General situation of die steel and its development trend
Mold material is the material and technical basis of the mold manufacturing industry, of which the mold steel is the traditional mold material, and its variety, specification and quality play a decisive role in mold performance, service life and manufacturing cycle. The development of mold steel has also promoted the industrial products to high-level, individual, high value-added direction.
First, the classification of mold The use of mold is very wide, a variety of mold working conditions vary greatly, so a wide range of materials used in the manufacture of molds, die steel is undoubtedly the most widely used die steel. From carbon steel, carbon tool steel, alloy structural steel, alloy tool steel, spring steel, high-speed tool steel, stainless steel until the special mold to meet the needs of special martensitic aging steel and powder high-speed steel, Powder high alloy die steel.
Die steel by general use can be divided into cold work die steel, hot work die steel and plastic molding die steel three categories
1.1 cold-working steel Cold-working die steel is mainly used to manufacture the cold state of the workpiece for compression molding. Such as: cold punching die, cold stamping die, cold drawing mold, imprint mold, cold extrusion die, screw pressing mold and powder pressing mold. Cold work die steel range, from a variety of carbon tool steel, alloy tool steel, high-speed tool steel to high-speed tool steel and powder high-alloy die steel.
1.2 Hot Working Die Steel hot working die steel is mainly used to manufacture the workpiece under high temperature pressure processing mold. Such as: hot forging die, hot extrusion die, die-casting mold, hot upsetting die. Commonly used hot work die steel are: the high carbon content of Cr, W, Mo, V and other alloying elements alloy die steel; special requirements for hot work die steel, and sometimes high alloy austenitic heat-resistant die steel .
1.3 Plastic mold steel Because of the many varieties of plastic, the requirements of plastic products are also very different, the manufacture of plastic mold materials also made a variety of different performance requirements. Therefore, many industrialized countries have formed a wide range of plastic mold steel series. Including carbon structural steel, carburized plastic mold steel, pre-hardened plastic mold steel, age-hardening plastic mold steel, corrosion-resistant plastic mold steel, easy-cutting plastic mold steel, the overall hardened plastic mold steel, martensitic Aging steel and mirror-polished plastic mold steel.
Second, die steel material selection
2.1 The basic principles of die steel material selection According to the mold production conditions and the working conditions of the mold needs, combined with the basic properties of die steel and related factors, the future selection of molds for the economically reasonable and technologically advanced die steel. For a mold, if you simply consider the basic properties of the material, several mold materials can meet the requirements, but must take into account the life of the mold, the mold manufacturing process ease, the cost of mold manufacturing and apportioned to the manufacture Every piece of the mold on the cost of a variety of factors, a comprehensive analysis and evaluation, can come to the correct conclusion in line with reality.
2.2 Selection of the main indicators of mold steel The main indicators of mold steel selection, including the following three aspects: the basic performance of mold steel; mold steel process performance; metallurgical quality of die steel.
2.2.1 The basic properties of die steel Generally refers to die steel wear resistance, toughness, hardness and red hardness. These three properties can more fully reflect the overall performance of die steel.
(1) wear resistance Mold work, the surface often have to produce multiple strong friction with the workpiece, which requires the production of mold material can withstand mechanical wear, even in heavy and high-speed friction to withstand, and be processed Adhesion occurs between the surfaces of the workpieces, and welding causes the surface of the workpieces to be scratched, so that the die can still maintain its dimensional accuracy and surface roughness.
(2) Toughness of die steel Toughness of die steel is a very important consideration for dies subjected to strong impact loads, such as punch for cold die, hammer forging die, cold heading die, hot forging die, etc. Molds that operate at high temperatures must also consider their high temperature toughness at high temperatures. For multi-directional impact-loaded molds, one must also consider the directionality.
(3) Hardness and red hardness Hardness is the main technical performance of the mold steel, the mold must have high hardness and strength at work, in order to maintain its original shape and size, the general cold work die steel, requiring its quenching and tempering hardness HRC60 or so, while the hot die steel is about HRC45-50. Red hard refers to the material at a certain temperature to maintain its hardness and stability of the anti-softening capacity of the hot work die steel and some heavy-duty die steel, is an important performance index.
2.2.2 abrasive steel process performance generally refers to the processability, quenching temperature range and degree of quench deformation, hardenability and hardenability, oxidation decarbonization sensitivity.
(1) Machinability includes cold working properties such as cutting, grinding, polishing, cold extrusion, cold drawing processability, hot working properties including thermoplastic and hot working range temperature, and the like.
(2) Quenching temperature range and quenching deformation requirements Die steel has a wide range of quenching temperature and a smaller degree of quenching deformation.
(3) hardenability and hardenability hardenability depends on the carbon content of steel, hardenability mainly depends on the chemical composition of steel, alloy content and the quenching before the state of the organization. For most of the requirements of high hardness of the cold mold, hardened on the higher; for most hot and plastic mold mold, the hardness is not too high, often more consideration of its hardenability; especially for some large Section deep cavity mold, in order to make the mold heart has also been well-organized and uniform hardness, require the use of hardened steel mold.
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