Process for hot immersion plating iron and steel with aluminium-zinc alloy

A hot-dip aluminum and zinc alloy technology, applied in hot-dip plating process, metal material coating process, coating and other directions, can solve the hazards of workers and plant equipment, reduce the corrosion resistance of the coating, with a layer of molten salt and other problems, to achieve the effect of improving working conditions, reducing growth rate, and easy implementation of the process

Inactive Publication Date: 2003-01-22
HUAZHONG UNIV OF SCI & TECH
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Problems solved by technology

"The flux method hot-dip plating process mainly has the following problems in production: (1) There is a layer of molten salt on the surface of the plated piece from the plating solution, and this layer of molten salt must be disposed of after plating
The general method is to use mixed acid containing nitric acid to react with the molten salt layer to make it dissolve in water, and the discharged waste cleaning solution contains acid and fluorine ions, which will pollute the environment; (2) molten salt will evaporate into the air at high temperature and contain Fluorine vapor will cause harm to the staff and plant equipment; (3) The salt film formed on the surface of the workpiece after assisted plating is easy to absorb moisture, and it must be fully dried before plating, otherwise pinholes, missing plating and virtual plating will easily occur, which will reduce the resistance of the coating. (4) In order to make the melting point of the salt film and molten salt lower than the melting point of the plating solution, some special and expensive compounds are often selected, the cost is high, and the cost of eliminating the molten salt on the surface of the workpiece after plating is also very high , accounting for about one-third of the production cost

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0027] Embodiment 1. Carbon steel (Q235) steel plate, 760 * 13 * 1.5mm. Add 0.5% Na with 20% NaOH 2 CO 3 solution, degreasing at 90°C for 20min. with 20% H 2 SO 4 Add a small amount of corrosion inhibitor solution, pickle at 70°C for 12 minutes, wash with water, soak in 3% dilute hydrochloric acid solution for 5 minutes, and wash with water. With a passivator solution (0.5% CrO 3 +0.05%K 2 MnO 4 +0.2%NaNO 2 + water), passivate at room temperature for 3 minutes, take out and wash with water, and blow dry. Preheat at 140°C for 15 minutes. When smelting aluminum-zinc alloy, anti-oxidation alloy is added at one time, and its content is: 73% aluminum, 7% mixed rare earth, 10% silicon, 5% nickel and 5% zinc. The chemical composition of the obtained aluminum-zinc alloy plating solution is 60% aluminum, 37.8% zinc, 1.6% silicon, 0.34% mixed rare earth and 0.26% nickel. Immerse the pre-plated workpiece in the aluminum-zinc alloy plating solution at 670°C and keep it warm for...

Embodiment 4

[0030] Embodiment 4. Carbon steel (Q235) steel plate, 760 * 13 * 1.5mm. Carry out degreasing and pickling with the method for embodiment 1. With a passivating agent solution (0.05% K 2 MnO 4 +5.2%NaNO 2 + water), treated at room temperature for 1 min, washed with water, and dried. Preheat at 200°C for 10 minutes. When smelting aluminum-zinc alloy, anti-oxidation alloy is added at one time, and its content is: 80% aluminum, 5% mixed rare earth, 8% silicon, 3% nickel and 4% zinc. The chemical composition of the obtained aluminum-zinc alloy plating solution is 60% aluminum, 37.8% zinc, 1.6% silicon, 0.34% mixed rare earth and 0.26% nickel. The temperature of the hot-dip aluminum-zinc alloy bath is 670°C, the hot-dip time is 12 minutes, and the plated parts are taken out of the furnace and then air-cooled. The total thickness of the coating of the plated parts is 89 μm, of which the thickness of the iron-aluminum-zinc alloy layer is 30 μm.

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Abstract

The present invention belongs to the field of hot immersion plating of iron and steel with aluminium-zinc alloy. The iron and steel after being pretreated with inactivation solution, compounded by using CrO3 0.2-5 wt%, K2MnO4 0.05-3 wt%, NaNO2 0.05-6 wt% and water, is hot immersion plated with aluminium-zinc alloy plating liquid with small amount of antioxidant alloy. The antioxidant alloy consists of Al 70-80 wt%, mixed RE 4-10 wt%, Si 8-10 wt%, Ni 3-5 wt%. The technological process can obtain high-quality smooth and bright coating without leakage, false plating, pinhole, color difference and other defects, and has low cost, simple operation and no drainage pollution.

Description

technical field [0001] The invention belongs to the technical field of iron and steel hot-dip plating, and is especially suitable for the hot-dip plating of iron and steel with an aluminum-zinc alloy containing 50-80% of aluminum. Background technique [0002] At present, the hot-dip aluminum-zinc alloy plating process for steel parts at home and abroad is mainly based on the flux method, but no matter what kind of solvent is used, it is necessary to form a salt film on the surface of the workpiece and cover a thick layer of molten salt on the surface of the plating solution. As application number 89109173.4 discloses a "dry and wet hot-dip aluminum-zinc alloy process." The flux method hot-dip plating process mainly has the following problems in production: (1) the surface of the plated part has a layer of molten metal when it is proposed from the plating solution. Salt, this layer of molten salt must be disposed of after plating. The general method is to use mixed acid con...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C23C2/02C23C2/12C23C22/24
Inventor 李华飞刘根凡
Owner HUAZHONG UNIV OF SCI & TECH
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