Basic knowledge of material heat treatment engineer necessary heat treatment - Foshan constant Yang mechanical and electrical company

by:Hengyang Furnace     2021-01-09
1, what methods commonly used in quenching, illustrate the principle of choose different quenching method? Single liquid quenching - — In a quenching medium cooling process, a single liquid quenching organization stress and thermal stress are big, quenching deformation is big. Double liquid quenching - — Objective: between 650 ~ Ms cold quickly, make V> Vc, under Ms slowly cooling, in order to reduce stress. Carbon steel: oil after water first. Alloy steel: oil after air first. Interrupted quenching - — Remove artifacts after a stay in a certain temperature to make the workpiece inside and outside temperature, and then air cooling technology, M phase transformation in the interrupted quenching is in air cooling, internal stress is small. Isothermal quenching - — Refers to the bainite isothermal temperature area, bainite transformation, reduce internal stress and deformation is small. The choosing principle of quenching method to consider both meet the requirements of performance, at the same time try to reduce the quenching stress, lest the quenching distortion and cracking. 2, chemical vapor deposition, and what is the difference between the physical vapor deposition technology, their main applications? Metalorganic chemical vapor deposition (CVD method, reaction medium containing coating material elements under the low temperature gasification, before being sent to the high temperature reaction chamber in contact with the workpiece surface to produce high temperature chemical reaction, carbide alloy deposit on the workpiece surface coating or metal and its compounds. The main characteristic of CVD method: 1) Can deposit a variety of crystalline or amorphous inorganic membrane materials. 2) High purity, the adhesion strength of the collective. 3) Sediment density, low porosity. 4) All good degrees, simple equipment and process. 5) Reaction temperature is higher. Applications: in the iron and steel, hard alloy, non-ferrous metal, inorganic non-metallic materials such as surface preparation of various USES of thin film, mainly insulation film, semiconductor thin film, conductor and superconductor thin films and the corrosion resistance of film. Physical vapor deposition: gaseous substances in the process of workpiece surface directly deposited into a solid film called PVD method. There are three basic methods, vacuum evaporation, sputtering deposition and ion plating. Application: wear-resistant coating, heat resistant coatings, corrosion resistant coating and lubricating coating, function coating decorative coating. 3, shows that fatigue fracture microstructure and macro. Micro: was observed under the micro electron microscope bar pattern, called fatigue stripe or fatigue striations. Fatigue with ductility and brittleness, banding has certain spacing, under some specific conditions, stripes and a corresponding stress cycle. Macro: say more cases with brittle fracture characteristics, not visible to the naked eye to macroscopic deformation, the typical fatigue fracture by the source area of crack, crack extension area, and the final of transient fault zone. Less fatigue source area of plain, sometimes a bright mirror, crack extension area or shell pattern in the beach, there are some spacing ranging in parallel arc centered fatigue source. Transient breaking the material characteristics of the load from the microstructure ways and size, etc. , may for toughening nest or quasi dissociation, disintegrate the intergranular fracture or hybrid form. 4, points out that the induction heating quenching often appear three kinds of quality problems, try to analyze its reasons. 1) Crack: uneven heating temperature is too high, temperature; Improper temperature quenching medium and temperature; Tempering is not timely and insufficient tempering; Material high hardenability, composition segregation, flawed, including excessive inclusion; Component design is not reasonable. 2) Uneven surface hardness: the unreasonable structure of induction; Uneven heating; Uneven cooling; Bad materials group ( Have banded structure, partial decarburization. 3) Surface melting: sensor structure is not reasonable; Parts such as sharp corners, holes, worse; Heating time is too long, the workpiece surface is cracked. Heat treatment production line 5, high speed steel new technology of low temperature tempering characteristic is what? ( In w18Cr4v, for example) Why it is better than the mechanical properties of normal after tempering? W18Cr4v steel quenching + 1275 320 540 to 560 * 1 * 1 h + h * 2 times of tempering. 1) Low temperature tempering high speed steel is larger than that of common high speed steel is tempered m2c carbide precipitates, m2c, V4c and Fe3c type carbide dispersion degree, good uniformity, and about 5% to 7% bainite exists, it is low temperature tempering HSS performance is superior to the ordinary tempered important organizational factors.
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