CN1392283A - Hot dipping aluminium and aluminium alloy inactivation process of plating - Google Patents

Abstract

The present invention belongs to the field of iron and steel material surface chemical and heat treatment technology. The technological process is that before hot dipping, the workpiece surface is filming treated with the inactivation solution compounded by using CrO3 0.2-5 wt%, K2MnO4 0.05-3 wt%, NaNO2 0.05-6 wt% and water, at room temperature for 0.5-5 min. The present invention features the repeated use of the inactivation solution, good filming effect, simple technological process, low cost and capacity of forming smooth, level plated coating without pinhole and leakage.

Description

Deactivation method hot dip aluminum plating and aluminium alloy technology

Technical field

The invention belongs to the surface chemical and heat treatment technical field, relate in particular to the hot dip aluminum plating and the aluminium alloy of carbon-steel parts, alloy steel piece, stainless steel part, ironcasting.

Background technology

Surface heat immersion plating aluminum or aluminum alloy at iron and steel is one of effective measure commonly used of steel protection, early being familiar with by people, hot dip aluminum plating or aluminium alloy ironware have been widely used in every field such as oil, chemical industry, metallurgy, machinery, light industry, traffic, building, electric power, communication, aviation.

The technology of iron and steel hot dip aluminum plating and aluminium alloy is a lot, mainly contains gas protection method and solvent method.The external at present main gas protection method hot dip process of adopting, as Sendzimir method, improvement Sendzimir, U.S. steel connection method etc., this technological equipment investment is big, the processing requirement height, the difficulty of going into operation can not stop production at any time, only is fit to the continuous production in enormous quantities of single product.Domesticly then generally adopt the solvent method hot dip process,, disclose a kind of " hot dipping aluminium plating technology for steel " as the patent No. 99100655.0.Which kind of solvent no matter existing solvent method adopt, at solvent with cover the selection of fused salt and produce and have following problem:

(1) fusing point of lyonium salt film will be lower than the fusing point of plating bath, so the selection of solvent composition is relatively harsher;

(2) the easy moisture absorption of lyonium salt film, palpus thorough drying before the plating, otherwise easily produce plating leakage and pin hole, diminish surface quality and corrosion resisting property;

(3) solvent valency height, in addition expensive, and the villiaumite component is toxic;

The fused salt of plating bath surface coverage is easily aging when (4) producing, and fusing point rises;

(5) the incidental fused salt in plating back cleaning workpiece surface is relatively more difficult.

Summary of the invention

The objective of the invention is to overcome above-mentioned the deficiencies in the prior art part, a kind of deactivation method hot dip aluminum plating and aluminium alloy technology are provided, adopt passivation film to handle the solvent that replaces the solvent method hot dip process and help plating to handle.

The objective of the invention is to realize by following technical scheme:

A kind of deactivation method hot dip aluminum plating and aluminium alloy technology comprise

(1) eliminates the grease of workpiece surface and carry out pickling;

(2) will carry out pre-film by passivator solution through the workpiece of pickled surface cleaning handles, passivator solution is by 0.2～5% chromium trioxide, 0.05～3% high manganese carbon potassium, 0.05～6% Sodium Nitrite and water are formulated, or by 0.2～5% chromium trioxide, 0.05～3% potassium permanganate and water are formulated, or by 0.2～5% chromium trioxide, 0.05～6% Sodium Nitrite and water are formulated, or by 0.05～3% potassium permanganate, 0.05～6% Sodium Nitrite and water are formulated, the component concentration of above-mentioned passivator solution is the quality percentage composition;

(3) dry up, the workpiece of preheating after handling through passivation film;

(4) workpiece is immersed hot dip process in aluminium plating bath or the aluminium alloy plating bath.

Below the present invention is described in further detail.

Remove grease and adopt electrochemical deoiling or heating oil removing.The workpiece surface greasy dirt adopts electrochemical deoiling more after a little while, and degreasing fluid is made up of 20～25%NaOH and a small amount of cleaning agent, and removing oil temperature is 80～100 ℃, and the oil removing time is generally 15～20min.Surface and oil contaminant adopts the heating oil removing more for a long time, and workpiece is placed 400～500 ℃ process furnace, insulation 15～25min.Ability pickling after workpiece behind the electrochemical deoiling wants water to wash, and the workpiece after the heating oil removing can directly carry out pickling.

