In-depth research and analysis mould steel surface enhancement technology, to improve the overall performance of the mold

In order to improve the life of the mold, not only high quality, good performance mold material, should also take reasonable heat treatment process to improve its performance, but the overall quenching conventional mold has been difficult to meet high surface abrasion resistance and matrix strength and toughness requirements. Surface hardening technology not only can improve the wear resistance of the mold surface and other properties, and the matrix can maintain adequate strength and toughness. This is to improve the overall performance of the mold, saving alloying elements, a significant reduction in cost, full potential of the material, as well as better use of new materials, are very effective.
HongChao(DongGuan) Mould & Technology Co.,Ltd. under the production practices that strengthen the skills to improve the mold surface quality and an important measure to extend tool life. Surface hardening techniques commonly used are the following:
⒈ chemical heat treatment
Chemical treatment is to mold heated to a temperature chemical reaction with the media to the surface as needed into a certain amount of other elements to improve its surface chemical composition, microstructure and properties, in order to effectively improve the wear resistance of the mold surface, corrosion resistance, anti-oxidation and anti-seize properties, the tool life significantly improved. Almost all of the chemical heat treatment process can be used to heat the mold.
⑴, carburizing and nitriding nitrocarburizing
Carburizing is the most widely used in machinery industry as a chemical treatment method. The process is characterized by a low-carbon low-alloy tool steel and high alloy die in the carbon steel in the active medium by carbon (carburizing agent) heated to 900 ~ 930 ℃ to make the mold into the surface layer of carbon atoms, followed by quenching and tempering, the Ministry of the mold surface and the heart has a different composition, organization and performance. Divided into solid carburizing carburizing, liquid carburizing, gas carburizing. Recently they developed to the controlled atmosphere carburizing, vacuum carburizing, benzene ion carburization. HongChao(DongGuan) Mould & Technology Co.,Ltd. sales Daido steel in Japan and Sweden Uddeholm tool steel of high quality mold steel, supporting professional technical services.
Seepage nitriding is also mold parts surface carbon and nitrogen into the heat treatment process.
3Cr2W8V steel casting mold, the first carburized and then quenched by the 1150 ℃, 550 ℃ tempered twice, the surface hardness of up to 58 ~ 61HRC, life can be increased by 1.8 to 3 times. 65Nb(6CrW3Mo2VNb) other substrate steel has high strength and toughness, but the wear resistance of the surface is often poor, with this type of steel molds for carburizing or nitriding, nitrocarburizing, can significantly improve their life.
⑵, nitriding or nitrocarburizing
Nitrogen into the steel surface nitriding process is called steel. Nitride can mold parts to obtain a higher surface hardness than carburizing, wear resistance, fatigue properties, red hardness and corrosion resistance. Because of lower nitrogen temperature (500 ~ 570 ℃), nitride mold parts deformation.
Nitriding nitriding methods are solid, liquid nitriding, gas nitriding. Currently widely used in ion nitriding, vacuum nitriding, electrolytic reminder infiltration nitriding, nitriding and other new high-frequency technology to shorten the nitriding time, and for high-quality nitrided layer.
Carburizing in the presence of permeation is activated carbon, nitrogen atom of the medium into both nitrogen and carbon, and low-temperature nitriding based nitrocarburizing process (530 ~ 580 ℃), carburizing brittle diffusion layer permeation of small , permeation time is much shorter than the nitriding time. Die casting, hot extrusion die after nitrocarburizing, may significantly increase the thermal fatigue performance.
Production proved, after nitriding and nitrocarburizing of steel mold their life, have a more substantial increase.
⑶, permeation of oxygen and nitrogen, sulfur and nitrogen permeation, diltiazem nitrocarburizing, and multi-rare-earth reminder of infiltration infiltration
In gas nitriding at the same time, which leads to oxygen-containing medium (usually air, the volume fraction of 5% or less), the oxygen can be achieved die steel nitriding, the nitriding and steam treatment of both results. As the hydrogen partial pressure of oxygen reduced to improve the nitrogen atom activity, accelerated the infiltration rate, the permeation of oxygen and nitrogen compound layer and diffusion layer thickness than the corresponding alcohol - ammonia as penetration enhancers of nitrocarburizing layer should be thick , in particular, compound layer thickness of 50% to 100%, and no brittleness, mold oxygen nitriding, its service life than nitrocarburizing has greatly improved. Oxygen-nitriding temperature of 540 ~ 590 ℃, holding time 1 ~ 3h.
