Method of production of hot dip galvannealed steel sheet with excellent workability, powderability, and slidability

Patent metadata

Field	Value
Publication number	US-10023931-B2
Application number	US-22517007-A
Country	US
Kind code	B2
Filing date	Mar 28, 2007
Priority date	Apr 7, 2006
Publication date	Jul 17, 2018
Grant date	Jul 17, 2018

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.

First claim

The invention claimed is:

1. A method of production of a hot dip galvannealed steel sheet with excellent powdering, slidability, and reduction in coil break, the hot dip galvannealed steel sheet having an amount of deterioration of elongation with respect to a cold rolled steel sheet of 2% or less, 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%,
N: 0.01% or less,
and having a balance of Fe and unavoidable impurities, by sequentially hot rolling, pickling, cold rolling, then annealing at 650 to 900° C., cooling to 250 to 450° C. by a cooling rate at 600° C. or less of 50° C./sec or more, overaging at a temperature range of 350° C. to 400° C. for 120 seconds or more, then cooling to room temperature, pickling, and temper rolling by 0.1 to 0.4% elongation rate, preplating Ni or Ni—Fe, and furthermore heating by 5° C./sec or more up to a temperature between 430 and 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 4 seconds or less, then cooling by 3° C./sec or more, and final temper rolling by a 0.4 to 2% elongation rate;
wherein the steps of overaging for 120 seconds or more and temper rolling by 0.1% to 0.4% elongation rate occur before the step of preplating Ni or Ni—Fe.

2. The method of production of a hot dip galvannealed steel sheet as set forth in claim 1 , characterized in that the slab contains, by mass %, B: 0.005% or less.

3. A method of production of a hot dip galvannealed steel sheet for motor vehicles, household electronics and buildings, said method comprising 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%,
N: 0.01% or less, and
a balance of Fe and unavoidable impurities;

said processing of the slab comprising the following steps, in this order:
(a) hot rolling;
(b) pickling;
(c) cold rolling;
(d) annealing at 650° C. to 900° C.;
(e) cooling down to a temperature range of 250° C. to 450° C. at a cooling rate at 600° C. or less of 50° C./sec or more;
(f) overaging at said temperature range for 120 seconds or more;
(g) cooling to room temperature;
(h) pickling;
(i) temper rolling, wherein the elongation rate of temper rolling is 0.4% or less;
(j) preplating Ni or Ni—Fe, wherein an amount of plating is 0.2 to 2 g/m 2 ;
(k) heating at a rate of 30° C./sec or more up to a temperature between 430° C. and 500° C.;
(l) galvanizing in a galvanization bath;
(m)wiping;
(n) heating up to 460° C. to 550° C. at a rate of temperature rise of 20° C./sec or more;
(o) cooling at a rate of 3° C/sec or more; and
(p) final temper rolling, wherein the elongation rate of the final temper rolling is 0.4 to 2%,
wherein, after the step of heating at a rate of 30° C./sec or more up to a temperature between 430° C. and 500° C., no soaking time is provided, or the slab is held for soaking for 4 seconds or less, after galvanizing in a galvanization bath.

Assignees

• Haji Junji
• Kawasaki Kaoru
• Ishizuka Kiyokazu
• Yamada Teruaki
• Nippon Steel & Sumitomo Metal Corp

Inventors

• Haji Junji
• Kawasaki Kaoru
• Ishizuka Kiyokazu
• Yamada Teruaki

Classifications

• C22C38/001

  containing N · CPC title

• C23C2/06

  Zinc or cadmium or alloys based thereon · CPC title

• C23C2/04

  characterised by the coating material · CPC title

• C22C38/02

  containing silicon · CPC title

• C21D9/46 Primary

  for sheet metals · CPC title