Earlier with 20～25%H ₂SO ₄The pickle solution that adds a small amount of inhibiter is at 70～80 ℃ of following pickling 15～20min, puts into 2～5% dilute hydrochloric acid solution after the washing again and at room temperature soaks somewhat and plant.Earlier can improve pickling efficient with the heating sulfuric acid washing, and the volatile disadvantage of hydrochloric acid when avoiding sulfuric acid and mixed in hydrochloric acid to heat pickling.The residual indissoluble molysite of workpiece surface is removed with the dilute hydrochloric acid soaking at room temperature in the back, occurs local plating leakage or empty plating phenomenon when avoiding hot dip process.

Carrying out passivation film after the workpiece pickling handles.Passivator solution can be by 0.2～5% chromium trioxide CrO ₃, 0.05～3% high manganese carbon potassium K ₂MnO ₄, 0.05～6% Sodium Nitrite NaNO ₂Formulated with water; Or by 0.2～5% chromium trioxide CrO ₃, 0.05～3% high manganese carbon potassium K ₂MnO ₄Formulated with water; Or by 0.2～5% chromium trioxide CrO ₃, 0.05～6% Sodium Nitrite NaNO ₂Formulated with water; Or by 0.05～3% high manganese carbon potassium K ₂MnO ₄, 0.05～6% Sodium Nitrite NaNO ₂Formulated with water.The component concentration of above-mentioned passivator solution is the quality percentage composition.During obtain solution, the chromium trioxide that can be dissolved in water earlier adds potassium permanganate then, and Sodium Nitrite is dissolved in the heated and stirred dissolving at last.

When the passivator solution that uses the present invention to prepare carries out Passivation Treatment to workpiece, need not the solution heating, at room temperature, the treatment time can both obtain evenly and easily by the Z 250 Fe of aluminium reducing at 0.5～5 minute ₃O ₄Film.For saving time, when passivator solution concentration was high, the treatment time was taken off limit.If workpiece will spread aftertreatment after the hot dip process, need not washing after passivation film is handled and directly dry up.But the passivator solution prolonged preservation and the use that prepare.Can not obtain satisfiedly when helping the plating effect if use after for some time because of concentration reduces, can be added to then and stir in the old passivator solution and can re-use by the passivator solution of above-mentioned process for preparation with the distilled water compounding high concentration.

The preheating temperature of workpiece is advisable with 100～250 ℃ before the hot dip process.In this temperature range, even longly also Fe can not occur warm up time ₃O ₄To Fe ₂O ₃Transformation.If preheating temperature surpasses 250 ℃, workpiece surface will become pale bluish green, and Fe takes place ₃O ₄To Fe ₂O ₃Transformation, make workpiece the plating leakage phenomenon when the hot dip process aluminum or aluminum alloy, occur.

Deactivation method hot dip aluminum plating liquid temp provided by the invention is 700～800 ℃, and the hot dipping time is 3～10 minutes.The top layer of workpiece after the hot dip aluminum plating is an aluminium lamination, and thick about 40～70 μ m have one deck ferro-aluminium layer between steel substrate and the aluminium lamination, and it is thick to be 60～120 μ m.

Among the present invention, described aluminium alloy can be aluminum silicon alloy, aluminium-zinc alloy or aluminum titanium alloy etc.

Hot dip aluminum-silicon plated liquid temp is 680～780 ℃, and the hot dipping time is 5～12 minutes.Workpiece top layer in hot dip aluminum-silicon plated back is the aluminum silicon alloy layer, and thickness is 30～60 μ m, and the ferro-aluminium layer thickness between steel substrate and the aluminum silicon alloy layer is 25～70 μ m.

Hot dip aluminum plating zinc liquid temperature is 640～730 ℃, and the hot dipping time is 7～15 minutes.

Behind the hot dip process aluminum or aluminum alloy,, can carry out different plating aftertreatments according to requirement to the workpiece different performance.Heat-resisting and anti-oxidant demanding workpiece is spread aftertreatment, and treatment temp is 850～1000 ℃, and be 2～5h diffusion time.Corrosion-resistant piece is carried out surface oxidation or polished finish, to strengthen its visual appearance and solidity to corrosion.

Compared with prior art, the present invention has following advantage:

(1) pre-film treatment effect is good, is difficult for transpassivation, and gained coating is smooth smooth, free of pinholes and plating leakage defective;

(2) passivator is easily prepared, and is difficult for wearing out, and places duration, and is reusable;

(3) technical process is simple, and is in industrial easy enforcement, easy and simple to handle;

(4) cost is low.

