General machinery parts supply
- Commodity name： General machinery parts supply
- Commodity ID： 1191888390601723904
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The external loads acting on general-purpose machine components vary in nature—such as tension, compression, torsion, impact, and cyclic loading—and accordingly, the required mechanical properties of the materials also differ. Therefore, the material selection for these components is determined based on the specific design requirements dictated by the type of external loading.
Product Details
Hardness and Testing of General-Purpose Machinery Components
When designing general-purpose machinery, a variety of materials must be used. It is well known that the mechanical properties of materials serve as the primary basis for component design and material selection.
The external loads acting on general-purpose machine components vary in nature—such as tension, compression, torsion, impact, and cyclic loading—and accordingly impose different requirements on the mechanical properties of the materials. Therefore, the material selection for these components is determined based on the specific design requirements dictated by the type of external loading. Subsequently, both the components and their constituent materials typically undergo cold and hot working processes—including casting, forging, machining, welding, and heat treatment—in order to achieve the desired mechanical and service performance.
The mechanical properties commonly referred to include strength, ductility, hardness, impact toughness, and fatigue limit. Hardness is correlated with these properties; therefore, hardness testing can serve as an indicator of a component’s mechanical performance. Since hardness is determined by the material’s resistance to initial plastic deformation and its resistance to continued plastic deformation, higher strength and greater resistance to plastic deformation result in higher hardness values and improved wear resistance. Moreover, hardness testing is convenient, rapid, and generally does not impair the functional integrity of components, which has led to its widespread application. Consequently, hardness has become one of the primary technical requirements in component design specifications.
I. Hardness Requirements for Main Component Types
(1) Fastening Parts
1. Bolts, screws, and studs
Bolts, screws, and studs are generally designed by selecting materials based on their mechanical property grades and specifying heat-treatment hardness requirements. Bolts, screws, and studs used in motorcycles, all-terrain vehicles, and general-purpose machinery...
The general requirement for mechanical property grades ranges from 8.8 to 12.9, with the specific grade selected based on the actual loading conditions of the application. For example, the front and rear wheel axles of motorcycles and engine mounting bolts typically use a mechanical property grade of 8.8.
Heat-treated hardness: HRC 22–HRC 32; motorcycle and ATV sprocket connecting bolts, mechanical property grade 10.9, with heat-treated hardness of HRC 32–HRC 39.
2. Nut
Nut designs typically specify material selection and hardness requirements for heat treatment based on the mechanical performance grade.
The mechanical property grade requirements for nuts used in motorcycles, all-terrain vehicles, and general-purpose engines range from 8 to 10.
Grade. Common nuts are typically graded as Grade 8 in mechanical performance, with a hardness of HV200–HV302.
(2) Shaft-type parts
1. Design of Shafts Subject to Impact Loads and Requiring Welding: Shaft components subjected to impact loads and requiring welding, such as steering columns, should be made from materials with high tensile strength, good ductility, and excellent weldability, such as 35 steel and O235 steel. The hardness should be in the range of HRC 20–HRC 28.
2. Shafts subjected to impact loads and serving to transmit power—such as rear-axle shafts and torsion bars—should be made from steels with high tensile strength and good ductility, such as 40Cr steel or 45 steel, with a hardness of HRC 25–35.
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