1. There are soft spots on the mold surface
After the heat treatment of the mold, there are soft spots on the surface, which will affect the wear resistance of the mold and reduce the service life of the mold.
(1) Causes 1) The mold has scale, rust and local decarburization on the surface before heat treatment.
2) After the mold is quenched and heated, the cooling and quenching medium is improperly selected, and the impurities in the quenching medium are excessive or aging.
(2) Preventive measures 1) Before the heat treatment of the mold, the scale and rust spots should be removed. When the mold surface is properly protected during quenching and heating, the vacuum furnace, salt bath furnace and protective atmosphere furnace should be used for heating.
2) When the mold is quenched and heated and cooled, the appropriate cooling medium should be selected. The cooling medium used for long-term use should be filtered frequently or periodically. 2. Poor organization before heat treatment of the mold
The final spheroidized structure of the mold is coarse and uneven, and the spheroidization is imperfect. The structure has mesh, band and chain carbides, which will cause the mold to be cracked after quenching, resulting in scrapping of the mold.
(1) Causes 1) There is serious carbide segregation in the original structure of the die steel material.
2) The forging process is not good, such as the forging heating temperature is too high, the deformation amount is small, the stop forging temperature is high, the cooling speed after forging is slow, etc., so that the forged structure is coarse and there are mesh, band and chain carbides present, so that the ball It is difficult to eliminate during annealing.
3) Poor spheroidizing annealing process, such as too high or too low annealing temperature, short isothermal annealing time, etc., may result in uneven spheroidizing annealing or poor spheroidization.
(2) Preventive measures 1) Generally, according to the working conditions of the mold, the production batch and the toughening performance of the material itself, try to select a good quality mold steel material.
2) Improve the forging process or use normalizing heat treatment to eliminate the non-uniformity of the network and chain carbides and carbides in the raw materials.
3) A high-carbon die steel with severe segregation of carbides that cannot be forged can be subjected to solid solution refining heat treatment.
4) Develop a correct spheroidizing annealing process specification for the forged blank, which can be tempered heat treatment and fast uniform spheroidizing annealing.
5) Reasonably install the furnace to ensure the uniformity of the temperature of the mold blank in the furnace. 3. The mold produces quench cracks
The cracking of the mold after quenching is the biggest defect in the heat treatment process of the mold, which will cause the finished mold to be scrapped, causing great loss in production and economy.
(1) Causes of occurrence 1) There is severe network carbide segregation in the mold material.
2) There are mechanical processing or cold plastic deformation stresses in the mold.
3) Improper heat treatment of the mold (heating or cooling too fast, improper selection of quenching cooling medium, low cooling temperature, too long cooling time, etc.).
4) The shape of the mold is complicated, the thickness is uneven, the sharp corners and the threaded holes are used, so that the thermal stress and the structural stress are excessive.
5) The mold quenching heating temperature is too high to produce overheating or overheating.
6) The tempering of the mold after quenching is not timely or the tempering holding time is insufficient.
7) When the mold is repaired and quenched, it is heated and quenched without intermediate annealing.
8) If the mold is heat treated, the grinding process is improper.
9) During the electrical discharge machining of the mold after heat treatment, there are high tensile stresses and microcracks in the hardened layer.
(2) Preventive measures 1) Strictly control the intrinsic quality of the mold raw materials 2) Improve the forging and spheroidizing annealing processes, eliminate the network, ribbon, and chain carbides, and improve the uniformity of the spheroidized structure. ,
3) After the mechanical processing or after the cold plastic deformation, the mold should be subjected to stress relief annealing (>600 ° C) and then heated and quenched.
4) For the complex shape of the mold, asbestos should be used to block the threaded hole, the dangerous section and the thin wall are wrapped, and the step quenching or austempering is adopted.
5) Annealing or high temperature tempering is required for rework or refurbishment of the mold.
6) The mold should be preheated during quenching heating, pre-cooling measures should be taken during cooling, and suitable quenching medium should be selected.
7) The quenching heating temperature and time should be strictly controlled to prevent overheating and over-burning of the mold.
8) After quenching, the mold should be tempered in time, the holding time should be sufficient, and the high alloy complex mold should be tempered 2-3 times.
9) Choose the right grinding process and the right grinding wheel.
10) Improve the mold EDM process and perform stress relief and tempering.
After the mold is quenched, the coarse structure will seriously affect the mechanical properties of the mold. When used, the mold will be broken, which will seriously affect the service life of the mold.
(1) Reasons for production 1) Mold steel is confused, the actual steel quenching temperature is much lower than the quenching temperature of the required mold material (such as GCr15 steel as 3Cr2W8V steel).
2) The correct spheroidization process is not performed before the mold steel is quenched, and the spheroidized structure is poor.
3) The mold quenching heating temperature is too high or the holding time is too long.
4) The mold is placed improperly in the furnace, and it is easy to generate heat in the vicinity of the electrode or the heating element.
5) For molds with large cross-section changes, the quenching heating process parameters are not properly selected, and overheating occurs at thin sections and sharp corners.
(2) Preventive measures 1) Before the steel is put into storage, it should be strictly inspected to prevent the steel from being confused.
2) Correct forging and spheroidizing annealing should be performed before the mold is quenched to ensure good spheroidized structure.
3) Properly formulate the mold quenching heating process specification and strictly control the quenching heating temperature and holding time.
4) Regularly detect and calibrate the temperature measuring instrument to ensure the normal operation of the instrument.
5) The mold should be kept at an appropriate distance from the electrode or heating element when heated in the furnace.
After the heat treatment of the mold, there are soft spots on the surface, which will affect the wear resistance of the mold and reduce the service life of the mold.
