Double-frequency induction quenching heat treatment method for large-diameter GCr15SiMn core mold

Abstract

The invention discloses a double-frequency induction quenching heat treatment method for a large-diameter GCr15SiMn core mold. The double-frequency induction quenching heat treatment method comprises the steps that S1, two inductors are installed on two quenching transformers correspondingly, and a water spraying ring is installed below the inductors; s2, the core mold is hung on a double-frequency quenching machine tool, and the lower end face of the core mold is placed in a power frequency inductor; s3, setting power frequency initial power, intermediate frequency initial power, core mold downward moving speed and autorotation speed; s4, the power frequency inductor and the medium-frequency inductor heat the core mold in sequence, finally, the core mold is moved out of the medium-frequency inductor and then cooled, and a quenched core mold is obtained; and S5, the quenched core mold is tempered, air cooling is conducted to the room temperature after tempering is finished, inspection is conducted, and the double-frequency induction quenching heat treatment on the core mold is completed. According to the double-frequency induction quenching heat treatment method for the large-diameter GCr15SiMn core mold, the problems that the hardness of an inner hole and a wall thickness part is too high and the overall plasticity and toughness of the core mold cannot be guaranteed in an overall quenching method are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of induction quenching heat treatment of a spinning core mold, and relates to a dual-frequency induction quenching heat treatment method for a large-diameter GCr15SiMn core mold. Background Art

[0002] The spinning core mold is a key tooling in the spinning process. During its use, the threaded hole on the end face of the core mold is connected to the rotating spindle on the spinning equipment. During operation, the spinning core mold is subjected to a large extrusion force from the spinning blank parts, so the working part of the spinning core mold must have high strength and surface wear resistance. Generally, the spinning core mold with a diameter greater than 500mm is designed as a hollow cylinder structure in order to reduce the deadweight of the workpiece. Its wall thickness is between 80-120mm. In order to ensure the strength, toughness and surface wear resistance during operation, the surface hardness must first reach HRC58-62 to meet the wear resistance; secondly, the depth of the hardened layer must reach more than 20mm to ensure a certain bending strength during operation; thirdly, the core of the core mold needs to maintain its original tempering state to meet the comprehensive mechanical performance during use.

[0003] However, the conventional medium-frequency quenching method cannot reach a hardened layer depth of more than 20 mm, and cannot guarantee the strength of use; the overall quenching method will make the hardness of the inner hole and the wall thickness too high, and cannot guarantee the overall plastic toughness of the core mold; therefore, it is necessary to invent a heat treatment method for large-diameter core molds made of GCr15SiMn to meet the use requirements of large-diameter spinning core molds. Summary of the invention

[0004] The purpose of the present invention is to provide a dual-frequency induction quenching heat treatment method for a large-diameter GCr15SiMn core mold, thereby ensuring that the surface hardness of the core mold is HRC58-62, the hardened layer depth is ≥20mm, and the original tempering state and performance of the thick-walled core mold are retained, thereby solving the problem that the existing overall quenching method will make the hardness of the inner hole and the thick wall part too high and the overall plastic toughness of the core mold cannot be guaranteed.

[0005] The technical solution adopted by the present invention is a dual-frequency induction quenching heat treatment method for a large-diameter GCr15SiMn core mold, and the specific steps are as follows:

[0006] S1. Install the selected power frequency sensor and medium frequency sensor on the two quenching transformers of the dual-frequency quenching machine respectively, and install the water spray ring under the two sensors;

[0007] S2. Hang the core mold vertically on the dual-frequency quenching machine, and place the lower end surface of the core mold in the power frequency sensor;

[0008] S3, setting the initial power of the power frequency, the initial power of the medium frequency, the downward movement speed of the core mold and the rotation speed;

[0009] S4, the core mold starts to be heated, and at the same time the core mold starts to rotate and move downward, the power frequency sensor and the medium frequency sensor heat the core mold successively, and finally the core mold moves out of the medium frequency sensor and enters the water spray circle and the water reservoir for cooling, so as to obtain the quenched core mold;

[0010] S5. The quenched core mold is placed in a trolley-type resistance furnace for tempering. After tempering, it is air-cooled to room temperature for inspection, thus completing the dual-frequency induction quenching heat treatment of the large-diameter GCr15SiMn core mold.

[0011] The present invention is also characterized in that:

[0012] The inner diameter of the power frequency sensor selected in S1 is 75mm larger than the outer diameter of the GCr15SiMn core mold, the inner diameter of the medium frequency sensor is 50mm larger than the outer diameter of the GCr15SiMn core mold, and the inner diameter of the water spray ring is 150-200mm larger than the outer diameter of the core mold; the power frequency sensor is installed on the power frequency quenching transformer, and the medium frequency sensor is installed on the medium frequency quenching transformer. The specifications of the power frequency quenching transformer are 1500kw / 36-60HZ, and the specifications of the medium frequency quenching transformer are 750KW / 180-275HZ;

[0013] During installation, the centers of the power frequency sensor and the medium frequency sensor are in a straight line, the power frequency sensor is above the medium frequency sensor, the distance between the two is 120mm, and the water spray circle is below the medium frequency sensor, the distance between the two is 30-50mm.

[0014] In S2, the core mold is vertically hung on the dual-frequency quenching machine using a special machine tool hanger, and the lower end surface of the core mold enters the industrial frequency sensor by 20 to 30 mm.

[0015] The specific operation of S3 is: first start the medium frequency power button to make the medium frequency power 40-60KW, the medium frequency sensor starts to heat slightly at no load, then start the industrial frequency power button, give the initial industrial frequency power of 400-500KW, and start the downward movement and rotation buttons of the machine tool while the industrial frequency sensor starts heating. The downward movement speed of the core mold is 40-45mm / min, and the rotation speed is 10-15r / min.

