JPS63312960A - Manufacture of zinc alloy hot dip galvanized steel sheet having superior workability - Google Patents

Abstract

PURPOSE:To manufacture a plated steel sheet having superior workability, by applying, prior to hot dip galvanizing, preplating of Ni-P, Co-P, or Fe-P in which P content is specified, respectively. CONSTITUTION:Preplating of Ni-P, Co-P, or Fe-P is applied to the surface of a cold-rolled steel sheet by >50mg/m<2> expressed in terms of P content. Subsequently, the sheet is passed through a hot dip galvanizing line and subjected to heating, reduction, and annealing, and then, this sheet is dipped into a zinc bath to undergo prescribed plating and is then heat-treated so as to be formed into a zinc-iron hot dip galvanized steel sheet. By this method, the problems of deterioration in plating, peeling, etc., due to working can be solved.

Description

[Detailed Description of the Invention] (Prior Art) Conventionally, hot-dip zinc-iron alloy plated steel sheets are heat-treated at the point when the plated steel strip rises from the hot-dip galvanizing bath to form an alloy of about 10% iron. As a steel plate with excellent corrosion resistance and weldability after painting, it was widely used for steel furniture and automobiles. However, the problem with the quality of this alloy-plated steel sheet is that the iron-zinc alloy is extremely brittle and cannot withstand processing. Therefore, those with less plating adhesion are generally used in the market. If the amount of zinc-iron alloy is more than 501 on one side, the workability will deteriorate and the plating will peel off, and the zinc-iron alloy will peel off into powder during pressing etc. and adhere to the mold, hindering productivity. It also adheres to pressed products and deteriorates their appearance.

There is a problem in that the peeling of the zinc alloy naturally deteriorates the corrosion resistance of the plate, and there has been an urgent need to improve this problem.

As a precedent example, a method of pre-plating metal to promote alloying is disclosed in Japanese Patent Publication No. 60-56790 and Japanese Patent Publication No. 58-1.
207711 etc.

(Problems to be Solved by the Invention) The object of the present invention is to provide a method for producing iron-zinc alloy plated steel sheets with good workability by improving such poor workability.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a method for manufacturing a plated steel sheet with good workability by pre-plating in a hot-dip galvanizing line. Specifically, at the front of the hot-dip galvanizing line, the surface of the steel plate is coated with 7" L/L of phosphorus and a metal alloy, and then the strip is sent to a furnace for hot-dip galvanizing. It is characterized by performing alloy plating.In other words, in the method of heat-reducing a steel plate, performing hot-dip lead plating, and then heat-treating it to produce a zinc-iron alloy plated steel sheet, it precedes hot-dip plating. Good processing PL, characterized by pre-plating of Ni-P, co-P or Fo-P with a P amount of more than 5σ189/FF1''! ＠This is a method for manufacturing galvanized steel sheets.

The usual manufacturing method for zinc-iron composite galvanized steel sheets is cold pressure IJj.
The ridged steel plate is passed through a hot-dip galvanizing line, the surface is reduced and annealed, and the plate is immersed in a hot-dip zinc bath without being exposed to the outside air to coat the galvanized steel.
The conventional method is to use iron (approximately 10%) alloy plating.

In non-invention, this process is as follows. Cold-rolled photonized steel sheets have a fibrous structure, and there are oil and oxide films on the surface, so heat treatment annealing and surface cleaning are necessary.

Prior to plating, the eight steps are degreasing and pickling. The surface of the steel plate is activated by degreasing and cleaning, and then pre-plating is performed.

The inventors conducted various studies on this pre-plated metal and found that special plating is effective in improving the workability of hot-dip zinc-iron alloy plating.

Normal hot-dip galvanizing is carried out in a hot-dip zinc bath. 0.1
Adding around 5% improves the fluidity of plating, prevents the generation of dross, etc., and suppresses the formation of brittle Zn-Fe'3 gold. However, this person becomes a harmful factor in alloying in the process of manufacturing Achi-iron alloy plated steel sheets, in which alloying is performed in a heating furnace at the rising part immediately after hot-dip galvanizing. However, in a normal galvanizing line, it is common work to perform zinc plating or zinc-iron alloy plating. Therefore, it is usually very difficult to significantly change the concentration of AP.

The concentration of AM has a subtle effect on zinc-iron alloying, and in order to minimize this effect and increase the %fA of zinc-iron gold-plated steel sheets with good workability, there is a control method using pre-plating. I found it to be the best. It has been found that alloying can be promoted or suppressed by pre-plating the metal. To promote the alloying of hot-dip galvanized steel sheets, the reaction characteristics were adjusted by pre-plating various metals before regular hot-dip galvanizing.
56790 and JP-A No. 58-120771, etc., methods using pre-plating are shown, but neither of them can be expected to improve workability as aimed at in the present invention.

It has become clear that it is difficult to plate a 4L lead-iron alloy with good workability using a single metal.

The inventors have discovered that alloy plating with good workability is possible only by plating with P-metal having a specific grade of 1 or higher. This processability improvement effect of the P-compound is due to the alloying reaction in the heating furnace after plating, which suppresses the formation of the 1st layer with poor workability and promotes the growth of the 6.0 layer with good workability. It is estimated that the workability of the plated steel plate is improved. If the amount of plating of the phosphorus compound is less than 50 Mr9/m'' in terms of phosphorus amount, the effect will be very weak.
On the other hand, when converting phosphorus to γ, it is 500 m9/yyl'' (
In both cases, the cost is too high and industrial application is not desirable.

Among the iron group elements (Fe, Co, Ni), 2
Pre-plating of an alloy consisting of one or more metal elements and phosphorus is also effective.

The P content in the pre-plated film is 1/l of adhesion.
:, improvement? It is effective if it contains 5 weight or more from the curse point.

(Actual example) Example 1 A cold-rolled steel plate with a thickness of 0.8 fl was degreased, pickled, and coated with Ni-
PfI: 60 rtu; 15
909/l (lead), leaving the specified plating
Zinc-
Manufactured a steel plate with fusion-plated iron. The manufactured steel plate had excellent engineering.

Example 2 Same as Example 1, but Fe-
Add P to P and get 120 LNI)/n? (One side) plated. The other steps were the same as in Example 1, and a lead-iron alloy plated steel sheet with good workability could be obtained.

(Effects of the Invention) The method of the present invention provides a bath with good workability ha! An Ilj lead alloy plated steel sheet was obtained.

7. Contents of the amendment Procedural amendment (method) % formula % 1. Indication of the case 1988 Patent Application No. 149102 2. Title of the invention Method for manufacturing hot-dip galvanized steel plate with good workability 3. Person making the amendment Relationship to the incident Patent applicant address 2-6-3 Otemachi, Chiyoda-ku, Tokyo Name
(665) Insert the item "Detailed explanation of Nippon Steel Corporation Representative Yutaka Saito 4, Agent 105 Den'503-4877 Ming."

Claims (1)

[Claims] In a method for manufacturing a zinc-iron alloy coated steel sheet by subjecting a steel plate to heat reduction treatment, hot-dip galvanizing, and then heat-treating, Ni-P, Co-
A method for producing a hot-dip zinc alloy plated steel sheet with good workability, characterized by pre-plating with P or Fe-P at a P content of more than 50 mg/m^3