JPS61261469A - Rust-preventing treatment for iron and steel product - Google Patents

Abstract

PURPOSE:To obtain products excelling in rust-preventing effect by subjecting un-heat-treated iron and steel products or the ones after surface heat treatment etc. to heat treatment in an atmosphere containing superheated steam of a prescribed temp. and then to dipping into oil. CONSTITUTION:The iron and steel products are subjected to any of surface heat treatment, gas soft nitriding treatment, carburizing treatment and carbonitriding treatment. The above treated iron and steel products or the un-heat-treated ones are allowed to stand in the atmosphere containing superheated steam of 300-600 deg.C for a prescribed period, which are then dipped in oil. Subsequently, if necessary, excess oil adhering to the surface is removed by washing with an oil solvent.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a novel anti-corrosion treatment method for various mechanical parts made of iron that have been subjected to unheated treatment or surface heat treatment, and in particular to foil cylinder pistons for automobile brakes. The present invention relates to a rust prevention treatment method that exhibits extremely good rust prevention performance by treating members to which rust prevention coating cannot be applied, such as releasing materials.

<Conventional technology> Conventionally used methods for rust prevention treatment of steel products include zinc plating for unheated steel products, and a more advanced treatment method is nickel plating. be. These anti-rust treatment methods using chemical treatments are relatively expensive and have a beautiful surface and high commercial value in the initial stage of use, but their anti-rust effects are proportional to the thickness of the treated film, and the anti-rust effects are Larger items had to be expensive.

<Problems to be Solved by the Invention> The present inventor arrived at the present invention in the process of repeated research in order to cope with the severe rust prevention requirements for wheel cylinder piston members of automobile brakes. is a component that is used in places that are not visible to the naked eye, and generates heat due to frictional resistance.
Also, because it is installed exposed close to the road surface,
Although a high level of rust prevention performance is required, only gas soft nitriding or carbonitriding and quenching treatments are required, and high-end products have shifted to hard chrome plating and even chemical nickel plating. However, at present, these rust-preventing effects are still not sufficient.

Means for Solving the Problems> The present invention applies steam treatment, which has conventionally been carried out for the purpose of improving the wear resistance and lubricity of high-speed steel such as tools, to the above-mentioned unheat-treated steel products and surface heat treatment. This is a method in which ordinary steel products are subjected to gas nitrocarburizing, carburizing, or carbonitriding, and then immersed in oil.Steam treatment, which has never been considered as a rust-preventing treatment, achieves significant rust prevention. Discovered that a product with excellent rusting effect could be obtained,
This is the method for rustproofing steel products of the present invention.

That is, the steel product is characterized by being left in a superheated steam atmosphere at about 300 to 600° C. for a predetermined period of time, then immersed in oil, and washed with an oil solvent if necessary.

As mentioned above, the steel products referred to here are unheat-treated products or surface-heat-treated products, and surface-heat-treated products can also be treated by ordinary quench hardening methods, such as carburizing, which generates a hardened layer of martensitic structure on the friction surface. These are steel products that have undergone treatments such as carbonitriding, induction hardening, and flame hardening, as well as soft nitriding, oxynitriding, and sulphonitriding, which produce surfaces with nonmetallic physical properties on the friction surface.

The anticorrosion treatment method of the present invention is a steam treatment that is on the same level as these treatments, and as described above, is a method that originally improves wear resistance. Steam treatment is also called homo treatment, and is usually carried out at 5QO to 600°C in an atmosphere of superheated steam.
9Fe3 is dense on the surface of the steel to be treated and has excellent adhesion to the base material.
The purpose is to generate an O4 film. The temperature of the steam treatment used in the present invention is 300 to 500, which is lower than that of conventional methods.
It is effective even at 0.degree. C., and is particularly advantageous when applied to steel products after carburizing or carbonitriding, since the steam treatment also serves as a tempering step. Approximately 30% in superheated steam
Leave it for a period of 1 minute to 2 hours, take it out, and immerse it in oil or rust preventive. The oil is mineral oil or vegetable oil, and the rust preventive agent is also an oil-based rust preventive oil. By immersing it in oil, the oil penetrates into the oxide film and gives it an excellent gloss.Excess oil adhering to the surface can be wiped off with a rag, or it can be washed with an oil solvent such as Triclean or other surfactant liquid. cleaning, alkaline cleaning, etc.

<Effect> The above is a rust prevention treatment method for steel products.

