CN116790866A - Heat treatment process for reducing quenching deformation cracking of die casting die steel - Google Patents
Heat treatment process for reducing quenching deformation cracking of die casting die steel Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 68
- 238000010438 heat treatment Methods 0.000 title claims abstract description 60
- 238000010791 quenching Methods 0.000 title claims abstract description 44
- 230000000171 quenching effect Effects 0.000 title claims abstract description 43
- 238000004512 die casting Methods 0.000 title claims abstract description 34
- 238000005336 cracking Methods 0.000 title claims abstract description 32
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 22
- 239000010959 steel Substances 0.000 title claims abstract description 22
- 238000001816 cooling Methods 0.000 claims abstract description 81
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 80
- 238000002844 melting Methods 0.000 claims description 60
- 230000008018 melting Effects 0.000 claims description 57
- 229910052757 nitrogen Inorganic materials 0.000 claims description 38
- 239000000843 powder Substances 0.000 claims description 30
- 229910052751 metal Inorganic materials 0.000 claims description 18
- 239000002184 metal Substances 0.000 claims description 18
- 239000007789 gas Substances 0.000 claims description 10
- 238000005253 cladding Methods 0.000 claims description 9
- 238000002425 crystallisation Methods 0.000 claims description 6
- 230000008025 crystallization Effects 0.000 claims description 6
- 230000002787 reinforcement Effects 0.000 claims description 6
- 230000001133 acceleration Effects 0.000 claims description 3
- 238000004321 preservation Methods 0.000 claims description 3
- 238000007711 solidification Methods 0.000 claims description 3
- 230000008023 solidification Effects 0.000 claims description 3
- 238000003892 spreading Methods 0.000 claims description 3
- 229910001873 dinitrogen Inorganic materials 0.000 claims 4
- 230000001276 controlling effect Effects 0.000 abstract description 5
- 239000000112 cooling gas Substances 0.000 abstract description 5
- 230000001105 regulatory effect Effects 0.000 abstract description 5
- 238000009827 uniform distribution Methods 0.000 abstract 1
- 230000035882 stress Effects 0.000 description 7
- 230000008646 thermal stress Effects 0.000 description 7
- 230000007547 defect Effects 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 238000001000 micrograph Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- 229910000861 Mg alloy Inorganic materials 0.000 description 1
- 229910000978 Pb alloy Inorganic materials 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 229910001338 liquidmetal Inorganic materials 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 238000004886 process control Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0062—Heat-treating apparatus with a cooling or quenching zone
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C24/00—Coating starting from inorganic powder
- C23C24/08—Coating starting from inorganic powder by application of heat or pressure and heat
- C23C24/10—Coating starting from inorganic powder by application of heat or pressure and heat with intermediate formation of a liquid phase in the layer
- C23C24/103—Coating with metallic material, i.e. metals or metal alloys, optionally comprising hard particles, e.g. oxides, carbides or nitrides
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
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- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Heat Treatment Of Articles (AREA)
Abstract
The application discloses a heat treatment process for reducing quenching deformation and cracking of die-casting die steel, which is high in operability, free from increasing process cost and simple in process, and the process realizes pre-cooling, weak cooling and strong cooling of the die at each stage of die quenching by regulating and controlling cooling gas pressure and fan rotating speed in a sectional manner so as to control the weak part of the die to be influenced by improper cooling to generate deformation and even cracking. The uniform distribution of the heat treatment hardness of the die is ensured by regulating and controlling the pressure of cooling gas and the rotation speed of a fan in a sectional manner, and the hardness unevenness of the die is less than 1.5HRC; compared with the conventional heat treatment process, the impact energy of 80-100J is improved. After 1000 times of thermal fatigue circulation, compared with the conventional heat treatment process, the main crack length is reduced by 250-260 mu m, the crack width is reduced by 7-24 mu m, and the thermal fatigue performance is good.
Description
Technical Field
The application relates to the technical field of material heat treatment, in particular to a heat treatment process for reducing quenching deformation cracking of die casting die steel.
Background
The mold is the most important process equipment in the manufacturing industry, and the mold manufacturing level is an important mark for measuring the national manufacturing level. Die casting die steel is the main tool for forming liquid metal. The die shape is very complicated under the influence of the product structure, more thin walls, sharp angles and the like are inevitably generated, particularly, the existence of stepped thickness differences can influence that the die is more or less deformed or even cracked during quenching, if the die is deformed excessively or cracked, the manufacturing cost of the die is directly increased, and meanwhile, the production exchange period of the product is also greatly influenced.