[0016] The specific method of S4 is as follows: when heating the core mold, the heating temperature of the core mold is observed according to the temperature measuring device of the quenching machine, and the heating power of the power frequency sensor is adjusted. The core mold is heated and moved downward in the power frequency sensor, so that the temperature measuring point T1 in the middle of the power frequency sensor reaches 700-740°C, and the temperature measuring point T2 near the outlet of the power frequency sensor reaches 820-840°C. Then the lower end surface of the core mold enters the intermediate frequency sensor, and the temperature measuring point T3 in the middle of the intermediate frequency sensor and the temperature measuring point T2 near the outlet are detected. 4 temperature, further adjust the heating power of the medium frequency sensor, so that the core mold in the medium frequency heating process T3 temperature reaches 860 ~ 870 ℃, T4 temperature reaches 870 ~ 880 ℃, then the core mold is removed from the medium frequency sensor and directly enters the water spray circle for cooling, the spray quenching water pressure is 0.4 ~ 0.5MPa, the core mold 11 passes through the water spray circle 6 and enters the water reservoir 7 to continue cooling for a certain time, the cooling time is calculated according to the effective cross-section of the core mold 11 at 0.5-1min / mm, and the quenched core mold is obtained.

[0017] When the lower end of the core mold enters the water spray ring for cooling, the rest of the core mold is continuously heated in the two inductors. The heating power of the medium frequency inductor and the industrial frequency inductor is basically stable, ensuring that the temperature of T2 is stable at 820-840℃ and the temperature of T4 is stable at 870-880℃. The core mold is continuously heated and sprayed from bottom to top for cooling;

[0018] When the upper end surface of the core mold moves to the industrial frequency sensor, due to the angular effect of induction heating, it is necessary to start reducing the heating power of the industrial frequency sensor to ensure that the temperature of the temperature measuring point T2 does not exceed 860°C. At the same time, when the upper end surface moves to the middle position of the industrial frequency sensor, the industrial frequency heating is stopped; when the upper end surface of the core mold continues to move downward into the medium frequency sensor, due to the angular effect of induction heating, it is necessary to start reducing the heating power of the medium frequency sensor to ensure that the temperature of the temperature measuring point T4 does not exceed 880°C. At the same time, when the upper end surface of the core mold moves to the middle position of the medium frequency sensor, the medium frequency heating is stopped.

[0019] The temperature measuring device of the quenching machine in S4 is composed of four dual-color infrared thermometers and matching temperature controllers. The temperature is measured at one point in the middle and near the outlet of the power frequency induction line, which are T1 and T2; the temperature is measured at one point in the middle and near the outlet of the medium frequency induction line, which are T3 and T4; if the temperature of T1 and T2 is too low or too high, the heating power of the power frequency is slightly adjusted by 100KW each time and the temperature change is observed; if the temperature of T3 and T4 is too low or too high, the heating power of the medium frequency is slightly adjusted by 50KW each time and the temperature change is observed.

[0020] The specific process of S5 tempering is as follows: after the core mold is removed from the quenching machine, it is placed horizontally in a trolley-type tempering furnace, and then heated to 230°C at 60°C / h and kept warm for 12 to 18 min / mm. The temperature uniformity of the tempering furnace is ±5°C.

[0021] The beneficial effects of the present invention are:

[0022] The dual-frequency induction quenching heat treatment method for a large-diameter GCr15SiMn material core mold provided by the present invention adopts a dual-frequency induction quenching method to perform induction quenching on the core mold, so that the surface hardness can reach HRC58-62, the surface hardness uniformity is ≤1.5HRC, and a hardened layer depth of 20mm-30mm is obtained. The hardness below the hardened layer depth will not drop suddenly, but will gradually decrease and transition to the matrix hardness, so that the core mold has sufficient wear resistance and strength when used; at the same time, the inner hole of the core mold is not affected by the induction quenching, and continues to maintain the original tempering performance, so that the plastic toughness of the core mold is better when used; through the heat treatment method of the present invention, the comprehensive use performance of the core mold can be greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the installation positions of various components in the equipment used in the quenching heat treatment method of the present invention;

[0024] Figure 2 It is a schematic diagram of the working state of the core mold when it is heated on the quenching machine tool in the quenching heat treatment method of the present invention;

[0025] Figure 3 It is a schematic diagram of the parts structure in Example 1 of the quenching heat treatment method of the present invention.

[0026] In the figure, 1. medium frequency quenching transformer, 2. power frequency quenching transformer, 3. connecting transition plate, 4. power frequency sensor, 5. medium frequency sensor, 6. water spray ring, 7. water reservoir, 8. lower tooling flange, 9. upper tooling flange, 10. special lifting fixture for machine tools, 11. core mold workpiece. DETAILED DESCRIPTION

[0027] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] The double-frequency induction quenching heat treatment method of large diameter GCr15SiMn core mold has the following specific steps:

[0029] S1. Install the selected power frequency sensor 4 and medium frequency sensor 5 on the two quenching transformers of the dual-frequency quenching machine respectively, and install the water spray ring 6 under the two sensors;

[0030] Among them, Figure 1As shown, the inner diameter of the selected power frequency inductor 4 is 75mm larger than the outer diameter of the GCr15SiMn core mold 11, the inner diameter of the medium frequency inductor 5 is 50mm larger than the outer diameter of the GCr15SiMn core mold 11, and the inner diameter of the water spray ring 6 is 150-200mm larger than the outer diameter of the core mold 11; the power frequency inductor 4 is installed on the power frequency quenching transformer 2 through the connecting transition plate 3, and the medium frequency inductor 5 is installed on the medium frequency quenching transformer 1 through another connecting transition plate 3. The specification of the power frequency quenching transformer 2 is 1500kw / 36-60HZ, and the specification of the medium frequency quenching transformer 1 is 750KW / 180-275HZ;

[0031] During installation, the centers of the power frequency sensor 4 and the medium frequency sensor 5 are in a straight line, the power frequency sensor 4 is above the medium frequency sensor 5, the distance between the two is 120 mm, and the water spray circle 6 is below the medium frequency sensor 5, the distance between the two is 30-50 mm.

