Round Bar refers to a long and cylindrical solid metal bar that is fully round and filled without any hollow space, unlike seamless pipes.

Types of Round Bars:

There are two main types of round bars: black round bars and polished round bars.

Black Round Bars are produced by hot rolling at high temperatures in steel mills. During the refining process in steel mills, a layer of oxide scale (black scale) forms on the surface, and the round bars are shipped with this scale intact. Due to this characteristic, the surface of black round bars is rough, black in color, and may have rust. They are sometimes referred to as "kuro" in Japanese, which means black. When machining parts from black round bars, surface processing is required to achieve dimensional accuracy, which incurs additional processing costs.

Polished Round Bars are produced by cold finishing hot-rolled steel bars or billets to improve precision and surface finish. They are often referred to as "migaki" in Japanese, which means polished. Polished round bars have smooth surfaces and are typically used without additional surface processing. They are commonly used in precision components and applications where a smooth surface finish is required. Despite being more expensive than black round bars, both types have similar physical properties and chemical compositions within the same material grade.

Materials Used in Round Bars:

The materials commonly used for black and polished round bars include structural steels such as S20C(AISI 1020, DIN ck22) and S45C(AISI 1045, DIN ck45), as well as stainless steels like SUS304(AISI 304, DIN Crni 1810) and SUS316(AISI 316L).

S20C is a general structural steel with similar carbon content to SS400, making it relatively easy to machine due to its lower hardness. It is primarily used for welding applications.

S45C has a higher carbon content compared to S20C, resulting in higher hardness and greater resistance to wear. It is used in applications where welding is not required and where a harder material is needed.

In stainless steel grades, SUS304 and SUS316L are commonly used. SUS304 stainless steel and SUS316L stainless steel are used for various applications depending on their corrosion resistance and mechanical properties.