JPS61177380A - Formation of lubricating film for plastic working - Google Patents

Abstract

PURPOSE:To form a lubricating film having superior seizing resistance on the surface of an Al-base material for plastic working by treating the Al-base material with an aqueous soln. of a specified pH contg. a specified amount each of Na ions and F ions and by applying a lubricant. CONSTITUTION:Sodium hydroxide or potassium hydroxide and hydrofluoric acid are dissolved in water to prepare an aqueous soln. of 1.5-4.0pH contg. 0.02-1.0mol/l Na or K ions and 0.02-2.0mol/l F ions. The surface of an Al-base material for plastic working is degreased and treated with the aqueous soln. at about 40-60 deg.C to form a fluoroaluminate-base film. A lubricant is then applied to the surface of the film. Thus, a lubricating film having superior seizing resistance and lubricant retentivity is formed on the surface of the Al-base material by chemical conversion treatment at a low temp. in a short time.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for forming a lubricating film for plastic working of aluminum and aluminum alloys, and more specifically, a method for forming a lubricating film with excellent seizure resistance on the surface of aluminum and its alloys. Concerning the method of forming.

(Prior Art) Aluminum and aluminum alloys are more ductile than other common metals, so plastic working is relatively easy. However, when performing very strong machining or plastic working on a high-strength aluminum alloy, machining without lubrication will cause seizure between the tool and the material, shortening the tool life and even causing the product to become damaged. The appearance is also defective due to scratches such as galling, so some kind of lubrication is required. Although various methods of lubrication can be considered, the most effective method is to form a film with high seizure resistance on the surface of the material through chemical conversion treatment.

The typical conventional method for chemical conversion treatment of lubricating coatings for plastic working on aluminum-based materials is the silicofluoride method, which performs chemical conversion treatment with a treatment solution containing sodium fluorosilicate and zinc fluoride. Since the film formed by this method lacks sufficient lubricity, it is common to further apply a lubricant 1, such as lubricating oil or stearate, which is a type of fatty acid metal soap, to the surface for plastic working.

(Problems with the prior art) The major disadvantage of the silicofluoride method is that sufficient lubrication performance cannot be obtained if the film is thin, so a thick film is required especially when severe plastic working is performed. However, it is difficult to form a required amount of film on the surface of the material in a short time with good adhesion. In particular, processing such as drilling that requires high processing pressure, long sliding distance, and a large proportion of the exposed surface requires a chemical conversion coating of 6 to 12 g/m. pH is usually 4.
2 to 5.0, it is difficult to form a film of 6 g/W or more even if aluminum-based plastically processed materials are immersed and boiled for a long time, and even if a thick film is obtained, Under such conditions, heating costs increase, and there are also problems with evaporation and replenishment of water in the bath, so it is desired to lower the temperature of the chemical conversion bath and improve the processing speed.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to overcome the drawbacks of the above-mentioned conventional chemical conversion treatment techniques regarding the method of forming a lubricating film for plastic working of aluminum-based materials.

(How to solve the problem) In other words, aluminum-based plastically processed materials.

(1) 0.02 to 1.0 mol of sodium ions or potassium ions and 0.02 mol of fluorine ions per liter of water
After treating with an aqueous solution containing mol to 2.0 mol and having a pH in the range of 1.5 to 4.0 to form a film mainly composed of fluoroaluminate, a lubricant is applied to the surface (hereinafter referred to as the first invention). or (2) 0.02 to 1.0 moles of sodium or potassium ions, 0.02 to 2.0 moles of fluorine ions, and 0.01 to 0.0 moles of zinc ions per 11 moles of water.
After forming a film consisting of fluoroaluminum salt and zinc by treating with an aqueous solution containing 5 mol and having a pH range of 1.5 to 4.0, a step of converting the zinc into a zinc surface is performed (hereinafter referred to as the second invention). As a result, a chemical conversion film with excellent seizure resistance and lubricant retention can be formed on the surface of the aluminum material at a lower temperature and in a shorter time than the conventional method described above, and it also improves bath stability. The present invention was completed based on these findings.

