Effect of mould expansion on pattern allowances in sand casting of steel

For steel castings produced in sand molds, the expansion of the sand and have a significant impact on the final size and shape of the casting. Experiments performed using a cylindrical solutions to study the effect to various sand (silica and zircon) and various sand binder systems (phenolic urethane and sodium silicate). Has a significant impact on the final solution features the type of sand, especially because he can not expand the silica sand to be irreversible. The effect is enhanced by the presence of sand expanding sodium silicate binder. In addition, the size of the heart, as in experiments at the controls of the amount of steel in the mold and thus the heat input to the model, affected strongly the internal and external aspects of the solutions as a result. And stress simulation solutions combined code used to predict the dimensional changes of the castings. In some cases, the allowances pattern successfully predict both free and blocked contraction cases. Possible disagreements between simulation and measurement results can be attributed the fact that the model does not account stress irreversible nature of the expanded silica sand, which is important when silica sand is heated to temperatures above y1200uC; and the outer mold sand of the solutions, which can cause inaccuracies when there is significant early expansion model, hindrance, or move. Dimensional errors can of castings can be divided into those due to random reasons and those due to errors pattern. Random errors are the cumulative result of many intermediate stages of production solutions, such as core making, mold making, assembly of cores into the mold, the final mold, pouring, heat treatment, cleaning and grinding.

Random errors increase the variability of measurements solutions. Double errors occur when the resultant average dimension solutions different from the size specified feature. When designing a new pattern, the three-dimensional model changes and anticipated solutions. These changes are estimated then applied to the pattern as something called traditionally the shrinkage allowance or the rule shrink. The factor is referred to as pattern allowance (PA) in this paper indicate that more than shrinkage factors to account. Many are very interdependent physical processes responsible for steel castings are not the same features as the pattern from which the molds are made. A contraction of the steel on solidification and cooling to room temperature the primary reason for dimensional changes. However, the potential is resizing, before and after the metal poured the mold as well. The model can also curb the contraction of the metal during solidification.

When metal shrinkage free or unrestricted model and forms an air gap between the casting and the mold, the allowance may have unpredictable pattern easily as discussed below. However, parts of its solutions into core contract or parts of the mold. In these cases, development and emphasized the contraction depends solutions lead the mechanical and physical properties of the sand and solidifying steel. Contraction is blocked such features are restricted solutions smaller in size than shrinking free. Emphasis also develop due to non-uniform cooling of the solutions which can result in distortion solutions. The final elements of steel casting is also strongly affected by changes in volumetric model and core sand.

Can the high temperature steel pouring cause significant heating and thermal expansion near the sand mold. When most of the liquid metal and it offers little resistance to the sand can extend into the cavity. The extension is captured when solidified shell metal develops against the sand. Since sand aggregate good insulator, the heat affected zone is usually narrow mold material. The amount depends on the type of sand extend sand, along with the binder system used.


What is Steel Casting

steel casting is an alloy of iron, carbon as the main elements and the carbon content of 0-2%. Steel casting is divided into carbon steel casting, low alloy steel casting and special steel casting .Steel casting is the most widely used stainless steel which has the following advantages:

steel casting1. The design of the greater flexibility

2. Flexibility and variability of metallurgical manufacturing

3. The strongest increase overall structure strength

4. A wide range of weight changing.

Compared with forged steel parts, the mechanical properties of steel casting in all directions were similar, dominant than forged steel parts. Designers must consider the properties of the material in three directions in the design processing of a number of high-tech products, so it highlights the advantages of the casting. Without considering the weight, volume, and the amount of time by the system , it is easy to make steel castings of complex shapes and non- stress concentrating member. Compared with iron casting and other alloy castings, steel castings can be used for all kinds of working conditions, and the mechanical properties superior to other alloy castings. When we need high tensile strength or dynamic load components, important pressure vessel casting and bear the heavy load of the core components at low or high temperature, in principle, we should use steel casting. Steel casting, however, the vibration absorption, abrasion resistance and mobility not as good as iron casting, moreover, it’s costing is higher than iron casting.