[0032] S2, such as Figure 2 As shown, the core mold 11 is vertically hung on the dual-frequency quenching machine by using a special hanger 10 for machine tools, and two tooling flanges are made in advance. The upper tooling flange 9 has multiple through holes, which are engaged with the lifting holes at the upper end of the core mold 11, and the lower tooling flange 8 with a top hole is engaged with the threaded hole at the lower end of the core mold 11. The special hanger 10 for the quenching machine tool is used to vertically hang the core mold on the quenching machine tool, and the top hole of the lower tooling flange 8 is against the lower top of the machine tool;

[0033] The lower end surface of the core mold 11 is placed in the power frequency inductor 4 , and the lower end surface of the core mold 11 enters the power frequency inductor 4 by 20 to 30 mm.

[0034] S3. Set the initial power of the industrial frequency, the initial power of the medium frequency, the downward movement speed and the rotation speed of the core mold 11. Specifically, start the medium frequency power button first to make the medium frequency power 40-60KW, and the medium frequency sensor 5 starts to heat slightly at no load. Then start the industrial frequency power button, and set the initial power of the industrial frequency to 400-500KW. When the industrial frequency sensor 4 starts heating, start the downward movement and rotation buttons of the machine tool. The downward movement speed of the core mold 11 is 40-45mm / min, and the rotation speed is 10-15r / min.

[0035] S4, start heating the core mold 11, and at the same time, the core mold 11 starts to rotate and move downward, the power frequency sensor 4 and the medium frequency sensor 5 heat the core mold 11 successively, and finally the core mold 11 is completely removed from the medium frequency sensor 5 and enters the water spray circle 6 and the water reservoir 7 for cooling, so as to obtain the quenched core mold 11;

[0036] The specific method for controlling the heating process of the lower end of the core mold is as follows: when heating the core mold 11, the heating temperature of the core mold 11 is observed according to the temperature measuring device of the quenching machine, and the heating power of the power frequency sensor 4 is adjusted. The core mold 11 is heated and moved downward in the power frequency sensor 4, so that the temperature measuring point T1 in the middle of the power frequency sensor 4 reaches 700-740°C, and the temperature measuring point T2 near the outlet of the power frequency sensor 4 reaches 820-840°C. Then the lower end surface of the core mold 11 enters the intermediate frequency sensor 5, and the temperature measuring point T3 in the middle of the intermediate frequency sensor 5 and the outlet are detected. The temperature of the temperature measuring point T4 nearby is further adjusted to adjust the heating power of the medium frequency sensor 5, so that the temperature of the core mold 11 reaches 860-870°C at T3 and 870-880°C at T4 during the medium frequency heating process. Subsequently, the core mold 11 is removed from the medium frequency sensor 5 and directly enters the water spray circle 6 for cooling. The spray quenching water pressure is 0.4-0.5Mpa. After passing through the water spray circle 6, the core mold 11 enters the water reservoir 7 to continue cooling for a certain period of time. The continuous cooling time is calculated based on the effective cross-section of the core mold 11 at 0.5-1min / mm to obtain the quenched core mold 11.

[0037] Control of the heating process of the middle part of the core mold: In the above process, after the lower end of the core mold 11 is heated by the industrial frequency sensor 4 and the medium frequency sensor 5 respectively, the T4 temperature reaches the quenching temperature of 870-880°C, and the core mold 11 continues to fall to the water spray circle 6 for cooling. At this time, the power of the industrial frequency and the medium frequency is basically stable, which can ensure that the T2 and T4 temperatures of the core mold 11 when heated meet the quenching requirements. The whole process only requires a slight adjustment of the two powers, focusing on controlling the T2 and T4 temperatures, and the T1 and T3 temperatures are only for reference.

[0038] When the lower end of the core mold 11 enters the water spray ring 6 for cooling, the remaining part is continuously heated in the two inductors, wherein the heating power of the medium frequency inductor 5 and the industrial frequency inductor 4 is basically stable, ensuring that the temperature of T2 is stable at 820-840°C, and the temperature of T4 is stable at 870-880°C, and the core mold 11 is continuously heated and spray-quenched from bottom to top.

[0039] Control of the heating process of the upper end of the core mold: when the upper end surface of the core mold 11 moves to the industrial frequency sensor 4, due to the angular effect of induction heating, it is necessary to start reducing the heating power of the industrial frequency sensor 4 to ensure that the temperature of the temperature measuring point T2 does not exceed 860°C. At the same time, when the upper end surface moves to the middle position of the industrial frequency sensor 4, the industrial frequency heating is stopped; when the upper end surface of the core mold 11 continues to move downward into the medium frequency sensor 5, due to the angular effect of induction heating, it is necessary to start reducing the heating power of the medium frequency sensor 5 to ensure that the temperature of the temperature measuring point T4 does not exceed 880°C. At the same time, when the upper end surface of the core mold 11 moves to the middle position of the medium frequency sensor 5, the medium frequency heating is stopped.

[0040] Below the water spray circle 6 is a water reservoir 7 with a diameter of 2m and a depth of 6m, and all the water in the water spray circle 6 flows into the water reservoir 7.

