JPH0254425B2 - - Google Patents

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. ing. However, iron and lead do not form a solid solution with each other, that is, the bonding force between iron atoms and lead atoms is weak. The drawback was that it did not provide good adhesion. Therefore, in order to eliminate the above-mentioned drawbacks, a lead-tin alloy containing usually 10 to 20% tin was applied to the surface of the steel plate, taking advantage of the fact that the lead-tin alloy has the property of being easily wetted with the steel plate. A method of hot-dip galvanizing to improve the adhesion between the galvanized 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 also 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 economy. Therefore, in order to solve the problems of conventional molten lead alloy plating, the present inventor conducted various experiments on the vacuum evaporation lead plating method, and found that the surface was coated using lead that does not actively contain tin. It has been found that a lead-plated steel sheet having excellent tamping adhesion can be obtained by performing vacuum evaporation of lead on an activated tamping substrate under appropriate conditions. That is, in the present invention, after cleaning the surface of a plated steel sheet by a commonly used method, the surface is further activated in an atmosphere containing hydrogen, and then the plated steel sheet is led to a vacuum deposition chamber to reduce the vacuum of the atmosphere. pressure
Provided is ^a method for producing a lead-plated steel sheet, characterized in that lead is vacuum evaporated and plated at a plating substrate steel sheet temperature of 50° C. or more and 250° C. or less at a plating substrate steel sheet temperature of ⁵⁰ ° C. or more and 250° C. or less. 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 preferable that impurity metal components with a vapor pressure lower than that of lead be as low as possible. . 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 is a known wet cleaning method 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. In the method of the present invention, the atmosphere containing hydrogen is
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 in a conventional manner to remove surface contaminants. In this state, as is well known, a considerable amount of dirt such as oil on the surface is removed, but since oxides and other substances remain on the surface, the surface of the plated substrate is inert, and the lead vacuum Even if vapor deposition is performed, excellent folding adhesion cannot be obtained. In the present invention, after chemically cleaning or gas cleaning the surface of a plating substrate, in order to activate the surface of the plating substrate, oxides on the surface of the plating substrate are removed in an atmosphere containing hydrogen, for example, a mixed gas atmosphere of hydrogen and nitrogen. After reduction, lead is vapor-deposited to improve plating adhesion. The activation conditions for the plated substrate surface depend on the gas composition, but for example, in a 50% H ₂ + 50% N ₂ atmosphere,
Heating at 650℃ for 10 seconds is sufficient. Although this treatment may be carried out at higher temperatures, temperatures below 900° C. are preferred, since very high temperatures are disadvantageous both in terms of thermal energy and in terms of furnace maintenance. The vacuum pressure of the atmosphere in the deposition chamber during deposition is 10 ^-1 Torr.
It is preferably 10 ^-2 Torr or less. Plating adhesion is excellent even when the vacuum pressure exceeds 10 ^-1 Torr and is around ¹⁰⁰ Torr, but due to the high vacuum pressure, lead oxide is generated on the plating surface, which causes white coloring and deteriorates the surface appearance. begins to damage. Vacuum pressure is 6
Even if it is less than ×10 ^-4 Torr, there is no commensurate effect. During vapor deposition, the plated substrate needs to be heated to a temperature of 50°C or higher and 250°C or lower. Plating board temperature is 50
If the temperature is less than 0.degree. C., the thermal kinetic energy of iron atoms is small, so the surface of the plated substrate is not sufficiently activated and 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, spoiling the appearance 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 the exhaust gas composition was 1 to 4%) to prepare a plating substrate. Activation of the plated substrate surface was performed under the conditions shown in Table 1. Note that annealing of the steel plate was also performed at the same time as this treatment. Lead vapor deposition is performed using 99.9% lead metal in a vapor deposition pot.
It was heated to 980°C to 1050°C under the conditions shown in Table 1. The thickness of the deposited lead plating was 3-5 μm. The plating adhesion of the obtained tempered steel plate was evaluated by the following method. Make a 0.5 mm square grid-like mark on the plating surface with a cutter knife, bend it 180 degrees with a bending radius of 0 mm so that this part is on the outside, and then attach Sellotape to this part. When the sellotape is removed, no lead in the plating layer adheres to the sellotape at all, and the adhesion is good (marked with a circle in the table), and a case with a large amount of lead adhering to it has poor adhesion (marked with a cross in the table). An intermediate type with a small amount of lead adhesion was classified as having medium adhesion (marked with △ in the table). The results obtained are shown in Table 1. In addition, sample code 27
is the one without activation processing. From this table, it is clear that the products according to the present invention exhibit excellent folding adhesion.

[Table] *The present invention Others are comparative examples In the above example, a case was shown in which a gas cleaning method was used for cleaning before activating the plated substrate, but the cleaning method does not need to be limited to gas cleaning. In addition, when a commercially available annealed steel plate (thickness: 1.0 mm) was chemically cleaned with an aqueous solution of sodium orthosilicate (3% sodium orthosilicate), exactly the same results as above were obtained.

Claims (1)

[Claims] 1. After cleaning the surface of the plated substrate steel sheet by a commonly used method, the surface is further activated in an atmosphere containing hydrogen, and then the plated substrate steel sheet is introduced into a vacuum deposition chamber where the vacuum pressure of the atmosphere is 10 ^{- 1} Torr or less6
×10 ^-4 Torr or more, plated substrate steel plate temperature 50℃ or more
A method for producing a lead-plated steel sheet, characterized by applying lead vacuum evaporation plating at a temperature below 250°C.