The Treatment Of Steel Casting Deformation

In the entire manufacturing process of steel castings, deformation occurs in almost every process. The causes of casting deformation are mainly divided into two categories. One is internal reasons, which are mainly manifested as casting stress deformation and heat treatment stress deformation.

Casting stress deformation refers to the casting stress caused by the different solidification sequence and solidification rate of different parts in the solidification process of the casting. This stress will be released in a certain process after the casting is boxed, which will lead to the deformation of the casting. Heat treatment deformation is mainly due to the reduction of the strength of the casting after thermal expansion and softening during the heat treatment process, the deformation of the casting caused by its own gravity, and the deformation caused by the release of the stress accumulated in the structure during the transformation of the structure.

Generally, the former has a greater impact on the size and shape of castings.

There are many reasons for the deformation of castings, and deformation may occur in every process of the whole production process. If the design structure and process plan are unreasonable, improper modeling, boxing, cleaning or heat treatment operations, etc., can all cause the casting to be deformed. Some of the casting deformations caused by the above-mentioned reasons can be reduced or avoided by improving the design, revising the process, improving the operation level and subjectively strengthening the sense of responsibility. However, it is difficult to avoid the deformation of some castings at the current technical level, so that the correction work for the deformed castings appears.

Generally, the correction methods of casting deformation are divided into two categories, that is, the deformation of the casting is the correction method of pressurization or impact at room temperature (referred to as the cold correction method); the correction method of heating the casting to a certain temperature, pressurizing or squeezing, and supporting (Referred to as thermal correction method).

Cold Correction Method

The cold straightening method is based on the size of the deformed casting and the thickness of the section. It can be hammered, impacted or squeezed at room temperature by using a hand hammer, a large and small straightening machine, a water (oil) press or some simple pressure method. Correction method.

Practice has proved that it is difficult to achieve the expected effect for the correction of general casting deformation by cold correction. However, for the correction of deformation of high manganese steel castings, cold correction can only be adopted (determined by material properties).

The Hot Correction Method

The hot correction method is to heat the deformed casting to above the elastoplastic temperature zone of the material, and restore the deformation of the casting through external forces such as extrusion and bracing, so as to achieve the purpose of correction.

The heating temperature of the thermal correction method is roughly divided into two types. One is high temperature (that is, austenitizing temperature); the other is low temperature, which is the heating temperature of low temperature annealing or high temperature tempering. The two heating temperatures have their own advantages and disadvantages. The "high temperature" requires high requirements for the operator and the operation is difficult, but the correction time is short; the "low temperature" does not require high requirements for the operator, the operation is simple, and the correction success rate is high, but the correction time is relatively long. long. In terms of comprehensive pros and cons, the correction success rate is the main one, so we often use low temperature correction.

According to the heated parts of the deformed castings, the author divides the thermal correction method into two types: the correction method and the local correction method.

The operation of the correction method is simple and convenient, and the correction effect is good; while the local correction method has strict requirements on the correction site, sometimes it is necessary to build a stove, sometimes use a gas cutting gun to manually operate, for a long time baking, poor working conditions, and unsafe, correction The effect is not very satisfactory (theoretically, stress relief treatment should be carried out after correction). Therefore, in actual production, we still focus on the correction method, and try not to use the local correction method (except for individual castings that cannot be used for the correction method).

The correction effect of the correction method depends on the correctness of the correction furnace and heating method. Such as the furnace loading method of deformed castings (including the determination of the correction gap value of the deformed part, the correction of the weight and position of the pressure, the selection of the weight, the stop, the support, the shim, the platform, the wedge, etc.), the correction of the heating temperature ( High temperature or low temperature) determination. The correction gap value (hereinafter referred to as the gap value) is the determining condition of the correction effect.

• (1) No matter what kind of deformation, it cannot be completely eliminated. Only a series of measures can be taken to reduce the amount of deformation and control the amount of deformation within an acceptable range.
• (2) The focus of deformation lies in prevention: starting from the modeling aspect, especially the design of the correction amount through the re-deformation process; starting from the welding aspect, the design of welding anti-deformation braces, the selection of welding parameters, etc.; starting from the heat treatment aspect, focusing on the study of castings The placement of the furnace and the selection of heat treatment parameters.
• (3) The control of deformation involves the entire casting and manufacturing process, and it needs to go through various procedures, especially the control of key procedures, in order to do a real anti-deformation work.

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By Minghe Die Casting Manufacturer |Categories: Helpful Articles |Material Tags: Aluminum Casting, Zinc Casting, Magnesium Casting, Titanium Casting, Stainless Steel Casting, Brass Casting,Bronze Casting,Casting Video,Company History,Aluminum Die Casting |Comments Off