[0041] Among them, the temperature measuring device of the quenching machine tool is composed of four dual-color infrared thermometers and matching temperature controllers. The temperature is measured at one point in the middle and near the outlet of the power frequency induction line, which are T1 and T2; the temperature is measured at one point in the middle and near the outlet of the medium frequency sensor 5, which are T3 and T4; if the temperature of T1 and T2 is too low or too high, the heating power of the power frequency is slightly adjusted, 100KW each time, and then the temperature change is observed; if the temperature of T3 and T4 is too low or too high, the heating power of the medium frequency is slightly adjusted, 50KW each time, and then the temperature change is observed.

[0042] S5. After quenching, the core mold 11 is placed in a trolley resistance furnace for tempering. The specific process is as follows: after the core mold 11 is removed from the quenching machine, it is placed horizontally in a trolley tempering furnace, and then heated to 230°C at 60°C / h and kept warm. The holding time is calculated according to the effective cross-section of the core mold 11, and the holding time is 12 to 18 min / mm. The furnace temperature uniformity of the tempering furnace is ±5°C. After the tempering is completed, it is air-cooled to room temperature for inspection, and the dual-frequency induction quenching heat treatment of the large-diameter GCr15SiMn core mold 11 is completed.

[0043] The core molds mentioned above in the present application are all core molds made of large diameter GCr15SiMn material.

[0044] The present invention adopts a dual-frequency induction quenching heat treatment method for large-diameter cylindrical GCr15SiMn material core mold parts, adopts industrial frequency and medium frequency two induction power supplies for simultaneous heating, and reaches a suitable heat penetration layer depth for the core mold wall thickness, and then through the rapid cooling of the water spray circle and the continued cooling of the water reservoir, the high quenching hardness and a certain quenching layer depth of the core mold surface are guaranteed, and then tempering is carried out at 230°C in a trolley resistance furnace, and finally the required quenching hardness and quenching layer depth are met, and the original excellent quenching and tempering mechanical properties of the core mold are guaranteed, and the shortcomings of insufficient layer depth of ordinary medium frequency induction quenching and the inability to guarantee the original quenching and tempering mechanical properties by overall quenching are solved, and a new heat treatment quenching method is provided for this type of large-diameter core mold.

[0045] Example 1

[0046] This embodiment uses a core mold made of GCr15SiMn material, and its product dimensions are: diameter 725mm, length 2800mm, wall thickness 107mm, 6 M30 screw holes on the upper end, 4 M16 screw holes on the lower end, and the appearance is as follows Figure 3 As shown, the quenching hardness requirement is HRC58-62, the layer depth is ≥20mm, and the material composition is shown in Table 1:

[0047] Table 1 GCr15SiMn core mold material composition

[0048] C Si Mn P S Cr Ni Cu 1.01 0.57 1.12 0.02 0.02 1.52 0.3 0.25

[0049] The basic parameters of the dual-frequency quenching transformer used in the core mold workpiece are shown in Table 2:

[0050] Table 2 Basic parameters of dual-frequency quenching transformer

[0051]

[0052] The double-frequency induction quenching heat treatment method of the GCr15SiMn material core mold has the following specific steps:

[0053] (1) Installation of sensors and water spray rings before quenching

[0054] According to the diameter of the core mold 11, the diameter of the power frequency sensor 4 is selected to be 800mm, the diameter of the medium frequency sensor 5 is selected to be 775mm, and the corresponding diameter of the water spray circle 6 is selected to be 900mm. During installation, the centers of the two sensors are on a vertical line, the power frequency sensor 4 is on the top, and the medium frequency sensor 5 is on the bottom, and the distance between the two sensors is 120mm; the water spray circle 6 is below the two sensors, and there is a distance of 50mm between it and the medium frequency sensor 5. Then the two sensors are installed on the two quenching transformers 1 and 2 of the dual-frequency quenching machine respectively, and the water spray circle 6 is installed below the two sensors.

[0055] (2) Clamping of the core mold on the quenching machine

[0056] The two tooling flanges made in advance, the upper tooling flange 9 has a diameter of 600mm and a thickness of 25mm. According to the 6 M30 lifting screw holes on the core mold 11, 6 through holes with a diameter of 35 are made on the upper tooling flange 9, and the core mold 11 is engaged; the lower tooling flange 8 has a diameter of 600mm and a thickness of 25mm. One side of it is made into a B12 top hole, and the other side is made into 4 through holes with a diameter of 20 according to the 4 M16 screw holes on the core mold 11 to engage with the threaded holes at the lower end of the core mold 11, and the upper tooling flange 9 is connected to the special hanger 10 for the quenching machine, so that the core mold is vertically hung on the quenching machine, and the top hole of the lower tooling flange 8 is pressed against the lower top of the machine tool, so that the lower end face of the core mold 11 is placed 25mm inside the power frequency sensor 4, and the clamping of the core mold on the quenching machine is completed.

[0057] (3) Control of the heating process at the lower end of the core mold

[0058] First, start the power button of the medium frequency quenching transformer 1, first make the medium frequency power 50KW, and the medium frequency inductor 5 starts no-load heating. Then start the power button of the industrial frequency quenching transformer 2, give the industrial frequency initial power 500KW, and start the downward movement and rotation buttons of the machine tool while the industrial frequency inductor 4 starts heating, so that the downward movement speed of the core mold 11 is controlled at 42mm / min, and the rotation speed is controlled at 15r / min.

[0059] Start heating the core mold 11, observe the heating temperature of the core mold 11 according to the 4 temperature measuring devices of the quenching machine, and start heating and moving down the core mold 11 in the power frequency sensor 4, so that the temperature measuring point T1 in the middle of the power frequency sensor 4 reaches 720℃, and the temperature measuring point T2 near the outlet reaches 840℃. If the temperatures of T1 and T2 are too low or too high, slightly adjust the power of the power frequency quenching transformer 2 by 100KW each time and observe the temperature change until the temperature of T2 reaches about 840℃ when it is adjusted to 750kw; then the core mold 11 exits the power frequency sensor 4 and enters the medium frequency sensor 5, adjust the heating power of the medium frequency sensor 5 to about 200KW, adjust 50KW each time and observe the temperature change until it is adjusted to 280KW, so that the temperature of T3 reaches 860-870℃, and the temperature of T4 reaches 870-880℃. Then the core mold 11 is moved out of the intermediate frequency inductor 5 and directly enters the water spray circle 6 for cooling.

