Hot-rolled and cold-drawn are two different types of steel manufacturing methods. Hot-rolled pipes and cold-drawn pipes are common mechanical structural accessories in life. There may still be many people who don't understand. Let me introduce the difference between hot-rolled pipes and cold-drawn pipes. If you are not sure, come and take a look. The difference between cold drawing and hot rolling: The main difference: hot rolling is rolling above the recrystallization temperature, cold rolling is rolling below the recrystallization temperature; cold rolling is sometimes heated, but the temperature is relatively low because processing will occur after cold rolling. Hard, if the molding requirements for the material are relatively high, annealing is required. Cold rolling and hot rolling are generally plates or profiles, while cold drawing is generally wire rods with cylindrical cross sections. In addition, hot-rolled plates are generally steels with higher alloy content and higher strength, while cold-rolled plates are low-carbon and low-alloy steels. Cold rolling can increase the strength and ensure the surface quality of the material. Cold drawing of oil casing: Cold drawn (rolled) pipes are divided into two types: round pipes and special-shaped pipes: Cold-drawn steel pipes generally require multiple drawings, and corresponding stress relief annealing is required between each drawing to ensure that the next cold drawing proceeds smoothly. From the appearance, cold-rolled seamless steel pipes tend to have small diameters, while hot-rolled seamless steel pipes tend to have large diameters. The precision of cold-rolled seamless steel pipe is higher than that of hot-rolled seamless steel pipe, and the price is also higher than that of hot-rolled seamless steel pipe. Cold-drawn seamless pipes generally have smaller diameters, mostly below 127mm. In particular, the accuracy of the outer diameter of cold-drawn seamless pipes is very high, and the length of cold-drawn seamless pipes is generally shorter than that of hot-rolled seamless pipes. In terms of wall thickness, cold-drawn seamless pipes are more uniform than hot-rolled seamless pipes. Petroleum casing tempering process: It is a heat treatment process in which the quenched workpiece is reheated to an appropriate temperature below the lower critical temperature, and then cooled to room temperature in air, water, oil and other media after being kept warm for a period of time. The purpose of tempering: (1) Eliminate the residual stress generated during quenching of the workpiece and prevent deformation and cracking; (2) Adjust the hardness, strength, plasticity and toughness of the workpiece to meet performance requirements; (3) Stabilize the structure and size to ensure Accuracy; (4) Improve and enhance processing performance. Oil casing tempering categories: 1. Low temperature tempering Meaning: refers to the tempering of the workpiece at 150~250℃. Purpose: To maintain high hardness and wear resistance of quenched workpieces and reduce quenching residual stress and brittleness. Tempered martensite is obtained after tempering, which refers to the structure obtained when quenched martensite is tempered at low temperature. Application scope: cutting tools, measuring tools, molds, rolling bearings, carburized and surface quenched parts, etc. 2. Medium temperature tempering Meaning: refers to the tempering of the workpiece between 350 and 500°C Purpose: to obtain higher elasticity and yield point, appropriate toughness. Tempered troostite is obtained after tempering, which refers to a complex structure in which extremely fine spherical carbides (or cementite) are distributed in the ferrite matrix formed during martensite tempering. Application scope: springs, forging dies, impact tools, etc. 3. High temperature tempering Meaning: refers to the tempering of the workpiece above 500°C. Purpose: To obtain comprehensive mechanical properties with good strength, plasticity and toughness. Tempered sorbite is obtained after tempering, which refers to a complex structure in which fine spherical carbides (including cementite) are distributed in the ferrite matrix formed during martensite tempering. Scope of application: Widely used in various important stress-bearing structural parts, such as connecting rods, bolts, gears and shaft parts, etc.