Influence of the parameters of the structure of heat-affected area on the tendency to intergranular embrittling in hydrogen-absorbing media

Abstract

0.13 C, 0.74 Si, 1.61 Mn, 0.012 P, 0.024 S, 0.11 Cr, 0.069 Ni, 0.17 Cu, 0.005 V, 0.03 A1, 0.005 Ti, and 0.01 Mo. Mechanical properties: r = 650 MPa, o t = 570 MPa, and 8 = 21%. In order to reproduce the structure of individual sites of the HAA, use was made of the method described in [1], in accordance with which the welding thermal cycle was simulated in a series of samples with the help of a high-frequency current generator. The maximum sample heating temperature was varied from 1350 to 750~ in steps of 100~ This made possible reproduction of the structural composition of seven sites of the HAA. The simulated parameters of the thermal cycles are given in Table 1. The samples so prepared were submitted to hydrogen absorption I by electrolytic method [2]. For this purpose, each sample was immersed in a 0.1 N sulfuric acid solution to which was added 0.05 g of thiourea (hydrogen absorption stimulator) per liter and was surrounded by a platinum spiral. The platinum spiral acted as the anode and the sample, as the cathode. The strength of the current supplied in keeping with the surface area of the sample immersed in the solution was 470 mA. Hydrogen absorption was effected by dissociating sulfuric acid over 1 h, whereafte{ the samples were placed in a specially made eudiometer [3] for determining the low-temperature fraction of the hydrogen. An alcohol-glycerine mixture (1:1) was used as the measuring liquid. The amount of hydrogen evolved was measured from the change in the liquid level in the eudiometer's microburet. The measurements were made every 5 min over the first hour and every 30 min over the next four hours. The last reading was taken after 24 h. The measurements were plotted to construct kinetic hydrogen evolution curves which were next analyzed mathematically using the fon~nal first-order kinetic equation [4]: