JPS5983764A - Manufacture of vacuum deposition lead plated steel sheet - Google Patents

Abstract

PURPOSE:To obtain the lead plating steel sheet having efficient adhesion properties, by a method wherein after cleaning the surface of plating base steel sheet, the surface of steel sheet is activated in an atmosphere containing hydrogen, conducted into a vacuum deposition chamber, made to be within a specified range of temperature under not more than a specified vacuum pressure and processed with lead vacuum deposition plating. CONSTITUTION:After cleaning the surface of plating base steel sheet by chemical cleaning or gas cleaning, its surface is activated by heat-treating at about 650 deg.C for about 10sec in an atmosphere containing hydrogen, for example, an atmosphere of 50% hydrogen and 50% nitrogen, Then, the plating base steel sheet is conducted into the vacuum deposition chamber, made to be at a temperature of 50-250 deg.C under a vacuum of 10<-1> Torr vacuum pressure (especially not more than 10<-2> Torr) and processed with lead vacuum deposition plating.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vacuum-deposited lead-plated steel sheet with excellent plating adhesion and a method for manufacturing the same.

Lead-plated steel sheets have both the excellent corrosion resistance and chemical resistance of lead and the excellent strength and workability of steel, so they are expected to have a wide range of uses in automobiles, electrical equipment, construction materials, etc. There is. However, iron and lead do not form a solid solution with each other, ie.

Because the bonding force between iron atoms and lead atoms is weak, even if the surface of a steel sheet is hot-dipped with lead, the wettability between the lead and the steel sheet is poor and excellent adhesion cannot be obtained.

For this reason, in order to eliminate the above-mentioned drawbacks, conventionally, an alloy of lead and tin containing 10 to 20% tin was applied to the surface of the steel plate, taking advantage of the fact that the alloy of lead and tin has the property of being easily wetted with the steel plate. A method of hot-dipping to improve the adhesion between the plating layer and the steel sheet has been adopted.

However, this method has the problem of requiring the use of tin, which is less of a resource than lead and is more expensive (approximately 20 times more expensive than lead). For this reason, there is a strong demand for the development of a lead-plated steel sheet that does not contain tin, both from the point of view of resource conservation and from the point of view of economic efficiency.

Therefore, in order to solve the problems of conventional dip-resistant lead alloy plating, the present inventor conducted two different experiments on vacuum evaporated lead plating methods. We have found that a lead-plated steel sheet with excellent adhesiveness can be obtained by vacuum-depositing lead under appropriate conditions on a activated-treated matting substrate.

That is, 2. the present invention activates the surface of a plated substrate in an atmosphere containing hydrogen, 1. then leads the plated substrate to a vacuum deposition chamber, and heats the plated substrate at a temperature of 50° C. or more to 250° C. in a vacuum of 10-' Torr or less. Provided is a method for manufacturing a lead-plated steel sheet, characterized in that vacuum evaporation plating of ζζ lead is applied to a plated substrate at the following temperature.

It goes without saying that the lead used in the method of the present invention does not actively contain tin, but there are no particular limitations on its purity, but it is desirable that impurity metal components with a vapor pressure lower than that of lead be as low as possible. Talented.

In the present invention, a method of cleaning the surface of a plated steel sheet by a conventional method means chemical cleaning or gas cleaning, and chemical cleaning refers to known wet cleaning methods such as cleaning with a solvent or treatment with an aqueous sodium orthosilicate solution. Gas cleaning refers to a method of burning and removing fats and oils from steel sheets in a non-oxidizing furnace or an oxidizing furnace.

What is the atmosphere containing hydrogen in the method of the present invention?

Hydrogen or a mixture of hydrogen and an inert gas, meaning a gaseous atmosphere containing at least 10% hydrogen. A typical inert gas is nitrogen.

The method of the invention can be carried out using known equipment.

