Influence of Predetermined Surface Defect to the Bendability of Ultra-High-Strength Steel

被引：2

作者：

Maatta, Antti ^{[1
]}

Jarvenpaa, Antti ^{[1
]}

Jaskari, Matias ^{[1
]}

Mantyjarvi, Kari ^{[1
]}

Karjalainen, Jussi A. ^{[2
]}

机构：

[1] Univ Oulu, Oulu So Inst, Pajatie 5, FI-85500 Nivala, Finland

[2] Univ Oulu, Dept Engn Mech, Oulu 90014, Finland

来源：

MATERIAL FORMING - ESAFORM 2012, PTS 1 & 2 | 2012年 / 504-506卷

关键词：

sheet metal; bending; defect; ultra-high-strength steel;

D O I：

10.4028/www.scientific.net/KEM.504-506.901

中图分类号：

T [工业技术];

学科分类号：

08 ;

摘要：

The use of ultra-high-strength steels (UHS) has become more and more popular within last decade. Higher strength levels provide lighter and more robust steel structures, but UHS-steels are also more sensitive to surface defects (e.g. scratches). Practically this means that the critical crack size decreases when hardness increases. The aim of the study was to define the critical surface defect size that causes failure in air bending process. The effect of the hardness was determined by using steel grades with different hardness levels (340 & 550 HV). Test material used were 4 mm thick direct quenched (DQ) bainitic-martensitic UHS steel DQ960 (YS/TS 960/1000) and abrasion resistant steel AR500 (YS/TS 1250/1600) Surface cracks with different depths were created by laser ablation. Effect of the scratch depth was determined by bending the specimens to 90 degrees. The bent shapes were then compared by visual inspection and classified by the maximum achieved crack size that does not cause a fracture during bending. Results showed that the critical crack size is strongly depended on the hardness of the sheet. Comparison of the test materials reveals that 36% decrease in hardness, increases the critical crack size by 138%.

引用

页码：901 / +

页数：2