JPS6267162A - Manufacture of plated hot rolled steel sheet preventing blistering - Google Patents

Abstract

PURPOSE:To prevent the blistering of a layer formed on a hot rolled steel sheet by plating due to hydrogen occluded in the steel sheet by pretreating the steel sheet by Selas system before plating by vacuum deposition. CONSTITUTION:A hot rolled steel sheet is descaled only by degreasing and pickling in a pretreating line without carrying out oxidation, reduction, annealing or treatment with a flux and an oxide film is removed from the surface by brushing. The steel sheet is then reduced in a preheating and reducing furnace to clean the surface and to obtain a state suitable for plating by vacuum deposition. The hot rolled steel sheet pretreated by Selas system as mentioned above is plated by vacuum deposition.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a method for producing a vacuum-deposited hot-rolled steel sheet that prevents the occurrence of blister when plating a hot-V steel sheet.

<Prior art> When plating metals such as zinc and aximinium on the surface of steel sheets, various plating methods are known.Currently, hot-dip plating and electroplating are generally carried out for thin sheet materials, and recently, young plating has become popular. is also at the stage of practical application. On the other hand, hot-rolled steel sheets are usually subjected to hot-dip plating. Here, 1 on the steel plate
Looking at the continuous hot-dip plating methods that are widely used in lead plating, these hot-dip plating companies use methods such as (a) Senshimi 7 type, (b) Wheeling type, and (c) Cirrus type. Are known.

(b) Each plating method has different pretreatments.
In the Sensimi 7 type, an oxidation furnace or a non-oxidation furnace is provided in the plating line, and after the steel plate is preheated by oxidation, it is further guided to a reduction annealing furnace. Here, the steel sheet is heated in a reducing atmosphere of decomposed ammonia gas to about 700 to 850 DEG C., the recrystallization temperature of the steel -1-, and subjected to reduction annealing, and then subsequently cooled and introduced into a zinc bath.

(b) The wheeling type does not have an annealing furnace in the plating line, and flux treatment is performed after degreasing and pickling.
Furthermore, the flux is dried while also preheating the steel plate.

(c) In the preheat type of Cirrus type,
An annealing furnace is not installed in the plating line, and the steel sheet is guided to a hand-heated furnace after degreasing and pickling. The steel plate is directly heated in the furnace and becomes HN.
It is introduced into a zinc bath while being reduced with X gas or AX gas. This method does not perform in-line annealing and does not use flux, so no equipment for processing corrosive flux gas is required.

Among the plating methods mentioned above, hot-rolled steel sheets are supplied with an acid detergent due to equipment reasons, and with Senshimi 7 type, hot-rolled steel sheets are supplied with an acid detergent, and with the Silas type, heat treatment is performed in a furnace after in-line pickling. : It has been implemented.

<Problems to be Solved by the Invention> In the conventional hot-dip galvanizing of hot-rolled materials, there is a problem in which pristar occurs in the galvanized layer. For example, in the Sendzimir type (1), a reduction annealing furnace is provided immediately before the plating bath, and the steel plate is heated and reduced in decomposed ammonia gas to about 700 to 850°C. Also, in the above-mentioned Sealas type, a preheating reduction furnace is provided immediately before the plating bath, and the steel sheet is heated to about 600° C. in the furnace and introduced into the zinc bath while being reduced with HNX gas or AX gas. In this way, in the 1-reporter plating method, the steel plate is reduced and activated at approximately 600°C in a reducing gas atmosphere just before introducing the steel plate into the plating bath.
Around or above I-Heating. However, when a steel plate is heated to a high temperature in the presence of hydrogen gas, a large amount of hydrogen acid is occluded in the steel, and this together with impurities adhering to the steel plate surface becomes a cause of prister formation. In other words, after hydrogen is stored in the steel, if plating is applied to the surface of the steel sheet, the hydrogen stored in the steel sheet will be extracted from the surface of the steel sheet over time.However, in this case, the hot-dip plating layer Since the layer thickness is thick, it is difficult for hydrogen to permeate and it is difficult for hydrogen to leak out to the outside, so it is interposed between the steel plate surface and the plating alloy layer. As a result, the plating layer is locally peeled off from the surface of the steel sheet and swells.