H13 steel is currently the most widely used and representative hot work die steel. It is known that thermal fatigue cracks are easy to propagate in grain boundaries, and the thermal fatigue performance of hot work die steel is improved at the present stage mainly by adding alloy elements to realize solid solution strengthening and second phase strengthening so as to inhibit the initiation and the propagation of the thermal fatigue cracks.
Prior art documents, patent numbers: 201010224086.8, patent name: a vacuum isothermal heat treatment process for a large-sized die casting mold, which can obtain ideal tissue performance and minimum deformation, is disclosed. The technical problems are that nitrogen of 9bar is filled at the beginning of quenching and cooling, and for large-scale, particularly complex die casting dies, large thermal stress and tissue stress are generated due to rapid cooling, a certain deformation or cracking risk exists, and the larger the pressure is, the larger the temperature difference acting on different structural surfaces of the die is, and the larger the temperature difference is, the larger the thermal stress and the tissue stress are.
Aiming at the defects, the application develops a method which is suitable for a low-cost, simple and feasible heat treatment process to reduce the heat treatment deformation or cracking of the H13 die casting die steel.
Disclosure of Invention
In order to overcome the defects, the application aims to provide a heat treatment process for reducing the quenching deformation and cracking of die-casting die steel, the process control is carried out by improving the heat treatment process, the operability is high, the process cost is not increased, the process is simple, and the pre-cooling, weak cooling and strong cooling are carried out at each stage of die quenching by regulating and controlling the pressure of cooling gas and the rotating speed of a fan in a segmented manner so as to control the weak part of the die to be influenced by improper cooling to generate deformation or even cracking.
In order to achieve the above purpose, the application adopts the following technical scheme:
a heat treatment process for reducing quenching deformation cracking of die casting die steel comprises the following steps:
(1) Placing the prepared mould in a vacuum high-pressure gas quenching furnace, heating and preserving heat by adopting a conventional quenching process to fully austenitize the mould;
(2) Filling 3bar of high-purity nitrogen into the die after full austenitizing in the step (1) in a slow inflation mode, wherein the inflation rate is 0.15 bar/s, starting a cooling fan, setting the rotating speed at 1800 rpm, and keeping cooling for 1min;
(3) After cooling the mold in the step (2) for 1min, filling high-purity nitrogen in a slow inflation mode to pressurize to 6bar, wherein the inflation rate is 0.30 bar/s, accelerating the rotating speed of a cooling fan to 2200 rpm, and keeping cooling for 1min;
(4) Filling high-purity nitrogen into the die after cooling and heat preservation in the step (3) in a slow inflation mode to pressurize to 9bar, wherein the inflation rate is 0.45 bar/s, accelerating the rotating speed of a cooling fan to 2600 rpm, and keeping cooling for 1min;
(5) After the step (4) is finished, high-purity nitrogen is filled into the vacuum high-pressure gas quenching furnace in a rapid charging mode to be pressurized to 12-14 bar, the charging speed is 0.80 bar/second, the rotating speed of the cooling fan is increased to 3000 rpm, when the temperature of the surface of the die is reduced to 450 ℃, the nitrogen pressure and the rotating speed of the fan are adjusted and reduced according to the temperature of the core of the die until the temperature difference between the surface of the die and the core is less than 100 ℃, the high-purity nitrogen with the pressure of 12-14 bar is filled into the vacuum high-pressure gas quenching furnace, the rotating speed of the cooling fan is increased to 3000 rpm, and cooling is stopped when the temperature of the core of the die is cooled to 110 ℃ by high-speed high pressure cooling.
Step (1) conventional quenching process: heating to 620 ℃ at 180-200 ℃/h, heating to 820 ℃ at 200 ℃/h after the die core is heated to 590 ℃, heating to 1015 ℃ at 30min after the die core is heated to 1005 ℃, and preserving heat for 45min after the die core is heated to 1005 ℃.
And (3) cooling the steps (2) to (5) in the same container, wherein the medium is 99.99% high-purity nitrogen.
The nitrogen pressure and the cooling fan rotating speed in the step (2) to the step (5) are in a sectional pressurizing and accelerating mode, and the cooling fan is a variable-frequency cooling fan.