[0060] (4) Heating process control of the middle part of the core mold

[0061] After the lower end of the core mold 11 is heated by the two inductors of power frequency and medium frequency, the temperature of T4 reaches the quenching temperature of 870-880℃, and the core mold 11 continues to fall to the water spray circle 6 for cooling, and the quenching water pressure is 0.5MPa. At this time, the power of power frequency and medium frequency is basically stable, which can ensure that the temperature of T2 of the core mold 11 reaches 840℃ and the temperature of T4 reaches about 880℃ when it is heated, which can meet the quenching requirements. The heating process of the middle part of the core mold 11 only needs to slightly adjust the two powers and control the temperatures of T2 and T4. The temperatures of T1 and T3 are only for reference.

[0062] (5) Heating process control of the upper end of the core mold

[0063] When the upper end face of the core mold 11 moves to the same level as the upper end face of the power frequency sensor 4, due to the angular effect of induction heating, the heating power of the power frequency quenching transformer 2 needs to be gradually reduced from 750KW to 500KW to ensure that the temperature of the temperature measuring point T2 does not exceed 860℃. At the same time, when the upper end face moves to the middle position of the power frequency sensor 4, the power frequency heating is stopped. When the upper end face continues to move downward to the medium frequency sensor 5, due to the angular effect of induction heating, the heating power of the medium frequency quenching transformer 1 needs to be gradually reduced from 280KW to 100KW to ensure that the temperature of the temperature measuring point T4 does not exceed 880℃. At the same time, when the upper end face moves to the middle position of the medium frequency sensor 5, the medium frequency heating is stopped. The core mold 11 continues to maintain the original speed and enters the water spray circle 6 and then enters the water reservoir 7 to continue cooling for 100 minutes.

[0064] (6) Tempering process of core mold

[0065] When the actual temperature of the core mold 11 after cooling is ≤40°C, it is removed from the quenching machine, and then the core mold 11 is horizontally placed in a trolley-type tempering furnace, and then the temperature is increased to 230°C at 60°C / h and kept warm for 26 hours. After the insulation is completed, it is taken out of the furnace and air-cooled to room temperature.

[0066] (7) Result detection

[0067] After tempering, the hardness of each part of the core mold was tested as shown in Table 3:

[0068] Table 3 Hardness test results of the core mold after tempering

[0069] Detection point ① Check point ② Check point ③ Check point ④ Detection point ⑤ HRC60 HRC61 HRC61 HRC60 HRC62

[0070] After cutting off the extended part at one end of the core mold, the depth of the hardened layer is tested from the end surface as shown in Table 4 below:

[0071] Table 4 Results of hardened layer depth of core mold after tempering

[0072]

[0073] After cutting off the extended part of the core mold, the mechanical properties of the samples were taken from the center of the wall thickness for testing as shown in Table 5 below:

[0074] Table 5 Mechanical properties test results of the core mold wall thickness center after tempering

[0075]

[0076] From Table 3-5 above, it can be seen that: first, the hardness of the core mold is tested to be around HRC60-62, and the layer depth of the cross-section hardness is also 23mm, which meets the technical requirements of the drawings. At the same time, the mechanical properties tested by taking the mechanical properties sample at the center of the wall thickness of the core mold are also close to the mechanical properties of the original quenching and tempering, proving that the dual-frequency quenching has no effect on the comprehensive mechanical properties of the core mold. Therefore, after the heat treatment method shown in the present invention, the GCr15SiM core mold of this specification reaches the required quenching hardness and layer depth, while ensuring the comprehensive mechanical properties of the original quenching and tempering state, which can meet the use requirements of the core mold during spinning.

[0077] Example 2

[0078] This embodiment uses a core mold made of GCr15SiMn material, and its product dimensions are: diameter 600mm, length 2200mm, wall thickness 100mm, quenching hardness requirement HRC58-62, layer depth ≥20mm, and the basic parameters of the dual-frequency quenching transformer are the same as those in Example 1.

[0079] The double-frequency induction quenching heat treatment method of the GCr15SiMn material core mold has the following specific steps:

[0080] (1) The installation method of the sensor and the water spray ring before quenching is the same as that of Example 1, except that the diameter of the water spray ring 6 is 750 mm; the diameter of the power frequency sensor 4 is 675 mm, the diameter of the medium frequency sensor 5 is 650 mm, and the distance between the water spray ring 6 and the medium frequency sensor 5 is 30 mm.

[0081] (2) Clamping of the core mold on the quenching machine

[0082] The specifications and installation method of the two tooling flanges are the same as those in Example 1, so that the lower end surface of the core mold 11 is placed 20 mm inside the power frequency sensor 4, and the core mold is clamped in the quenching machine.

[0083] (3) Control of the heating process at the lower end of the core mold

[0084] First, start the power button of the medium frequency quenching transformer 1, and make the medium frequency power about 40KW. The medium frequency inductor 5 starts no-load heating. Then start the power button of the industrial frequency quenching transformer 2, give the initial industrial frequency power of 400KW, and start the downward movement and rotation buttons of the machine tool while the industrial frequency inductor 4 starts heating, so that the downward movement speed of the core mold 11 is controlled at 40mm / min, and the rotation speed is controlled at 10r / min.

