Stainless Steel Casting The Design Should Be Reasonable
Most of the key parts of the turbine using stainless steel castings, such as ZG06Cr13Ni4Mo, ZG06Cr16Ni5Mo and so on. This kind of material casting performance is poor, poor mobility, Stainless Steel Casting body shrinkage and line shrinkage larger, thermal stress, easy to produce cracks. Once the castings crack, not only the heavy workload, serious may also be scrapped, resulting in significant economic losses. Casting cracks in the main factors are casting structure, casting process, the production of the following measures are generally used to prevent:
Casting to fully consider the casting structure, Stainless Steel Casting shape, large, wall thickness and its impact on the casting liquid and solid shrinkage factors, select the appropriate process parameters to prevent shrinkage and other casting defects. Casting riser system design should be reasonable, if you want to use cold iron and other technical measures, the placement of the site to be reasonable, Stainless Steel Casting it is necessary to ensure the internal organization of the compact, but also try to avoid stress concentration situation.
Smelting process, try to reduce the P, S and other harmful elements content, reduce the N, H, O and other gases and inclusions content. Through the use of low-phosphorus steel alloy, Stainless Steel Casting can play a very good effect.
Through the appropriate extension of the casting in the sand in the holding time, mainly to control the out of the box temperature below 70 ℃, Stainless Steel Casting to ensure that the casting in the sand in the full completion of liquid and solid shrinkage, to avoid external factors caused by stress concentration occurs.
In the process of sand casting and cleaning, it is strictly forbidden to water the sand and castings when it is boxed. It is forbidden to use sand and other strong external shocks to avoid cracking between the external force and the stress in the casting.
According to the casting conditions to select the appropriate thermal cutting riser process to ensure that the thermal start temperature of not less than 300 ℃. Operation, Stainless Steel Casting gas cutting torch and oxygen tube with vibration cutting. Important pieces of gas cutting in a timely manner with asbestos cloth cover the furnace or into the furnace heat treatment. For the crown and axial flow of a class of complex structure, the process to take special measures for the casting, the use of secondary thermal cutting.
In the stainless steel casting defect handling,Stainless Steel Casting we must adhere to the principle of preheating. In the blowing, welding process, the workpiece should be preheated to 108 ° C above the operation. If you find a large crack defects, should be carried out to stress annealing, and then processed.
The main stainless steel castings to increase the final elimination of stress annealing process, strictly control the holding time and baked temperature. Its purpose is to reduce the production process to produce new stress concentration, more completely eliminate the casting stress, Stainless Steel Casting to prevent the occurrence of cracks.
Surface shot peening method. This method is to use a round hammer beating the gap, by tapping to close, can be achieved into the film for the purpose. We have to choose according to the degree of contamination of stainless steel casting corresponding to the corresponding method. Stainless Steel Casting According to the relevant information, casting is not cleared before the pit filled with slag material. The lithofacies analysis shows that there are chemicals such as ferric silicate, manganese silicate and chromium silicate in the slag material at the defect. The results of electron diffraction show that the black pitting is composed of magnetite (Fe3O4) and iron chrome spinel (FeO · Cr2O3). As a result of the spectral analysis, the silicon content in the metal component at the defect is increased and the amount of manganese is very small. After the castings are shot blasting and blasted, Stainless Steel Casting the surface of the castings will have gray and black pits, which often appear in the local thick sections, corners and bore parts of the castings, and even the entire surface of the castings.