And (5) when the temperature of the surface of the die is reduced to 450 ℃, adjusting and reducing the nitrogen pressure and the rotating speed of a cooling fan according to the temperature of the core of the die, wherein the method specifically comprises the following steps of: the nitrogen pressure is fixedly reduced to 3bar, the isothermal temperature is set to 450 ℃, the upper deviation is +10 ℃, the lower deviation is-20 ℃, namely, the surface temperature of the die is controlled to be within the range of 460-430 ℃, when the surface temperature of the die rises due to the conduction of the core temperature, the fan operates at high speed when the surface temperature of the die rises to more than 460 ℃, when the surface temperature of the die falls to 430 ℃, the fan operates at low speed or even stops, when the surface temperature of the die still falls, the self-starting heating is carried out, the surface temperature of the die is always kept within the set isothermal temperature range, and the isothermal is ended after the core temperature of the die is reduced to 530 ℃ (450+80 ℃) for 3-8 minutes. The mould enters the lower section program to run-12-14 bar nitrogen is filled, and the fan rotates 3000 rpm.
The method also comprises a step (6) of hot melting treatment for carrying out hot melting crystallization reinforcement on the thin-wall surface of the die, and specifically comprises the following steps:
(6.1) transferring the die into a laser melting chamber, wherein a laser melting system, an infrared temperature sensor and a powder feeding system are arranged in the laser melting chamber, the powder feeding system is used for spreading metal powder on the surface of the die, the laser melting system is used for generating laser used for carrying out thermal melting on the surface of the die, the infrared temperature sensor is used for acquiring the temperature of a melting surface in real time, the laser melting system comprises a plurality of laser emission points, the laser emission points form a laser scanning heating surface, and the surface of the die is scanned and ablated;
(6.2) starting a powder feeding system, covering metal powder on the surface of the die, and carrying out laser hot melting and solidification on the metal powder on the surface of the die until the metal powder is clad on the surface of the die to form a cladding structure; in the process of carrying out hot melting treatment on the surface of the die, an infrared temperature sensor acquires the temperature of a melting surface in real time, correspondingly adjusts laser parameters, enables the temperature of the melting surface of the die to be in a proper heating temperature range, adjusts the laser parameters according to the shape of the melting surface of the die, and correspondingly adjusts laser power, scanning speed and spot diameter based on the temperature of the melting surface and the thickness value of a cladding structure.
Compared with the prior art, the application has the beneficial effects that:
1. the sectional pressurizing acceleration mode is adopted in the initial cooling stage, and the weak part (such as sharp corner, thin wall, hole site and the like) of the die is cooled in advance, so that the die has no larger thermal stress and tissue stress due to the lower cooling speed, and the deformation and even cracking phenomenon of the weak part of the die can be effectively avoided. Then pressurizing and accelerating step by step until reaching cooling air pressure of 12-14 bar, and running the fan at full speed, wherein the effective quenching cooling air pressure can be 3-5 bar higher than the original quenching cooling air pressure due to avoiding the deformation and cracking risks of weak parts of the die, and the cooling capacity of the die casting die core is increased, so that the ideal depth of the quenching layer can be achieved;
2. the process ensures the even distribution of the heat treatment hardness of the die by sectionally regulating and controlling the pressure of cooling gas and the rotation speed of a fan, taking 1800 x 960 x 560mm as an example: the hardness unevenness of the die is less than 1.5HRC; compared with the conventional heat treatment process, the impact energy of 80-100J is improved. After 1000 times of thermal fatigue circulation, the main crack length of the treatment process is reduced by 250-260 mu m, the crack width is reduced by 7-24 mu m, and the treatment process has good thermal fatigue performance.
3. The method is also added with a hot melting treatment process for carrying out hot melting crystallization reinforcement on the thin-wall surface of the die, so that the internal defect of the thin-wall surface of the die is eliminated, and the metal powder is subjected to laser hot melting and solidifies the surface of the die until the metal powder is melted and coated on the surface of the die to form a cladding structure; in the process of carrying out hot melting treatment on the surface of the die, the infrared temperature sensor acquires the temperature of the melting surface in real time, so that the temperature of the melting surface of the die is in a proper preset temperature range, the die thin-wall surface is thermally fused and crystallized to be reinforced, the warping and cracking of the die thin-wall surface is obviously reduced, the phenomena of cracking, cracking and warping deformation are effectively avoided, the internal and external quality of the die and the mechanical comprehensive performance of the surface of the die are improved, and the phenomenon of deformation and even cracking of the weak part of the die can be effectively avoided.
