Effect Of Strain Ageing In Welded And Non Welded Low Carbon Steel

Abstract

Low carbon steels are susceptible to strain ageing as a result of which there is an increase in yield strength at the cost of ductility. These steels are used for structural applications, in which welding is used as a method of joining. There are certain regions away from the weldment which pass through the temperature range of 80 to 2500c during cooling after welding. Since in many of the structures like ship building these steels are welded in deformed condition thus the above said regions are subjected to straining and ageing, thus leading to strain ageing.
In the present study an attempt has been made to study the effect of strain ageing in welded low carbon steel and the results are compared with those obtained after strain ageing of the same steel in the non welded condition. The parameters used were : (1) % The extent of pre-strain of pre-strain used was 6 ± 2 %.(2)The temperature of ageing used was 150 ±300c.(3)The time of ageing used was 4 ± 2 hrs. Using the method of Statistical Design Of Experiments the results were analysed to develop regression equations for welded as well as non welded steels. The equations developed are shown in eqn(1) and eqn(2) respectively.
For non welded: ΔY = 24.04 - 2.18X1 + 4.9 X2 + 1.4 X3 – 0.03X1X2 – 0.018X1X3 + 35X2X3 - 0.28X1X2X3