Such blisters in the plating layer make the plating layer extremely susceptible to damage, causing a significant deterioration in product quality.

Conventionally, various means have been tried to prevent the blister as described in (1) above, but they are still not sufficient. For example,
In each plating method such as JP-A No. 9-14325, JP-A-52-95543, JP-A-54-130443, JP-A-54-124837 and JP-A-55-64029,
Attempts have been made to prevent pristar by limiting the composition of the plating bath to a specific range, lowering the reduction temperature to a predetermined temperature, or limiting the hydrogen gas concentration.

However, all of the -I-reporter plating methods are four-curing methods within the range of hot-dip plating, and the effect of Plister Prevention II- is not necessarily sufficient.

Means for Solving the Problem> The present inventors believe that, unlike hot-dip galvanized layers, vapor-deposited galvanized layers have fine porous crystals when viewed microscopically. We obtained the knowledge that it is easy to pass through and extract to the outside. Furthermore, if the Cirrus type pretreatment described in -1- is carried out as a pretreatment for the vapor deposition plating, it is suitable as a plating line for hot rolled materials that does not require an annealing furnace,
Furthermore, there is an advantage that the preheating reduction furnace can also be used as a pretreatment furnace for vapor deposition plating.

The present invention is based on the above knowledge, and is based on the original idea of utilizing vacuum vapor deposition plating, which has not been conventionally applied to hot rolled materials, and combining the vacuum vapor deposition plating with the pretreatment process of sealer type. This method solves the conventional problems and achieves a method for producing high-quality galvanized hot-rolled steel sheets without pristar.

(-Structure of the Invention) 1110Accordingly, the plating pretreatment of the Cirrus method, in which oxidation annealing and flux treatment are carried out in the plating pretreatment line, followed by f@ρ, is applied to hot rolled steel sheets (this treatment is carried out). 44 of the hot-rolled and galvanized steel plate that prevents the occurrence of 111.
117 people will be provided.

More specifically, in the hot rolled steel sheet plating method described in step 1, the steel sheet is removed 111-i, M-washed 1. There is provided a method for producing a hot-rolled galvanized steel sheet, which comprises: removing scale, removing an oxide film on the surface of the hot-rolled steel sheet by brushing, and performing vacuum Ik plating under gamma and hot tempering. Ru.

In the present invention, hot-rolled steel sheets are pre-plated with a sealer type and then subjected to vacuum-based young plating.An example of one treatment for the sealer type is that the steel sheet is subjected to alkaline degreasing, brush cleaning, and acid cleaning. -Spray cleaning-Drying-Y
・Annealing is carried out in the plating pre-treatment line via heat and ρ-1 each, and then ρ-treated with HNX gas or AX gas.
activated. In this pretreatment, stains on the surface of the steel plate are removed by using one culm of alkaline fat. Further 1. ″Steel plate table +1
1i 4 scales are removed by pickling. Note that the scale treatment is not limited to pickling, but may be a mechanical method, or a combination of a chemical method such as pickling and mechanical force 11. Furthermore, the surface of the thermal V steel plate has black oxide bites, which are removed by brushing.

Here, the 1.4 oxide film on the surface of the thermal V steel sheet is firmly attached, so it cannot be removed sufficiently by normal ρ light treatment. 1, 1 is not suitable for 7i plating. The present invention does not undergo descaling treatment such as pickling treatment, heat ρ source, and II.
/7! After the descaling, brushing treatment is applied to i.
By using MfI, a surface condition suitable for plating can be obtained.

The Y/heat-reduced hot-rolled steel sheet is guided to vacuum-based young plating step 1. An example of the vacuum A7i plating apparatus is a vacuum/
A seal roll chamber on the 11 side and a seal roll chamber on the 111u side are provided before and after the 7+ chamber, and a pressure chamber is attached to the introduction end of the seal roll chamber on the 1 side, and A chamber in which the pressurizing chamber and the preheating reduction furnace described in 1-1 are communicated with each other is preferably used. [-.

