JPS6144194A - Manufacture of heat exchange medium made of friction drive type extruded material - Google Patents

Abstract

PURPOSE:To manufacture a heat exchange medium having superior corrosion resistance by forming a zinc film on the surface of a friction drive type extruded Al material by galvanizing, working mechanically the material, and heat treating it at a specified atmospheric temp. CONSTITUTION:The surface of a friction drive type extruded Al or Al alloy material is galvanized in a bath contg. about 5-110g/l ZnO and about 45- 500g/l NaOH to form a zinc film by 7-20g/m<2>. At this time, the temp. of the bath is about 20-60 deg.C, the current density is about 2-4A/dm<2>, and the electrolytic time is about 1-2min. The galvanized material is mechanically worked to the prescribed shape of a heat exchange medium and heat treated at an atmospheric temp. between the m.p. of the zinc film and the m.p. of the material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a friction-driven extruded material heat exchange medium for use in members such as tubes for heat exchangers for air conditioners of automobiles, etc.

[Prior art and its problems]

For example, members such as the tubes of heat exchangers for air conditioners in automobiles etc. are not used in severely corrosive environments, and the aluminum or aluminum alloy (referred to as aluminum material) that is used in the tubes has corrosion resistance, especially pitting corrosion resistance. is required.

As a means to meet these requirements, it has been proposed to form a zinc layer on the surface of aluminum materials.
For example, an aluminum material is immersed in a zincate solution prepared by dissolving a zinc oxide can into a caustic nodder, and an a-conversion reaction with zinc occurs as the aluminum is eluted (thus, zinc is precipitated on the surface of the aluminum material). It has been proposed to form a zinc film by the kimetsugi method or the molten zinc deposition method, and then heat-treat it to form a zinc expansion layer. However, it is difficult to form such a lead expansion layer. Although this improves the corrosion resistance of aluminum materials, when we manufacture heat exchange media such as heat exchanger tubes using aluminum materials that have been surface-treated in this way, we find that the surface-treated aluminum materials before manufacturing the heat exchange media No superior corrosion resistance is observed, i.e. mechanical processing means to the heat exchange medium,
For example, it has been found that the zinc layer on the aluminum surface peels off or is missing due to bending or cutting.
For this reason, it was found that the corrosion resistance after heat treatment deteriorated.

[Disclosure of the invention]

As a result of continuing various studies to solve the above-mentioned drawbacks, the present inventor used an extruded material of aluminum or aluminum alloy 1 extruded using a friction-driven extrusion device Ut as a material for the heat exchange medium, and After forming a zinc film on the surface of the material by electroplating with a basic aqueous solution containing zinc oxide, a specified machining process such as bending or cutting is performed to form the extruded material with the zinc film formed on it. It has been found that a heat exchange medium having a shape that is then heat-treated in an atmosphere above the melting point of the zinc coating and below the melting point of the extruded material has extremely high corrosion resistance6.

For example, a channel is formed between the groove surface of a drive wheel having a groove on its outer circumferential surface and the inner wall surface of a fixed shoe block that is engaged with a part of the outer circumference of the drive wheel. The rear end in the driving direction is closed, and near the rear end there is provided an extrusion chamber that communicates with the υ pipe in the perpendicular direction, for example, and an extrusion die is installed therein. Continuously manufactured aluminum or aluminum alloy tube coil materials, i.e. friction-driven extrusions, which have been fully formed with zinc skin III using electroplating means, are superior to other extrusions. In addition to those in which the zinc coating is formed by electroplating, it is also possible to form the zinc coating by other means such as displacement treatment or hot-dip zinc deposition on friction-driven extruded materials. This is because the adhesion of the film is excellent, and it has been found that the zinc film is not easily damaged by machining of the heat exchange medium, which is performed after the zinc film is formed and before heat treatment.