Embodiment

Embodiment 1. carbon steel Q235,760 * 13 * 1.5mm.Use by 20%NaOH and 0.5%Na ₂CO ₃The 90 ℃ of following oil removing 20min of solution that form.Use 20%H ₂SO ₄The solution that adds a small amount of inhibiter is at 70 ℃ of following pickling 15min, and washing is put into 3% dilute hydrochloric acid liquid and soaked 5min, washing.Immerse passivator solution (0.4%CrO ₃+ 0.1%K ₂MnO ₄+ 0.4%NaNO ₂+ water) in, handle 2min under the room temperature, washing dries up.150 ℃ of following preheating insulation 15min.Immerse in 730 ℃ the fine aluminium plating bath and be incubated 5min, the pulling speed of coming out of the stove is 6m/min, and air cooling can obtain smooth smooth, no plating leakage, not have the aluminium coat of empty plating.Coating total thickness 132 μ m, wherein master alloy bed thickness 78 μ m.

Embodiment 2. ironcastings, 80 * 35 * 5mm, its chemical ingredients is 3.24%C, 1.82%Si, 1.01%Mn, 0.06%P, 0.08%S, cast(ing) surface is through sandblasting.100 ℃ of following oil removing 15min of the aqueous solution with 20%NaOH.Use 25%H ₂SO ₄The solution that adds a small amount of inhibiter is at 70 ℃ of following pickling 10min, puts into 3% dilute hydrochloric acid liquid after the washing and soaks 5min, washing.With passivator solution (2%CrO ₃+ 0.3%NaNO ₂+ water), handle 3min under the room temperature, dry up.At 160 ℃ of following preheating insulation 15min, immerse then in 760 ℃ the fine aluminium plating bath and be incubated 7min, the pulling speed of coming out of the stove is 4.5m/min.Coating total thickness 116 μ m, wherein master alloy bed thickness 62 μ m.

Embodiment 3. Oil Tube Steel 50Mn, φ 60 * 5 * 110mm.Press embodiment 1 identical method oil removing and pickling.With passivator solution (1.5%CrO ₃+ 0.2%K ₂MnO ₄+ water), handle 1.5min under the room temperature, washing dries up.180 ℃ of following preheating insulation 20min.Immerse in 780 ℃ aluminum silicon alloy (siliceous 3%) plating bath and be incubated 10min, the pulling speed of coming out of the stove is 7.5m/min.Gained coating light, no plating leakage.Coating total thickness 106 μ m, wherein master alloy bed thickness 53 μ m.

Embodiment 4. carbon steels 20,76 * 30 * 1.5mm.Press embodiment 1 identical method oil removing and pickling.With passivator solution (3%CrO ₃+ 0.05K ₂MnO ₄+ 0.1%NaNO ₂+ water) at room temperature handle 3.5min, washing dries up.150 ℃ of following preheating insulation 13min.Immerse in 690 ℃ aluminium-zinc alloy (the containing zinc 45%) plating bath and be incubated 12min, promote the back air cooling, speed is 5m/min, promptly get smooth smooth, no plating leakage, does not have the al-zn alloy coating that void is plated.Coating total thickness 78 μ m, wherein master alloy bed thickness 31 μ m.

Embodiment 5. stainless steel 1cr18Ni9Ti, 70 * 30 * 1mm.Press embodiment 1 identical method oil removing and pickling.With passivator solution (4.5%CrO ₃+ 0.2K ₂MnO ₄+ 1%NaNO ₂+ water) at room temperature handle 1min, washing dries up.200 ℃ of following preheating insulation 10min.Immerse in 800 ℃ aluminum titanium alloy (titaniferous 4%) plating bath and be incubated 3min, promote the back air cooling, speed is 7.5m/min, promptly get smooth smooth, no plating leakage, does not have the aluminum titanium alloy coating that void is plated.Coating total thickness 98 μ m, wherein master alloy bed thickness 35 μ m.

Claims (2)

1, a kind of deactivation method hot dip aluminum plating and aluminium alloy technology is characterized in that: comprise

(1) eliminates the grease of workpiece surface and carry out pickling;

(2) will carry out pre-film by passivator solution through the workpiece of pickled surface cleaning handles, passivator solution is by 0.2～5% chromium trioxide, 0.05～3% high manganese carbon potassium, 0.05～6% Sodium Nitrite and water are formulated, or by 0.2～5% chromium trioxide, 0.05～3% potassium permanganate and water are formulated, or by 0.2～5% chromium trioxide, 0.05～6% Sodium Nitrite and water are formulated, or by 0.05～3% potassium permanganate, 0.05～6% Sodium Nitrite and water are formulated, the component concentration of above-mentioned passivator solution is the quality percentage composition;

(3) dry up, the workpiece of preheating after handling through passivation film;

(4) workpiece is immersed hot dip process in aluminium plating bath or the aluminium alloy plating bath.

2, deactivation method hot dip aluminum plating according to claim 1 and aluminium alloy technology is characterized in that: described preheating temperature is 100～250 ℃.