Poster international conference on engineering failure analysis 2008


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Poster international conference on engineering failure analysis 2008

  1. 1. EXPERIMENTAL PROCEDURE D. Casellas, I. Picas, J. Caro, I. Valls 1 , B. Casas 1 Materials Technology Area, CTM Centre Tecnològic Av. Bases de Manresa 1, 08242 Manresa (Spain) 1 ROVALMA S.A., Apol.lo 51, Terrassa, Spain FRACTURE MECHANISM INTRODUCTION FRACTURE OF COLD WORK TOOLS DURING HIGH STRENGTH STEELS FORMING New Materials Requirements in Automobile Industry <ul><ul><li>High yield stress of high strength steels </li></ul></ul><ul><li>High forming pressures on tools </li></ul><ul><li>Accelerates wear </li></ul><ul><li>Premature fractures </li></ul>AIM : To evaluate the effect of the tool steels microstructure on the fracture behaviour of tools during high strength steels sheet forming <ul><li>Sheet steel: </li></ul><ul><li>B steel 1500 MPa </li></ul><ul><li>Tool steel: </li></ul><ul><li>DIN 1.3202 (AISI T15) 62 HRC </li></ul><ul><li>HWS (ROVALMA) 60 HRC </li></ul>Hot stamping of B steels FRACTROGRAPHY Fractures and wear at the cutting edge Broken carbides near the cutting edge Fracture toughness of carbides “ Fracture toughness of carbides in tool steels evaluated by nanoindentation” D. Casellas et al., Acta Materialia 55 (2007) DIN 1.3202 HWS CONCLUSIONS The need for high performance forming tools implies that microstructure of tool steels must be tailored, containing hard and tough carbides. Nanoindentation can be used for characterizing carbides in tool steels ≤ 140 MPa 180 - 240 MPa 260 - 300 MPa 320 - 420 MPa ≥ 1000 MPa Broken carbides M 6 C carbide Element Weight% V 3.4 Cr 2.7 Fe 24.8 W 66.7 MC carbide Element Weight% V 40.8 Cr 4.3 Fe 18.4 W 36.5 M 7 C 3 carbide Element Weight% V 9.6 Cr 32.1 Fe 33.9 W 1.9 MC carbide Element Weight% V 55.8 Cr 8.5 Fe 4.3 W 10.5