Stainless steel castingInvestment casting is a minimal or no-cutting process, considered an excellent technology in the casting industry with a wide range of applications. Stainless steel casting is suitable for various types and alloys. Simply put, the stainless steel casting process uses fusible materials to create a fusible model, which is then coated with several layers of a special refractory coating. After melting and drying to form a single shell, the model is melted away from the shell using hot water or steam. Stainless steel casting offers high dimensional accuracy. However, the complex investment casting process means that many factors directly affect the dimensional accuracy of the castings, including linear changes in the shell during heating and cooling, the alloy's shrinkage rate, and deformation during solidification.
Stainless steel casting is a process used to produce irregularly shaped products when it is not possible to use processes such as pipe bending. It involves creating a wax mold, making a sand mold, and then filling the mold with liquid material.
The advantages and disadvantages of stainless steel casting processing technology are as follows:
1. Due to the poor fluidity of molten steel, in order to prevent cold shuts and incomplete pouring in cast steel parts, the wall thickness of cast steel parts should not be less than 8mm.
The gating system should have a simple structure and a larger cross-sectional dimension than cast iron.
2. Since the shrinkage of stainless steel casting exceeds that of cast iron, in order to prevent shrinkage cavities and porosity defects in castings, risers, chills, and padding are mostly used in the casting process to achieve sequential solidification.
Stainless steel castings feature uniform wall thickness, avoid sharp corners and right angles, add sawdust to the molding sand, add coke to the core, and use hollow cores and oil sand cores to improve the collapsibility and permeability of the sand mold or core.
Stainless steel casting exhibits good fluidity in the melt during transfer. The casting temperature for stainless steel needs to be determined based on factors such as the transfer distance, the transfer process, and the flow rate. Due to its small transition zone size, stainless steel casting offers good mechanical properties during use. The temperature range is generally 715~740℃, prioritizing fluidity and preventing the formation of bright crystals. Flat stainless steel ingots have a high tendency for hot cracking, requiring relatively low casting temperatures, typically 680~735℃. Round stainless steel ingots have a lower tendency for cracking and possess good venting and feeding capabilities. Creating optimal conditions for increasing density and improving the alloy's density, the casting temperature is generally higher, with ingots with a diameter of 350mm or more typically casting at 730~750℃.
Furthermore, the furnace charge in stainless steel casting production mainly consists of pig iron, scrap steel, coke, limestone, molding sand, and core sand. The processes primarily involve transporting raw sand, clay, coal powder, resin and other binders, curing agents, and used sand, as well as mixing, molding, core making, baking, melting, pouring, cooling, sand removal, cleaning, and post-processing. These operations are conducted amidst mechanical vibration and noise, and some are even performed at high temperatures, such as during melting and pouring. Some processes produce irritating odors, and the dusty working environment is particularly harsh. The gating system design is also flawed. Due to improper design, defects such as air entrapment and inclusions exist, leading to low casting yield and pass rates. These are the current problems in stainless steel casting technology. Some problems that we can solve should be addressed promptly; for objective problems that we cannot solve, there is nothing we can do.
Stainless steel castings possess relatively high mechanical properties during use, primarily due to their high melting point. Molten stainless steel is prone to oxygen reaction, exhibiting poor fluidity and significant shrinkage during operation, with a volume shrinkage rate of 10~14%. To prevent defects such as incomplete pouring, shrinkage cavities, porosity, cold shuts, cracks, and sand adhesion in stainless steel castings, more complex processing measures than those for cast iron are required during use.