[0085] Start heating the core mold 11, and observe the heating temperature of the core mold 11 according to the 4 temperature measuring devices of the quenching machine. The core mold 11 starts to heat and move down in the power frequency sensor 4, so that the temperature measuring point T1 in the middle of the power frequency sensor 4 reaches 700℃, and the temperature measuring point T2 near the outlet reaches 820℃. If the temperatures of T1 and T2 are too low or too high, slightly adjust the power of the power frequency quenching transformer 2, adjust 100KW each time and observe the temperature change until it is adjusted to 750kw and the temperature of T2 reaches about 820℃; then the core mold 11 exits the power frequency sensor 4 and enters the medium frequency sensor 5, adjust the heating power of the medium frequency sensor 5 to about 200KW, adjust 50KW each time and observe the temperature change until it is adjusted to 280KW, so that the temperature of T3 reaches 860-870℃, and the temperature of T4 reaches 870-880℃. Then the core mold 11 is moved out of the intermediate frequency inductor 5 and directly enters the water spray circle 6 for cooling.

[0086] (4) Heating process control of the middle part of the core mold:

[0087] After the lower end of the core mold 11 is heated by the two inductors of power frequency and medium frequency, the temperature of T4 reaches the quenching temperature of 870-880℃, and the core mold 11 continues to fall to the water spray circle 6 for cooling, and the quenching water pressure is 0.5MPa. At this time, the power of power frequency and medium frequency is basically stable, which can ensure that the temperature of T2 of the core mold 11 reaches 820℃ and the temperature of T4 reaches about 880℃ when it is heated, which can meet the quenching requirements. The heating process of the middle part of the core mold 11 only needs to slightly adjust the two powers, and focus on controlling the temperatures of T2 and T4.

[0088] (5) Heating process control of the upper end of the core mold

[0089] When the upper end face of the core mold 11 moves to the same level as the upper end face of the power frequency sensor 4, due to the angular effect of induction heating, the heating power of the power frequency quenching transformer 2 needs to be gradually reduced from 750KW to 500KW to ensure that the temperature of the temperature measuring point T2 does not exceed 860℃. At the same time, when the upper end face moves to the middle position of the power frequency sensor 4, the power frequency heating is stopped. When the upper end face continues to move downward to the medium frequency sensor 5, due to the angular effect of induction heating, the heating power of the medium frequency quenching transformer 1 needs to be gradually reduced from 280KW to 100KW to ensure that the temperature of the temperature measuring point T4 does not exceed 880℃. At the same time, when the upper end face moves to the middle position of the medium frequency sensor 5, the medium frequency heating is stopped. The core mold 11 continues to maintain the original speed and enters the water spray circle 6 and then enters the water reservoir 7 to continue cooling for 100 minutes.

[0090] (6) Tempering process of core mold

[0091] When the actual temperature of the core mold 11 after cooling is ≤40°C, it is removed from the quenching machine, and then the core mold 11 is placed horizontally in a trolley-type tempering furnace, and then the temperature is increased to 230°C at 60°C / h and kept warm for 25h. After the insulation is completed, it is taken out of the furnace and air-cooled to room temperature.

[0092] (7) Result detection

[0093] After tempering, the hardness of each part of the core mold was tested as shown in Table 6 below:

[0094] Table 6 Hardness test results of the core mold after tempering

[0095] Detection point ① Check point ② Detection point ③ Check point ④ Detection point ⑤ HRC61 HRC61 HRC61 HRC59 HRC60

[0096] After cutting off the extended part at one end of the core mold, the depth of the hardened layer is tested from the end surface as shown in Table 7 below:

[0097] Table 7 Results of hardened layer depth of core mold after tempering

[0098]

[0099] After cutting off the extended part of the core mold, the mechanical properties of the samples were taken from the center of the wall thickness for testing as shown in Table 8 below:

[0100] Table 8 Mechanical properties test results of the core mold wall thickness center after tempering

[0101]

[0102] From Table 6-8 above, we can see that: firstly, the hardness of the core mold reaches about HRC59-61, and the layer depth of the cross-section hardness is also 25mm, which meets the technical requirements of the drawings. At the same time, the mechanical properties of the mechanical properties test sample taken at the center of the wall thickness of the core mold are also close to the mechanical properties of the original quenching and tempering, proving that the dual-frequency quenching has no effect on the comprehensive mechanical properties of the core mold.

[0103] Example 3

[0104] This embodiment uses a core mold made of GCr15SiMn material, and its product dimensions are: diameter 700mm, length 2500mm, wall thickness 105mm, quenching hardness requirement HRC58-62, layer depth ≥20mm, and the basic parameters of the dual-frequency quenching transformer are the same as those in Example 1.

[0105] The double-frequency induction quenching heat treatment method of the GCr15SiMn material core mold has the following specific steps:

[0106] (1) The installation method of the sensor and the water spray ring before quenching is the same as that of Example 1, except that the diameter of the water spray ring 6 is 900 mm; the diameter of the power frequency sensor 4 is 775 mm, the diameter of the medium frequency sensor 5 is 750 mm, and the distance between the water spray ring 6 and the medium frequency sensor 5 is 40 mm.

[0107] (2) Clamping of the core mold on the quenching machine

[0108] The specifications and installation methods of the two tooling flanges are the same as those in Example 1, so that the lower end surface of the core mold 11 is placed 30 mm inside the power frequency sensor 4, and the core mold is clamped in the quenching machine.

[0109] (3) Control of the heating process at the lower end of the core mold

[0110] First, start the power button of the medium frequency quenching transformer 1, and make the medium frequency power about 60KW. The medium frequency inductor 5 starts no-load heating. Then start the power button of the industrial frequency quenching transformer 2, give the industrial frequency initial power of 450KW, and start the downward movement and rotation buttons of the machine tool while the industrial frequency inductor 4 starts heating, so that the downward movement speed of the core mold 11 is controlled at 45mm / min, and the rotation speed is controlled at 13r / min.