As shown in the salt spray test examples below, this rust prevention effect is due to Fe3O4, which is dense and forms on the surface of the treated steel and has excellent adhesion to the substrate. However, it is completely unexpected that this far outperforms the chemical nickel plating process.

In other words, it has been discovered that steam treatment, which was conventionally considered only as a means to increase the surface hardness of high-speed steel and improve its wear resistance, has a remarkable rust-preventing effect by the method of the present invention.

<Example> The method for rust prevention treatment of steel products of the present invention will be specifically explained below with reference to Examples.

Example 1 An automobile brake wheel cylinder piston member having a diameter of 19 mm and a height of 38 mm with a constriction in the middle, made of 520C steel and having a diameter of 57 mm after machining.
After gas nitrocarburizing treatment at 0°C for 1.5 hours, steam treatment was performed at 560°C for 1 hour in almost the same manner as for high-speed steel tools. After steam treatment, it was immersed in mineral oil to absorb the oil, and then washed with trichlene to remove the mineral oil adhering to the surface.

The surface condition was a shiny silver-black color, and the black color was not as harsh as that of triiron tetroxide coatings produced by normal alkali treatment, and the coating was dense even with the naked eye. Rust prevention effect is JISZ23
Comparison was made by a salt spray test according to the method described in 71,
Shown in the table.

As a comparative example, only chemical nickel treatment, gas soft nitriding treatment, and triiron tetroxide coating treatment after carbonitriding and quenching were added. The number of samples for each is 4.

Table 1 As is clear from Table 1, according to the rust prevention treatment method for steel products of the present invention, an excellent rust prevention effect is obtained in which nothing resembling rust is found after 24 hours of spraying, whereas others No. 3
As seen in the comparative example of the species, spot rust was observed even with fairly thick nickel plating coatings and gas nitrocarburizing coatings.
In Comparative Example 3, in which carbonitriding and quenching and triiron tetroxide coating were formed in two layers, spot rust of 25% or more occurred, making it completely unusable.

What is even more surprising is that even after 288 hours of salt water spraying, as shown in the bottom column of Table 1, the results of the Examples were 2 out of 4.
There was no abnormality in the test piece of 1, and the remaining 2 test pieces were 1 to 5%.
Comparative Example 1 was stained with spot rust of 5% or more, Comparative Example 2 was stained with spot rust of 25% or more, and Comparative Example 3 had severe corrosion of the base material, making the product unusable. It became intangible.

Note that Comparative Example 3 is a treatment method that has been widely used in the past.

Examples 2 to 4 Automotive brake wheel cylinder piston members similar to those in Example 1 were machined without surface treatment (Example 2), carburized products (Example 3), carbonitrided products (Example 4) (The total thickness of the cured layer is 500 μm in both cases.
) was subjected to steam treatment at 400° C. for 2 hours in the same manner as in Example 1. After steam treatment, the sample was immersed in an oil-based rust preventive manufactured by Idemitsu Kosan for 10 minutes, and then the adhering rust preventive was wiped off with a rag.

Each sample obtained was tested in the same manner as in Example 1 according to JIS Z237.
The rust prevention effect was compared by the salt spray test described in 1, and Examples 2 to 4 of Table 2 shown in Table 2 for 24 hours and 216 hours were found to have rust prevention effects equivalent to or close to Example 1. It was observed that the effect of steam treatment was significant even on untreated products.

<Effects of the Invention> The rust prevention treatment method of the present invention is easy to process and has a low treatment cost, so it is possible to supply inexpensive steel products, and the rust prevention treatment method of the present invention is much more effective than conventionally known rust prevention treatment products. Excellent rust prevention effects can be obtained.

Applicant: Hirozo Mori, Patent Attorney, Sanyo Hydrick Industries Co., Ltd.

Claims (1)

[Scope of Claims] 1. A method for rust prevention treatment of steel products, which comprises leaving the steel products in a superheated steam atmosphere at about 300 to 600° C. for a predetermined period of time, then immersing them in oil, and cleaning with an oil solvent if necessary. 2 The first claim that the steel product is an unheat-treated product
Rust prevention treatment method for steel products as described in section. 3. The method for antirust treatment of steel products according to claim 1, wherein the steel products are surface heat treated products. 4. The method for rust prevention treatment of steel products according to claim 3, wherein the steel products are gas nitrocarburized products. 5. The method for rust prevention treatment of steel products according to claim 3, wherein the steel products are carburized or carbonitrided products.