Medium-frequency induction normalizing method for cast iron guide rail
The cast iron guide rail is subjected to induction normalization through the medium frequency induction normalization method, and the microstructure is adjusted, which solves the problems of guide rail hardness uniformity and residual stress, achieving high hardness and uniformity, and ensuring the stability of the guide rail.
Patent Information
- Application Number
- CN202510128625.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-05
- Publication Date
- 2025-05-06
AI Technical Summary
The prior art is difficult to achieve hardness uniformity and high hardness in cast iron guide rails while avoiding residual stress and risk of cracking or deformation caused by overall normalization treatment.
The medium-frequency induction normalization method is used to induction normalization on cast iron guide rails, adjust the microstructure of the guide rails, improve hardness uniformity, and ensure the stability of the guide rails through stress removal and machining.
The surface hardness of cast iron guide rails is improved and the uniformity of hardness distribution is achieved, while the residual stress and structural risks caused by overall normalization treatment are avoided.
Smart Images
Figure CN119932291A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of heat treatment, and in particular relates to a medium frequency induction normalizing method for a cast iron guide rail. Background Art
[0002] Guide rails are the reference components to ensure the motion accuracy of machine tools. Compared with steel-lined guide rails or linear guide rails that are often used in large and medium-sized high-precision machine tools, cast iron guide rails have obvious advantages in terms of shock absorption, stability and overall rigidity. Due to the large size of the bed guide rails, in order to improve their mechanical properties, the most widely used heat treatment method is induction quenching. Affected by the differences in the composition and organizational state of the casting matrix, the poor consistency of the guide rails after induction quenching seriously restricts the performance of the machine tool guide rails. In order to improve the hardness and hardness uniformity of the guide rails after quenching, it is necessary to adjust the organizational state of cast iron before the guide rail quenching heat treatment, especially the pearlite content and lamellar spacing, shorten the element diffusion time during heat treatment, and complete the diffusion in a short time to obtain high surface hardness and surface uniformity.
[0003] In order to improve the hardness and hardness uniformity of the guide rail after quenching, normalizing treatment can be carried out before the guide rail quenching heat treatment. For the extra-long guide rail with a cast iron base and the guide rail as an integrated structure, it is difficult to carry out overall normalizing treatment due to equipment limitations, or because large residual stress will be generated after overall normalizing treatment, there is a risk of cracking or deformation of the machine tool bed and the guide rail.
[0004] Therefore, a new normalizing method is now needed to adapt to the ultra-long guide rail with a cast iron base and the guide rail as an integrated structure. Summary of the invention
[0005] In order to solve the above technical problems, the present invention provides a medium frequency induction normalizing method for cast iron guide rails. This method can be widely used in the induction normalizing treatment of cast iron guide rails of machine tools, and is particularly suitable for the preparation of the organization before the induction quenching heat treatment of the machine tool guide rails. For guide rails with extra-long bed and cast iron integrated structure, or cast iron guide rails with very long guide rails themselves, it is difficult to perform overall normalizing treatment due to equipment limitations, or because the overall normalizing treatment will cause large residual stress, which makes the machine tool bed and guide rails have the risk of cracking or deformation. At this time, the induction normalizing method is adopted to perform induction normalizing heat treatment on the guide rail parts that need to be induction quenched. Induction normalizing treatment is used to adjust the microstructure of the cast iron guide rail before induction quenching, to prepare the organization to improve the surface hardness of the guide rail and improve the hardness uniformity, and to ensure that the hardness of the guide rail is high and the hardness distribution is uniform.
[0006] In order to achieve the above object, the present invention provides the following technical solutions.
[0007] A medium frequency induction normalizing method for a cast iron guide rail comprises the following steps: Step 1: Perform stress relief and aging treatment on the cast iron bed and guide rails; Step 2: Machining the cast iron bed and guide rails after stress relief and aging treatment; Step 3: Stress relief treatment is performed on the machined cast iron bed and guide rails; Step 4: Induction normalizing the machined cast iron bed and guide rails; Step 5: Perform medium frequency induction quenching on the guide rail after induction normalizing treatment; Step six: Temper the cast iron guide rail after medium frequency induction quenching to obtain the cast iron guide rail.