[0111] Start heating the core mold 11, observe the heating temperature of the core mold 11 according to the 4 temperature measuring devices of the quenching machine, and start heating and moving down the core mold 11 in the power frequency sensor 4, so that the temperature measuring point T1 in the middle of the power frequency sensor 4 reaches 740℃, and the temperature measuring point T2 near the outlet reaches 830℃. If the temperatures of T1 and T2 are too low or too high, slightly adjust the power of the power frequency quenching transformer 2 by 100KW each time and observe the temperature change until the temperature of T2 reaches about 830℃ when it is adjusted to 750kw; then the core mold 11 exits the power frequency sensor 4 and enters the medium frequency sensor 5, adjust the heating power of the medium frequency sensor 5 to about 200KW, adjust 50KW each time and observe the temperature change until it is adjusted to 280KW, so that the temperature of T3 reaches 860-870℃, and the temperature of T4 reaches 870-880℃. Then the core mold 11 is moved out of the intermediate frequency inductor 5 and directly enters the water spray circle 6 for cooling.

[0112] (4) Heating process control of the middle part of the core mold:

[0113] After the lower end of the core mold 11 is heated by the two inductors of power frequency and medium frequency, the temperature of T4 reaches the quenching temperature of 870-880℃, and the core mold 11 continues to fall to the water spray circle 6 for cooling, and the quenching water pressure is 0.4MPa. At this time, the power of power frequency and medium frequency is basically stable, which can ensure that the temperature of T2 of the core mold 11 reaches 820℃ and the temperature of T4 reaches about 880℃ when it is heated, which can meet the quenching requirements. The heating process of the middle part of the core mold 11 only needs to slightly adjust the two powers, and focus on controlling the temperatures of T2 and T4.

[0114] (5) Heating process control of the upper end of the core mold

[0115] When the upper end face of the core mold 11 moves to the same level as the upper end face of the power frequency sensor 4, due to the angular effect of induction heating, the heating power of the power frequency quenching transformer 2 needs to be gradually reduced from 750KW to 500KW to ensure that the temperature of the temperature measuring point T2 does not exceed 860℃. At the same time, when the upper end face moves to the middle position of the power frequency sensor 4, the power frequency heating is stopped. When the upper end face continues to move downward to the medium frequency sensor 5, due to the angular effect of induction heating, the heating power of the medium frequency quenching transformer 1 needs to be gradually reduced from 280KW to 100KW to ensure that the temperature of the temperature measuring point T4 does not exceed 880℃. At the same time, when the upper end face moves to the middle position of the medium frequency sensor 5, the medium frequency heating is stopped. The core mold 11 continues to maintain the original speed and enters the water spray circle 6 and then enters the water reservoir 7 to continue cooling for 100 minutes.

[0116] (6) Tempering process of core mold

[0117] When the actual temperature of the core mold 11 after cooling is ≤40°C, it is removed from the quenching machine, and then the core mold 11 is horizontally placed in a trolley-type tempering furnace, and then the temperature is increased to 230°C at 60°C / h and kept warm for 26 hours. After the insulation is completed, it is taken out of the furnace and air-cooled to room temperature.

[0118] (7) Result detection

[0119] After tempering, the hardness of each part of the core mold is tested as shown in Table 9 below:

[0120] Table 9 Hardness test results of the core mold after tempering

[0121] Detection point ① Check point ② Check point ③ Check point ④ Detection point ⑤ HRC62 HRC61 HRC60 HRC61 HRC60

[0122] After cutting off the extended part at one end of the core mold, the depth of the hardened layer is tested from the end surface as shown in Table 10 below:

[0123] Table 10 Results of hardened layer depth of core mold after tempering

[0124]

[0125] After cutting off the extended part of the core mold, the mechanical properties of the samples were taken from the center of the wall thickness for testing as shown in Table 11:

[0126] Table 11 Mechanical properties test results of the core mold wall thickness center after tempering

[0127]

[0128] From Tables 9-11 above, we can see that: firstly, the hardness of the core mold reaches about HRC60-62, and the layer depth of the cross-section hardness is also 25mm, which meets the technical requirements of the drawings. At the same time, the mechanical properties of the mechanical properties test sample taken at the center of the wall thickness of the core mold are also close to the mechanical properties of the original quenching and tempering, proving that the dual-frequency quenching has no effect on the comprehensive mechanical properties of the core mold.

Claims

1. A dual-frequency induction quenching heat treatment method for a large diameter GCr15SiMn core mold, characterized in that: The specific steps are as follows: S1. Install the selected power frequency sensor (4) and medium frequency sensor (5) on two quenching transformers of the dual-frequency quenching machine respectively, and install the water spray ring (6) under the two sensors; S2, vertically hanging the core mold (11) on the dual-frequency quenching machine, and placing the lower end surface of the core mold (11) in the power frequency sensor (4); S3, setting the industrial frequency initial power, the intermediate frequency initial power, the downward movement speed and the rotation speed of the core mold (11); S4, the core mold (11) starts to be heated, and the core mold (11) starts to rotate and move downward, and the power frequency sensor (4) and the medium frequency sensor (5) heat the core mold (11) successively, and finally the core mold (11) moves out of the medium frequency sensor (5) and enters the water spray circle (6) and the water reservoir (7) for cooling, thereby obtaining the quenched core mold (11); S5, placing the quenched core mold (11) into a trolley-type resistance furnace for tempering, air-cooling to room temperature after tempering for inspection, and completing the dual-frequency induction quenching heat treatment of the large-diameter GCr15SiMn material core mold (11).

