Some tips for preventing cracks in stainless steel casting

1. Casting structure

During the forging process, the structure and shape of the casting, large and medium-sized, should be fully considered. For factors such as wall thickness, connections, etc. that endanger the closure of the liquid and solid parts of the casting, appropriate processing parameters should be selected to avoid welding defects such as shrinkage and porosity. .The gate control system design of castings should be effective. If processing technology countermeasures such as cold iron are chosen, their placement should be effective, not only to ensure the high density of the internal mechanisms of the castings, but also to minimize stress.

2. Smelter

During the entire process of the smelting plant, PS should be reduced as much as possible to reduce harmful elements, steam and impurities such as NHO. By selecting low-phosphorus steel and intermediate aluminum alloys, good results can be achieved.

3. Thermal insulation

According to the appropriate increase in the heat preservation time of the casting in the sand mold, the main purpose is to control the unboxing temperature to less than 70 degrees Celsius to ensure that the casting has enough liquid and solid to gather in the sand mold to prevent stress caused by external factors.

4. Falling sand

During the entire process of removing falling sand from castings, it is prohibited to pour sand molds and castings during boxing, and it is prohibited to use impact methods such as impact boxes with strong external forces to prevent cracks caused by the interaction between external forces and thermal stress of castings.

5. Laser cutting riser

According to the casting standards, select appropriate hot cutting and riser processing methods to ensure that the starting and ending temperatures of hot cutting are not less than 3000 degrees Celsius. In actual operations, oxygen cutting guns and oxygen blow pipes are cut with vibration lasers. Key parts should be cut immediately after oxygen cutting Use asbestos cloth to cover the partition or enter the furnace for heat treatment. For the upper crown and axial flow fan blades, the structure is complicated. A unique casting processing technology is adopted, and 2-pass hot cutting is used.

6.Heating

When solving the shortcomings of stainless steel castings, the heating standards must be adhered to. When blowing... When solving the welding process, the product workpiece should be heated to 108 degrees Celsius for actual operation. If large crack defects are found, perform in-situ stress quenching first, and then to resolve.

7. Improve quenching

To enhance heavy-duty and heavy-duty stainless steel castings, the ground stress quenching process is finally cleared, and the holding time and published temperature are strictly controlled. The purpose is to reduce the new stress generated during the processing, more completely remove the thermal stress of the casting, and avoid cracks.