Hunan Steel Industrial Zone, No.9 Xiangfu Road, Yuhua District, Changsha, China
Carbon steel pipe to normalizing and tempering heat treatment, machining port, wall thickness should be with burning and machining allowance. General allowance for the elbow theory of wall thickness is 10% ~ 20%. Elbow wall thickness and the smaller the diameter D, delta and section and the better the performance of mold joint, the easier but bend inner arc instability wrinkling. According to the metal plastic deformation volume, push into shape when the wall thickness unchanged (actual micro thinning), elbow pipe length is equal to the characteristics of the outer arc length and push pipe billet diameter is deduced formula: if the actual selection of pipe diameter is smaller than the Dp value calculated by the formula, and mold joint performance is good, but in the elbow arc instability of wrinkle easily. If the actual selection of pipe diameter is larger than the Dp value calculated according to the formula, the result is just the opposite.
The principle of determining the carbon steel pipe heating temperature is above material austenitizing temperature, and push the system elbow inside the main compressive stress is less than the yield limit under the temperature of materials. Material austenitizing temperature is higher, the higher the heating temperature. The higher the material yield limit of high temperature, the higher the heating temperature. Medium frequency induction heating, the WB36 steel is 850 ~ 900 ℃, the highest temperature A335P22 steel for 900 ~ 900 ℃, A335P91 material of heating temperature peak is 900 ~ 1000 ℃. Temperature measurement way for stationary infrared thermometer and combined manual type far infrared thermometer. Temperature distribution is an important process parameters, induction coil, induction coil, the shape and directly with mandrel head position control. Shape is the major factor, induction coil, induction coil and the mandrel head position is the secondary factor.
The heating temperature is high, stamping elbow thickness increases. Advance speed impact on the geometry of the carbon steel pipes push as an important part of the process parameters, directly controlled by hydraulic system flow control. To promote the principle of determining speed elbow inside the main compressive stress is less than the yield limit of material under this temperature, the outer wall of elbow elongation of materials under this temperature is less than the largest elongation. Material heat-transmitting coefficient of permeability and intermediate frequency power, promote the speed is fast. Advance speed, productivity increases, but the carbon steel pipes wall thickness reduction ratio increased.