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How to prevent cracks in stainless steel castings? What are the preventive measures?

Edit:Xiangyang Liqiang Machinery Co., Ltd.UpDate:2020-04-07

Because stainless steel die-casting parts have weak forging characteristics, poor circulation, large body shrinkage and line shrinkage, and high welding stress, they are very easy to cause cracks. Once the castings cause cracks, not only the maintenance labor will be large, but the more serious ones will also be reported, which will lead to heavy property losses. Stainless steel die casting is a general term for stainless steel castings produced from various stainless steel plates, which are mainly used under various corrosion standards. So how do people prevent stainless steel die castings from causing cracks? What are the preventive measures?

The main factors that cause cracks in castings are the structure of the castings and the forging process. The following countermeasures can be used to prevent them in many aspects.

1. Casting structure: When forging stainless steel die castings, it is necessary to take into account the structure, appearance, large and medium-sized, wall thickness and connection of the castings and other factors that harm the liquid and solid gathering of the castings, and select the main parameters of the appropriate processing technology. Avoid welding defects such as shrinkage casting defects. The design of the pouring and riser control system for castings must be effective. If cold iron and other processing techniques are to be used, the location must be effective. It is necessary to ensure the high density of the internal mechanism of the castings and minimize the stress caused by the situation.

2. Smelting: In the whole process of smelting stainless steel die castings, reduce the harmful elements such as P and S as much as possible, and reduce the vapor and impurities such as N, H, and O. According to the selection of low-phosphorus steel and middle stainless steel, it can have very good practical effects.

3. Thermal insulation: increase the thermal insulation time of the casting in the sand mold appropriately. People must manipulate the unpacking temperature to be less than 70°C to ensure that the stainless steel die-casting parts are fully liquid and solid in the sand mold to prevent stress caused by external forces.

4. Sand falling: During the whole process of removing sand from castings, it is forbidden to pour sand molds and castings during boxing. It is forbidden to use impact methods such as box collision to prevent sand falling from external force and thermal stress of casting The interaction forces cause cracks.

5. Laser cutting riser: According to the standard of casting parts, select the appropriate processing method of hot cutting and pouring riser to ensure that the starting and ending temperature of hot cutting is not less than 300℃. In actual operation, the oxygen cutting gun and the oxygen blowing tube are cut by vibration laser. After oxygen cutting the key parts, immediately cover the compartment with asbestos cloth or enter the furnace for quenching and tempering. For castings such as the upper crown and axial fan leaves, which have complicated structures and unique processing techniques, secondary thermal cutting is selected.

6. Heating: When solving the shortcomings of stainless steel die castings, we must persist in heating standards. When the blowing and welding process is solved, the steel parts must be heated to above 108°C for actual operation. If a large crack defect is found, the in-situ stress quenching must be carried out first, and then the solution will be carried out.

7. Quenching: For heavy and extra-large stainless steel die-casting parts, a final removal of ground stress quenching process must be carried out, and heat insulation time and published temperature must be strictly controlled. The purpose is to reduce the new stress caused during the processing, more completely remove the thermal stress of the casting, and avoid the cracks.

The above is to preventStainless steel precision castingI look forward to showing some assistance to everyone in the way of causing the rift.

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