2. The dual-frequency induction quenching heat treatment method of the large-diameter GCr15SiMn material core mold (11) according to claim 1 is characterized in that: The inner diameter of the industrial frequency inductor (4) selected in S1 is 75 mm larger than the outer diameter of the GCr15SiMn core mold (11), the inner diameter of the medium frequency inductor (5) is 50 mm larger than the outer diameter of the GCr15SiMn core mold (11), and the inner diameter of the water spray ring (6) is 150-200 mm larger than the outer diameter of the core mold (11); the industrial frequency inductor (4) is installed on the industrial frequency quenching transformer (2), and the medium frequency inductor (5) is installed on the medium frequency quenching transformer (1), the specification of the industrial frequency quenching transformer (2) is 1500 kW / 36-60 Hz, and the specification of the medium frequency quenching transformer (1) is 750 kW / 180-275 Hz; During installation, the centers of the power frequency sensor (4) and the medium frequency sensor (5) are on a straight line, the power frequency sensor (4) is above the medium frequency sensor (5), and the distance between the two is 120 mm, and the water spray circle (6) is below the medium frequency sensor (5), and the distance between the two is 30 to 50 mm.

3. The dual-frequency induction quenching heat treatment method of the large-diameter GCr15SiMn material core mold (11) according to claim 1 is characterized in that: In S2, a special machine tool hanger (10) is used to vertically hang the core mold (11) on a dual-frequency quenching machine, and the lower end surface of the core mold (11) enters the power frequency sensor (4) by 20 to 30 mm.

4. The dual-frequency induction quenching heat treatment method for the large-diameter GCr15SiMn core mold (11) according to claim 1 is characterized in that: The specific operation of S3 is: first start the medium frequency power button to make the medium frequency power 40-60KW, the medium frequency sensor (5) starts to heat slightly at no load, then start the industrial frequency power button, give the industrial frequency initial power of 400-500KW, the industrial frequency sensor (4) starts heating and at the same time starts the downward movement and rotation buttons of the machine tool, the downward movement speed of the core mold (11) is 40-45mm / min, and the rotation speed is 10-15r / min.

5. The dual-frequency induction quenching heat treatment method for the large-diameter GCr15SiMn material core mold (11) according to claim 1 is characterized in that: The specific method of S4 is as follows: when heating the core mold (11), the heating temperature of the core mold (11) is observed according to the temperature measuring device of the quenching machine, and the heating power of the power frequency sensor (4) is adjusted. The core mold (11) is heated and moved downward in the power frequency sensor (4), so that the temperature measuring point T1 in the middle of the power frequency sensor (4) reaches 700-740° C., and the temperature measuring point T2 near the outlet of the power frequency sensor (4) reaches 820-840° C. Then, the lower end surface of the core mold (11) enters the intermediate frequency sensor (5), and the temperature measuring point T3 in the middle of the intermediate frequency sensor (5) is detected. and the temperature of the temperature measuring point T4 near the outlet, and further adjust the heating power of the medium frequency sensor (5) so that the temperature T3 of the core mold (11) reaches 860-870°C and the temperature T4 reaches 870-880°C during the medium frequency heating process. Subsequently, the core mold (11) is removed from the medium frequency sensor (5) and directly enters the water spray circle (6) for cooling. The spray quenching water pressure is 0.4-0.5MPa. After passing through the water spray circle 6, the core mold 11 enters the water reservoir 7 and continues to cool for a certain period of time. The cooling time is calculated based on the effective cross-section of the core mold 11 at 0.5-1min / mm to obtain the quenched core mold.

6. The dual-frequency induction quenching heat treatment method for a large-diameter GCr15SiMn core mold (11) according to claim 5 is characterized in that: When the lower end of the core mold (11) enters the water spray ring (6) for cooling, the remaining part is continuously heated in the two inductors, wherein the heating power of the medium frequency inductor (5) and the industrial frequency inductor (4) is basically stable, ensuring that the temperature of T2 is stable at 820-840°C and the temperature of T4 is stable at 870-880°C, and the core mold (11) is continuously heated and spray-quenched from bottom to top; When the upper end surface of the core mold (11) moves to the industrial frequency sensor (4), due to the angular effect of induction heating, the heating power of the industrial frequency sensor (4) needs to be reduced to ensure that the temperature of the temperature measuring point T2 does not exceed 860°C. At the same time, when the upper end surface moves to the middle position of the industrial frequency sensor (4), the industrial frequency heating is stopped; when the upper end surface of the core mold (11) continues to move downward to the intermediate frequency sensor (5), due to the angular effect of induction heating, the heating power of the intermediate frequency sensor (5) needs to be reduced to ensure that the temperature of the temperature measuring point T4 does not exceed 880°C. At the same time, when the upper end surface of the core mold (11) moves to the middle position of the intermediate frequency sensor (5), the intermediate frequency heating is stopped.

7. The dual-frequency induction quenching heat treatment method for a large-diameter GCr15SiMn core mold (11) according to claim 5 is characterized in that: The temperature measuring device of the quenching machine tool in S4 is composed of four dual-color infrared thermometers and a matching temperature controller. The temperature is measured at a point in the middle and near the outlet of the power frequency induction line, which are T1 and T2; the temperature is measured at a point in the middle and near the outlet of the medium frequency induction line (5), which are T3 and T4; if the temperature of T1 and T2 is too low or too high, the heating power of the power frequency is slightly adjusted by 100KW each time and the temperature change is observed; if the temperature of T3 and T4 is too low or too high, the heating power of the medium frequency is slightly adjusted by 50KW each time and the temperature change is observed.

8. The dual-frequency induction quenching heat treatment method for the large-diameter GCr15SiMn material core mold (11) according to claim 1 is characterized in that: The specific process of the S5 tempering is as follows: after the core mold (11) is removed from the quenching machine, it is placed horizontally in a trolley-type tempering furnace, and then the temperature is raised to 230°C at 60°C / h and kept warm for 12 to 18 min / mm. The temperature uniformity of the tempering furnace is ±5°C.

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