Furthermore, the step of forming a zinc film by electroplating before machining a heat exchange medium can be performed, for example, by electroplating after machining a friction-driven extruded material to form a heat exchange medium of a predetermined shape. Forming a zinc film by plating means is easier to form than by other processes, and a zinc film with a uniform thickness can be formed, resulting in a heat exchange body with better corrosion resistance. In addition, the processing process is simple and can be performed at low cost.

In addition, after being machined into the shape of a heat exchange medium, heat! l! !
The process of processing and processing is more effective than the process of heat treatment and then machining to produce a heat exchange medium.
The appearance is uniform regardless of the location, and the corrosion resistance is uniform and exhibits excellent corrosion resistance physically.

f・~1, friction j Although it is difficult to use electroplating means when forming a zinc film on the surface of the imaginary extruded material, π1
．． From the viewpoint of zinc film adhesion, it is best to immerse the abrasive extruded material in the same -IFL bath as the electrometallurgical solution for about 5 to 30 seconds before electroplating, and then electroplate the surface without washing it with water. It's very desirable.

This zinc substitution treatment, for example, reduces ZnO to about 5 to 110
g/I-, more preferably about 50 to 100 gl, and its 47S combined caustic soda concentration is about 45 to 500 g/l depending on the Zn0719 degree.
Baths adjusted to remove water, Rimari Na, ZnO snow, Na
It is preferable to use a bath composed of OH1Na/LLOr (aluminum is dissolved during zinc substitution and NaAt0 is present.This ZnO-concentrated and NaOH
The reason why 1 iF 1 degree was set as a trap as described above is because if the Znofi degree and NaOH concentration are too low or too high, the adhesion of the zinc film is rather lower than that without the zinc replacement treatment. Further, from the viewpoint of corrosion resistance, it is desirable that metal salts such as copper, nickel, and iron are not contained in the zinc 1 and conversion treatment bath. In addition, it is preferable that it does not contain cyanide ions, and furthermore, organic amine compounds such as triethanolamine and EDTA,
It is also preferable that basic compounds such as tartrate, KOH, and Ca(OH)j are not included.

Further, the bath temperature during the zinc substitution treatment is desirably 20 to 60°C, more preferably about 20 to 40°C, particularly preferably about 30°C. That is, if the bath temperature is too high, the adhesion will decrease, and if the bath temperature is too low, the dissolution will be slow and the improvement in the adhesion will be small.

Moreover, the zinc substitution reaction time is carried out as a base treatment when conventionally electroplating copper, nickel, tin, chromium, and silver on the surface of an aluminum material! II! Unlike the case of lead substitution treatment, it is as short as about 5 to 30 seconds, in other words, it does not require electroplating after 9 rows from a state where the substitution reaction is urgent to saturation. The zinc displacement reaction is terminated before the condition is reached.

And 1 zinc! ! After the replacement treatment, electroplating is performed in a basic zinc plating bath, and this electroplating bath is carried out using the aforementioned zinc replacement treatment bath in which zinc oxide is dissolved in caustic powder.

As for electrolytic conditions, if the current density is too high, the adhesion will decrease and the plating coverage will decrease, and conversely, if the current density is too high, the plating coverage will decrease.
f. If the density is too low, it will take too much time, so the adhesion is uniform 1! From the viewpoints of adhesion and economy, it is desirable to use a current of about 2 to 4 people/day per day, and the electrolysis time is usually about 1 to 2 minutes, and the bath temperature is about 2 to 4 people/day. In view of machining and corrosion resistance, it is desirable that the thickness of the zinc skin obtained in this manner be approximately 7 to 20 g and 7 m thick.

In addition, during the electroplating process, the plating bath is subjected to ultrasonic waves, preferably about 15 to 50K) Iz, more preferably about 20K)
Applying ultrasonic waves of ~30 KHz is desirable because it improves adhesion.