[0008] Furthermore, in step one, a resistance furnace or other heating equipment is used to perform overall stress relief and aging treatment on the cast iron bed and guide rails, an aging treatment is performed once after casting, and a secondary aging treatment is performed after rough machining; the aging treatment process is as follows: the furnace is loaded below 200°C, the temperature is increased to 320-380°C at a heating rate of 50-80°C / h, and the temperature is kept for 2-3h, the temperature is increased to 520-580°C at a heating rate of 40-60°C / h, and the temperature is kept for 6-8h, and the furnace is cooled to below 250°C and then taken out of the furnace.
[0009] Furthermore, after the machining process in step 2, the surface roughness Ra is less than 3.2 and there is no defect.
[0010] Furthermore, in step 4, induction normalizing uses a single inductor or a double inductor.
[0011] Furthermore, in step 4, the induction normalizing process parameters are as follows: the cooling method after induction heating is air cooling; the output power of induction normalizing is 40-60kW, the frequency is 2-5kHz, the transformer turns ratio is 9:2, the moving speed is 180-250mm / min, and the induction heating temperature is 880-910℃; the cross-sectional width of the part used for normalizing of the inductor is more than 15mm (the cross-sectional dimension is greater than 15×10mm); the distance between the surface of the inductor and the normalizing surface of the guide rail is 3-6mm; the size of the normalizing surface inductor should be 10-12mm wider than the cross-sectional area of the guide rail; the magnetic conductor or silicon steel sheet should be matched with the inductor copper tube, and should be moderately tight after installation, and be bonded and fixed with electrical insulating glue; the spacing between the two loops of the inductor is 12-20mm; when using dual inductors, one inductor is a preheating inductor and the other is a normalizing inductor, and the distance between the dual inductors is 15-20mm.
[0012] Furthermore, the sensor is designed to be overall contour-profiling or partially decomposed contour-profiling according to the cross-sectional shape of the guide rail.
[0013] Further, in step 5, the process parameters of medium frequency induction quenching are as follows: output power 40-70kW, frequency 2-6kHz, transformer turn ratio 9:2, moving speed 180-240mm / min, induction heating temperature 850-900℃, cooling medium water, continuous water spray cooling; dual inductor quenching, one inductor is a preheating inductor, without water spray, preheating temperature 840-850℃, and one is a quenching inductor with its own quenching water spray, and auxiliary cooling is added as needed; the inductor should be based on The shape of the guide rail cross section is designed by overall profiling or partial decomposition profiling; the distance between the sensor surface and the quenching surface of the guide rail is 4-6mm; the size of the quenching sensor should be 6-12mm wider than the guide rail cross section, the water spray holes should be reasonably set according to the width of the sensor and evenly distributed, the water pressure is 0.2-0.3MPa, the water spray direction is opposite to the forward direction of the sensor, and is 40-50° to the quenching surface of the guide rail, the air pressure of the hair dryer is 0.6-0.8MPa, the wind direction is parallel to the guide rail surface to prevent water backflow, and the distance between the two sensors is 15-20mm.
[0014] Furthermore, in step six, the tempering treatment should be completed within 12 hours after medium frequency induction quenching, the tempering temperature is 180-260° C., and the tempering time is 6-8 hours.
[0015] Compared with the prior art, the beneficial effects of the present invention are as follows.
[0016] The present invention adopts an induction normalizing method to perform induction normalizing heat treatment on the guide rail portion that needs to be induction quenched; the induction normalizing treatment is used to adjust the microstructure of the cast iron guide rail before induction quenching, to prepare the structure for improving the surface hardness of the guide rail and improving the hardness uniformity, to ensure that the guide rail has high hardness and uniform hardness distribution, so as to facilitate machining of the cast iron bed and the guide rail. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 Example 1 organizational phase diagram.
[0018] Figure 2 Example 2 organizational phase diagram. DETAILED DESCRIPTION
[0019] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.
[0020] A medium frequency induction normalizing method for cast iron guide rails, the specific implementation steps are as follows: Step 1: Perform stress relief and aging treatment on the cast iron guide rail. Use high-temperature box-type resistance furnace and other heating equipment to perform stress relief and aging treatment on the entire casting. After casting, perform an aging treatment once before rough machining, and perform a secondary aging treatment after rough machining. The aging treatment process is as follows: load the furnace below 200℃, heat up to 320~380℃ at a heating rate of 50~80℃ / h, keep warm for 2~3h, heat up to 520~580℃ at a heating rate of 40~60℃ / h, keep warm for 6~8h (the holding time depends on the furnace load and the wall thickness of the thickest part), and cool down to below 250℃ with the furnace and take out of the furnace.
[0021] Step 2: Machining the cast iron guide rail after stress relief and aging treatment to make the surface roughness Ra <3.2 and free of defects.
