Why is the mold selected for quenching?

Answer:

This is mainly due to the steel in the range of the solid as the change of heating temperature and cooling speed, organization structure change, so the use of different heating temperature and cooling rate to control or change the organization structure steel, can get different performance. (a) prepare heat treatment, annealing, normalizing heat the steel to the phase transition point above a certain temperature, heat preservation time, and then slowly along with the furnace cooled to 500 'C below, after cooling in the air. So you get an approximate equilibrium organization, and it's called annealing. The so-called positive fire is to heat a piece of steel to a certain temperature above the point of phase change and then remove it from the furnace and cool it in the air. Annealing or normalizing and technical requirements of the parts service condition has no direct relation, but simply brought by the procedure in order to improve the defects, and organization prepare for the next procedure, make the grain refinement, eliminate the internal stress of normalizing, annealing, etc. When the fire is hot, it cools quickly; Slow down when annealing. Annealing reduces the hardness of the material; Positive fire can improve the hardness of the material. After normalizing steel hardness is larger than that of annealing steel hardness is high, so in order to facilitate machining, the carbon content of high carbon tool steel materials such as using the annealing treatment. In order to reduce the hardness.

Medium temperature tempering ^ (350-350 - c) : organization for tempered troostite after tempering. Hardness in the range of roughly HRC35 ^ - 45, within the scope of the elastic limit and yield strength of steel is higher, so it is mainly used for all kinds of springs, spring clip first class. High temperature tempering (500 ^ - 6800 - c) : the organization for tempering sorbite, hardness range for HRC23-35. The strength, plasticity, toughness and good overall mechanical properties of steel can be obtained by tempering the heat within this temperature range. It is mainly used for shaft parts, gears, rods, poles, screws, etc. The tempering of the hardened and subsequent heat is usually referred to as the adjustment of steel. The hardness of modified treatment weeken the scope for H RC25 ^ - 32. Tempering treatment is widely used in various important structure parts. As the final heat treatment, but also can be used as a certain precision parts, such as molding parts heat treatment in advance. It provides a uniform and small body tissue to reduce the deformation in the final heat treatment process and provide the foundation for the better final performance. (3) the surface heat treatment The so-called surface heat treatment is by changing the parts surface layer organization or change to the surface chemical composition. At the same time give parts surface layer and the core of different performance. That is, a method of heat treatment with the properties of external hard toughness. Surface treatment is divided into two categories: surface hardening and chemical heat treatment.

It is suitable for low and medium carbon structure steel to improve the hardness of the material. As for alloy steel, the hardness of steel is improved due to the addition of alloy elements. So in most cases, the alloys that are more than carbon need to be annealed, not right. (2) the final heat treatment, quenching and tempering Quenching refers to in order to improve the hardness of steel or increase its strength. The steel is heated to above phase transition temperature, heat preservation time, and then in the appropriate liquid (water, oil, or brine) rapid cooling, martensite structure is obtained. After hardening, the hardness, strength, and abrasion resistance can be obtained. But the hardening of the steel will cause the internal stress to make the steel brittle, so it must be tempered in time. The return fire is to heat the hardened steel parts to a certain temperature (below the phase change point). The purpose of tempering is to eliminate the internal stress caused by quenching and improve the plasticity and toughness of the material. . According to the scope of the heating temperature can be divided into: the tempering tempering at low temperature (150 ^ - 2500 - c) : it is mainly used for high hardness (H RC55 ^ - 62) and wear resistance of various parts, such as mold molding parts. By tempering, reducing stress and brittleness, and obtaining the tempering martensite tissue

Mold quenching process is in order to improve the wear resistance of molding parts are generally must carry on the quenching process, and achieve H RC52-57 0 in the parts of structure USES, core plate and ejector plate and plate type of components at the top of the molding or out of the plastic parts. When the bear larger unit extrusion pressure, also want to quenching process. Mold (mu ju), industrial production to injection molding, blow molding, extrusion, die casting or forging molding, smelting, the methods of stamping products of various molds and tools required. In short, the mold is a tool for molding objects, which are made up of various parts, and different parts are made of different parts. It mainly USES the physical state of the forming material to realize the processing of the physical appearance. There is the title of "mother of industry".

In order to improve the wear resistance of molding parts are generally must carry on the quenching process, and achieve H RC52-57 0 in the parts of structure USES, core plate and ejector plate and plate type of components at the top of the molding or out of the plastic parts. When the bear larger unit extrusion pressure, also want to quenching treatment, made of 45 # steel parts required hardness reaches HRC40 ^ - 45. Other parts, such as guides, guides, etc., will also be hardened by means of extending their service life. Some of the complex die parts. Size is bad control. In the case of little plastic parts production, allowing the tempering treatment as a final heat treatment process, in this no longer after finishing. Some important die parts in the process of processing, should arrange the heat treatment procedure properly (annealing or positive fire, adjustment of quality processing etc. When using low carbon steel (such as 20th steel) or alloy steel (such as 38CrMoA1A) for forming parts, the surface heat treatment such as carburizing or nitriding is required. Heat treatment of the so-called steel is a process of changing the performance of steel by using different heating, insulation and cooling in the solid state