil quenching; and solves the technical difficulties of processing costs such as the difficulty in controlling the curling deformation of the wire after the original heat treatment and the difficulty in removing the surface decarburization layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Schematic diagram of a snap-on buckle interface for a spring steel wire in an embodiment of the present invention; Figure 2 For the embodiment of the present invention Figure 1 Schematic diagram of the cross-sectional structure of AA; Figure 3 Schematic diagram of induction rotary heating of spring steel wire in an embodiment of the present invention; Figure 4 Schematic diagram of heat setting of the rotary clamping curvature tooling in an embodiment of the present invention; Figure 5 Schematic diagram of the cross-sectional structure of the heat setting processing position in an embodiment of the present invention; Figure 6 This is a microstructure diagram of the spring steel wire main bearing after processing and forming in an embodiment of the present invention. DETAILED DESCRIPTION

[0012] The embodiment of the hot forming method of the spring steel wire raceway main bearing for CT machine of the present invention is as follows: Figures 1 to 5 As shown: Step 1: Cut the bright cold-drawn spring steel wire, curl it into a ring shape through a curling machine, machine snap fasteners at both ends of the wire, fix the shape and adjust the warping and roundness; Step 2: The coiled spring steel wire ring is heated by rotation to austenite by an induction heating device and then sprayed with quenching liquid to cool to room temperature; Step 3: After quenching, adjust the induction quenching parameters for the steel wire ring to perform induction tempering treatment and spray quenching liquid to cool to room temperature; Step 4: The steel wire ring after induction tempering is heated at low temperature, and the residual heat is used to perform heat setting processing on the main bearing; Step 5: Process the raceway of the heat-set wire ring to the main bearing accuracy; The bright cold-drawn spring steel wire described in step 1 is made of 54SiCr6, with a tensile strength of 1120 MPa and a hardness of 33 HRC. It is coiled into a 900 mm ring. The induction heating austenitization process described in step 2 is performed at a temperature of 920-960°C for wire diameters up to 9 mm; 940-960°C for wire diameters larger than 9 mm. In this case, the wire diameter is 7 mm, and the heating temperature is 950°C for a 2-minute hold. The induction heating parameters are 35 kHz and 200 kW. The quenching fluid described in step 2 is a polymer quenching fluid with a mass fraction of 10-15%. The tempering temperature described in step 3 is 450°C for a 30-second hold. The induction heating parameters are 160 kHz and 4 kW. The low-temperature heating process described in step 4 is performed at a temperature of 350°C, 50°C below the induction tempering temperature. The heat setting process is performed using a rotary clamping tool with a specified curvature to control warpage and roundness while also eliminating stress. After the wire raceway main bearing described in step five is processed and formed, it is coated with anti-rust oil for protection.

[0013] According to the above steps, the CT machine wire raceway main bearing is formed. The results are tested. The roundness difference of the wire raceway bearing is less than 0.006mm, the hardness is 55.3HRC, the tensile strength is 1982MPa, the cross-sectional shrinkage is 49%, and the microstructure is a fine troostite structure. Figure 6 As shown, there is no decarburized layer on the surface.

[0014] The above example is only one preferred specific example of the present invention. Common changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention are all included in the protection scope of the present invention.

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 crimping 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. Step 2: The coiled steel wire ring is heated by rotation through an induction heating device until it reaches austenite and then sprayed with quenching liquid to cool to room temperature; 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; 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 steel wire in step 1 is bright cold-drawn spring steel wire, and the bright cold-drawn spring steel wire has a tensile strength of ≥950 MPa and a hardness of ≤35 HRC.

3. The hot forming method of the spring steel wire raceway main bearing for CT machine according to claim 2, characterized in that: When the induction heating device in step 2 performs austenitizing heating, the heating temperature for steel wire with a diameter less than or equal to 9 mm is 920-960°C; for steel wire with a diameter greater than 9 mm, the heating temperature is 940-960°C; the parameters of the induction heating device are 20-60kHz, 160-220kW.

4. 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.

5. 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.

6. The hot forming method of the spring steel wire raceway main bearing for CT machine according to claim 5, characterized in that: The low-temperature heating temperature in step 4 is lower than the tempering temperature setting, and the temperature difference between the low-temperature heating temperature and the tempering temperature is 30-50°C.

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