1: Castability (castability): refers to the ability of metal materials to obtain qualified castings by casting. Castability mainly includes fluidity, shrinkage and segregation. Liquidity refers to the ability of liquid metal to fill the mold. Shrinkage refers to the degree of volume shrinkage when the casting solidifies. Segregation refers to the inhomogeneity of chemical composition and structure in the metal due to the difference of crystallization sequence during the cooling and solidification process.
2: Forgeability: refers to the ability of metal materials to change shape without cracks during pressure processing. It includes hammer forging, rolling, stretching, extrusion and other processing in hot or cold state. The forgeability is mainly related to the chemical composition of metal materials.
3: Machinability (machinability, machinability): refers to the difficulty of turning metal materials into qualified workpieces after being cut by tools. Machinability is usually measured by the surface roughness of the workpiece after machining, the allowable cutting speed and the wear degree of the tool. It is related to many factors such as chemical composition, mechanical properties, thermal conductivity and work hardening degree of metal materials. Generally, hardness and toughness are used to roughly judge the machinability. Generally speaking, the higher the hardness of metal materials, the more difficult it is to cut. Although the hardness is not high, it is tough and difficult to cut.
4: Weldability (weldability): refers to the adaptability of metal materials to welding processing. It mainly refers to the difficulty of obtaining high-quality welding joints under certain welding process conditions. It includes two aspects: one is bonding performance, that is, under certain welding process conditions, certain metal is sensitive to forming welding defects; the other is service performance, that is, under certain welding process conditions, certain metal welding joints are applicable to service requirements.
5: Heat treatment
(1) Annealing: refers to the heat treatment process in which metal materials are heated to an appropriate temperature, kept for a certain time, and then slowly cooled. Common annealing processes include recrystallization annealing, stress relief annealing, spheroidizing annealing, complete annealing, etc. The purpose of annealing is mainly to reduce the hardness of metal materials, improve plasticity, facilitate cutting or pressure processing, reduce residual stress, improve the homogenization of structures and components, or prepare for the subsequent heat treatment.
(2) : Normalization: refers to the heat treatment process of heating steel or steel parts to 30~50 ℃ above Ac3 or Acm (upper critical point temperature of steel) and cooling them in still air after holding them for an appropriate time. The purpose of normalizing is mainly to improve the mechanical properties of low carbon steel, improve the machinability, refine the grains, eliminate the structural defects, and prepare the structure for the subsequent heat treatment.
(3) : Quenching: refers to the heat treatment process of heating steel parts to a temperature above Ac3 or Ac1 (the lower critical point temperature of steel) for a certain time, and then obtaining martensite (or bainite) structure at an appropriate cooling rate. Common quenching processes include salt bath quenching, martensite graded quenching, bainite isothermal quenching, surface quenching and local quenching. The purpose of quenching: to obtain the required martensite structure for the steel parts, improve the hardness, strength and wear resistance of the workpiece, and prepare the structure for the subsequent heat treatment.
(4) : Tempering: refers to the heat treatment process in which steel parts are quenched, heated to a temperature below Ac1, held for a certain time, and then cooled to room temperature. Common tempering processes include: low temperature tempering, medium temperature tempering, high temperature tempering and multiple tempering. The purpose of tempering is mainly to eliminate the stress generated during quenching of steel parts, so that the steel parts have high hardness and wear resistance, as well as the required plasticity and toughness.
(5) : Quenching and tempering: refers to the composite heat treatment process of quenching and tempering steel or steel parts. The steel used for quenching and tempering is called quenched and tempered steel. It generally refers to medium carbon structural steel and medium carbon alloy structural steel.
(6) Chemical heat treatment: refers to the heat treatment process in which a metal or alloy workpiece is placed in an active medium at a certain temperature for heat preservation, so that one or several elements can penetrate into its surface layer to change its chemical composition, structure and performance. Common chemical heat treatment processes include carburizing, nitriding, carbonitriding, aluminizing, boronizing, etc. The purpose of chemical heat treatment is mainly to improve the surface hardness, wear resistance, corrosion resistance, fatigue strength and oxidation resistance of steel parts.
(7) : Solution treatment: refers to the heat treatment process that heats the alloy to the high-temperature single-phase area and maintains the constant temperature, so that the surplus phase can be fully dissolved in the solid solution and then rapidly cooled to obtain the supersaturated solid solution. The purpose of solution treatment is mainly to improve the plasticity and toughness of steel and alloy and prepare for precipitation hardening treatment.
(8) Precipitation hardening (precipitation strengthening): refers to a heat treatment process in which the metal hardens due to the dispersion and distribution of solute atoms in the supersaturated solid solution and (or) the desolved particles in the matrix. For example, after solution treatment or cold working, austenitic precipitation stainless steel can obtain high strength by precipitation hardening at 400~500 ℃ or 700~800 ℃.