[0022] Step 3: Perform secondary stress relief treatment on the cast iron guide rail according to the process parameters of step 1.
[0023] Step 4: Use a single inductor or a double inductor to perform induction normalizing on the machined cast iron guide rail. When using double inductors for heating, one inductor is a preheating inductor and the other is a normalizing inductor. Air cooling is used after heating. The output power of induction normalizing is 40-60kW, the frequency is 2-5kHz, the transformer turns ratio is 9:2, the moving speed is 180-250mm / min, and the induction heating temperature is 880-910℃. The width of the section used for normalizing of the inductor is more than 15mm (the section size is greater than 15×10mm); the inductor should be designed in whole or partially decomposed according to the cross-sectional shape of the guide rail; the distance between the inductor surface and the normalizing surface of the guide rail is 3-6mm; the size of the inductor on the normalizing surface should be 10-12mm wider than the cross-sectional area of the guide rail; the magnetic conductor or silicon steel sheet should be matched with the inductor copper tube, and should be of moderate tightness after installation, and can be bonded and fixed with electrical insulating glue; the distance between the two loops of the inductor is 12-20mm; the distance between the double inductors is 15-20mm.
[0024] Step 5: Perform medium frequency induction quenching on the guide rail after induction normalizing. The process parameters of medium frequency induction quenching are as follows: output power 40-70kW, frequency 2-6kHz, transformer turn ratio 9:2, moving speed 180-240mm / min, induction heating temperature 850-900℃, cooling medium water, continuous water spray cooling method is adopted to make the hardness reach above 50HRC; double inductor quenching is adopted, one inductor is a preheating inductor without water spray, preheating temperature 840-850℃, and the other is a quenching inductor with self-contained quenching water spray, and auxiliary cooling is added as needed. The inductor should be designed for overall profiling or partial decomposition profiling according to the cross-sectional shape of the guide rail. The distance between the sensor surface and the quenching surface is 4-6mm; the quenching surface sensor size should be 6-12mm wider than the rail section. The water spray holes should be reasonably set according to the width of the sensor and evenly distributed. The water pressure is 0.2-0.3MPa. The water spray direction is opposite to the sensor forward direction and 40-50° to the rail quenching surface. The air pressure of the hair dryer is 0.6-0.8MPa, and the wind direction is parallel to the rail surface to prevent water backflow. The distance between the two sensors is 15-20mm.
[0025] Step 6: Temper the quenched cast iron guide rail. The tempering treatment should be completed within 12 hours after induction quenching. The tempering temperature is 180-260℃ and the tempering holding time is 6-8h.
[0026] Example 1.
[0027] A medium frequency induction normalizing method for cast iron guide rails, which is specifically implemented as follows: Step 1: Perform stress relief and aging treatment on the cast iron HT300 guide rail, and use high-temperature box-type resistance furnace heating equipment to perform stress relief and aging treatment on the entire casting; the stress relief and aging treatment process is as follows: load the furnace at 180℃, heat up to 350℃ at a heating rate of 60℃ / h, keep warm for 2h, heat up to 550℃ at a heating rate of 50℃ / h, keep warm for 6h, cool to 220℃ with the furnace and take out of the furnace.
[0028] Step 2: Machining the cast iron HT300 guide rail after stress relief and aging treatment, the surface roughness Ra is less than 2.5 and there are no defects.
[0029] Step 3: Perform secondary stress relief treatment on the cast iron guide rail according to the process parameters of step 1.
[0030] Step 4: Use dual inductors to perform induction normalizing on the machined cast iron HT300 guide rail, one inductor is a preheating inductor and the other is a normalizing inductor, which are air-cooled after heating; the output power of induction normalizing is 50kW, the frequency is 4kHz, the transformer turns ratio is 9:2, the moving speed is 220mm / min, and the induction heating temperature is 880℃; the width of the section used for inductor normalizing is 16mm (section size is 15×10mm); the inductor is designed for overall profiling or partial decomposition profiling according to the cross-sectional shape of the guide rail, and the distance between the inductor surface and the normalizing surface of the guide rail is 5mm; the normalizing surface inductor size is 11mm wider than the guide rail section; the silicon steel sheet should be matched with the inductor copper tube, and electrical insulating glue should be used for bonding and fixing. The spacing between the two loops of the inductor is 15mm, and the spacing between the two inductors is 15mm.
