Machinery is a combination of human-made physical components, with definite relative motion between each component, which can help people reduce the difficulty of work or save money.
Power tool device. complex A machine is composed of two or more simple machines, and complex machines are usually called machines.
There are many types of machinery, which can be divided into agricultural machinery, mining machinery, construction machinery, petrochemical general machinery, electrical machinery, and machine tools according to the industries served, Instrumentation, foundation. Machinery, packaging machinery, environmental protection machinery, etc. Steel for machinery manufacturing, structural steel used to manufacture mechanical parts that bear load or transmit work and force, also known as machine structural steel. Divided by purpose
Quenched and tempered steel, hard surface
Chemical steel (including carburizing steel, nitriding steel, low hardenability steel), free-cutting steel, elastic steel and rolling bearing steel, etc.
1. Quenched and tempered steel
Quenched and tempered steel is generally quenched and then tempered before use to achieve the required strength and toughness. The carbon content of carbon quenched and tempered steel is 0.03 ~ 0.60%.
Because of its low hardenability,
It is only used to manufacture mechanical parts with small cross-section size, simple shape or low load. Alloy quenched and tempered steel is made in carbon
On the basis of high-quality steel, one or more elements are added
The total amount of alloying elements added-generally does not exceed 5%. Alloy quenched and tempered steel has good hardenability and can be used in
Hardened in oil, small quenching deformation, better strength and toughness
The commonly used steel grades are 40Cr, 35CrMo, 40MnB, etc. The cross-section size is large
, Important parts with high load, such as aero engine main shaft, high-speed diesel engine crankshaft
And connecting rods, main shafts of steam turbines and generators, etc.
Steel grades with high content of alloying elements, such as 40CrNiMo, 18CrNiW, 25Cr2Ni4MoV, etc.
2. Carburized steel
Carburized steel is used to manufacture parts that require hard and wear-resistant surfaces and strong and impact-resistant cores, such as chain pins, piston pins, gears, etc. The carbon content of carburized steel is low, which is 0.10~0.30%, in order to ensure the toughness of the core of the part, after carburizing treatment, a high-carbon and high-hardness wear-resistant layer can be formed on the surface. Alloy carburizing can be used for more important parts. Steel, commonly used steel grades are 20CrMnTi, 20CrMo, 20Cr, etc.
3. Nitrided steel
Nitrided steel contains alloying elements with a strong affinity for nitrogen, such as aluminum, chromium, molybdenum, vanadium, etc., to facilitate the infiltration of nitrogen. The nitrided layer is harder, more wear-resistant and corrosion-resistant than the carburized layer, but the carburized layer
The nitrogen layer is thinner. After nitriding, the deformation of parts is small, and it is commonly used to manufacture precision parts with small allowable wear, such as grinding machine spindles, plunger pairs, precision gears, valve stems, etc., commonly used steel grades. There is 38CrMoAl.
4. Low hardenability steel
Low hardenability steel is a special carbon steel with low residual elements such as manganese and silicon. The central part of parts made of this kind of steel is more difficult to quench than ordinary carbon structural steel during quenching. Moreover, the hardened layer is basically evenly distributed along the surface contour of the part, while the center part maintains a softer and tougher matrix to replace carburized steel to make gears, bushings, etc., which can save money. Time carburizing process, saving energy consumption. In order to match the toughness of the central part with the hardness of the surface properly, its carbon content is generally 0.50 ~ 0.70%.
5. Free cutting steel
Free-cutting steel is the addition of one or more elements such as sulfur, lead, calcium, selenium, etc. to the steel to reduce the cutting force. The added amount is generally only a few thousandths or less. Body, or adding elements combined with other elements in the steel to form a kind of inclusions that reduce friction and promote chip breaking during the cutting process, so as to extend tool life and reduce cutting. The purpose of cutting force, improving surface roughness, etc. Since the addition of sulfur will reduce the mechanical properties of steel, it is generally only used to manufacture light-loaded parts. Modern free-cutting steel due to performance. Improvements are also widely used in the manufacture of auto parts.
6. Spring steel
The elastic steel has a high elastic limit, fatigue limit and yield ratio. Its main application is springs. Springs are widely used in various machinery and instruments. Their appearance can be divided. There are two types of leaf springs and coil springs. The main function of the spring is shock absorption and energy storage. The elastic deformation, absorption of impact energy, alleviation of impact, Such as the buffer springs on automobiles and other vehicles; the spring can also release the absorbed energy to make other parts complete certain actions, such as the valve spring on the engine, the instrument Table springs, etc.
7. Bearing steel
Bearing steel has high and uniform hardness and wear resistance, as well as high elastic limit. The uniformity of the chemical composition of the bearing steel, the content and distribution of non-metallic inclusions, and carbides. The distribution and other requirements of the steel are very strict, and it is one of the most stringent steel grades in all steel production. Bearing steel is used to manufacture the balls, rollers and sleeves of rolling bearings. Steel grade can also be used to make precision tools, cold die, machine tool screw, such as die, tool, tap and diesel oil pump precision parts.