Stainless steel cold worked steel bars
Cold-finished stainless steel bars are produced through cold working processes such as cold drawing and cold rolling. Compared to hot-rolled bars, they offer higher dimensional accuracy, better surface quality, and superior mechanical properties. They are widely used in machinery manufacturing, automotive parts, precision instruments, and other fields. These bars are made from hot-rolled steel bars and undergo multiple cold working passes to remove surface defects and refine the grain structure, achieving dimensional tolerances above h9 and surface roughness as low as Ra1.6. They can be directly used for subsequent precision machining such as cutting and grinding, reducing machining allowances and improving production efficiency.
The production process for cold-worked stainless steel bars involves key steps, including raw material pretreatment, cold working, and heat treatment. First, the hot-rolled bars undergo pickling to remove surface scale and oil, ensuring that the dies are not scratched during the cold working process. Subsequently, appropriate cold-drawing dies or cold-rolling rollers are selected based on the product specifications. The process is performed by gradually reducing the cross-sectional area, with each pass controlled to between 10% and 20% to avoid breakage due to excessive deformation. For products with more demanding requirements, intermediate annealing is also required during the cold working process to eliminate work hardening and restore the material’s plasticity. After finishing and straightening, the final product achieves a straightness of less than 1 mm/m, meeting the requirements of high-precision assembly.
From the perspective of material properties, the mechanical properties of cold-worked stainless steel bars show significant differences due to different processing techniques. The plastic deformation during the cold working process causes dislocation proliferation inside the steel, and the grains are elongated and refined, thereby significantly improving the tensile strength and hardness of the steel bar. For example, the tensile strength of 304 stainless steel cold-drawn steel bars can reach over 650MPa, and the hardness reaches HV200-250, which is more than 30% higher than the hot-rolled state. At the same time, cold working can also improve the cutting performance of steel, reduce the sticking phenomenon during the cutting process, and improve the surface processing quality of parts. In addition, by adjusting the amount of cold working deformation, the performance of the steel bar can be customized to meet the needs of different application scenarios. For example, steel bars for high-strength bolts require a higher deformation to ensure strength, while steel bars for precision shaft parts need to appropriately reduce the deformation to take into account both strength and toughness.
The high precision and excellent performance of cold-formed stainless steel bar make it a vital component in a variety of applications. In the automotive industry, it is used to manufacture engine valve guides, fuel injector components, and other components. Its high dimensional accuracy ensures uniform assembly clearances and reduces wear. In medical devices, such as surgical instrument handles and connectors for implantable prostheses, the excellent surface quality of cold-formed steel bar reduces bacterial adhesion and improves product safety. In precision instruments, such as the gears and bearings in watch movements, the bar’s high hardness and dimensional stability ensure the instrument’s operating accuracy and longevity. With the upgrading of the manufacturing industry, demand for cold-formed stainless steel bar is shifting from general specifications to customized, high-precision products.
In terms of industry development, the production of cold-worked stainless steel bars is facing opportunities for technological upgrades and product restructuring. On the one hand, the introduction of CNC cold-drawing equipment and automated loading and unloading systems is improving production efficiency and product quality consistency. On the other hand, the development of ultra-slender cold-worked bar production technology addresses the bending and vibration issues associated with cold-drawing bars with aspect ratios greater than 50. Furthermore, to meet the demands of new energy vehicles and high-end equipment, companies are developing high-strength, highly corrosion-resistant cold-worked stainless steel bars. For example, molybdenum-containing 316L cold-drawn bars offer over 50% greater pitting resistance than 304 bars. In the future, with the application of intelligent manufacturing technologies, the production of cold-worked stainless steel bars will achieve full digital control, further enhancing product competitiveness.
