Search Results

Deep drawing quality high strength (400 MPa grade) cold-rolled steel sheet for automotive use has been developed. This steel sheet is characterized by its chemical composition of extra low carbon, high phosphorus and small niobium together with aluminum. It exhibits very high r̄-value and elongation in tensile test and also an excellent deep draw-ability in small cup test and actual press test of automotive panel parts. The resistance to cold-work embrittlement are improved by controlling the compositions and the cooling rate after final annealing. Spot weldability and the weld performances are very good like as ordinary mild steel sheets. These properties are compared with those of DDQ grade mild steel sheet and previously developed high strength dual phase or rephosphorized steel sheets.

Exhaust manifolds have been fabricated from stainless steels such as type 409 in place of cast iron in order to reduce the weight and to increase performance of the engine. In this paper, thermal fatigue and high temperature fatigue resistances of Nb-bearing ferritic stainless steels and type 409 have been investigated. The results obtained are as follows: Nb-bearing steels were superior to type 409 in high temperature fatigue resistance. Thermal fatigue resistance depended on a restraint ratio. The fatigue life of Nb-bearing steels was longer than that of type 409 in the condition of a low restraint ratio which might be near to the actual automobile exhaust system.