JPH08319591A - Rust-preventing method of stainless steel product - Google Patents

Abstract

PURPOSE: To effectively suppress the rust generation of a stainless steel by cleaning a stainless steel product with an alkali and nitric acid to remove a cutting oil, dipping into a caustic alkali after quenching and after that, applying a rust preventive oil. CONSTITUTION: The cutting-worked stainless steel product is cleaned with the alkali and nitric acid in a water vessel to remove the sticking cutting oil and cutting oil seizured material. Next, after the product is washed and dehydrated, the surface skin stuck to the surface of the stainless steel and composed mainly of iron oxide is dissolved and removed by quenching. Next, after being washed and dehydrated, the product is dipped into 0.05-1g/l caustic alkali aq. solution for 12-20hr. After the product is washed and dehydrated, a rust preventive oil is applied. The alkali portion is infiltrated to the surface of the stainless steel by the dipping treatment of the 3rd process with the alkali aq. solution to form a rust preventive coating film. As a result, the stainless steel product coated with the rust preventive oil is easily prevented from rusting even in an inferior environment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of rustproofing stainless steel products, particularly small stainless steel products such as stainless steel screws.

[0002]

2. Description of the Related Art A stainless material is cut into a desired shape by a cutting tool under the injection of cutting oil. Cutting waste adheres to the cutting surface, and due to the heat generated by cutting, the cutting oil and stainless steel material are seized and turned black. In particular, screws made of stainless steel have cutting dust and cutting oil accumulated in the thread grooves. This stainless steel screw product varies in size, but for example, about 100 pieces are put in a barrel made of a stainless steel basket and alkali-cleaned for about 30 minutes in an alkaline solution at 40 to 80 ° C. Cutting waste and cutting oil left in the groove due to alkali cleaning are removed by washing. Next, it is washed with water to remove the alkali content, and then pickled with about 10% nitric acid. Washing with water is performed to prevent the alkali and the acid from directly mixing. The pickling with nitric acid dissolves and removes the baking products formed by baking the stainless steel and cutting oil formed on the stainless steel surface. Nitric acid is removed by washing with water and dehydrated. The first process is completed by the above cleaning process.

After the first step, the product is taken out of the barrel and hardened by quenching at 850 ° C., for example. The hardened screw is re-inserted into the barrel and treated in a second step of pickling with nitric acid to remove oxides generated by hardening, washing with nitric acid, and centrifugal dehydration.

To prevent rust, the screw that has undergone the second step is immersed in rust-preventing oil and is processed into a product through a step of removing excess oil by a centrifugal dehydrator.

[0005]

The products according to the above-mentioned prior art have a problem that rust is generated when used for a long time, especially near the coast, depending on environmental conditions.

It is an object of the present invention to provide a method of anticorrosion of stainless steel products which solves the above mentioned problems and which makes it possible to obtain products which are much less rusty than those of the prior art.

[0007]

SUMMARY OF THE INVENTION The present invention comprises a first step of removing cutting oil by alkali cleaning and nitric acid cleaning, and a second step of removing cutting oil-baked material, a second step of quenching, and a caustic alkaline cleaning step. 0.05-1 g / l, preferably 0.1
Anticorrosion of stainless steel products, characterized by treating a stainless steel product cut by a third step of immersing in a 0.5 g / l aqueous solution for 12 to 20 hours and a fourth step of applying rust preventive oil. Is the way. Further, the present invention is characterized in that the cut stainless steel product is a stainless steel screw product.

[0008]

According to the present invention, the cut stainless steel product has a third step, which is the second step conventionally used, which is 0.05 to 1 g / l, preferably 0.1 to 1 g / l of caustic alkali. Immerse in ca. 0.5 g / l caustic, for example sodium hydroxide solution, for 12 to 20 hours. It is considered that during the immersion in the dilute caustic solution, the alkali content permeates the surface of the stainless steel to form an anticorrosive film. As a result, the stainless steel product which has finished the fourth step of applying the rust preventive oil does not easily rust even in a bad environment.

When the concentration of caustic is 0.05 g / l or less, the effect of addition is not effective, and when it is 1 g / l or more, the effect is not changed, and the concentration range is used for the purpose of saving drug cost and safety To be Also, after putting the stainless steel product in the barrel, at first slowly in the caustic solution tank,
It is preferable to rotate for ˜2 hours, and especially when many small products are put in the same barrel, it is preferable to lengthen the rotation time. If the immersion time is 12 hours or less, there is no effect, and if it is 20 hours or more, the effect remains unchanged. Generally, when many small products are put in the same barrel, they are soaked in high concentration liquid for a long time in the above range, and when a small number of small products are put in the same barrel, they are soaked in low concentration liquid for a short time. .

[0010]

EXAMPLE 100 100 slotted cheese screws made of SUS410 stainless steel and having a screw diameter of 4.7 mm and a length of 20 mm are placed in a barrel 10 shown in FIG. Barrel 1
No. 0 has a flange portion 11 at the upper portion and a main body 12 made of a stainless steel net having a cylindrical bottom at the lower portion. The barrel 10 is vertically moved or slowly rotated with the suspending tool 13 attached to the flange 11.
The barrel 10 is attached to a centrifugal dehydrator (not shown) with the suspenders 13 removed, and is rotated at high speed to remove liquid.