In order to increase the chemical conversion treatment rate in a silicofluoride bath without raising the bath temperature, it is possible to add hydrofluoric acid to the bath to increase the amount of aluminum ions supplied from the material, but as shown in Figure 2. When either sodium salt or potassium salt is used, the weight of the film does not increase, and only the etching of the material becomes more severe. Furthermore, as shown in Figure 3, the same effect occurs when hydrofluoric acid is added to a conventional bath containing zinc ions, and when the amount added is 0.1 mol/fL or more and the pH is lowered to 3 or less. Although the film weight increases, blistering becomes severe and a film with good adhesion cannot be obtained.In this way, it is not possible to obtain a thick film with good adhesion simply by adding hydrofluoric acid to the silicofluoride bath. However, according to the method of the present invention, the kings of alkali metal ions, fluorine ions, and aluminum ions are reacted in a bath, and the surface of the aluminum-based material is coated with anti-seizure properties mainly composed of fluoroaluminate. A chemical conversion film with high lubricant retention and good adhesion can be formed in a short time at a relatively low temperature.For example, as shown in FIG. 1, the chemical conversion treatment speed of the present invention is as follows: Compared to conventional methods, it is possible to lower the bath temperature or shorten the processing time because it is larger even at lower temperatures.

In both the first invention and the second invention, alkali metal ions and fluorine ions are essential in the chemical conversion treatment bath. That is, the treatment bath requires a compound containing an alkali metal salt and fluorine, and in the second invention, a compound containing zinc, and the pH of the bath is adjusted to 1.5 to 4.0 with hydrofluoric acid or the like.
Adjust to.

Specifically, alkali metal hydroxides and carbonate groups.

In addition to fluoride, acidic fluoride, etc., in the second invention, metallic zinc, zinc oxide, zinc hydroxide, zinc carbonate, zinc fluoride, etc. are used as a zinc ion source, and hydrofluoric acid is used to adjust the pH to 7ft7.
In particular, if acidic fluorides of alkali metals and zinc fluoride are used, they are easy to handle because they are solids with low hygroscopicity and have high solubility in water, and the pH of the solution is appropriate. Note that the solution composition is simple in both the first invention and the second invention, and bath management is easy.

As the alkali metal salt in the present invention, sodium salt and potassium salt can be used.

In particular, acidic fluoride baths consisting of only one alkali metal ion are preferred; lithium, rubidium, and cesium salts of other alkali metals are expensive.

It is not economical to apply alkali metal salts other than sodium and potassium to the present invention, and when sodium and potassium salts are mixed, 2Na has a lower solubility than the fluoroaluminium molten salt alone.
A dense film mainly composed of fluoroaluminate, such as A-F6, is formed thinly on the surface of the aluminum material, making it difficult to obtain a sufficient film in the amount required for plastic working, so it is better to use it alone. In particular, when potassium salt is used as an alkali metal salt, fine needle-like crystals are formed on the surface, so the lubricant retention is even better. For example, when lubricating oil is used, lubrication failure due to oil shortage There's nothing to wake up.

Next, the reason for limiting the solution concentration will be described.

The chemical conversion bath used in the method for forming a chemical conversion film for plastic working of aluminum or its alloy in the present invention, in both the first and second inventions, contains 0.02 to 1.0 mol of sodium ions or potassium ions per liter of water. , and contains 0.02 to 2.0 moles of fluorine ions p) 11.5 to
In the second invention, the aqueous solution further contains 0.01 to 0.5 mol of zinc ions, more preferably sodium ions or potassium ions.
os~0.2 mole, 0.1 to 1.0 mole of fluorine ions, and 0.02 to 0.1 mole of zinc ions.

Alkali metal ion of sodium or potassium is 0.0
If the amount of fluorine ions is less than 0.02 mol/i, and the amount of zinc ions is less than 0.01 mol/i, the conversion rate is slow and it takes a long time to obtain the required amount of chemical conversion coating.
On the other hand, at concentrations exceeding 1.0 mol/l of alkali metal ions and 2.0 mol/l of fluorine ions, it is not economical to take the liquid out, and furthermore, when potassium salts are used, Only a thin and dense film of 3A and F6 can be obtained, making it difficult to obtain a thick film. If the zinc ion used in the second invention is less than 0.01 mol/cross, the amount of zinc precipitated is too small, so when treated with an alkali metal soap solution in an attempt to form a zinc soap layer as a lubricant in a subsequent step,
A zinc soap layer with excellent lubricity cannot be produced in sufficient quantity and is ineffective; on the other hand, zinc ions are 0.35 mol/!
2. If it exceeds KZnF: +
It is unsuitable because the precipitates of 'J tend to form and the amount of zinc precipitated on the resulting chemical conversion coating is too large, resulting in poor adhesion of the chemical conversion coating.

