Effects of weld strength undermatch on fracture toughness of HAZ notched weldments in a HSLA steel |
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Authors: | Yaowu Shi Zhunxiang Han Jianqin Fu |
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Affiliation: | (1) School of Materials Science and Engineering, Beijing Polytechnic University, Beijing, 100022, P.R.China; e-mail |
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Abstract: | In the present work the effects of weld strength undermatch on fracture toughness of heat affected zone (HAZ) have been studied.
In the investigation a high strength low alloyed steel (HSLA) with 800 MPa strength class was used, and the undermatched welded
joints were made with two weld strength mismatch levels. Three-point bending test specimens with crack depth to specimen width
ratio a/W ranging from 0.05 to 0.5 were extracted from the welded joints. The test results show that strength mismatching
gives an obvious influence on the fracture toughness of coarse grained HAZ for the undermatched joints. The lower the weld
strength mismatching, the higher the fracture toughness of the HAZ. In addition the tendency of fracture toughness change
with crack depths is much the same as in previous studies on base metals or weld metals, that is, fracture toughness of the
HAZ is increased with reduction of crack depths. From the measured results it shows that the macroscopically mechanical heterogeneity
of the welds may have more important influence on the fracture toughness of the HAZ than the meso-heterogeneity in the reheated
coarse grained HAZ. Furthermore, numerical verification indicates that the stress triaxiality at crack tip may be the essential
reason for the change of fracture toughness of HAZ. It is also shown that the yield strength of HAZ determined by the limit
load in the three-point bend test represents the combinative effects of HAZ and its surrounding materials.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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