How to solve the shell expansion defects on stainless steel castings

During production of stainless steel castings, we often encounter the quality problems of the shell expansion defects. Such defects are caused by crystal expansion happened during the volume solidification and eutectic transformation process of the stainless steel.

Below, let PARFECT talking about the solutions to solve such problems,

1. Strict control on pre-processes, such as wax ingredients, shell pressuring, location of the ingot welding, coating hardening and drying the wax tree. New and used wax material rate to be controlled within 50%:50%. Wax shell pressed by pneumatic press. The wax injection gun should be electrical temperature controlled and temperature of the wax material controlled between 42 - 50°C. Place of gate welding should be at the biggest hot tear areas on the investment castings, thus to solve the shrinkage problems and control solidification processes. The coating material should be with high strength. The surface coating contains silica powder, silica sand, and the reinforcement layer includes high aluminum powder, high aluminum sand. All coatings liquid are mixed with rate of 1:1. To increase the coating property and strength of the shells, we usually add 0.05% surface activator.

The viscosity of the coating: surface layer of 10-15s, reinforcement layer of 18-25s (using funnel viscometer IOOmL/6mm). The hardening agent is ammonium chloride with concentration range of 22% to 25%. The temperature controlled within 30 – 50% with the hardening time within 5 -15min. The drying equipment use warm wind kiln with drying time between 15-30 rain.

The above technical process will control the shell dried sufficiently, baking appropriately, no layers, solid and tight enough.

2. Modify the shell expansions problems during de-wax process. To solve the expansion defects caused by de-wax, we made the below modification on technical process: removing the wax bars before de-wax, using joint melting processes. Melt the wax material or draw out the wax bars by using vapor, then melt the wax shell in hot water. This will help to melt all the wax materials at one time, thus ensure the channels unblocked. We do according to the above principles, changing the sequence from digging the shells completely with wax bars up to digging the wax bars down first partially. The good thermal conductivity allows the aluminum wax bars to separate from the wax tree rapidly. We take the wax bar out and dig the shells in the water to melt the wax materials and overflow uniformly.

3. Strictly control the temperature, speed and height of steel liquid during casting. We should achieve ‘Medium temperature, stable flow and low press’, thus to reduce the destruction to the shells during casting.

if you want to know more information , welcome to visit our website at :www.casting-forgings.com to know more .

Ningbo Parfect machnery Co.,Ltd starting since 2001, is a casting factory, specialized in manufacturing all kinds of steel casting,carbon steel casting, alloy steel casting,ductile iron casting ,gray iron casting and so on, which are used in the field of transportation equipment(train parts/vessel parts), agricultural machinery, mining machinery, rubber machinery, some other heavy machineries, etc. Such goods are exported mainly to the North America, Europe, Australia amp South Africa market. Our factory is located in Ningbo city, which is one of the largest port cities in China and also the China lost wax casting process and Sand casting process production base. If you have any other question, please feel free to contact us.

Room 1009, Minghui Building, Siming Zhong Road, Yin zhou district, Ningbo 315100,

This release was published on openPR.