The first is the raw material factor. High-manganese steel materials used in stainless steel precision seamless steel pipe casting, columnar crystals, fine equiaxed crystals, low-temperature casting will make the crystal grains small, emerging column crystals, too high casting measurement and even appearing through the crystal. It is easy to produce unfamiliar pine, crack and other stainless steel precision casting defects and toughness storage have some functional shortcomings. Exiting the rare earth can also suppress grain growth.
Second, the environmental factors of stainless steel precision casting. Below 650 °C, the high-manganese steel is in the inertial form. Under this measure, the high-manganese steel grain boundary network carbide has been formed, so the plasticity is increased. When the expansion hits the wall, the expansion stress exceeds the strength of the high-manganese steel. The grain boundary germinates, and under the action of the stress position, the crystal is broken and forms a cold crack.
In order to ensure the reduction of cold cracking in stainless steel seamless pipe casting, attention should be paid to raw materials and manufacturing processes. The wall thickness of the casting is as uniform as possible, and the principle of simultaneous solidification is adopted to strictly control the phosphorus content to prevent cold brittleness. For castings with large differences in wall thickness, complex shapes or large and thin castings, castings of high manganese steel are used as much as possible.
The casting process design is based on the structural characteristics of the castings, combined with the actual production, to design a set of operational guidance documents and quality control documents that ensure quality and obtain high economic benefits, and produce a conformity under the premise of implementation guarantee. Required product. Large-scale Shandong precision casting process design process factors, the use of design methods, some inconspicuous factors in small pieces, have a significant impact in large pieces.
Large-scale castings are small in batch size, difficult in process testing and improvement. Designers require a wealth of knowledge and experience. The engineering and content of the design mainly include: process analysis of stainless steel casting, selection of stainless steel casting process plan, selection of stainless steel casting process parameters. The control of stainless steel casting, the heat treatment technology of castings, the design of casting process equipment, and the post-processing technology of castings are the core of casting process design. The meaning of casting process design in the usual sense is this part.
The stainless steel casting process design is based on summarization and improvement. It is a technical management measure for obtaining high quality and high yield castings. When selecting a stainless steel casting process plan, specific conditions of the foundry must be considered, such as the operation of the casting equipment, production capacity, structure and dimensions of the steel castings, technical requirements, and production quantities. A preliminary discussion was held on the main principles of the choice of casting process options.