Seamless steel pipes are mostly produced by cold-drawn and hot-rolled processes. Cold-drawn seamless steel pipes are mostly manufactured by a combined cold-drawn and cold-rolled process. Cold-drawn steel pipes are more accurate in size and smoother than hot-rolled steel pipes. They are mostly used in the manufacture of mechanical parts , Some cold drawn steel pipes require annealing treatment before they leave the factory, and some do not, so what is the change in the hardness of seamless steel pipes after annealing, which is greater than that of unannealed steel pipes?

First of all, let's first understand what is the role of seamless steel pipe annealing. The main role of annealing is to soften the metal and strengthen its toughness. It is applied to a variety of metal processing; seamless steel pipe annealing is to heat the steel to an appropriate temperature and keep it for a certain period of time. Then cool slowly to obtain a heat treatment process close to the equilibrium structure. The purpose of annealing is to homogenize chemical composition, improve mechanical properties and process performance, eliminate or reduce internal stress, and prepare the parts for final heat treatment. After annealing, most of the machine parts and the blanks of tools and dies can eliminate the internal stress of casting, forging and welding parts and the structural unevenness of the composition; it can improve and adjust the mechanical properties of steel, and prepare the organization for the next process .

From the above analysis, we can see that the chemical composition of the seamless steel pipe is uniform after annealing, the metal structure is softened, and the toughness is strengthened. The softening of the metal structure and toughness indicate that the hardness has decreased, which means that the hardness of the seamless steel pipe will not increase after annealing. , But will decrease.