[0031] Step 5: Perform medium frequency induction quenching on the HT300 guide rail after induction normalizing. The process parameters of medium frequency induction quenching are as follows: output power 60kW, frequency 4kHz, transformer turn ratio 9:2, moving speed 200mm / min, induction heating temperature 900℃, cooling medium water, continuous water spray cooling method, double inductor quenching, one inductor is a preheating inductor, without water spray, preheating temperature 845℃, and the other is a quenching inductor with built-in quenching water spray, and auxiliary inductors are added as needed. Cooling, the sensor should be designed according to the shape of the guide rail cross-section for overall profiling or partial decomposition profiling. The distance between the sensor surface and the quenching surface is 5mm. The quenching surface sensor size should be 10mm wider than the guide rail cross-section. The water spray holes should be reasonably set according to the width of the sensor and evenly distributed. The water pressure is 0.2MPa, and the water spray direction is opposite to the forward direction of the sensor and is 45° to the quenching surface of the guide rail. The wind pressure of the hair dryer is 0.6MPa, and the wind direction is parallel to the guide rail surface to prevent water backflow. The martensite distance between the two sensors is 15mm.
[0032] Step 6: Temper the quenched cast iron guide rail. The tempering treatment is completed 8 hours after induction quenching. The tempering temperature is 220℃ and the tempering time is 7 hours.
[0033] After the induction normalizing process, the hardness of HT300 for guide rails is 55HRC, and the effective hardened layer depth reaches 5.0mm. Figure 1 This is the alloy structure phase diagram of Example 1 of the present invention. It can be seen that the martensite content of this example is relatively high.
[0034] Example 2.
[0035] A medium frequency induction normalizing method for cast iron guide rails, which is specifically implemented as follows: Step 1: Perform stress relief and aging treatment on the cast iron HT300 guide rail, and use high-temperature box-type resistance furnace heating equipment to perform stress relief and aging treatment on the entire casting; the stress relief and aging treatment process is as follows: load the furnace at 180℃, heat up to 350℃ at a heating rate of 60℃ / h, keep warm for 2h, heat up to 550℃ at a heating rate of 50℃ / h, keep warm for 6h, cool to 220℃ with the furnace and take out of the furnace.
[0036] Step 2: Machining the cast iron HT300 guide rail after stress relief and aging treatment, the surface roughness Ra is less than 2.5 and there are no defects.
[0037] Step 3: Perform secondary stress relief treatment on the cast iron guide rail according to the process parameters of step 1.
[0038] Step 4: Use a single inductor to induction normalize the machined cast iron HT300 guide rail, and use air cooling after induction heating; the output power of induction normalizing is 50kW, the frequency is 4kHz, the transformer turns ratio is 9:2, the moving speed is 220mm / min, the induction heating temperature is 880℃, and the section width size of the inductor normalizing part is 16mm (section size is 15×10mm). The inductor should be designed according to the cross-sectional shape of the guide rail for overall profiling or partial decomposition profiling. The distance between the inductor surface and the normalizing surface of the guide rail is 5mm. The size of the normalizing surface inductor is 11mm wider than the guide rail section. The silicon steel sheet should be matched with the inductor copper tube and fixed with electrical insulating glue. The distance between the two loops of the inductor is 15mm.
[0039] Step 5: Perform medium frequency induction quenching on the HT300 rail after induction normalizing. The process parameters of medium frequency induction quenching are as follows: output power 60kW, frequency 4kHz, transformer turn ratio 9:2, moving speed 200mm / min, induction heating temperature 900℃, cooling medium water, continuous water spray cooling method, double inductor quenching, one inductor is a preheating inductor without water spray, preheating temperature 845℃, and the other is a quenching inductor with self-contained quenching water spray, and auxiliary cooling is added as needed. The inductor should be designed for overall profiling or partial decomposition profiling according to the cross-sectional shape of the rail. The distance between the sensor surface and the quenching surface is 5mm. The size of the quenching surface sensor should be 10mm wider than the guide rail section. The water spray holes should be reasonably set according to the width of the sensor and evenly distributed. The water pressure is 0.2MPa. The water spray direction is opposite to the forward direction of the sensor and is 45° to the quenching surface of the guide rail. The air pressure of the hair dryer is 0.6MPa, and the wind direction is parallel to the guide rail surface to prevent water backflow. The distance between the two sensors is 15mm.
[0040] Step 6: Temper the quenched cast iron guide rail. The tempering treatment is completed 8 hours after induction quenching. The tempering temperature is 220℃ and the tempering time is 7 hours.