In order to more clearly illustrate the structural features and efficacy of the present application, a detailed description thereof will be given below with reference to the accompanying drawings and examples.
Drawings
FIG. 1 is a metallographic micrograph (100 x) of a die casting die after the heat treatment method of the present application;
FIG. 2 is a metallographic micrograph (500X) of a die casting die after the heat treatment method of the present application;
FIG. 3 is a metallographic micrograph (1000X) of a die casting die after the heat treatment method of the present application;
FIG. 4 is a graph showing the measurement of the performance of a die casting mold after the heat treatment method of the present application.
Detailed Description
The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Examples: referring to fig. 1-4, this embodiment provides a heat treatment process for reducing quenching deformation cracking of die casting die steel, comprising the following steps:
(1) Placing the prepared mould in a vacuum high-pressure gas quenching furnace, heating and preserving heat by adopting a conventional quenching process to fully austenitize the mould;
(2) Filling 3bar of high-purity nitrogen into the die after full austenitizing in the step (1) in a slow inflation mode, wherein the inflation rate is 0.15 bar/s, starting a cooling fan, setting the rotating speed at 1800 rpm, and keeping cooling for 1min;
(3) After cooling the mold in the step (2) for 1min, filling high-purity nitrogen in a slow inflation mode to pressurize to 6bar, wherein the inflation rate is 0.30 bar/s, accelerating the rotating speed of a cooling fan to 2200 rpm, and keeping cooling for 1min;
(4) Filling high-purity nitrogen into the die after cooling and heat preservation in the step (3) in a slow inflation mode to pressurize to 9bar, wherein the inflation rate is 0.45 bar/s, accelerating the rotating speed of a cooling fan to 2600 rpm, and keeping cooling for 1min;
(5) After the step (4) is finished, high-purity nitrogen is filled into the vacuum high-pressure gas quenching furnace in a rapid charging mode to be pressurized to 12-14 bar, the charging speed is 0.80 bar/second, the rotating speed of the cooling fan is increased to 3000 rpm, when the temperature of the surface of the die is reduced to 450 ℃, the nitrogen pressure and the rotating speed of the fan are adjusted and reduced according to the temperature of the core of the die until the temperature difference between the surface of the die and the core is less than 100 ℃, the high-purity nitrogen with the pressure of 12-14 bar is filled into the vacuum high-pressure gas quenching furnace, the rotating speed of the cooling fan is increased to 3000 rpm, and cooling is stopped when the temperature of the core of the die is cooled to 110 ℃ by high-speed high pressure cooling.
Step (1) conventional quenching process: heating to 620 ℃ at 180-200 ℃/h, heating to 820 ℃ at 200 ℃/h after the die core is heated to 590 ℃, heating to 1015 ℃ at 30min after the die core is heated to 1005 ℃, and preserving heat for 45min after the die core is heated to 1005 ℃.
And (3) cooling the steps (2) to (5) in the same container, wherein the medium is 99.99% high-purity nitrogen.
The nitrogen pressure and the cooling fan rotating speed in the step (2) to the step (5) are in a sectional pressurizing and accelerating mode, and the cooling fan is a variable-frequency cooling fan.
And (5) when the temperature of the surface of the die is reduced to 450 ℃, adjusting and reducing the nitrogen pressure and the rotating speed of a cooling fan according to the temperature of the core of the die, wherein the method specifically comprises the following steps of: the nitrogen pressure is fixedly reduced to 3bar, the isothermal temperature is set to 450 ℃, the upper deviation is +10 ℃, the lower deviation is-20 ℃, namely, the surface temperature of the die is controlled to be within the range of 460-430 ℃, when the surface temperature of the die rises due to the conduction of the core temperature, the fan operates at high speed when the surface temperature of the die rises to more than 460 ℃, when the surface temperature of the die falls to 430 ℃, the fan operates at low speed or even stops, when the surface temperature of the die still falls, the self-starting heating is carried out, the surface temperature of the die is always kept within the set isothermal temperature range, and the isothermal is ended after the core temperature of the die is reduced to 530 ℃ (450+80 ℃) for 3-8 minutes. The mould enters the lower section program to run-12-14 bar nitrogen is filled, and the fan rotates 3000 rpm.
