Cut edge condition and its effect on resistance to hydrogen embrittlement in martensitic steel grades
Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
Hydrogen embrittlement (HE) occurs for ultra-high strength steels (UHS) in combination with corrosion protection by electro galvanizing. The purpose of the project has been investigating the impact of the cut edge condition to HE. Several different cut edges were investigated including cutting with shear parallel blades with different cutting clearance, punching, grinding (grinded edge) and laser cutting. A method of charging hydrogen into the steel specimens during static tensile testing at 80 % of the ultimate tensile strength (UTS) was set up, called constant load testing. Also U-bend testing, static load testing and slow strain rate testing (SSRT) was performed.
The materials used in this project were all cold rolled martensitic steels with different alloying and with UTS exceeding 1300 MPa.
The results show that the cut edge condition has a big impact on the sensitivity for HE. The laser cut and grinded specimens passed the constant load test and showed no sensitivity for HE in that test. The laser cut samples also passed the U-bend test and the grinded samples managed the U-bend test significantly better than the cut edges with different cutting clearances. The cut samples show the same HE sensitivity regardless which cutting clearance were used.
Since the grinded and laser cut samples shows great improvement in these tests, there is reason to believe that these edges either equalize stresses from the edge, prevents hydrogen absorption or both. However, the different cutting clearances do not seem to affect the sensitivity for HE. Punching or cutting is equal considering sensitivity for HE.
Place, publisher, year, edition, pages
2014. , 48 p.
Hydrogen embrittlement, electro galvanizing, ultra-high strength steel, cut edge, cutting clearance, constant load test, in situ, U-bend test, SSRT
Other Materials Engineering
IdentifiersURN: urn:nbn:se:kth:diva-146028OAI: oai:DiVA.org:kth-146028DiVA: diva2:721781
Subject / course
Materials Design and Engineering
Master of Science in Engineering - Materials Design and Engineering
Bexell, Ulf, Univ lektor
Eliasson, Anders, Dr