It is known as“Liquid Metal Embrittlement (LME)”that fracture stress, elongation and reduction of area can be markedly reduced when a solid metal is coated with a certain liquid metal and then immediately deformed in tension.
In this study, LME of some steels contacting with liquid zinc was examined using a special tensile apparatus. The materials used were SS41, SB42, SM50A and STK55 steels. Tensile tests were carried out in 460°C liquid zinc, and fractographic features of LME cracking were examined.
The results obtained are as follows:
(1) Stress-elongation curves of tensile tests in liquid zinc at 460°C were similar to those in air at 460°C, but rupturing elongations in liquid zinc were reduced to 30-40% of those in air. At the same time elongation and reduction of area were reduced to 11-41% and 14-32%, respectively.
(2) In liquid zinc at 460°C, elongation of SB42 and STK55 steel specimens pickled in 10% H2
solution was reduced to 50% compared with that of #120 grinder finished one. Other materials also showed some changes in elongation and reduction of area depending upon their surface condition.
(3) The yield point, tensile strength and elongation of hot dip zinc galvanized steels at room temperature became higher than those of materials not galvanized, but reduction of area was not affected.
(4) Intergranular facet patterns were predominant on the surface cracked by liquid zinc embrittlement of steels.