The pH of the treatment bath is preferably in the range of 1.5 to 4.0, more preferably in the range of 2.5 to 3.5. If the pH is less than 1.5, the elution rate of aluminum is too high and a film with good adhesion properties is obtained. The fluoroaluminum salt simply precipitates as sludge, as seen in the zinc phosphate method, which is known as a chemical conversion treatment for painting bases on aluminum alloys.
Also.

If the pH is higher than 4.0, the etching rate of aluminum is low, so it is difficult to obtain a thick film in a short time at a low temperature.
Precipitates of No. 3 are likely to form, making the bath unstable, which is also not preferable.

The treatment temperature in the present invention is room temperature to 70°C, preferably 4°C.
The temperature is 0 to 60°C, and it is possible to obtain a sufficient amount of film for plastic working in a shorter time at a lower temperature than the conventional silicofluoride method. Furthermore, since the bath composition is particularly simple, liquid management is easier and stability is superior compared to the zinc phosphate method and the silicide method.

In the chemical conversion treatment step, first, the surface of the aluminum material is degreased with an organic solvent such as trichlorethylene or a general-purpose alkaline degreaser for aluminum materials, and then washed with water. If necessary, etching with hydrofluoric acid or the like is performed to remove the surface maceration layer.The chemical conversion treatment of the present invention is applied.Contact with the treatment solution can be carried out by methods such as spray coating or dipping. By subsequently drying with hot air, unreacted components can be converted into a chemical conversion treatment layer, but drying may be performed after washing with water.

Next, a lubricant is applied and the plastic working process is carried out.The lubricant can be either a liquid lubricant or a solid lubricant such as metal soap. Solid lubricants dispersed in water can also be used. The lubricant can be applied by spraying, brushing, dipping, etc. The treated film of the present invention has a large surface area and has good lubricant retention properties.1 For example, it is impregnated with lubricating oil. However, the amount of lubricating oil can be maintained to provide good lubrication performance. In particular, if a bath containing potassium ions is used, an acicular chemical conversion film will be formed and the lubricant retention will be excellent. Furthermore, in the second invention, since the chemical conversion coating contains metallic zinc, the metallic soap can be firmly attached.

This is because metal soap and zinc chemically react. For example, a material obtained by applying the chemical conversion treatment of the second invention to a 20 g/aqueous solution of sodium stearate is heated to 80 to 90°C for 10 min.
If soaked for ~15 minutes, sodium stearate and zinc can react to produce zinc stearate.

The amount of zinc stearate deposited is 2-3 g/m'. Aluminum-based materials that have been surface-treated in this way have excellent lubricity and seizure resistance, so they can be pulled out of an aqueous solution and dried as they are, allowing unreacted sodium stearate to adhere to them. Strong machining can be performed during machining.

Although the formation mechanism of the chemical conversion film is unknown in detail,
First, the oxide film on the surface of the aluminum-based material is destroyed, and aluminum ions, potassium (or sodium) ions, and fluorine ions react chemically to form 2A.
Fluoroaluminum salts such as lF2 (or N 5L3 An Fg ) are generated, and in the second invention, zinc ions in the solution are replaced with aluminum to become metallic zinc, forming a coating layer together with fluoroaluminum salts on the surface of the aluminum-based material. It precipitates as The above reaction is thought to occur when the surface of the aluminum-based material is divided into a 7-node part and a cathode part, and it proceeds in these parts. For example, in the second invention, when a potassium salt is included, in the 7-node part, 2Al → 2Al +6e (1
)2A! Q, 3ゝ+4 ÷ +l0F-→-2 to 2A AC Fs (2) At the cathode part, 3Zn+6e+3Zn (3) Adding the right and left sides of equations (1), (2), and (3) respectively, 3Zn+4 becomes ◆+l0F −+2Ai+3
Zn+2 becomes 2AJLFs. This precipitated Zn is
When treated in a metal soap solution, Zn ions are dissolved and combined with fatty acid ions to form fatty acid zinc salts. It is thought that this makes it firmly held by the fluoroaluminium salt of the underlying chemical conversion coating, forming a lubricating coating with good adhesion to the aluminum-based material.

