A method for preparing a mold

Abstract

The present invention discloses a method for preparing a mold, wherein the mold comprises a template and a mold core embedded in a matching hole of the template, wherein the template is made of hot working die steel and the mold core is made of hard alloy. The preparation method comprises the following steps: (1) determining a set working temperature T of the mold; (2) determining the outer dimensions of the matching surface of the mold core at room temperature; (3) calculating the dimensions of the matching hole of the template at room temperature according to the following formula; L DAC =L WC +[α WC *L WC *(T‑t)]‑[(α DAC ‑α WC )*L WC *(T‑t)*B]; (4) processing the inserting hole of the template according to the result calculated in step (3); (5) inserting the mold core into the inserting hole of the template at a set working temperature T. The application can reduce the production cost of the mold and ensure the normal use of the mold at high temperature and the storage at room temperature.

Description

Technical Field

[0001] The invention relates to a method for preparing a mould. Background Art

[0002] Microchannel aluminum flat tubes are the main components for manufacturing heat exchangers for automobiles, home and commercial air conditioners. Due to the small cross-section, thin wall thickness, high dimensional accuracy, light density, and large extrusion ratio of microchannel aluminum flat tubes, the material, design and processing requirements of the mold are extremely high. This has caused the processing cost of the microchannel aluminum flat tube production mold to remain high. Summary of the invention

[0003] In order to solve the above problems, the present invention proposes a method for preparing a mold, wherein the mold comprises a template and a mold core, and the mold core is embedded in an inserting hole of the template, wherein the template is made of hot working die steel, and the mold core is made of cemented carbide. The preparation method comprises the following steps:

[0004] (1) Determine the set working temperature T of the mold;

[0005] (2) Determine the outer dimensions of the mold core's mating surface at room temperature;

[0006] (3) Calculate the size of the template's mounting hole at room temperature according to the following formula;

[0007] L DAC =L WC +[α WC *L WC *(Tt)]-[(α DAC -α WC )*L WC *(Tt)*B]

[0008] in:

[0009] L DAC Represents the size of the template's mounting hole at room temperature;

[0010] L WC Represents the outer dimensions of the mold core's mounting surface at room temperature;

[0011] α DAC Represents the thermal expansion coefficient of hot working die steel;

[0012] α WC Represents the thermal expansion coefficient of hot-working tungsten steel;

[0013] t represents room temperature;

[0014] B is a constant;

[0015] (4) processing the mounting holes of the template according to the result calculated in step (3);

[0016] (5) At the set working temperature T, the mold core is inserted into the inserting hole of the template.

[0017] In this application, t is 20°C.

[0018] Specifically, the hot working die steel is DAC steel, and the hard alloy is VD45 tungsten steel. The die in the present application is used to produce microchannel aluminum flat tubes.

[0019] In order to reduce the production cost of the mold, this application uses hot working die steel and tungsten steel to produce insert-type molds, wherein the template is made of hot working die steel and the mold core is made of cemented carbide. Since the cost of hot working die steel is lower than that of cemented carbide, the production cost of the mold can be reduced.

[0020] However, due to the different thermal expansion coefficients of hot working die steel and cemented carbide, among which the thermal expansion coefficient of hot working die steel is larger than that of cemented carbide, if the interference fit of the structure is too small, when the mold works at high temperature, the expansion of the hot working die steel will be much larger than that of the cemented carbide, resulting in a gap between the mold core and the template, causing the mold core to loosen in the template, resulting in a large dimensional tolerance of the microchannel aluminum flat tube; if the interference fit of the structure is too large, at room temperature, the shrinkage of the hot working die steel will be much larger than that of the cemented carbide, causing the pressure of the template on the mold core to be too large, resulting in cracking of the mold core and causing failure of the mold. The use of the present application can effectively avoid the occurrence of the above phenomenon, which can not only ensure the normal use of the mold at high temperature, but also ensure the preservation of the mold at room temperature.

[0021] Specifically, to further ensure that the mold can remain stable at room temperature and during operation, B is 1.25-1.35.

[0022] Specifically, in order to ensure that the template and the mold core can remain stable throughout the entire working temperature range, the working temperature T is set to the arithmetic mean of the highest and lowest values ​​of the mold working temperature.

