JPS5830941B2 - Manufacturing method for single-sided hot-dip galvanized steel sheet with excellent workability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a single-sided hot-dip galvanized steel sheet with excellent workability.

Single-sided hot-dip galvanized steel sheets are mainly used as rust-proof steel sheets for automobiles, and are required to have better plating adhesion and workability.

Conventional single-sided hot-dip galvanized steel sheets have been manufactured by taking galvanized steel sheets manufactured through the normal manufacturing process of cold-rolled steel sheets, cooling them to the plating temperature after reduction annealing, galvanizing them, and subjecting them to overaging.

However, since the steel sheets used for plating contain a large amount of C exceeding 0.010% and a large amount of N exceeding 0.0040%, the temperature rapidly reaches the plating bath humidity after reduction annealing. Even after overaging treatment, a large amount of C,
There is a problem in that the material of the steel sheet is hardened by dissolving N or precipitating fine charcoal materials.

In addition, during the immersion time of the steel plate in the hot-dip galvanizing bath for 1 to 20 seconds, a non-uniform growth layer of Zn-Fe based binary alloy is formed,
Since the formation of a dense Zn-Al-Fe ternary alloy layer is prevented, there is also the problem that it is easy to produce a steel plate with poor plating adhesion.

Furthermore, with such a long galvanizing bath immersion time,
There was also the problem of forming a deep alloy layer on the steel plate to make the steel plate hard.

The present invention solves the drawbacks of the conventional method for manufacturing single-sided hot-dip galvanized steel sheets, and makes it possible to manufacture single-sided hot-dip galvanized steel sheets that maintain a high level of plating adhesion and have excellent workability as steel sheets for automobiles. It provides law.

The gist is that acid-soluble Al20, which has been deoxidized with 11' etc.
02 to 0.08 section, C: 0.01 section or less, N: 0O04
% or less, the steel plate contains Ti: 0.02 to 0,
Steel plate containing 10φ or acid soluble A7:0□04%
Below, after reducing and annealing a steel plate containing B in an amount of 0.8 to 2.5 times the N content, a molten zinc bath flowing at a flow rate of 0.1 m/see or higher is applied to one side for 0.05 to 760 seconds. This is a method for producing single-sided hot-dip galvanized steel sheets by colliding and contacting them to adhere molten zinc.

The present invention will be explained in detail below.

Acid-soluble Al that was deoxidized with FCAl etc. to prevent preferential oxidation of Ti: 0.02-0.08%, c: o, oi
% or less, a steel plate containing N: 0.004% or less, a steel plate containing Ti: 0.02 to 0.10%, acid-soluble Al: 0.04φ or less, and B with a N content of 08-2.
A cold-rolled steel plate (As Co1d material) containing 5 times the amount of carbon dioxide and produced through a normal rolling process is subjected to oxidation or non-oxidation heating based on the pre-treatment process and conditions of a normal galvanizing method, The surface is reduced and annealed to activate it and soften it.

The components of the cold-rolled steel sheet used in the present invention are limited in terms of the workability of the material, the effect of aging on the processing method, and the effect on plating adhesion.

That is, in the present invention, it is essential to use a steel plate that has been deoxidized with A1 etc. and has C and N of 0.019% or less and 0.0040% or less, respectively.
If the diameter exceeds 010φ, C precipitated during the cooling process to plating after reduction and annealing will have an adverse effect.

Therefore, it is absolutely necessary to suppress C to 0.010% or less in order to obtain a galvanized steel sheet with sufficiently excellent formability as desired, even without performing an overaging treatment.

In particular, to further improve workability, add 0.00% C.
It is preferable to reduce the diameter to 5φ or less.

At the same time, it is necessary to suppress the N content to 0.0040% or less in order to reduce deterioration of mechanical properties due to aging.

Furthermore, the reason why the acid-soluble A7 content was limited to 0102% to 0608% is that if the amount of l used for deoxidizing adjustment is small (less than 0.02% remaining in the steel sheet), bubbles may be formed due to oxygen gas. It is difficult to prevent the occurrence of
If the amount exceeds A7. This is because the segregation of Al-based oxides inhibits plating adhesion.

The addition of Ti is 0 within the above specified ranges of C, N, and Al.
．． It is added in a range of 0.02 to 0.10%.