[Example 1] A friction-driven extruded coil material was produced from an aluminum material using a friction m@m extrusion device, and the friction-driven extruded coil material was not subjected to degreasing or oxide film removal treatment (Zn01
00g/L, composition bath of NaOH 350g/L, temperature 3
Electroplating is performed under the conditions of 0° C., current density of 2 to 5 A/d, and time of 60 to 120 seconds to form a zinc film on the surface with a thickness of about 7 to 10 g/d.

After forming the above-mentioned zinc film, predetermined machining such as cutting and bending was performed, and the height was 321 m, height 5 + wgI.
7) JIS A1050 car cooler conditioner/? −
A multi-hole flat tube is formed into a heat exchange medium having a predetermined shape.

Thereafter, the heat exchange medium of a predetermined shape was heat-treated in a furnace with an atmosphere temperature of 600°C for 2 minutes at a tip convergence of 600°C, resulting in a surface zinc concentration of 3 to 4% and a zinc diffusion depth of approximately 100 to 450.
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The manufacturing yield of the heat exchange medium obtained as described above,
Table 1 shows the adhesion and corrosion resistance of the zinc coating.

The film thickness of the zinc film was calculated by reducing the film removal after immersion in 30Wt HNOIK.
Depending on the degree of peeling, the case where there is no peeling at all is marked ◎, the case with slight peeling is marked 1-0, and the case where there is a lot of peeling is marked x. Items with no pitting corrosion observed after testing are marked with ◎.
Items with slight pitting corrosion are marked with an O mark, and items with a large amount of pitting corrosion are marked with an x mark.

Table 1 [Example 2] During the electroplating process in Example 1, 10
Do not use 20 KHz ultrasonic waves with 0W output.
A heat exchange medium is produced in exactly the same manner, except that electroplating is performed to form a zinc coating on the surface with a thickness of about 7 to 101 m.

The production yield, adhesion and corrosion resistance of the zinc coating of the thus obtained heat exchange medium were investigated as shown in Table 2.

In Table 2, the electroplating conditions and heat treatment conditions are exactly the same as in Table 1, so these conditions are omitted.

Responsibility 2 (Example 3) 1 g before the electroplating treatment in Example 1! Friction drive type extruded coil material n O70-100 g/l, NaOH3
Zinc replacement treatment is performed in a bath with a composition of 50 to 370 g/L at a temperature of 30°C for 5 to 30 seconds, and then electroplating process 1 machining and heat treatment are carried out to achieve a surface zinc Q degree of 3 to 3. 4%, zinc diffusion depth of about 100-150 μm in 32 dews, height of 5 parrots JIS A1050 g and Jl
, 9 A heat exchange medium is manufactured by forming a condenser multi-hole flat tube made of A3003 into a predetermined shape.

The production yield, adhesion and corrosion resistance of the zinc coating of the thus obtained heat exchange medium were examined and the results are shown in Table 3.

[Comparative Example 1] A heat exchange medium was produced in exactly the same manner as in Example 1, except that a zinc coating was formed only by a zinc substitution treatment instead of the treatment in an electric bath.

Table 4 shows the manufacturing procedure of the heat exchange medium thus obtained, and the adhesion and corrosion resistance of the zinc coating.

Table 4 [Comparative Example 2] A heat exchange medium was produced using a normal hot extrusion material (extrusion @ [480°C)] in place of the friction-driven extruded coil material in Example 1 and following exactly the same process f and diameter. do.

Manufacturing yield of heat exchange medium thus obtained, 11
U jf) Examining the film density and corrosion resistance, Table 5 shows
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Claims (1)

[Claims] After electroplating the surface of a friction-pivotal extruded material made of aluminum or aluminum alloy with a basic aqueous solution containing zinc oxide to form a zinc film, it is machined into the shape of a predetermined heat exchange medium, and then A method for producing a friction-driven extruded material heat exchange medium, characterized in that heat treatment is carried out at an ambient temperature that is higher than the melting point of the zinc coating and lower than the melting point of the friction-driven extruded material.