[0023] Specifically, when the cross section of the fitting surface of the mold core is circular, the cross section of the fitting hole is circular, the outer dimension of the fitting surface at room temperature is the outer diameter of the fitting surface at room temperature, and the dimension of the fitting hole at room temperature is the inner diameter of the fitting hole at room temperature;

[0024] When the cross-section of the mating surface of the mold core is rectangular, the mating hole is rectangular, and the outer dimensions of the mating surface at room temperature include a first length and a first width of the cross-section of the mating surface at room temperature, and the dimensions of the mating hole at room temperature include a second length and a second width of the cross-section of the mating hole at room temperature; the second length is calculated based on the first length, and the second width is calculated based on the first width.

[0025] According to the different shapes of the mold core, select the corresponding calculation method.

[0026] Further, step (5) is specifically as follows: the mold core and the template with the fitting hole are heated to a set working temperature T at the same time, and then kept warm. After the insulation is completed, the mold core is fitted into the fitting hole at the set working temperature. This design can smoothly fit the mold core to the template.

[0027] Specifically, to ensure that the mold core and the mold plate can fully expand, the insulation time is 1.8-3 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of an embodiment of the present invention.

[0029] Figure 2 yes Figure 1 View along center line A-A.

[0030] Figure 3 It is a schematic diagram of the structure of the template.

[0031] Figure 4 It is a structural diagram of the mold core. DETAILED DESCRIPTION

[0032] Example 1

[0033] The following first describes the structure of the mold, please refer to Figure 1 and Figure 2 The mold includes a template 10 with a circular outer surface and a core 20 embedded in the template 10. A fitting hole 11 with a rectangular cross section is provided in the center of the template 10. The core is embedded in the fitting hole 11 of the template. The template is made of hot working die steel and the core is made of cemented carbide. Specifically in this embodiment, the hot working die steel is DAC steel produced by Hitachi Metals Co., Ltd. of Japan, that is, the hot working die steel is DAC steel, and the cemented carbide is Fuji VD45 tungsten steel of Japan, that is, the cemented carbide is VD45 tungsten steel.

[0034] The following is an explanation of the method for preparing the mold, which comprises the following steps:

[0035] (1) Determine the set working temperature T of the mold; specifically, in this embodiment, the working temperature of the mold is 500-600°C, and the arithmetic average of 500°C and 600°C, 550°C, is taken as the set working temperature T.

[0036] (2) Determine the outer dimensions of the inserting surface of the mold core at room temperature, wherein the cross section of the inserting surface is rectangular, and at room temperature, the first length L of the cross section of the inserting surface is WC长 The first width L of the cross section of the mounting surface is 30 mm. WC宽 20mm

[0037] (3) Calculate the size of the template's mounting hole at room temperature according to the following formula;

[0038] L DAC =L WC +[α WC *L WC *(Tt)]-[(α DAC -α WC )*L WC *(Tt)*B]

[0039] in:

[0040] L DAC Represents the size of the template's mounting hole at room temperature;

[0041] L WC Represents the outer dimensions of the mold core's mounting surface at room temperature;

[0042] α DAC Represents the thermal expansion coefficient of hot working die steel. In this embodiment, α DAC is 13.02*10 -6 / ℃;

[0043] α WC Represents the thermal expansion coefficient of hot-working tungsten steel. In this embodiment, α WC is 6.04*10 -6 / ℃;

[0044] t represents normal temperature, specifically 20°C;

[0045] B is a constant. In the embodiment, B=1.3;

[0046] According to the formula, the second length L of the cross section of the mounting hole at room temperature is obtained. DAC长 The second width L of the cross section of the mounting hole at room temperature is 29.952 mm. DAC宽 It is 19.968mm.

[0047] (4) According to the result calculated in step (3), the mounting hole 11 of the template 10 is processed.

[0048] (5) At the set working temperature T, the mold core is inserted into the inserting hole of the template. The specific operation steps are as follows:

[0049] The core mold 20 and the template 10 are heated to a set working temperature of 550° C. at the same time, and then kept warm for 2 hours. After the insulation is completed, the core mold is inserted into the inserting hole at the set working temperature.

