Production method of ultra-thin steel belt plated with precious metal

Abstract

Provided is a production method of an ultra-thin steel belt plated with precious metal. The production method includes the steps that a DC01 cold-rolled steel plate is used as a raw material, and conventional degreasing is conducted after the steel plate is cold-rolled repeatedly; annealing is conducted; the belt is prepared, specifically, uncoiling, striping and burr removal are carried out; Zn / Fe electroplating, primary water-washing and drying, primary physical vapor deposition, secondary water-washing and drying and secondary physical vapor deposition are carried out sequentially; and the belt is rolled after being naturally cooled to be at the room temperature. According to the steel belt, the Rm is 200-230 MPa, the percentage of elongation is 45%-50%, the surface roughness of an Au-plated or Ag-plated coating is 0.05-0.10 micron, and the specular reflection is 99%-99.9%; after the coating is stored on the indoor atmospheric condition for 1800 days, the specular reflection of the coating is 98.7%-99.7%, the gloss loss rate is not higher than 0.5%, and the rate of the corroded area is not higher than 0.05%; after the coating is exposed in air containing 30 ppmH2S for 1200 days, the specular reflection of the coating is 98.5%-99.5%, the gloss loss rate is not higher than 0.6%, and the rate of the corroded area is not higher than 0.08%; for a Pt-plated steel belt, the surface roughness is 0.03-0.06 micron, the porosity is not higher than five each square centimeter, and the specular reflection is 99.5%-99.9%; and after the coating is stored in the 50-KHz ultrasonic environment continuously for 2400 hours, the thickness of the coating is not changed, and the surface has no crack.

Description

technical field [0001] The invention relates to a production method of a steel strip, in particular to a production method of an ultra-thin steel strip coated with precious metals, which is especially suitable for industries such as jewelry, clocks and watches, precision instruments, and photoelectric communications. Background technique [0002] Noble metals generally refer to metal elements such as Au, Ag, Pt, and Pd. Because precious metals have excellent ductility, surface properties, electrical conductivity and thermal conductivity, they are widely used in jewelry, watches, precision instruments, optoelectronic communications and other industries, and the market demand is huge. However, since precious metals are scarce in the Earth's crust, they are extremely expensive. The traditional practice in the industry is to electroplate a thin layer of precious metals on the surface of cold-rolled steel strips to achieve certain specific functions and reduce production costs...

AI Technical Summary

Problems solved by technology

[0004] One is that the coating uses Cu as the inner coating, which is prone to oxidation, resulting in a decrease in the stability of the coating

In addition, once the corrosive medium passes through the cracks and pinholes of the Au or Ag layer, passes through the pores of Ni and Cu, and reaches the Fe matrix, since the Fe matrix is ​​the anode of the corroded galvanic couple, it will be corroded soon and rust spots will appear.

[0005] Second, in the process of electroplating Au and Ag, it is necessary to use highly toxic cyanide as the electroplating solution, which will seriously pollute the environment

[0006] The third is that the surface of the steel strip is easily passivated after continuous electroplating, and the comprehensive performance of the obtained composite coating is difficult to control

[0007] Fourth, the continuous electroplating process leads to large production energy consumption and more waste liquid

In particular, a large amount of precious metals Au and Ag are required to be used in production, and the production cost is quite high

Although it has been reported in the literature that Au or Ag can be plated by thermal spraying, on the one hand, the thickness of the resulting coating is often large, generally up to more than ten microns, or even higher, and there is still some waste in the use of raw materials, and the cost performance is not high.

On the other hand, in the process of thermal spraying, since the heating temperature has reached or exceeded the melting point of the metal, oxides are easily formed on the surface of the coating, which seriously affects its surface quality.

[0008] Fifth, Cu, Au, and Ag in the entire coating system are susceptible to H 2 Strong corrosion of sulfides such as S, after long-term exposure, the specular reflectance and gloss of the coating will be greatly reduced

[0010] One is that the main component of the plating solution is still P salt (Pt(NH 3 ) 2 (NO 2 ) 2 ), during electroplating, a large amount of carcinogen nitrite is likely to be produced in the solution, which will seriously damage the environment and human body

And electroplating needs to be carried out at about 100 °C, high temperature electroplating further aggravates the pollution

[0011] Second, because the current efficiency is difficult to reach 100%, more waste liquid will be generated during the electroplating process, resulting in a waste of Pt

Generally, it can only be recycled through cumbersome follow-up treatment, which will increase additional production costs

[0012] Third, due to the passivation effect caused by long-term electroplating, the surface quality of Pt coatings is often poor, with many pores, high stress, and low gloss

Although the surface performance, electrical conductivity and thermal conductivity of the product are good, but because the Au-Sn binary alloy is composed of many brittle and hard intermediate phases, the processing and forming performance and welding performance of the product are insufficient.

Especially Cu and Au are easy to corrode in the face of sulfide, which is easy to affect the surface quality

In addition, this product uses a thermal spraying process, the thickness of the coating is relatively large, there is still some waste in the use of raw materials, the cost performance is not high, and high temperature has an adverse effect on the surface quality of the coating

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