The vacuum isothermal heat treatment process of the die casting die in the prior art comprises the steps of firstly heating and preserving heat, then performing air cooling under the pressure of not lower than 9Bar, and when the surface temperature of the die is quenched to 427 ℃, reducing the cooling pressure to 2Bar, and stopping air cooling. Then isothermal treatment is carried out by a convection fan, and after the equipotential treatment is finished, the pressure is increased to more than 6Bar, and air cooling is carried out. Nitrogen of 9bar is filled at the beginning of quenching cooling, for large, especially complex die casting dies, larger thermal stress and tissue stress are generated due to rapid cooling, a certain deformation or cracking risk exists, the larger the pressure is, the larger the temperature difference acting on different structural surfaces of the die is, the larger the temperature difference is, the larger the thermal stress and tissue stress are,
the application uses a sectional gradual pressurizing accelerating mode, on the premise of not generating a pearlite structure, the cooling speed approaches to and exceeds the proeutectoid ferrite and proeutectoid carbide interval at a higher cooling speed, at the moment, the temperature difference between the surfaces of the structures of the quenching die-casting die is smaller, and the generated thermal stress and the structure stress have little influence, thereby avoiding the deformation or cracking phenomenon of the die.
The isothermal process of the application is more reliable than the isothermal process of the vacuum isothermal heat treatment process of the large die casting mold, the vacuum isothermal heat treatment process of the large die casting mold is rotated at a fixed speed by a convection fan, the temperature of the surface of the mold is controlled to be within a range by 2bar nitrogen pressure, the nitrogen pressure is fixedly reduced to 3bar, the isothermal temperature is set to be 450 ℃, the upper deviation is +10 ℃, the lower deviation is-20 ℃, namely, the temperature of the surface of the mold is controlled to be within the range of 460-430 ℃, when the temperature of the surface of the mold is increased due to the conduction of the core temperature, the fan is operated at a high speed, when the temperature of the surface of the mold is increased to exceed 460 ℃, the fan is operated at a low speed and even stopped, when the temperature of the surface of the mold is still reduced, the heating is started automatically, the surface of the mold is always kept within the set isothermal temperature range until the core of the mold is cooled to 530 ℃ (450+80 ℃), and the isothermal is ended after 3-8 minutes. The mould enters the lower section program to run-12-14 bar nitrogen is filled, and the fan rotates 3000 rpm.
Compared with the prior art, the pressure of cooling nitrogen crossing a coarse bainite interval after isothermal completion is 6-8 bar, the probability of obtaining a non-martensitic structure for a die-casting die, particularly a large die-casting die, is low, a hardening layer is deeper, the impact toughness is higher, and the cold and hot fatigue resistance of the die is improved.
The sectional pressurizing acceleration mode is adopted in the initial cooling stage, and the weak part (such as sharp corner, thin wall, hole site and the like) of the die is cooled in advance, so that the die has no larger thermal stress and tissue stress due to the lower cooling speed, and the deformation and even cracking phenomenon of the weak part of the die can be effectively avoided. Then pressurizing and accelerating step by step until reaching cooling air pressure of 12-14 bar, and running the fan at full speed, wherein the effective quenching cooling air pressure can be 3-5 bar higher than the original quenching cooling air pressure due to avoiding the deformation and cracking risks of weak parts of the die, and the cooling capacity of the die casting die core is increased, so that the ideal depth of the quenching layer can be achieved;
the process ensures the even distribution of the heat treatment hardness of the die by sectionally regulating and controlling the pressure of cooling gas and the rotation speed of a fan, taking 1800 x 960 x 560mm as an example: the hardness unevenness of the die was less than 1.5HRC.
Compared with the conventional heat treatment process, the treatment process improves the impact energy by 80-100J. After 1000 times of thermal fatigue circulation, the main crack length of the treatment process is reduced by 250-260 mu m, the crack width is reduced by 7-24 mu m, and the treatment process has good thermal fatigue performance.