[0041] After the induction normalizing process and then induction quenching, the hardness of HT300 for guide rails is 53HRC, and the effective hardened layer depth reaches 3.5mm. Figure 2 This is the microstructure phase diagram of the alloy of Example 2 of the present invention. It can be seen that the martensite content of this example is relatively high.
Claims
1. A medium frequency induction normalizing method for cast iron guide rails, characterized in that: The following steps are involved: Step 1: Perform stress relief and aging treatment on the cast iron bed and guide rails; Step 2: Machining the cast iron bed and guide rails after stress relief and aging treatment; Step 3: Stress relief treatment is performed on the machined cast iron bed and guide rails; Step 4: Induction normalizing the machined cast iron bed and guide rails; Step 5: Perform medium frequency induction quenching on the guide rail after induction normalizing treatment; Step six: Temper the cast iron guide rail after medium frequency induction quenching to obtain the cast iron guide rail.
2. The medium frequency induction normalizing method for cast iron guide rails according to claim 1, characterized in that: In the step 1, a resistance furnace or other heating equipment is used to perform overall stress relief aging treatment on the cast iron bed and guide rails, an aging treatment is performed once after casting, and a secondary aging treatment is performed after rough machining; the aging treatment process is as follows: the furnace is charged below 200°C, the temperature is increased to 320-380°C at a heating rate of 50-80°C / h, and the temperature is kept for 2-3h, the temperature is increased to 520-580°C at a heating rate of 40-60°C / h, and the temperature is kept for 6-8h, and the furnace is cooled to below 250°C and discharged from the furnace.
3. The medium frequency induction normalizing method for cast iron guide rails according to claim 1, characterized in that: After the machining process in step 2, the surface roughness Ra is less than 3.2 and there are no defects.
4. The medium frequency induction normalizing method for cast iron guide rails according to claim 1, characterized in that: In the step 4, the induction normalizing adopts a single inductor or a double inductor.
5. The medium frequency induction normalizing method for cast iron guide rails according to claim 1, characterized in that: In the step 4, the induction normalizing process parameters are as follows: the cooling method after induction heating is air cooling; the output power of induction normalizing is 40-60kW, the frequency is 2-5kHz, the transformer turns ratio is 9:2, the moving speed is 180-250mm / min, and the induction heating temperature is 880-910℃; the cross-sectional width of the part used for normalizing of the inductor is more than 15mm; the distance between the surface of the inductor and the normalizing surface of the guide rail is 3-6mm; the size of the inductor on the normalizing surface should be 10-12mm wider than the cross-section of the guide rail; the magnetic conductor or silicon steel sheet should be matched with the inductor copper tube and bonded and fixed with electrical insulating glue; the spacing between the two loops of the inductor is 12-20mm; when using dual inductors, one inductor is a preheating inductor and the other is a normalizing inductor, and the distance between the dual inductors is 15-20mm.
6. The medium frequency induction normalizing method for cast iron guide rails according to any one of claims 4 to 5, characterized in that: The sensor is designed to be overall contour-profiling or partially decomposed contour-profiling according to the cross-sectional shape of the guide rail.
7. The medium frequency induction normalizing method for cast iron guide rails according to claim 1, characterized in that: In the step 5, the process parameters of medium frequency induction quenching are as follows: output power 40-70kW, frequency 2-6kHz, transformer turns ratio 9:2, moving speed 180-240mm / min, induction heating temperature 850-900℃, cooling medium water, and continuous water spray cooling; dual inductor quenching is adopted, one inductor is a preheating inductor without water spray, the preheating temperature is 840-850℃, and the other is a quenching inductor with its own quenching water spray, and auxiliary cooling is added as needed; the distance between the inductor surface and the quenching surface of the guide rail is 4-6mm; the size of the quenching inductor should be 6-12mm wider than the cross section of the guide rail, the water spray holes should be evenly distributed, the water pressure should be 0.2-0.3MPa, the water spray direction should be opposite to the forward direction of the inductor, and should be 40-50° with the quenching surface of the guide rail, the wind pressure of the hair dryer should be 0.6-0.8MPa, the wind direction should be parallel to the surface of the guide rail, and the distance between the dual inductors should be 15-20mm.
8. The medium frequency induction normalizing method for cast iron guide rails according to claim 1, characterized in that: In the step six, the tempering treatment should be completed within 12 hours after the medium frequency induction quenching, the tempering temperature is 180-260° C., and the tempering time is 6-8 hours.