Mold Material Selection Needs To Meet The Performance Requirements
Mold manufacturing generally involves several processes such as forging, cutting, and heat treatment. In order to ensure the quality of the mold and reduce the production cost, the material should have good forgeability, machinability, hardenability, hardenability and grindability; it should also have small oxidation, decarburization sensitivity and quenching. Deformation cracking tendency.
Hardenability refers to the material characteristics characterized by the depth and hardness distribution of the sample under the specified conditions, which depends mainly on the critical quenching rate of the material. Under the specified conditions, the characteristics of the hardening depth and hardness distribution of the steel are determined. That is, the ability to obtain the depth of the hardened layer when the steel is quenched, which indicates the ability of the steel to undergo quenching. The hardenability of the steel is good and poor, and it is usually expressed by the depth of the hardened layer.
The greater the depth of the hardened layer, the better the hardenability of the steel. The hardenability of steel is an inherent property of steel itself, which depends only on its own internal factors and is independent of external factors. The hardenability of steel depends mainly on its chemical composition, especially the alloying elements and grain size with increased hardenability, heating temperature and holding time. The steel with good hardenability can obtain uniform and uniform mechanical properties of the whole section of the steel and quenching agent with small quenching stress of steel parts to reduce deformation and cracking.
In the narrow sense of oxidation, the chemical reaction between oxygen and other material elements, called oxidation, is also an important chemical unit process. Generalized oxidation refers to the process of material loss of electrons (increased oxidation number). Human metabolism is also like oxidation, that is, the human body is rusting every day. The rust produced in medicine is called free radicals in medicine. A free radical is a particle with unpaired electrons. Because it has a singular number of electrons, it is very unstable, has a high degree of chemical reactivity, and easily reacts with surrounding molecules, making the stability molecules also become free radicals. Repeatedly and repeatedly, a large amount of free radicals will be derived. The properties of free radicals are very active and very unstable.
3. Decarburization sensitivity
A process for purifying a gas refers to removing carbon dioxide from a mixed gas, mainly in the treatment of raw gas or gas produced by synthetic ammonia. The method for removing carbon dioxide from the raw material gas is divided into physical absorption method and chemical absorption method.
The physical absorption method first uses pressurized water to remove carbon dioxide, and regenerates the water after decompression. The method is simple, but the carbon dioxide purification degree is poor, and the carbon dioxide for export is generally below 2% (volume), and the power consumption is also high. In the past 20 years, methanol washing method, propylene carbonate method, polyethylene glycol dimethyl ether method, etc. have been developed. Compared with pressurized water decarburization, they have the advantages of high purification degree, low energy consumption, high purity of recovered carbon dioxide, and the like. It is also possible to selectively remove hydrogen sulfide, which is a widely used decarburization method in the industry.
The chemical absorption method has the advantages of good absorption effect, easy regeneration, and dehydrogenation. The main methods are ethanolamine method and catalytic hot potash method. In order to increase the absorption and regeneration rate of carbon dioxide, some inorganic or organic substances may be added as an activator in the potassium carbonate solution, and a corrosion inhibitor may be added to reduce the corrosion of the solution to the equipment.
Machinability (cuttability, machinability): Refers to the ease with which a metal material is machined and becomes a qualified workpiece. The machinability is usually measured by the surface roughness of the workpiece after machining, the allowable cutting speed and the degree of wear of the tool. It is related to many factors such as chemical composition, mechanical properties, thermal conductivity and degree of work hardening of metal materials. Hardness and toughness are generally used for the rough judgment of the machinability. Generally speaking, the higher the hardness of the metal material, the harder it is to cut, and the hardness is not high, but the toughness is large and the cutting is difficult. Generally, non-ferrous metals (non-ferrous metals) have better machinability than iron metal, and cast iron is better than steel.
5. Annealing processability
Annealing is a metal heat treatment process that involves slowly heating a metal to a temperature for a sufficient period of time and then cooling it at a suitable rate. The purpose is to reduce hardness, improve machinability, eliminate residual stress, stabilize size, reduce deformation and crack tendency, refine grains, adjust microstructure, and eliminate tissue defects. Accurately, annealing is a heat treatment process for materials, including metallic materials and non-metallic materials. Moreover, the annealing purpose of the new material is also different from the traditional metal annealing.
The ability of steel to obtain hardness after quenching is called hardenability of steel. The hardenability and hardenability of steel are two completely different concepts. The hardenability of steel refers to the ability of steel to achieve the highest hardness under ideal conditions, which depends mainly on the carbon content of martensite. Steel with good hardenability does not necessarily have high hardenability. For example, the hardenability of low carbon alloy steel is quite good, but its hardenability is not high, and the hardenability of high carbon tool steel is poor, but its hardenability is high.
The metal has thermoplastic properties and can be subjected to press working in a heated state (various temperatures are required for various metals), and is said to be malleable. Refers to the ability of metal materials to change shape without cracking during press working. It includes the ability to perform hammering, rolling, drawing, extrusion and the like in a hot or cold state. The forgeability is mainly related to the chemical composition of the metal material.
The ability of metal materials to withstand plastic deformation without cracking during forging, also known as process plasticity. The forgeability index is usually expressed by the amount of deformation of the metal material when the surface begins to crack under a certain plastic deformation mode. This deformation amount is called the critical deformation amount. The deformation modes of various forging processes are different, and the indicators indicating the forgeability are also different. The upset is expressed in terms of compression ratio, the extension is expressed as elongation or the reduction ratio, and the torsion is expressed in twist angle.
8. Quenching deformation cracking tendency
The conventional quenching volume change is small, the shape is warped, the distortion is slight, and the abnormal deformation tendency is low. Conventional quenching cracking has low sensitivity and is not sensitive to quenching temperature and workpiece shape.
The relative loss of the grinding wheel is small, the amount of grinding without the limit of grinding is large, and it is not sensitive to the quality of the grinding wheel and the cooling condition, and it is not easy to cause abrasion and grinding crack.