Carbon spring steel wires (YB/T5220-1993) are widely used as elastic element and main material for non-mechanical springs. This type of material is characterized by having excellent mechanical properties, fatigue and corrosion resistance, and is often used for wire springs, especially for squeezing and vibration reducing. YB/T5220-1993 sets out a detailed technical standard for this type of material, including the mechanical, microstructure and chemical properties of the carbon spring steel wires.
The material of the carbon spring steel wire is typically 0.12 - 0.60% carbon, less than 0.25% silicon, 0.50 - 1.70% manganese, and 0.50-1.00% chromium. The carbon content affects the mechanical properties, such as the tensile strength, and the impact of welding, while the manganese and chromium content contributes to the strength and hardness when heat-treated. The allowable variances in mechanical properties for YB/T5220-1993 are laid out in the standard, in order to ensure the quality of the carbon spring steel wires.
For the microstructure, the main elements of the material are usually distributed in the form of wormy ferrite and spheroidized carbide. The microstructure consists of a large number of carbon precipitated particles, acicular and isometric bainite, and recrystallized ferrite. Temper embrittlement occurs when the material is heated, due to the redistribution of the carbon particles and the precipitation of carbon in the austenitic domains. The tensile properties of alloys of this type depends on the size and distribution of these elements and they must meet the requirements of the standard before being used as an elastic element.
For the chemical elements, YB/T5220-1993 specifies a range of maximum and minimum allowable levels for the chemical elements, in order to ensure a certain level of corrosion resistance and tensile strength. The maximum allowable levels for sulfur and phosphorus are 0.035%, for copper 1.00%, for nickel 0.50%, for chromium 0.50%, for molybdenum 0.15%, and for nitrogen 0.020%. The maximum allowable levels for lead and boron are 0.50% and 0.003% respectively. Anything outside of these limits can cause the material to become brittle or too soft for a use as an elastic element.
In conclusion, carbon spring steel wires are extensively used as elastic elements and main material for non-mechanical springs due to their excellent mechanical properties, fatigue resistance and corrosion resistance. YB/T5220-1993 provides detailed technical standard regarding the material, mechanical, microstructure and chemical aspects of the material. It sets out a range of requirements and maximum and minimum levels which must be adhered to in order to ensure a good quality of the carbon spring steel wires.