Prior to vapor deposition, the surface of the plated substrate is first chemically or gas-cleaned using a conventional method to remove surface contamination. As is well known, in this state, dirt such as oil on the surface is removed to a large extent, but oxides and other substances remain on the surface, so the surface of the plated substrate is inactive.
Even if lead is vacuum-deposited on this, excellent adhesion cannot be obtained.

In the present invention, after chemically annealing or gas cleaning the surface of the plated substrate, in order to activate the surface of the plated substrate, the oxide on the surface of the plated substrate is removed in an atmosphere containing hydrogen, for example, hydrogen, After reduction in a mixed gas atmosphere, lead is vapor-deposited to improve plating adhesion.

The activation conditions for the surface of the plated substrate depend on the gas composition, but for example, in a 50% H2 + 50% N2 atmosphere, 650
Heating for 10 seconds at °C is sufficient. This treatment may be carried out at higher temperatures, but very high temperatures are disadvantageous both in terms of thermal energy and in terms of furnace maintenance.
A temperature W of 00°C or less is preferable.

The vacuum pressure of the atmosphere in the vapor deposition chamber during vapor deposition is preferably 10' Tarr or less, preferably 1 rr2 Torr or less. Plating adhesion is excellent even when the vacuum pressure exceeds 10"-'Torr and 10°'rorr'i degrees, but because the vacuum pressure is high,
Lead oxide is produced on the plating surface, resulting in white coloration and deteriorating the appearance of the surface.

During vapor deposition, the temperature of the plated substrate must be between 50°C and 250°C. When the plating substrate temperature is less than 50° C., the thermal kinetic energy of iron atoms is small, so the surface of the plating substrate is not sufficiently activated.

Excellent adhesion cannot be obtained. On the other hand, if the temperature of the plated substrate exceeds 250°C, granular lead with a size of 0.1 to 1 mm will be formed on the plated surface, impairing the exfoliation of the plated surface.

Examples of the present invention will be described below.

A cold-rolled steel plate with a thickness of 1.0 mm was gas-cleaned (butane combustion, 600° C., 5 to 10 seconds, CO concentration in exhaust gas composition of 1 to 4 parts) to obtain a plating substrate. Activation of the plated substrate surface was carried out under the conditions shown in Table 1. In addition +
'Annealing of AA plate was also carried out at the same time as Q) treatment. Vapor deposition of lead (999 yen of lead metal is heated to 980°C to 1050°C in a vapor deposition pot.
It was heated to 1°C under the conditions shown in Table 1. The thickness of the deposited lead plating was 5-5 μm.

The plating adhesion of the obtained tempered steel plate was measured by the following method.

Make a 0.5 mm square base mark on the plating surface with a cutter knife, bend it 180° with a bending radius of [ ] rnm so that this part is on the outside, and first attach sellotape to this part. When the sellotape is removed, no lead from the plating layer adheres to the sellotape, and the plating has good adhesion (marked with a circle in the table), and one with a large amount of lead attached has poor adhesion (marked with a cross in the table). An intermediate sample with a small amount of lead adhesion was defined as the adhesion neutralization degree (denoted as △ in the table).

The results obtained are shown in Table 1. Note that sample number 27 was not subjected to activation treatment. It is clear from the wood surface that the material according to the invention exhibits excellent mating tightness.

In the above example, a gas cleaning method was used after cleaning the plated substrate before activating it. However, the cleaning method need not be limited to gas cleaning, and a commercially available annealed steel plate (sheet plate) may be used. Thickness: 1.0 mm
) was chemically cleaned with sodium orthosilicate water M solution (5% sodium orthosilicate), the same results as above were obtained.

Patent d entrance Nisshin Steel Co., Ltd.

Claims (1)

[Claims] After the surface of the plated steel sheet is cleaned by a commonly used method, the surface is further activated in an atmosphere containing hydrogen.
Next, the plated substrate steel sheet is led to a vacuum deposition chamber, and vacuum evaporation plating of lead is applied to the tight substrate with a toughness of 50° C. or more and 250° C. or less in a vacuum atmosphere of 10-' Torr or less. A method for producing lead-plated steel sheets.