Method of Production of Hot Dip Galvannealed Steel Sheet with Excellent Workability, Powderability, and Slidability

Abstract

The present invention provides a method of production of hot dip galvannealed steel sheet with excellent workability compared with the Sendzimir method or non-oxidizing furnace method and further with excellent powdering or slidability, that is, a method of production of hot dip galvannealed steel sheet with excellent workability, powdering, and slidability characterized by processing a slab containing, by mass %, C: 0.01 to 0.12%, Mn: 0.05 to 0.6%, Si: 0.002 to 0.1%, P: 0.05% or less, S: 0.03% or less, sol. Al: 0.005 to 0.1%, and N: 0.01% or less and having a balance of Fe and unavoidable impurities by hot rolling, pickling, cold rolling, then annealing at 650 to 900° C., cooling to 250 to 450° C., holding at said temperature range for 120 seconds or more, then cooling to room temperature, pickling, preplating Ni or Ni—Fe without intermediate temper rolling, heating by 5° C./sec or more down to 430 to 500° C., galvanizing in a galvanization bath, wiping, then heating by a rate of temperature rise of 20° C./sec or more up to 460 to 550° C., not providing any soaking time or holding for soaking for less than 5 seconds, then cooling by 3° C./sec or more, and final temper rolling by a 0.4 to 2% elongation rate.

Dependencies are inferred from the claim text.