Now Jinan Hongjie mould Co., Ltd. will take you to know how to deal with and prevent the heat treatment deformation and cracking of Shandong Aluminum alloy die casting mould?
There are many reasons for forming the deformation and cracking of die-casting mould during heat treatment, including the chemical composition and original structure of steel, the structural shape and section size of parts, and heat treatment process. In the practice of consumption, deformation is often not completely rooted, only to minimize the level of its attack, but only to take the appropriate wrist, the complete situation of cracking can be prevented.
Prepare for heat treatment
The so-called preparation heat treatment is related to the final heat treatment, which is to add a preparation step before the final heat treatment, which can provide a good mechanical performance or microstructure for the final heat treatment. Common heat treatment processes include annealing, normalizing and tempering..
Quenching heating mode and protection of parts
Quenching and tempering are the processes that are most likely to cause deformation and cracking of parts. For some small die-casting dies, slender cylindrical parts or high alloy steel die parts, the quenching method of direct heating should be prevented. Instead, they should be preheated to 520-580 ℃, and then put into the medium temperature salt bath furnace for heating to the quenching temperature. The theory proves that the deformation of the parts heated by this way is obviously smaller than that of the parts directly heated and quenched in the electric furnace or reverberatory furnace, and the cracking condition can be fundamentally prevented.
In addition, when quenching and tempering are stopped, it is necessary to take measures to stop the effective maintenance of the parts prone to deformation and cracking, so that the shape and section are symmetrical, and the internal stress is kept in balance. Especially for those parts with complex shape. Common maintenance methods include baling method, filling method and infarct method.
Optimization of cooling mode and selection of coolant
When the die-casting die parts are heated up, they should not be directly put into the coolant after being taken out of the furnace, which is easy to cause deformation and cracking due to excessive temperature difference. The correct way is to put the parts in the air to stop precooling, and then put them into the coolant for quenching. In order to ensure the average cooling speed of each part, the proper rotation should be stopped after the coolant is put in, and the rotation direction should preferably be not fixed.
The choice of coolant is equally important. As for alloy steel, the use of isothermally or step quenching with potassium nitrate and sodium nitrite hot bath is an effective way to reduce the deformation, especially for die-casting dies with complex shape and accurate size requirements. Some porous die parts have the characteristics of cooling shrinkage in oil and cooling shrinkage in nitrate. Reasonable application of two different media can also reduce the deformation of parts due to quenching.
Control of tempering treatment
After quenching in the coolant, die-casting die parts should not stay in the air for too long, but should be put into the tempering furnace in time to stop tempering, so as to eliminate the internal stress of parts and reduce the deformation and cracking tendency. Especially for some die-casting die parts that need to stop the WEDM, the use of graded quenching and repeated heat treatment before the WEDM can effectively improve the hardenability of the parts, so that the internal stress distribution is average, and it is not easy to deform and crack. In the process of tempering treatment, it is necessary to prevent the appearance of low temperature temper brittleness and high temperature temper brittleness.
The above is the introduction of Jinan Hongjie mould Co., Ltd. to the treatment and prevention of deformation and cracking in heat treatment of die casting mould. I hope to help you. Welcome to the official website //www.yfrmbf.com.cn