Heat treatment is critical to making good molds in metal forming!（2）

The relationship between heat treatment process and metal forming sheet metal processing, deep drawing, metal stamping, stamping die and progressive stamping die is reflected in the fact that heat treatment is a key step to enhance the performance of metal materials, which, by adjusting the hardness, plasticity and toughness of the material, provides a suitable material state for the molding processes such as sheet metal processing, deep drawing and stamping, and at the same time ensures that the stamping die and progressive stamping die in a continuous high load operation Maintain stable performance and life, thus ensuring the quality and efficiency of molded products.

 

(1) mold heat treatment as far as possible to choose the vacuum heat treatment, in order to obtain the smallest amount of deformation.

(2) The mold can be spliced structure, divided into small pieces of good heat treatment. It is best to use slow wire cutting, high precision, high finish, small deformation. The gap is guaranteed, the burr will be small. See if the precision of your equipment is poor.

(3) large burrs on the cutting edge In addition to the above mentioned, I think the convex mold single-sided force, the possibility of insufficient strength. Is the convex mold too thin? Is the design of the knife? There are residual stresses after heat treatment of the sheet, wire cutting will appear after deformation, you can consider a larger wire cutting holes pre-mill out and then heat treatment, leaving 3 ~ 4mm wire cutting.

 

(1) forging temperature is about 900 ~ 1000 ℃? It is possible that the temperature is too high, the mold is not fully preheated before use may also be prone to cracking. The mold design is not reasonable, it may also be easy to crack. Increase the tempering temperature of the mold to narrow the gap between the actual forging temperature and the actual longer tempering.

(2) This should be considered comprehensively, if necessary, to do the next metallographic, in order to determine the basic reasons.

 

Generate causes:

1) mold in the heat treatment before the surface of the oxide skin, rust spots and local decarburization.

2) mold quenching and heating, cooling and quenching medium is not the right choice, too many impurities in the quenching medium or aging.

Preventive measures:

1) mold heat treatment should be removed before the oxide skin, rust spots, quenching and heating in the appropriate protection of the mold surface, should try to use a vacuum electric furnace, salt bath furnace and protective atmosphere furnace heating.

2) mold quenching and heating after cooling, should choose the appropriate cooling medium, the long-term use of the cooling medium should be filtered frequently, or regularly replaced.

 

Causes:

1) the original organization of the mold steel material there are serious carbide segregation.

2) Forging process is not good, such as forging heating temperature is too high, deformation is small, stop forging temperature is high, after forging cooling rate is slow, etc., so that the forging organization is coarse and there is a network, banded and chain carbide, so that spheroidal annealing is difficult to eliminate.

3) balling annealing process is not good, such as annealing temperature is too high or too low, isothermal annealing time is short, etc., can cause balling annealing organization is not uniform or poor balling.

1) Generally should be based on the working conditions of the mold, the production batch and the material itself strong toughening properties, try to choose good quality mold steel materials.

2) Improve the forging process or the use of normalizing preparatory heat treatment, to eliminate the raw material in the network and chain carbides and carbide inhomogeneity.

3) Can not be forged carbide segregation of serious high-carbon die steel can be solid solution refining heat treatment.

4) After forging the mold blank to develop the correct ball annealing process specifications, can be used for tempering heat treatment and fast uniform fine ball annealing.

5) Reasonable loading furnace, to ensure the uniformity of the temperature of the mold blank furnace.

 

Causes:

1) mold steel confusion, 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) mold steel quenching is not carried out before the correct spheroidization treatment process, poor spheroidization organization.

3) mold quenching heating temperature is too high or holding time is too long.

4) mold in the furnace placed in the wrong location, in close proximity to the electrode or heating element area prone to overheating.

5)For molds with large changes in cross-section, improper selection of quenching and heating process parameters, overheating in the thin cross-section and sharp corners.

1) Steel should be strictly inspected before storage, to prevent confusion and disorganization of steel.

2) Die quenching should be carried out before the correct forging and spheroidal annealing to ensure good spheroidal organization.

3) Correctly formulate the mold quenching and heating process specifications, strictly control the quenching and heating temperature and holding time.

4) Regular testing and calibration of temperature measuring instruments to ensure that the instrument works properly.

5) The mold should be heated in the furnace with the electrode or heating element to maintain an appropriate distance.

 

High hardness, high wear resistance and high toughness optimization treatment: 980 ~ 1200 ℃ heating quenching, oil quenching (oil) 400 ℃ tempering once, 240 ℃ tempering once, HRC57 ~ 61, ultra-durable non-crashing edge.

 

    Metallographic analysis can be carried out to see if the surface of the material is decarburization phenomenon, cracking is generally decarburization caused by H13 are generally extrusion mold, the hardness of the material requirements are not very high, you are not using a vacuum furnace is recommended to use 1030 ~ 1050 ℃ to try.

 

(1) in the Mainland with 45 # carbon structural steel or carbon tool steel, heat treatment quenching hardness HRC45 or so, not up to HRC58 ~ 62, is so high, it is easy to break.