The method of the application is also added with a hot melting treatment process for hot melting treatment of the die thin wall surface hot melting crystallization reinforcement, and eliminates the internal defects of the die thin wall surface, and specifically comprises the following steps:
transferring the die into a laser melting chamber, wherein a laser melting system, an infrared temperature sensor and a powder feeding system are arranged in the laser melting chamber, the powder feeding system is used for spreading metal powder on the surface of the die, the laser melting system is used for generating laser used for carrying out thermal melting on the surface of the die, the infrared temperature sensor is used for acquiring the temperature of a melting surface in real time, the laser melting system comprises a plurality of laser emission points, the laser emission points form a laser scanning heating surface, and the surface of the die is scanned and ablated; the temperature of the laser scanning heating surface is 600-800 ℃.
Starting a powder feeding system, covering metal powder on the surface of the die, and carrying out laser hot melting and solidification on the metal powder on the surface of the die until the metal powder is clad on the surface of the die to form a cladding structure; in the process of carrying out hot melting treatment on the surface of the die, an infrared temperature sensor acquires the temperature of a melting surface in real time, correspondingly adjusts laser parameters, enables the temperature of the melting surface of the die to be in a proper heating temperature range, adjusts the laser parameters according to the shape of the melting surface of the die, and correspondingly adjusts laser power, scanning speed and spot diameter based on the temperature of the melting surface and the thickness value of a cladding structure.
The metal powder of the embodiment is one or more of magnesium alloy powder, lead alloy powder and aluminum alloy powder, and the granularity of the metal powder is 20-100 meshes, and optimally 20-30 meshes; the cladding structure layer thickness is 1000-3000 micrometers, the laser power is 400-10000W, the scanning speed is 1-10mm/s, the spot diameter is 1-5mm, and the shielding gas is inert gas.
According to the method, a hot melting treatment process is added and is used for carrying out hot melting treatment on the die thin-wall surface for hot melting crystallization reinforcement, so that the defect of the die thin-wall surface is eliminated, and the metal powder is subjected to laser hot melting and solidifies on the surface of the die until the metal powder is melted and coated on the surface of the die to form a cladding structure; in the process of carrying out hot melting treatment on the surface of the die, the infrared temperature sensor acquires the temperature of the melting surface in real time, so that the temperature of the melting surface of the die is in a proper preset temperature range,
by the hot-melting crystallization reinforcement of the thin-wall surface of the die, the warping and cracking of the thin-wall surface of the die are obviously reduced, the phenomena of cracking, cracking and buckling deformation are effectively avoided, the inner and outer quality of the die and the mechanical comprehensive performance of the surface of the die are improved, and the phenomena of deformation and even cracking of the weak part of the die can be effectively avoided.
The above description is only of the preferred embodiment of the present application, and is not intended to limit the present application in any way. Any person skilled in the art can make many possible variations and modifications to the technical solution of the present application or modifications to equivalent embodiments using the methods and technical contents disclosed above, without departing from the scope of the technical solution of the present application. Therefore, all equivalent changes according to the shape, structure and principle of the present application are covered in the protection scope of the present application.
Claims (10)
1. The heat treatment process for reducing the quenching deformation cracking of the die casting die steel is characterized by comprising the following steps of:
(1) Placing the prepared mould in a vacuum high-pressure gas quenching furnace, heating and preserving heat by adopting a quenching process to fully austenitize the mould;
(2) Filling 3bar of high-purity nitrogen into the die after full austenitizing in the step (1) in a slow inflation mode, starting a cooling fan, setting the rotating speed at 1800 revolutions per minute, and keeping cooling for 1min;
(3) After cooling the mold in the step (2) for 1min, charging high-purity nitrogen in a slow charging mode to pressurize to 6bar, accelerating the rotating speed of a cooling fan to 2200 rpm, and keeping cooling for 1min;
(4) Filling high-purity nitrogen into the die after cooling and heat preservation in the step (3) in a slow inflation mode to pressurize to 9bar, accelerating the rotating speed of a cooling fan to 2600 revolutions per minute, and keeping cooling for 1min;
(5) After the step (4) is finished, high-purity nitrogen is filled into the vacuum high-pressure gas quenching furnace in a rapid charging mode to be pressurized to 12-14 bar, the rotating speed of the cooling fan is increased to 3000 rpm, when the temperature of the surface of the die is reduced to 450 ℃, the nitrogen pressure and the rotating speed of the fan are adjusted and reduced according to the core temperature of the die until the temperature difference between the surface of the die and the core is less than 100 ℃, the high-purity nitrogen with the pressure of 12-14 bar is filled into the vacuum high-pressure gas quenching furnace, the rotating speed of the cooling fan is increased to 3000 rpm, and cooling is stopped when the core temperature of the high-speed high-pressure cooling die is reduced to 110 ℃.