(1) Causes 1) The mold has scale, rust and local decarburization on the surface before heat treatment.
2) After the mold is quenched and heated, the cooling and quenching medium is improperly selected, and the impurities in the quenching medium are excessive or aging.
(2) Preventive measures 1) Before the heat treatment of the mold, the scale and rust spots should be removed. When the mold surface is properly protected during quenching and heating, the vacuum furnace, salt bath furnace and protective atmosphere furnace should be used for heating.
2) When the mold is quenched and heated and cooled, the appropriate cooling medium should be selected. The cooling medium used for long-term use should be filtered frequently or periodically. 2. Poor organization before heat treatment of the mold
The final spheroidized structure of the mold is coarse and uneven, and the spheroidization is imperfect. The structure has mesh, band and chain carbides, which will cause the mold to be cracked after quenching, resulting in scrapping of the mold.
(1) Causes 1) There is serious carbide segregation in the original structure of the die steel material.
2) The forging process is not good, such as the forging heating temperature is too high, the deformation amount is small, the stop forging temperature is high, the cooling speed after forging is slow, etc., so that the forged structure is coarse and there are mesh, band and chain carbides present, so that the ball It is difficult to eliminate during annealing.
3) Poor spheroidizing annealing process, such as too high or too low annealing temperature, short isothermal annealing time, etc., may result in uneven spheroidizing annealing or poor spheroidization.
(2) Preventive measures 1) Generally, according to the working conditions of the mold, the production batch and the toughening performance of the material itself, try to select a good quality mold steel material.
2) Improve the forging process or use normalizing heat treatment to eliminate the non-uniformity of the network and chain carbides and carbides in the raw materials.
3) A high-carbon die steel with severe segregation of carbides that cannot be forged can be subjected to solid solution refining heat treatment.
4) Develop a correct spheroidizing annealing process specification for the forged blank, which can be tempered heat treatment and fast uniform spheroidizing annealing.
5) Reasonably install the furnace to ensure the uniformity of the temperature of the mold blank in the furnace. 3. The mold produces quench cracks
The cracking of the mold after quenching is the biggest defect in the heat treatment process of the mold, which will cause the finished mold to be scrapped, causing great loss in production and economy.
(1) Causes of occurrence 1) There is severe network carbide segregation in the mold material.
2) There are mechanical processing or cold plastic deformation stresses in the mold.
3) Improper heat treatment of the mold (heating or cooling too fast, improper selection of quenching cooling medium, low cooling temperature, too long cooling time, etc.).
4) The shape of the mold is complicated, the thickness is uneven, the sharp corners and the threaded holes are used, so that the thermal stress and the structural stress are excessive.
5) The mold quenching heating temperature is too high to produce overheating or overheating.
6) The tempering of the mold after quenching is not timely or the tempering holding time is insufficient.
7) When the mold is repaired and quenched, it is heated and quenched without intermediate annealing.
8) If the mold is heat treated, the grinding process is improper.
9) During the electrical discharge machining of the mold after heat treatment, there are high tensile stresses and microcracks in the hardened layer.
(2) Preventive measures 1) Strictly control the intrinsic quality of the mold raw materials 2) Improve the forging and spheroidizing annealing processes, eliminate the network, ribbon, and chain carbides, and improve the uniformity of the spheroidized structure. ,
3) After the mechanical processing or after the cold plastic deformation, the mold should be subjected to stress relief annealing (>600 ° C) and then heated and quenched.
4) For the complex shape of the mold, asbestos should be used to block the threaded hole, the dangerous section and the thin wall are wrapped, and the step quenching or austempering is adopted.
5) Annealing or high temperature tempering is required for rework or refurbishment of the mold.
6) The mold should be preheated during quenching heating, pre-cooling measures should be taken during cooling, and suitable quenching medium should be selected.
7) The quenching heating temperature and time should be strictly controlled to prevent overheating and over-burning of the mold.
8) After quenching, the mold should be tempered in time, the holding time should be sufficient, and the high alloy complex mold should be tempered 2-3 times.
9) Choose the right grinding process and the right grinding wheel.
10) Improve the mold EDM process and perform stress relief and tempering.
After the mold is quenched, the coarse structure will seriously affect the mechanical properties of the mold. When used, the mold will be broken, which will seriously affect the service life of the mold.
(1) Reasons for production 1) Mold steel is confused, the actual steel quenching temperature is much lower than the quenching temperature of the required mold material (such as GCr15 steel as 3Cr2W8V steel).
2) The correct spheroidization process is not performed before the mold steel is quenched, and the spheroidized structure is poor.
3) The mold quenching heating temperature is too high or the holding time is too long.
4) The mold is placed improperly in the furnace, and it is easy to generate heat in the vicinity of the electrode or the heating element.
5) For molds with large cross-section changes, the quenching heating process parameters are not properly selected, and overheating occurs at thin sections and sharp corners.
(2) Preventive measures 1) Before the steel is put into storage, it should be strictly inspected to prevent the steel from being confused.
2) Correct forging and spheroidizing annealing should be performed before the mold is quenched to ensure good spheroidized structure.
3) Properly formulate the mold quenching heating process specification and strictly control the quenching heating temperature and holding time.
4) Regularly detect and calibrate the temperature measuring instrument to ensure the normal operation of the instrument.
5) The mold should be kept at an appropriate distance from the electrode or heating element when heated in the furnace.
Bathroom Hardware Set Including Towel Bar , Towel Shelf , Towel Ring, Toilet Paper Holder, Robe Hook , Soap Holder and Glass Holder can choose.
Kaiping Jenor Sanitary Ware Co., Ltd , https://www.jenorsanitary.com