That is, if less than 0.02% is added, it is insufficient to fix C and H, and the desired effect cannot be obtained. Further, addition of more than o or ioφ is not preferable due to economic efficiency and the material hardening due to the influence of solid solution titanium, precipitated Ti, etc.

In addition, the addition of B in the present invention suppresses the amount of aluminum nitride produced, which has an adverse effect on mechanical properties, and fixes N as boron nitride, thereby further improving mechanical properties and improving mechanical properties due to aging. Effective in eliminating negative effects on properties.

So, in this case, AJI? It is necessary to limit the content to 0.040% or less in order to reduce the formation of aluminum nitride as much as possible.

That is, since Al has a greater affinity for nitrogen than B, Al in the steel sheet should be limited to 0.040% or less in order to reduce the formation of aluminum nitride and fix N as boron nitride. .

This lower limit does not need to be specified because B acts as a deoxidizing agent like Ti, but from the economic point of view,
It is preferable to perform deoxidation adjustment before addition.

Furthermore, the amount of B added is limited to the above ranges for C, N, and Al, and in order to fix and precipitate N as boron nitride (BN), B is added to N in steel from the viewpoint of economy and production rate. /H ratio is in the range of O68 to 2.5.

If the B/N ratio is less than 0.018, boron nitride will not be generated smoothly and the performance of the steel plate used in the present invention cannot be obtained, and if it is 2.5 or more, it is not preferred from the economic point of view.

In the present invention, the single-sided galvanizing method is a plating method in which the surface of the steel sheet collides with and comes into contact with a flowing molten zinc bath, so a uniform and dense Zn-Fe-Ax ternary alloy layer is formed on the surface of the steel sheet. It has the effect of producing it in a short time, and since the contact reaction time with molten zinc is set to an extremely short time of 0.05 to 0.6 seconds, the production of a brittle Zn-Fe binary alloy is prevented. This has the effect of significantly suppressing plating adhesion and preventing deterioration of plating adhesion.

In this case, the flow velocity of the flowing galvanizing bath is 0, 1 m
/see, the very short-time collision/contact reaction in the above range with respect to the steel plate surface results in a uniform and dense Zn-Fe-A.
It is difficult to generate an l-based ternary alloy layer, and
At a high flow rate of 0.1 m/sec or higher, the above effects are saturated and the equipment materials such as plating equipment and plating pots become severely corroded. It is desirable to flow the molten zinc at a flow rate of

In addition, if the contact time is 0.05 seconds or less, there is a risk that the molten zinc will not adhere uniformly across the width of the steel plate surface, making it difficult to produce a uniformly dense Zn-Fe-Al1 ternary alloy. be.

Further, if the time exceeds 0.6 seconds, the formation of Zn-Fe binary alloy increases, which deteriorates plating adhesion, which is not preferable.

Therefore, in order to further improve the effects of the present invention,
It is preferred to keep the contact time in the range of 0.1 to 0.3 seconds.

As explained above, according to the manufacturing method of the present invention, a single-sided galvanized steel sheet with excellent formability, plating adhesion, and plating appearance as desired can be obtained without performing heat treatment such as overaging treatment or low-humidity annealing. .

Furthermore, considering the manufacturing process, over-aging treatment or low-temperature annealing is not necessary, which improves productivity and is advantageous in terms of equipment.

Next, examples of the present invention will be described.

Temperature 8 of steel plates A and B shown in Table 1 in HNX gas atmosphere
After reduction annealing at 80° C. for 30 seconds, plating was applied to a molten zinc bath at a flow rate of 0.6 m/sec using an electromagnetic pump at various contact times.

The mechanical properties and plating adhesion at that time are shown in Table 2.

Steel plate C is a comparison material.

As is clear from the above results, the method of the present invention produces a steel plate with superior plating adhesion and workability compared to comparative materials.

Claims (1)

[Claims] I C deoxidized with AI: 0.010% or less, N
:0.004% or less, acid soluble, l:o, 02-0608
A steel plate containing φ, or a steel plate containing Ti: 002 to 0
, A steel plate containing 10 or less acid-soluble Al20040 and containing 0.8 to 2.5 times as much B as N is reduced and annealed, and one side of the steel plate is flowed at a flow rate of 0.1 m/sec or more. A method for manufacturing a single-sided hot-dip galvanized steel sheet with excellent workability, characterized by colliding and contacting a molten zinc bath for 0.05 to 0.60 seconds to cause molten zinc to adhere.