Study On Microstructures And Mechanical Properties Of The Welded Joints Of 20Cr Steel And ZG25MnNi Steel

Bogie is the key part of steel construction of railway vehicles.It absorbs both moving and static load while railway vehicles running.And axle box body is the key part of bogie. So welding quality of axle box body and locating stud has much effect on whole bogie quality.In the paper,12mm quenched plus average tempering and high tempering 20Cr steel as locating stud material were respectively jointed with axle box body material ZG25MnNi steel by different welding methods and material. Cold crack sensitivity test and hot crack sensitivity test were conducted to these welding joints. The mechanical property and microstructure of welding joints were investigated by -40℃low-temperature impact test,room-temperature tensile test,hardness test and microscopic test.The results show that adopted J506,A302,J502 electrode and ER50-6 soldering wire to weld quenched plus average tempering 20Cr steel and ZG25MnNi steel or quenched plus high tempering 20Cr steel and ZG25MnNi steel can obtain good cold cracking resistance ability and hot cracking resistance ability. The cold crack ratio and hot crack ratio are zero. -40℃impact energy and fracture morphology indicate impact toughness of welding joints,HAZ on 20Cr steel side and HAZ on ZG25MnNi steel side are higher than that of base metal.The tension strength and yield strength of welding joints are also higher than that of base metal .Adopted J502 electrode to weld whether quenched plus average tempering 20Cr steel and ZG25MnNi steel or quenched plus high tempering 20Cr steel and ZG25MnNi steel, the microstructure of weld metal is basically white proeutectoid ferrite,needle-like ferrite and a little pearlite. In addition, widmanstatten that appears in HAZ at ZG25MnNi steel side of quenched plus average tempering 20Cr steel and ZG25MnNi steel welding joint , seriously reduces low temperature toughness of joint. Using ER50-6 soldering wire to weld whether quenched plus average tempering 20Cr steel and ZG25MnNi steel or quenched plus high tempering 20Cr steel and ZG25MnNi steel, the microstructure of weld metal is basically fine needle-like ferrite,pearlite and a few carbon-free bainite. Furthermore, widmanstatten also appears in HAZ at 20Cr steel side of quenched plus high tempering 20Cr steel and ZG25MnNi steel welding joint ,which decreases low temperature toughness of joint.