The Research On Processing And Properties Of 20 Steel And 35CrMo Steel Seamless Tube

Seamless steel tube is hollow section, the steel tube and round steel solid steel have same bending tor sional. strength phase at the same time while the weight is lighter and it is a kind of economic cross section steel. Seamless steel tube is widely used in the manufacture of structural and mechanical parts, such as petroleum drill tube, auto transmission shaft, bicycle frame and construction of steel scaffolding. The production process and mechanical properties are important index to ensure that the steel processing performance and the final use(mechanical properties).In seamless steel tube production process, according to the different using requirements,make different production process. At present, the seamless steel tube production of the cooperation unit exist many problems: in the 20 steel boiler tube later stage honing process appears different batch steel tubes had different honing time. The 35 Cr Mo seamless steel tube transverse and longitudinal section microstructure exist serious band structure.The 35 Cr Mo seamless steel tube is easy to crack in cold bending to automobile transverse stability rod process. To solve the cooperation unit production problems, this topic which is based on the actual situation of cooperation unit and on the basis of practice to research. And according to the practice and theory to put forward prevention and improvement measures, and provide the practical reference basis for the actual production. Execute the labeled in seamless steel tube production index, Using the Germany Broke Q4-170 direct reading spectrometer, Germany Leica DM4000 M microscope, hydraulic universal testing machine, metallographic sample polishing machine, metallographic sample polishing machine, ed wire cutting machine, chamber electric furnace, laser measurement instrument to study three parts from chemical component, deformation processing technology, heat treatment process: put forward optimize 20 steel boiler tube new production process and solve the problem of later stage honing process low efficiency.Solve the problem of 35 Cr Mo seamless steel tube transverse and longitudinal section microstructure exist serious band structure.Improve the original heat treatment process of 35 Cr Mo seamless steel tube to make steel automobile transverse stability rod.Improve processing properties and reduce the risk of appear crack in cold bending process.The study found that:1、While 20 steel boiler tube is in the middle in the process of heat treatment process, cooling method(cooling speed) has an important influences on the mechanical property of materials, the cooling rate is faster, the strength of the material, hardness increased, the plasticity decreased, and vice versa. The test shoued the tensile strength, yield strength and hardness of 20 steel boiler tube increases with the increase of cooling rate of heat treatment. Elongation decreases with the increase of cooling rate. Subsequent girder grinding time obviously reduce with the increase of cooling rate. This improve the production process efficiency greatly and save the production cost and improve the economic efficiency of enterprises.Combine with practical production the best production process of 20 steel boiler tube is heating temperature of 880 and 20 min, and air℃-colded heat treatment.2、The pre heat treatment to eliminate banded structure of 35 Cr Mo auto stabilizer bar with seamless steel tube test found that with the cooling speed is faster, 35 Cr Mo seamless steel tube banded structure tend to be weakened. When at the same cooling speed, the holding time is lengthened and banded structure tend to be weakened. The test result showed that the heating temperature of 870 ~ 880 ℃45 ~ 75 min air cooling heat preservation and heating temperature of 1190 ~ 1200 heat 45 ~ 75 min air cooling can ℃effectively improve the banded structure.3、 The final heat treatment of 35 Cr Mo steel seamless tube is annealing process. annealing temperature of 860 ~ 890 ℃, 60 min annealing time and along with the furnace cooling. The internal microstructure specimens for lamellar pearlite and bright ferrite. As the temperature increased, tensile strength, yield strength and hardness of the samples increased and the elongation decreased. Annealing temperature is 790 ~ 790 ℃, 60 min annealing time and along with the furnace cooling, internal microstructure specimens for flocculent pearlite and a small amount of granular carbide, the tensile strength, yield strength and hardness is decreased than complete annealing and elongation increased. When heated at constant temperature with the increase of annealing time, it separate out more granular carbide precipitation and the strength of the specimen decreases further and elongation are improved obviously. And 35 Cr Mo auto stabilizer bar of cold bending production process it is of great significance. Reduce the risk of cold bending.Combine with the practical production,the heating temperature of annealing at 790 ~ 820 ℃, 60 ~ 70 min, along with the furnace cooling is the best production process.