plastic mould, injection mould

Eight high-quality requirements for steel mold(2)

2, die steel in the process performance requirements
(1)machinability
Including steel machinability by cutting both hot forging and cold, depending on the chemical composition of steel after heat treatment of internal organization and the quality of metallurgical production, in recent years, in order to improve the machinability of steel in add some steel in the steel cutting element or change in the distribution of the inclusions to improve the surface quality of die steel and reduce the die wear. In thermal processing, a number of high-carbon high-alloy tool steel, in particular, to improve the carbide morphology and distribution, grain size and degree of austenitic alloy is very important.
In addition should have good processability, but also has good electrical turning model of processing and processing of such impression.
(2) hardenability and hardenability
Die under these two performance requirements are different emphases in different working conditions, and for the requirements of the hardness of the uniformity of the high cross-section of the mold, such as hammer forging die steel, its high hardenability more important, while only requires a small die with high hardness, such as blanking blanking die steel, even more emphasis on high hardenability.
(3) heat deformation
Mold parts in the heat, require little deformation in all directions to have similar changes, and organizational stability. Quenching distortion is small, except with the quenching temperature] time and cooling medium and other factors, but it mainly depends on the composition of the steel uniform, metallurgical quality and organizational stability.
(4) decarburization sensitivity
Die steel forging, annealing or quenching, in the absence of heated under protective atmosphere, its surface will have defects such as oxidation and decarbonization, so that die down in durability. In addition to decarburization and heat treatment process, equipment related, in respect of material itself, depending on the chemical composition of steel, especially carbon, in the presence of high silicon, molybdenum and other elements, it will also increase decarburization.
In addition, the conditions should be based on the use of molds should be considered mirror polishing of the mold making, and so grinding and electrochemical properties.
3, mold steel in metallurgical quality requirements
Can play a high metallurgical quality of the properties of the steel substrate, die within the metallurgical quality of steel and its basic performance with the same importance in the study of performance, we must study the quality of metallurgical factors. More frequently encountered in general internal and external quality of die steel in the following areas:
(1)the uniformity of chemical composition
Die steel usually contains many elements of the alloy steel, steel ingot mold from the liquid during solidification, crystallization of the separation were the reason, various elements in liquid steel solidification structure in the formation of uneven distribution of segregation, the chemical composition segregation will result in differences in microstructure and properties, which affect the quality of steel is one important factor. Reduce the segregation of steel, can effectively improve the performance of steel. In recent years, many of metallurgical plant and abroad to study in the production of uniform, grain refinement of steel.
(2) the content of harmful elements
Sulfur and phosphorus in steel during solidification and the formation of phosphide and sulfide precipitation in the grain boundary, resulting in the intergranular brittleness of the plastic reduction of the steel, high S, P content, easy to make the ingot cracks in the rolling and may significantly reduce the mechanical properties of steel. Fortunately, the Japanese discipline and other studies Matsuda S, P content on the W (Cr) 5% hot work die steel (H13) of the impact toughness and thermal fatigue performance results show that, as the W (S, P) content of 0.025% from and 0.010% to W (P) 0.005%, and W (S) 0.001%, the thermal fatigue crack length and number will be reduced by half. Hitachi Metals will SKD61 steel in W (P) content from 0.03% to 0.001%, while steel can be 45HRC toughness increased by the 39.2J/cm2 to 127.5J/cm2. In addition, the reduction of steel in the S, P content also can increase the isotropic steel.
(3) non-metallic inclusions in steel
Good quality steel chemical composition not only to comply with technical standards and non-metallic inclusions in steel content should be kept as small as non-metallic inclusions in steel volume occupied by the small, but for steel Performance is great. Reduce non-metallic inclusions in steel is the steel of the main tasks. Commonly referred to as non-metallic inclusions in steel, mainly refers to the iron and other alloying elements with oxygen, sulfur and nitrogen compounds formed by the role, such as FeO, MnO, Al2O3, SiO2, FeS, MnS, AlN, VN, etc. , as well as steel and pouring into the refractory, which elements are mainly Si, Al, Fe, Cr, Ca, Mg and other oxides. Non-metallic inclusions in steel on its source, can be divided into internal and external inclusions inclusions, the inclusions cents in the liquid and the solidification of steel in the process of formation of compounds.
Non-metallic inclusions in steel in the basic kinds of sense to stay a certain size as a crack, it destroys the continuity of the metal, causing stress concentration, the role of stress in the outside world, the crack extension is easy to develop and expand the lead to performance reduced. The presence of plastic inclusions, with the extension of forging deformation rolling process, resulting in anisotropy of steel produced. While inclusion of peeling polishing process to improve the surface roughness of the mold. Therefore, the mold is large and important to improve the purity of steel is very important.


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