Cold Rolling Characteristics of Spring Steel
Due to the different uses and processing requirements of cold-rolled spring steel, spring steel needs to have certain excellent properties after cold rolling, such as good elasticity, high tension, strong increase of force, large processing deformation and low scrap rate. Commonly used spring steel after cold rolling can not only obtain certain mechanical properties, but also be used in various parts according to the desired physical and mechanical properties.
There are different grades of spring steel available in the market, and each grade has its own mechanical and physical properties. The grades are usually named after the carbon content of the alloy, and the higher the carbon content, the higher the rate of return. Cold rolling is one of the most common ways for spring steels to achieve its full potential.
Cold rolling spring steel involves passing the metal through two rotating rolls to reduce its thickness and increase its strength. Spring steel can be reduced in thickness more than 80%, while its yield strength and tensile strength increase significantly. The rolling temperature of spring steel varies according to the thickness and type of steel, and is usually around 850-950 ℃ in the hot rolling state. The cold rolling temperature should be controlled below 650 ℃. When the forming temperature is lower than 350℃, it can be rolled directly.
Another benefit of cold rolling spring steel is that the metal grains are aligned in the same direction, increasing the strength and stiffness of the metal. This is why cold rolling is favored for creating flat sheet metal for high-strength applications such as springs. Cold rolling also improves corrosion resistance, a key benefit for products used in harsh environments or industries.
Cold rolling of spring steel also has certain requirements for the operating temperature and operating speed as well as the roll surface roughness. The general requirements for the roll surface roughness are: the static friction coefficient of the roll surface is 0.40-0.55, and the dynamic friction coefficient is 0.25-0.45. The surface profile is generally Ra 0.20-0.25μm. When the roll surface roughness is too high, the sheet surface will be scratched, which is not conducive to the rolling process.
In addition, different types of spring steel have different mechanical properties, and these properties must be taken into account when processing. For example, cold-rolled boron spring steel is more resistant to plastic deformation and has high strength, while chromium-silicon spring steel has higher tensile strength and hardness.
In conclusion, cold rolling of spring steel can have many beneficial effects, such as an increase in strength, stiffness, and corrosion resistance, while also allowing for a greater reduction in thickness. It is important to note that cold rolling is only beneficial if the rolling temperature and operating speeds are accurately and tightly controlled to ensure the desired properties of the metal are achieved. By understanding the properties and requirements of the spring steel being cold worked, manufacturers can optimize their cold rolling processes for better performance and better quality parts.