The seal roll chamber maintains the vacuum in the vacuum deposition chamber as the steel plate is introduced and taken out, and is provided with a length of wL along the conveyance path of the steel plate, and has a pinch roll that pinches the steel plate inside and a seal partition wall. A plurality of them are arranged along the conveyance path and are configured to be able to reduce the pressure in stages. The interior of the vacuum deposition chamber is depressurized, and an oxidation tank is provided in which the plating metal is stored.
A chamber extends from the developing tank toward the steel plate. Note that the vacuum A right chamber is necessarily provided in two stages, and the front and back surfaces of the steel plate are extensively plated. On the other hand, the pressure chamber is used to prevent hydrogen from flowing into the seal roll chamber from the p-heat reduction furnace, and is filled with an inert gas such as nitrogen gas. In addition, when connecting the vacuum evaporation plating apparatus to the plating pretreatment step 1, the seal roll chamber is connected to the preheating reduction furnace of the hot-dip plating line of the sealer type through the duct 17. Then, it can be used for both hot-dip plating and vacuum deposition plating. It can be used as a continuous plating line.

The hot-rolled steel sheet that has been preheated and reduced passes through a pressure chamber and then a seal roll chamber. The hydrogen occluded in the steel sheet is replaced by nitrogen, an inert gas, by passing through a pressure chamber, and most of it is removed by passing through a seal roll chamber under reduced pressure.

<Effects of the Invention> According to 1--Plating power of the present invention explained below, the hot rolled steel sheet is subjected to the descaling process of alkaline degreasing, pickling and brushing, and then subjected to Y and heat ρ. Since the black oxide film that adheres firmly to the surface is reliably removed, a good & f licking layer with high peeling resistance can be obtained. In addition, the heat-reduced steel sheet is heated in the pressurization chamber so that the nitrogen of the inert gas filled in the pressurization chamber is replaced with the hydrogen occluded in the steel sheet. ! J! Most of the hydrogen stored in the steel plate is removed while the steel plate passes through a seal roll chamber under reduced pressure. Moreover, unlike a hot-dip plating layer, the vapor-deposited plating layer has fine porous crystals when viewed microscopically, so even after the plating process, hydrogen in the steel sheet easily passes through the inside of the plating layer and is extracted to the outside. Therefore, it is possible to obtain an extremely high-quality hot-rolled plated steel sheet in which no pristar occurs due to hydrogen occluded in the steel sheet.

<Example> A hot-rolled steel sheet was subjected to vacuum evaporation plating through the pretreatment process shown in the figure. The operating conditions are as follows.

A. Steel strip: 2.3+u+thickness 1. 0sec Reduction furnace: Plate temperature 500℃ Gas composition 50H2-5ON2 2. Vapor deposition plating Vapor deposition zinc 2 Commercial electrolytic zinc evaporation temperature: 460-470℃ Pressure residue composition 2N2 E. Pressure chamber pressure Crab atmospheric pressure + 3-10vH70 Deposition vacuum degree: 0, 01~0, 1 Torr, plate temperature: 19
0 to 280° C. Seal chamber: length approximately 11 m Vacuum pressure 10-' Torr In this example, a hot-rolled plated steel sheet was obtained in which no pristar was formed on the galvanized film.

[Brief explanation of drawings]

The figure is a T diagram of the plating method according to the present invention. Patent applicant [1 Shin Steel Co., Ltd. Mitsubishi Heavy Industries, Ltd. Agent: Attorney: Seibutsu Matsui (1 other person)

Claims (1)

[Claims] 1. A hot rolled steel sheet is subjected to a Cirrus method plating pretreatment in which descaling is performed and then preheated and reduced without undergoing oxidation-reduction annealing or flux treatment in a plating pretreatment line, and then vacuum evaporation plating is performed. A method for producing a hot-rolled plated steel sheet that prevents the occurrence of pristar, characterized by: 2. After the steel plate is degreased and pickled to remove scale, the oxide film on the surface of the hot rolled steel plate is removed by brushing, and vacuum evaporation plating is performed by preheating reduction. Manufacturing method of section.