Inland Steel Company

Ram S Patil

Donald F Johnson

John T Quasney

Frederick F Jones, Jr

John N Polakowski

A differentially coated, galvanized steel strip is produced by hot dip coating both sides of a steel strip and adjusting the weight of coating metal on opposite sides of the strip to produce a light coated side and a heavy coated side. The strip is then precooled to fully solidify the heavy coated side following which the galvanized strip is subjected to a treating step in which simultaneously the light coated side is heated and the heavy coated side is cooled. This fully transforms the light coated side to iron-zinc alloy throughout while only partially transforming an inner layer on the heavy coated side to iron-zinc alloy. The outer layer on the heavy coated side consists entirely of coating metal, and there are no intermittent bleed-throughs of iron-zinc alloy to the outer surface of the heavy coated side.

Differentially coated galvanized steel strip

Differentially coated galvanized steel strip and method and apparatus

A method of producing a hot-dip galvanized steel strip having a uniform zinc-iron alloy coating on one surface and a formable hot-dip metallic zinc coating on the opposite surface which comprises forming a thin uniform hot-dip metallic zinc coating which has a coating weight less than 0.10 ounces per square foot on one side and a heavier metallic zinc coating on the opposite surface and passing the coated strip through a chamber having heating means and cooling means therein, said heating means, such as gas jets, adapted to apply heat directly only to the thin zinc coated side of the strip to convert the thin zinc coating into a fully alloyed zinc-iron coating, and said cooling means, such as air jets, adapted to blow cooling air onto the heavier zinc coating to effect rapid cooling thereof while the thin zinc coated side is being heated; thereby preventing formation of a thick zinc-iron intermetallic subsurface layer on the heavier coated side.

Process of hot-dip galvanizing and alloying

A drawing quality hot-dip coated low carbon aluminum killed steel strip produced by conventional steel strip forming and continuous hot-dip coating procedures wherein the hot rolled coiling temperature is maintained within a temperature range of 1250.degree. F. - 1300.degree. F. and the cold rolled steel strip is continuously heat treated on a Sendzimir-type continuous hot-dip coating line at a temperature of between 1850.degree. F. and 1950.degree. F. before cooling the strip to about the temperature of the hot-dip coating bath and immersing the strip in a hot-dip galvanizing or aluminum coating bath followed by conventional annealing. The microstructure of the drawing quality hot-dip coated steel strip is characterized by spaced islands formed of fine pearlite and fine ferrite having a grain size of about ASTM 9-10 surrounded by areas of large ferrite grains having the grain size of about ASTM 7.5-8. A typical hot-dip coated drawing quality steel strip produced by the process has a Rockwell B hardness of about 47, an average lower yield strength of about 32 KSI and an average ultimate tensile strength of 50 KSI and an average total elongation percent in two inches of about 40 percent.

Growing community of inventors

Munster, IN, United States of America

Ram S Patil