The main difference between hot finished tubing and cold finished tubing is the manufacturing process used to produce them.
Hot finished tubing is produced by heating a steel billet or round bar to a temperature above its recrystallization point and then using a piercing mill or rotary piercing process to create a hollow tube. The tube is then rolled or extruded to its final size and shape. This process results in a rougher surface finish and a larger dimensional tolerance compared to cold finished tubing.
On the other hand, cold finished tubing is produced by drawing or rolling a steel tube through a series of dies or rollers at room temperature. This process results in a smoother surface finish and tighter dimensional tolerances compared to hot finished tubing. The cold finishing process can be used to produce a wide range of shapes and sizes, including round, square, and rectangular tubing.
In addition to the differences in surface finish and dimensional tolerances, hot finished tubing and cold finished tubing also have different mechanical properties. Hot finished tubing is typically stronger and more ductile, while cold finished tubing is more brittle but has a higher dimensional stability.
Hot finished tubing is typically used in applications that require high strength and toughness, such as structural components and pressure vessels. Cold finished tubing is often used in applications that require precise dimensions and a smooth surface finish, such as hydraulic cylinders, bearings, and instrumentation.