(Example) Examples of the present invention will be described below with reference to comparative examples.

Example 1 (first invention) Ring compression test piece of aluminum alloy (JIS standard A2014) (size outer diameter 40 mm, inner diameter 20 mm)
, height 10 mm) were prepared, subjected to chemical conversion treatment for 4 minutes under the conditions shown in Table 1, and dried with warm air. A small amount of paraffin-based additive-free mineral oil (viscosity: a3 cst at 40° C.) was brushed onto the treated film, and the remaining oil was wiped off with paper rag. After that, a ring compression test was performed at room temperature (the press used was a 250t nut joint press (55Spm), and the platen was a 5KH51
Steel is finished to a surface roughness of Rmax=IJLm. Before the test, the platen surface was degreased with acetone, and the test was conducted with the compressibility constant at 30%. ) to investigate the lubricity. As a comparative example, there is a case (C-5) in which chemical conversion treatment was performed for 5 minutes in a bath containing sodium silicofluoride and zinc fluoride (Patent No. 173530) using a conventional method, and a case in which chemical conversion treatment was performed for 4 minutes in a bath under conditions different from the conditions of the present invention. Shows the case of chemical conversion treatment (C-1~
C-4) As shown in Table 1, according to the present invention, a film with excellent anti-seizure performance can be obtained at a relatively low temperature in a short time. Note that under the conditions of the present invention, the film did not peel or fall off from the ring test piece during the compression test, and the adhesion of the film was good. Furthermore, the film formed in the bath containing potassium ions had particularly good oil retention. On the other hand, if the conditions of the present invention are not met, it becomes difficult to obtain a thick film, or the T:1 of the film becomes difficult to obtain.
As a result of the lubrication test, seizure occurred and the lubrication performance was insufficient.

Nao implementation number 1 is Na3 A! ;LF6.2 is 2
It was confirmed by X-ray diffraction that a film consisting of a fluoroaluminium salt containing AfLFs .H2O as a main component was formed.

(Left below) Example 2 (Second Invention) Several ring compression test pieces similar to those in Example 1 were prepared and subjected to chemical conversion treatment for 4 minutes under the conditions shown in Table 2. From the X-ray diffraction results of the film, Na5A! ;LF6 +Z
It was confirmed that 2AIF5''H20+Zn was produced in No.n and 2. Thereafter, each sample was immersed in an aqueous solution containing 20 g of sodium stearate at 90.degree. C. for 10 minutes.

It was dried with warm air and subjected to X-ray diffraction.

Zn in the film reacted with sodium stearate, and the adhesion was good. The lubricity of each test piece at room temperature was examined under the same conditions as in Example 1. As a comparative example, the bath described in Japanese Patent No. 173530 (sodium fluorosilicate 0.14 mol/l).

(C-5) which was boiled for 5 minutes with 0.02 mol of zinc fluoride/further), and chemically treated (C-1 to C-4) for 4 minutes in a bath with conditions different from the conditions of the present invention. Afterwards, a ring compression test was performed on the specimens immersed in an aqueous sodium stearate solution to compare the lubrication performance. As shown in Table 2: According to the method of the present invention, a film with high seizure resistance is formed at a lower temperature and in a shorter time than in the comparative example. Further, during the compression test, the film did not peel off or fall off from the ring test surface, and the adhesion of the film was good. - If the strength wood invention conditions are not met, it will be difficult to obtain a thick film or the adhesion of the film will be poor.
As a result of the lubrication test, seizure occurred and the lubricity was poor.

