Abstract: To obtain a high tensile strength steel sheet which has an improved lubricating ability during press working, coating sharpness and defect-formation resistance, and which is useful as an outer plate of automobiles and electrical appliances, by forming uniform recesses and protrusions thereon and regulating the shapes of the recesses and protrusions, the recesses each having a flat portion at their bottom, and the size of the protrusion top faces, the depth between the recesses and the protrusions and the peak-to-peak distance being restricted. The recesses and protrusions formed thereon satisfy the following conditions; oil pools are formed thereon in an area covering 30% of the surface thereof; the top faces of the protrusions each having a size of 10 to 450 .mu.m; the level difference between the recesses and the protrusions being from 2 to 20 .mu.m; the peak-to-peak distance of the protrusions being from 50 to 1000 .mu.m; P and D satisfying the relationship 2.

Abstract: A galvannealed steel sheet having distinguished anti-powdering property and anti-flaking property is disclosed. The steel sheet comprises a matrix steel sheet and a galvannealed coating layer having a coating weight of 45 to 90 g/m.sup.2, composed of 8.about.12 wt. % Fe and 0.05.about.0.35 wt. %, preferably 0.05.about.0.30 wt. % Al, the balance being Zn, provided on at least one side of the matrix steel sheet, the galvannealed coating layer having a .GAMMA. phase with a thickness of not more than 1.3 .mu.m, preferably not more than 1.0 .mu.m in the region at the boundary to the matrix steel sheet, and the surface region of galvannealed coating layer has a structure either (1) .eta. and .zeta. phases do not exist in the surface region of the galvannealed coating layer, or, (2) when at least one of .eta. and .zeta. phases exist therein, the total amount of the at least one of .eta. and .zeta. phases in the galvannealed coating layer is not more than 1.5 g/m.sup.2.

Abstract: A plated steel strip having an enhanced corrosion and rust resistance and an improved paint-coating property comprises a principal plating layer formed on a steel strip substrate and comprising a co-deposited zinc-chromium based alloy which comprises more than 5% by weight but not more than 40% by weight of chromium and the balance of zinc.

Abstract: A plated steel strip having an enhanced corrosion and rust resistance and an improved paint-coating property comprises a principal plating layer formed on a steel strip substrate and comprising a co-deposited zinc-chromium based alloy which comprises more than 5% by weight but not more than 40% by weight of chromium and the balance of zinc.

Abstract: A metallic material is electroplated with an iron-zinc alloy with an improved efficiency by using an insoluble anode and an electroplating liquid containing, in addition to necessary amounts of zinc and ferrous ions, 0.01 to 10 g/l of an additive consisting of at least one member selected from oxyalkylene compounds of the formulae (I) to (VIII), ##STR1## and ##STR2## wherein n, n.sup.1 or n.sup.5 =1 to 200,n.sup.2 or n.sup.6 =6 to 2000,n.sup.3 or n.sup.7 =4 to 2000,n.sup.4 =2 to 2000,R or R.sup.3 =alkyl (C.sub.1 -C.sub.20)R.sup.1, R.sup.2, R.sup.4 or R.sup.5 =H or alkyl (C.sub.1 -C.sub.2)and sulfation products of the above-mentioned compounds.

Abstract: A method of and an apparatus for overaging treatment of low melting point-metal plated steel band, in which a hearth roll having surface layer which consists mainly of phenol resin, mineral fiber and small quantity of additive as necessary is used under the overaging treatment temperature range and within weak oxidation, inactive or reducing high temperature gas atmosphere such that the phenol resin substantially does not oxidize and evaporate.The method and apparatus allow overaging treatment of low melting point-metal plated steel band in continuous annealing furnace having many hearth rolls to guide the steel band, and prevent the low melting point metal from being picked up on the surface of the hearth roll.

Abstract: A steel sheet having a zinc coating on one side and a uniformly alloyed layer of iron and zinc on the other side, the amount of the alloyed layer being from 0.001 g/m.sup.2 to 1 g/m.sup.2 of zinc and containing from 6 to 20 percent by weight iron.

Abstract: A method for producing a one-side zinc plated steel sheet, comprising;(a) a step of coating a steel sheet with zinc,(b) a step of heating the zinc-coated steel sheet to alloy at least the coated zinc on one side of the steel sheet with the steel sheet, and(c) a step of mechanically removing the coated zinc thus alloyed.