2. The heat treatment process for reducing quench deformation cracking of die-casting die steel according to claim 1, wherein the step (1) of quenching process:
heating to 620 ℃ at 180-200 ℃/h, heating to 820 ℃ at 200 ℃/h after the die core is heated to 590 ℃, heating to 1015 ℃ at 30min after the die core is heated to 1005 ℃, and preserving heat for 45min after the die core is heated to 1005 ℃.
3. The heat treatment process for reducing quenching deformation cracks of die casting die steel according to claim 1, wherein the step (2) is pressurized to 3bar by charging high purity nitrogen gas, and the charging rate is 0.15 bar/sec.
4. The heat treatment process for reducing quenching deformation cracks of die casting die steel according to claim 1, wherein the high purity nitrogen gas is filled in the step (3) and pressurized to 6bar, and the filling rate is 0.30 bar/sec.
5. The heat treatment process for reducing quenching deformation cracks of die casting die steel according to claim 1, wherein the step (4) is pressurized to 9bar by charging high purity nitrogen gas, and the charging rate is 0.45 bar/sec.
6. The heat treatment process for reducing the quenching deformation cracking of the die casting die steel according to claim 1, wherein the high purity nitrogen gas is filled in the step (5) and pressurized to 12-14 bar, and the filling rate is 0.80 bar/sec.
7. The heat treatment process for reducing the quenching deformation cracking of the die casting die steel according to claim 1, wherein the steps (2) to (5) are cooled in the same container, and the medium is 99.99% high-purity nitrogen.
8. The heat treatment process for reducing the quenching deformation cracking of the die casting die steel according to claim 1, wherein the nitrogen pressure and the cooling fan rotating speed in the steps (2) to (5) are in a sectional pressurizing acceleration mode, and the cooling fan is a variable-frequency cooling fan.
9. The heat treatment process for reducing the quenching deformation cracking of the die casting die steel according to claim 1, wherein the step (5) is to adjust and reduce the nitrogen pressure and the cooling fan rotation speed according to the die core temperature when the die surface temperature is reduced to 450 ℃, and specifically comprises the following steps:
the nitrogen pressure is fixedly reduced to 3bar, the isothermal temperature is set to 450 ℃, the upper deviation is +10 ℃, the lower deviation is-20 ℃, namely the surface temperature of the die is controlled within the range of 460-430 ℃, when the surface temperature of the die rises due to the conduction of the core temperature, the fan operates at high speed when the surface temperature of the die rises to more than 460 ℃, when the surface temperature of the die falls to 430 ℃, the fan operates at low speed or even stops, when the surface temperature of the die still falls, the self-starting heating is carried out, the surface temperature of the die is always kept within the set isothermal temperature range, and after the core temperature of the die is reduced to 530 ℃, the isothermal is ended for 3-8 minutes.
10. The heat treatment process for reducing the quenching deformation cracking of the die casting die steel according to claim 1, further comprising a step (6) of heat-melting treatment for heat-melting crystallization reinforcement of the die thin-wall surface, specifically comprising the steps of:
(6.1) transferring the die into a laser melting chamber, wherein a laser melting system, an infrared temperature sensor and a powder feeding system are arranged in the laser melting chamber, the powder feeding system is used for spreading metal powder on the surface of the die, the laser melting system is used for generating laser used for carrying out thermal melting on the surface of the die, the infrared temperature sensor is used for acquiring the temperature of a melting surface in real time, the laser melting system comprises a plurality of laser emission points, the laser emission points form a laser scanning heating surface, and the surface of the die is scanned and ablated;
(6.2) starting a powder feeding system, covering metal powder on the surface of the die, and carrying out laser hot melting and solidification on the metal powder on the surface of the die until the metal powder is clad on the surface of the die to form a cladding structure; in the process of carrying out hot melting treatment on the surface of the die, an infrared temperature sensor acquires the temperature of a melting surface in real time, correspondingly adjusts laser parameters, enables the temperature of the melting surface of the die to be in a proper heating temperature range, adjusts the laser parameters according to the shape of the melting surface of the die, and correspondingly adjusts laser power, scanning speed and spot diameter based on the temperature of the melting surface and the thickness value of a cladding structure.
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