(The following is a blank space) (Effects of the Invention) The method for forming a lubricating film for plastic working of aluminum-based materials of the present invention includes only sodium ions or potassium ions and fluorine ions in the first invention, and in the second invention, it is further applied to the first invention. Since a chemical conversion treatment bath with a simple composition containing only zinc ions is used, bath management is easier than with the complicated bath composition of the conventional zinc phosphate method. has a long life. In addition, in the conventional silicofluoride bath, it is difficult to obtain a film with good adhesion of Log/rn' or higher even after long boiling treatment.
Since the bath of the present invention has a low pH of 1.5 to 4.0, it has a strong film-forming effect, and it can be
A film of 0 g/m'' or more can be obtained with good adhesion. Therefore,
It is possible to reduce energy costs and processing time. Furthermore, the film mainly composed of fluoroaluminate obtained by the present invention has good lubricant retention properties, so it prevents the lubricant from dissipating due to the habitual deformation of aluminum-based materials, and prevents lubrication failure due to oil depletion. There is little risk of it happening.

Furthermore, the chemical conversion coating itself prevents direct contact between the aluminum-based material and the mold, and exhibits the effect of reducing seizure.

Furthermore, since the chemical conversion coating containing metal soap has a large surface area, it also has excellent retention of metal soap.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the temperature dependence of the film weight produced by the method of the present invention and the conventional method, Figure 2 is a diagram showing the effect of adding HF to the silicofluoride bath, and Figure 3 is a diagram showing the conventional method (patented method). No. 1735
30) is a diagram showing the effect of adding HF to the bath. Applicant Toyota Central Research Institute Co., Ltd. Representative Patent Attorney Asa Kato Figure 2 HF addition amount (sol/L) Figure 3 HF knife a)

Claims (10)

[Claims] (1) 0.02 to 1.0 mol of sodium ions or potassium ions and 0.02 mol of fluorine ions per liter of water
An aqueous solution with a pH range of 1.5 to 4.0 containing ~2.0 mol (
A method for forming a lubricating film for plastic working of aluminum or an aluminum alloy, which comprises applying a lubricant to the surface after forming a film mainly composed of fluoroaluminum salt by treatment in A). (2) The method for forming a lubricating film for plastic working of aluminum or aluminum alloy according to claim 1, wherein the aqueous solution (A) is an aqueous solution of sodium hydroxide and hydrofluoric acid. (3) The method for forming a lubricating film for plastic working of aluminum or aluminum alloy according to claim 1, wherein the aqueous solution (A) is an aqueous solution of potassium hydroxide and hydrofluoric acid. (4) The method for forming a lubricating film for plastic working of aluminum or aluminum alloy according to claim 1, wherein the aqueous solution (A) is an aqueous solution of acidic sodium fluoride. (5) The method for forming a lubricating film for plastic working of aluminum or aluminum alloy according to claim 1, wherein the aqueous solution (A) is an aqueous solution of acidic potassium fluoride. (6) 0.02 to 1.0 mol of sodium ions or potassium ions and 0.02 mol of fluorine ions per liter of water
After forming a film consisting of fluoroaluminate and zinc by treating with an aqueous solution (B) containing ~2.0 mol and 0.01 to 0.5 mol of zinc ions and having a pH range of 1.5 to 4.0,
A method for forming a lubricating film for plastic working of aluminum or aluminum alloy, which comprises performing a step of converting the zinc into zinc soap. (7) Claim 6, wherein the aqueous solution (B) is an aqueous solution of sodium hydroxide, hydrofluoric acid, and zinc oxide.
A method for forming a lubricating film for plastic working of aluminum or aluminum alloy as described in 2. (8) The method for forming a lubricating film for plastic working of aluminum or aluminum alloy according to claim 6, wherein the aqueous solution (B) is an aqueous solution of potassium hydroxide, hydrofluoric acid, and zinc oxide. (9) The method for forming a lubricating film for plastic working of aluminum or aluminum alloy according to claim 6, wherein the aqueous solution (B) is an aqueous solution of acidic sodium fluoride and zinc fluoride. (10) The method for forming a lubricating film for plastic working of aluminum or aluminum alloy according to claim 6, wherein the aqueous solution (B) is an aqueous solution of acidic potassium fluoride and zinc fluoride.