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Heat treatment

Metal heat treatment process can be broadly divided into overall heat treatment, surface heat treatment, local heat treatment and chemical heat treatment. Depending on the heating medium, the heating temperature and the cooling method, each major category can be distinguished as several different heat treatment processes. The same metal using different heat treatment process, access to different organizations, which have different properties. Steel is the most widely used metal in the industry, and its microstructure is also the most complex, resulting in a wide range of steel heat treatment processes.

The overall heat treatment is the overall heating of the workpiece, and then cooled at an appropriate speed to change the overall mechanical properties of the metal heat treatment process.

heating

Heating is one of the important steps in heat treatment. Metal heat treatment of many heating methods, the earliest use of charcoal and coal as a heat source, and then the application of liquid and gaseous fuels. Electric applications make heating easy to control, and without environmental pollution. These heat sources allow direct heating, as well as indirect heating of the floating particles by molten salt or metal.

Metal heating, the workpiece exposed to the air, oxidation, decarburization often occur (that is, the carbon content of steel parts surface), which has a negative impact on the surface properties of parts after heat treatment. Therefore, the metal should usually be heated in a controlled atmosphere or in a protective atmosphere, in a molten salt and in a vacuum, or by a protective coating or a packaging method.

Heating temperature is one of the important process parameters of heat treatment process, select and control the heating temperature is to ensure the quality of heat treatment the main problem. The heating temperature varies with the metal material being treated and the purpose of the heat treatment but is generally heated above the phase transition temperature to obtain the desired texture. In addition, the transformation takes a certain amount of time. Therefore, when the metal workpiece surface reaches the required heating temperature, it must be kept at this temperature for a certain period of time so that the temperature inside and outside are the same so that the transformation of the microstructure is complete. This time is called the holding time. The use of high-energy density heating and surface heat treatment, the heating rate is extremely fast, generally there is no holding time or holding time is very short, and chemical heat treatment holding time is often longer.

cool down

It is also an indispensable step in the heat treatment process. The cooling method varies with the process and mainly controls the cooling rate. General annealing the slowest cooling, normalizing cooling faster quenching cooling faster. However, it also has different requirements due to different types of steel. For example, an empty hard steel can be hardened with a normal cooling rate.

Heat treatment technology

Heat treatment technology is the metal material in the process of processing to improve the mechanical properties of the treatment. In order to make the metal parts have the required mechanical properties, physical properties and chemical properties, in addition to the rational choice of materials and a variety of forming processes, heat treatment process is often essential. An improper surface treatment will make the product in the process of making the whole process of the bubble as a whole, virtually reduce the productivity and quality of products and increase manufacturing costs, and also relatively reduce the competitiveness of the industry, in light of this We introduce several modern heat treatment technology for your reference application.

1, vacuum heat treatment technology methods: vacuum heat treatment will be placed in the metal workpiece has been vacuum-filled containers, and then according to the desired purpose for a variety of repeated heating and cooling operation of a technology. Uses or advantages: the surface of the workpiece is brilliant surface, the workpiece deformation is small, the workpiece will not be oxidized and decarburization or carburizing, non-corrosive and pollution problems, quality and stability, suitable for tool or mold heat treatment for the future of heat treatment technology mainstream .

2, zero treatment technology: zero treatment is the metal parts placed in a low temperature environment, forcing the metal parts to change the material properties of a heat treatment method, the traditional zero treatment is usually quenched in the steel material after the implementation of effective Reduce the residual content of Otis steel, steel can make the dimensional stability and wear resistance characteristics, especially the high carbon content of tool steel, the best results. Uses or Benefits: The application of zero treatment will be applied to non-ferrous metals such as super-hard alloy and copper alloy to improve the internal application of residual problems in the workpiece to enhance the life of the original workpiece for more than double the original.

3, ion nitriding method: first metal workpiece placed in a vacuum vessel, then pass nitrogen, the container itself as an anode, the workpiece as a cathode, and then through the high-voltage direct current, forcing the nitrogen dissociated into positive nitrogen Ion, and at very high speed toward the cathode metal workpiece, making the metal surface to an instant nitriding surface heat treatment technology. Uses or advantages: Effectively improve the wear resistance of metal materials, fatigue resistance, corrosion resistance and other properties, in addition it also has a small deformation of the workpiece, pollution-free and energy-saving features. Widely used in various steel parts and non-ferrous metal parts of the nitriding.

