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Galvanneal powdering was examined on a stabilized ultra low carbon steel substrate as a function of strain state using cup drawing and in-plane stretching experiments to simulate deformations encountered in production stampings. Significant powdering was encountered in drawing while minimal powdering occurred in in-plane stretching. Powdering was measured at specific locations and correlated with strains in those locations. A powdering map was generated in strain space using the experimental data. A few measurements of powdering on selected regions of an automotive stamped part are reported.

Coating mass losses occurring on two galvannealed sheet steel samples, one with and one without significant amounts of zeta in the coating, were measured in draw bead simulator tests at different bead penetrations, sliding speeds and with different amounts of oil on the surface. Coating mass losses were small relative to the coating weight. The galvanneal coating without zeta exhibited a greater mass loss than the coating with zeta. Bead penetration was an important variable affecting coating mass loss in both coils, and through an interaction with sliding speed in one coil. Compressive strains due to bending and unbending are the primary cause for coating mass loss; sliding friction did not enhance coating mass loss. The quantitative results are compared with coating mass losses that occur in other formability tests.