Gas-N-permeation in nitriding furnace, penetration enhancers for the ammonia (volume fraction of 30% to 50%) and hydrogen sulfide (0.02% volume fraction). Nitrocarburizing gas-N-ammonia is used drip molten sulfur veins, permeation temperature is generally 540 ~ 570 ℃, permeation time of 1 ~ 3h. Sulfur compounds with iron to form FeS and FeS2, covering the surface, can reduce the friction factor, effectively improve the surface abrasion resistance and resistance to the ability to bite. The use of this technology in the mold, the mold life has improved significantly. In recent years, has developed oxygen, sulfur, boron, nitrogen, per EPA permeation process, five-permeation, it can in the mold surface carbides, sulfides, oxides, borides and nitrides, the mold surface significantly improve the hardness of the diffusion layer in the infiltration of nitrogen and carbon, the hardness also increased, can greatly improve the life of the mold.
Many units of production practices that adding a small amount of rare earth elements in the chemical heat treatment, a more visible reminder seepage effect, acceleration: [C], [N], [B] the generation of light atoms such as activity, can change the surface chemical composition, structure, improve material performance, increase the use of penetration enhancers to the development of rare-earth-nitriding, nitrocarburizing of rare earth and other new technology. Reducing the nitriding and nitrocarburizing time, improve product quality, increase die life.
⑷, boronizing and alloying
Boronizing is a common mold manufacturing industry, high-temperature chemical heat treatment process. The physical media used by the state, can be divided into solid boronizing boronizing, liquid boronizing, gas boronizing, and electrolytic boronizing paste boronizing, etc. The temperature of the solid boronizing 800 ~ 950 ℃, holding time 2 ~ 6h, boride layer thickness of 0.10 ~ 0.20mm, solid surface hardness after boriding up to 1400 ~ 2800HV, advantages of simple equipment, convenient operation, easy to clean surface, which are widely used. More brittle boride layer, diffusion layer is thinner, strong support for the diffusion layer, this can be used boron nitriding, carbonitriding or boron, to enhance the transition zone, the hardness changes to flat. Rare earth elements can significantly increase the rate of boriding, the uniform layer dense, with the matrix to improve the bonding. After boriding of parts can be post-heat treatment in order to boronizing diffusion layer and the substrate with reasonable performance.
Boronizing heat treatment process often used with a variety of cold-working die, due to the improvement of wear resistance, can increase the life of the mold several times or ten times. Sometimes used in carbon steel boronizing of high alloy steel production molds can be replaced. Boronizing also be applied to hot molds, such as hot extrusion mold.
With industrial development, the performance of the steel made more specific requirements. Use of chemical alloying heat treatment method, the surface of the mold can be a special performance to meet the requirements. Alloying including infiltration chromium, vanadium permeability, infiltration niobium, titanium and other infiltration process can be applied to deal with cold and hot die die. Molten metal infiltration method (molten carbide coating process and TD method) can be obtained in a series of high steel surface hardness carbide, nitrided layer hardness up to 1800 ~ 3200HV, can improve the life of the mold several times or even ten several times. HongChao(DongGuan) Mould & Technology Co.,Ltd. sales Daido steel in Japan and Sweden Uddeholm tool steel of high quality mold steel, supporting professional technical services.
⒉ energy beam surface hardening technology
With great energy density of the instantaneous supply of the mold surface, so that a phase transformation hardening, surface melting and rapid solidification effect of alloying heat treatment, said high energy beam surface hardening technology (also known as high-density surface hardening), the heat source usually refers to the laser, electron beam, ion beam and so on.
Their common characteristics: fast heating, the workpiece deformation is small, without the cooling medium, controlled performance, easy to automate processing. China often uses laser surface transformation hardening, small and medium-power electron beam ion implantation to increase the surface hardness of the mold, and achieved good results.
⒊ mold surface enhanced vapor deposition
Vapor deposition according to the basic principles of form, can be divided into chemical vapor deposition (CVD) and physical vapor deposition (PVD). Vapor deposition on the mold surface covered with a layer thickness of 0.5 ~ 10μm over group elements (Ti, V, Cr, W, Nb, etc.) of carbon, nitrogen, oxygen, boron compounds or single metal and non-metallic coating.
Vapor deposition layer has high hardness, low friction coefficient and self-lubricating properties, good anti-wear particles and wear properties, and has a strong resistance to corrosion and good resistance to atmospheric oxidation capacity, is a promising new type of mold surface hardening techniques.
CVD method is the use of chemical composition of the reaction gases to the substrate surface in the mold to form a chemical reaction coating method, available within the mill super-hard coating, is an effective way to improve tool life.
Metal, alloy or compound in a vacuum chamber evaporation (or sputtering), or a branch of these gas atoms under certain conditions in the mold surface precipitation process called physical vapor deposition (referred to as PVD). Physical vapor deposition can be divided into vacuum evaporation, cathode sputtering and ion plating three categories, with low processing temperature, deposition speed, pollution, etc., is very suitable for surface hardening mold, can greatly improve the life of the mold.

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Source: HongChao(DongGuan) Mould & Technology Co.,Ltd.
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