4, low pressure nitriding technology: low pressure nitriding technology in the role of about 300mba pressure, into the NH3, N2O and N2 gas nitriding, can also be combined with gas nitriding and carbonation of carbonation. Processing temperature is about 400 ~ 600 ℃ or so. Nitriding under low pressure and carburizing can make nitriding layer with higher hardness on the surface of workpiece, which can increase the compressive stress on the surface of workpiece and improve the wear resistance and fatigue resistance. Nitriding speed is high, nitriding layer organization can be pure Diffusion layer or dense white layer, nitrided deep-hole slits, clean workpiece surface, good mass productivity, labor-saving, provincial gas energy, excellent working environment, and its application is more and more widely used. Uses or advantages: Because of low pressure nitriding for complex shapes, deep holes in the workpiece can be uniform hardened layer, so for die-casting molds, forging dies, aluminum extrusion die and wheel, tooth plate, nozzle, engine cylinder wear , Fatigue-resistant parts are very suitable.

5, salt bath carbonitriding technology: salt bath carbonitriding technology is to place the workpiece in the soft nitriding salt bath for treatment, the workpiece surface to form a layer of wear-resistant diffusion nitride layer, then The workpiece is rapidly displaced in the oxidation of salt oxidation treatment, so that the outer surface of the workpiece to form a layer of erosion resistant oxide layer. Uses or advantages: The use of salt bath is simple and easy to operate, the deformation of the workpiece is small, and can effectively improve the workpiece wear resistance, fatigue resistance, corrosion resistance and other mechanical properties can be applied to knives and various mechanical components.

6, physical vapor deposition technology: physical vapor deposition technology is in high vacuum substrate coated with a layer of ceramic film, this film is also harder than tungsten carbide alloy, with high corrosion resistance, wear resistance, adhesion And low friction coefficient and so on. At present, there are two types of physical vapor deposition systems, cathodic arc plasma and unbalanced magnetron sputtering. TiN, TiCN, CrN, CrCN, TiAIN and amorphous carbon films have been developed and applied. Uses or advantages: physical vapor deposition temperature is about 100 ~ 500 ℃, higher than high-speed steel, die steel tempering temperature is low, so the workpiece will not soften and deformation can be applied to hard alloy, high speed steel, die steel, stainless steel, Titanium and aluminum products. When the tool evaporated ceramic film can reduce the melting edge, reducing blade wear rate and improve tool life of 2 to 7 times; die by evaporation treatment can increase the mold release, wear resistance, reduce wear and burn Phenomenon, can effectively improve the life of the mold several times, not only reduce production costs, but also increase product competitiveness.

7, plasma chemical vapor deposition techniques: the use of plasma CVD CVD TiN, TiCN, TiC and other hard films, with high CVD adhesion and PVD low temperature processing characteristics, etc., can reduce the processing temperature (about 500 ℃) , Effectively prevent the workpiece deformation, coating uniform adhesion, the complex shape of the tool and mold, the coating of the best. Uses or advantages: Evaporation hard film on the surface of metal parts, such as forming tools, knives and molds and the need to improve the material wear resistance / adhesion and other workpieces, can increase the life of the workpiece, improve processing speed, Increase production, save costs

8, TD carbide coating Technology: TD treatment (Toyota Diffusion Process) is added to the molten borax bath alloying elements, so that the surface of the steel material impregnated carbide coating treatment method. The main features of the coated layer of high hardness, excellent wear resistance, with PVD or CVD treatment of the same level of hardness, but the device is simple and easy to operate. Uses or Benefits: The vanadium carbide (VC) obtained by TD treatment has a hardness of more than HV2200 and strong bonding with base metal, so it can be used in die-casting molds, cutting and cutting tools, dies, knives or other mechanical parts that need to be wearable On, such as sheet metal die, cold forging die, hot forging die, pipe molding tools, plastic mold, roller, mechanical parts and so on.

Water-soluble oil quenching fluid can be used for forging steel, cast steel, cast iron and stamping parts such as quenching. Suitable for open-type quenching tank, continuous furnace, quenching tank peripheral multi-purpose furnace and induction hardening furnace.

1, forging steel: As small as a kilogram up to a few tons of low hardenability forged steel or high hardenability alloy forgings can be quenched with sea water quenching agent, the concentration varies with the alloy composition, ranging from 10% to 30%.

2, cast steel: as forged steel, single disparity, different hardenability of cast steel and alloy steel can also be quenched with sea water quenching agent, the concentration of the alloy composition and casting body varies, ranging from 10% to 30%.

3, cast iron: Ductile iron and malleable iron usually use 20% -30% concentration of sea water quenching agent.

4, Induction hardening: The gears, mandrels, camshafts, bearing journal often flame or induction quenching, sea water quenching agent is quenching oil is the best substitute, can completely eliminate fumes and fire hazards.

The above is only the scope of application of water-soluble oil quenching fluid, the scene can be processed according to the type of steel, shape complexity, size, heat treatment requirements of the workpiece and the workshop cooling equipment comprehensive consideration, the final selection of the best determined by experiment.