[0050] The mold in this embodiment has good stability both at room temperature and at working temperature. Even if the mold can be stored at room temperature, it can be smoothly produced at working temperature, and the produced microchannel aluminum flat tube meets the design requirements.

[0051] When the size of the fitting hole at room temperature in this embodiment is the same as the size of the mold core at room temperature, the template and the mold core are matched with zero clearance at room temperature, and the mold core can be stably embedded in the fitting hole of the template. However, at the set working temperature T of 550°C, the size of the cross section of the mold core is 20.064*30.096mm, and the size of the cross section of the fitting hole of the template is 20.138*30.207mm. There is a large gap between the template and the mold core. When working, the mold core has a large range of motion, resulting in excessive dimensional deviation of the microchannel aluminum flat tube, causing the product to be unqualified.

[0052] When the size of the fitting hole in this embodiment at the set working temperature T is the same as the size of the mold core at the set working temperature T, that is, at the set working temperature T, the size of the cross section of the fitting hole and the size of the cross section of the mold core are both 20.064*30.096mm. When the mold is cooled to room temperature, the size of the cross section of the fitting hole is 19.92*29.89mm, and the size of the cross section of the mold core is 20*30mm. The mold core is strongly squeezed by the template, causing the mold core to crack.

[0053] Example 2

[0054] This embodiment is basically the same as Embodiment 1, except that:

[0055] In this embodiment, the cross-section of the fitting surface of the mold core is circular, the cross-section of the fitting hole is circular, the outer dimension of the fitting surface at room temperature is the outer diameter of the fitting surface at room temperature, and the dimension of the fitting hole at room temperature is the inner diameter of the fitting hole at room temperature.

[0056] Specifically in this embodiment, the outer diameter of the fitting surface at room temperature is 26 mm, and according to the formula, the inner diameter of the fitting hole at room temperature is 25.958 mm.

Claims

1. A method for preparing a mold, characterized in that: The mold comprises a template and a mold core, wherein the mold core is embedded in the inserting hole of the template, wherein the template is made of hot working die steel, and the mold core is made of hard alloy. The preparation method comprises the following steps: (1) Determine the set working temperature T of the mold, which is the arithmetic mean of the highest and lowest working temperatures of the mold; (2) Determine the outer dimensions of the mold core's mating surface at room temperature; (3) Calculate the size of the template's mounting hole at room temperature according to the following formula; L DAC =L WC +[α WC *L WC *(T-t)]-[(α DAC -α WC )*L WC *(T-t)*B] in: L DAC Represents the size of the template's mounting hole at room temperature; L WC Represents the outer dimensions of the mold core's mounting surface at room temperature; α DAC Represents the thermal expansion coefficient of hot working die steel; α WC Represents the thermal expansion coefficient of hot-working tungsten steel; t represents room temperature; B is a constant; When the cross section of the fitting surface of the mold core is circular, the cross section of the fitting hole is circular, the outer dimension of the fitting surface at room temperature is the outer diameter of the fitting surface at room temperature, and the dimension of the fitting hole at room temperature is the inner diameter of the fitting hole at room temperature; When the cross section of the fitting surface of the mold core is rectangular, the fitting hole is rectangular, the outer dimensions of the fitting surface at room temperature include a first length and a first width of the cross section of the fitting surface at room temperature, and the dimensions of the fitting hole at room temperature include a second length and a second width of the cross section of the fitting hole at room temperature; the second length is calculated based on the first length, and the second width is calculated based on the first width; (4) processing the mounting holes of the template according to the result calculated in step (3); (5) At a set working temperature T, the mold core is inserted into the inserting hole of the template. Specifically, the mold core and the template with the inserting hole are heated to the set working temperature T at the same time, and then kept warm. After the insulation is completed, the mold core is inserted into the inserting hole at the set working temperature.

2. The preparation method according to claim 1, characterized in that: B is 1.25-1.

35.

3. The preparation method according to claim 1, characterized in that: The length of time for this incubation is 1.8-3 hours.

4. The preparation method according to claim 1, characterized in that: The hot working die steel is DAC steel and the cemented carbide is VD45 tungsten steel.

Images