FIG. 2 is a block diagram of the first step. The screw put in barrel 10 in step a1 is 0.1g
In a sodium hydroxide solution bath heated to 70 ° C./l,
30 while being slowly rotated by the hanger 13
Soak for a minute. As a result, the cutting debris and cutting oil adhering to the screw are washed away. At step a2, the barrel 10 is lifted from the sodium hydroxide solution tank and immersed in the water tank for 2 minutes while slowly rotating. At step a3, the barrel 10 is mounted on the centrifugal dehydrator, the suspenders 13 are removed, and the barrel 10 is centrifugally dehydrated. In step a4, it is again immersed in the 10% nitric acid solution tank by the suspending tool 13 for 2 minutes while slowly rotating to dissolve and remove the burned material seized on the screw surface together with the stainless steel on the surface. In step a5, the barrel 10 is lifted from the nitric acid tank and immersed in the water tank for 1 minute while slowly rotating. In step a6, the barrel 10 is mounted on the centrifugal dehydrator, the suspenders 13 are removed, and the barrel 10 is centrifugally dehydrated.
After that, the barrel 10 is taken out from the centrifugal dehydrator, and the screw is taken out by reversing the barrel 10.

Next, the screw moves to the second step of hardening. FIG. 3 is a block diagram of the second step. Step b1
The screws are placed in a furnace at 850 ° C. The heating time varies depending on the size and shape of the product, but in the case of this embodiment, the quenching is completed in about 5 hours. The screw ejected from the heating furnace is cooled to room temperature. In step b2, the screw is put into the barrel 10 again, the hanging tool 13 is attached to the barrel 10, and the barrel is immersed in a 10% nitric acid bath for 3 minutes while slowly rotating to dissolve the skin mainly composed of iron oxide adhered to the stainless steel surface by quenching. Remove. Barrel 1 in step b3
0 is lifted from a nitric acid tank and immersed in a water tank for 1 minute while slowly rotating. At step b4, the barrel 10 is mounted on a centrifugal dehydrator and dehydrated.

Next, the third step newly added in the present invention will be described. FIG. 4 is a block diagram of the third step. Step c
The barrel 10 screwed in 1 is immersed in a 0.1 g / l sodium hydroxide solution bath for 1 hour and a half while slowly rotating. At step c2, the barrel 10 is further 15 in the stationary state.
Immerse in the liquid bath for a period of time. Barrel 10 in step c3
Is withdrawn from the sodium hydroxide bath and immersed in a water bath for 1 minute with slow rotation. At step c4, the barrel 10 is mounted on a centrifugal dehydrator and dehydrated.

Next, the screw enters the fourth step for applying the final rust preventive oil. FIG. 5 is a block diagram of the fourth step. In step d1, the barrel 10 is immersed in a water bath at 70 ° C. for 1 minute while slowly rotating, and the screw is heated to 70 ° C. At step d2, the barrel 10 is mounted on a centrifugal dehydrator and dehydrated. At step d3, the barrel 10 is immersed in an oil tank made of rapeseed oil or the like. At step d4, the barrel 10 is attached to the centrifugal dehydrator to remove excess oil,
The screw product is removed to the outside by inverting the barrel 10.

The products treated by the present invention, the products treated by the conventional method (the products not treated by the third step) and the products in which the immersion time of the caustic alkali solution in the third step is changed are defined in JIS Z 2371. According to 5
Table 1 shows the results of a spray test in which a 1% NaCl solution is sprayed.
Shown in

[0016]

[Table 1]

As a result of conducting the salt spray test on large and small screws, it was found that it is necessary to lengthen the alkali immersion time for the smaller screws, but it is effective even if immersed for more than 20 hours. No change, even with large screws 1
It was found that a dipping time of 2 hours or more was required.

[0018]

As described above, according to the present invention, a rust preventive coating is formed on the surface of stainless steel by adding a step of dipping in a dilute alkaline solution for 12 to 20 hours after the quenching step, whereby the stainless steel is formed. Prevents rusting of steel.

[Brief description of drawings]

FIG. 1 is a perspective view of a barrel for processing a small stainless steel product.

FIG. 2 is a block diagram showing a first step of the present invention.

FIG. 3 is a block diagram showing a second step of the present invention.

FIG. 4 is a block diagram showing a third step of the present invention.

FIG. 5 is a block diagram showing a fourth step of the present invention.

[Explanation of symbols]

 10 Barrel 11 Flange 12 Barrel Main Body 13 Lifting Tool

Claims (3)

[Claims] 1. A first step of removing cutting oil by alkali cleaning and nitric acid cleaning and a cutting oil baking product, a second step of quenching, and 0.05 to 1 g / l of caustic alkali. 12 to 2 in aqueous solution
A rust preventive method for a stainless steel product, which comprises treating a stainless steel product cut by a third step of soaking for 0 hour and a fourth step of applying a rust preventive oil. 2. The machined stainless steel product comprises:
The method for rust prevention of a stainless steel product according to claim 1, which is a screw product made of stainless steel. 3. The method for preventing rusting of stainless steel products according to claim 1, wherein the concentration of caustic used in the third step is 0.1 to 0.5 g / l.