JPH07233460A - Alloy having oxidized film and its production - Google Patents

Abstract

PURPOSE:To form a protective film having sufficient insulating properties, on the surface of an alloy material contg. a specific amt. of protective film forming components, by applying a composite layer of the oxides of the same components and the oxides of the oxidation promoting elements to the specified thickness. CONSTITUTION:The surface of an alloy material contg. >=7wt.% pretective film forming components such as Cr, Al, Ti and Nb is applied with a surface layer contg. multiple oxides consisting of the oxides of the same components and the oxides of elements such as the Ia group of K, Na or the like and elements such as B and P promoting the oxidation of the same components to 0.5 to 50mum thickness by about 7 to 70mg/cm<2>. This surface layer is formed in such a manner that the compounds of the same oxidation promoting elements such as oxides, carbonate, nitrate and organic salt are applied to the surface of the alloy material by using a small amt. of water, which is heated in an oxidizing atmosphere of a relatively low temp. not so as to degenerate the alloy material of <=1200 deg.C. Thus, the alloy having an oxidized film with sufficient insulating properties can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a heat resistant and abrasion resistant member that requires insulation in a resistance welding jig and various electric parts, or an oxide film used as a member that requires corrosion resistance, weather resistance and wear resistance. The present invention relates to an alloy and a method for manufacturing the alloy.

[0002]

2. Description of the Related Art Conventionally, plastics and ceramics have been used for members that require insulation in resistance welding jigs and various electric parts. However, for example, the guide pin for positioning when the nut is resistance-welded to a steel plate or the like is required to have insulating properties, and is also subjected to heat and impact, and must also be resistant to abrasion with the nut. Therefore, depending on the usage conditions, strength, heat resistance, and wear resistance may be insufficient for plastic, and reliability may be compromised for ceramics.

In order to impart strength, heat resistance, and wear resistance to the member requiring insulation, it is also practiced to oxidize the surface of the iron-based material to form an insulation coating. In order to facilitate the formation of an oxide film on the iron-based material and to improve its insulating property, strength and wear resistance, C
It is possible to add easily oxidizable alloy materials such as r and Al, but it is not preferable because it changes the characteristics of the alloy itself and affects the characteristics during post-processing and use.

As an Fe-based alloy in which the denseness and uniformity of the oxide film are improved, for example, in JP-A-64-87759, by weight ratio, Cr is 10 to 25%, Al is 2 to 10%, and C is.
0.004% or less, N 0.005-0.05%, Ti
Those containing 0.39 to 0.43% and Zr 0.21 to 0.25% are disclosed.

[0005]

However, the alloy disclosed in the publication is formed on the surface because it is used for a jig of a high-temperature fired product which requires wear resistance and strength of the base material at high temperatures. The oxide film needs to be oxidized and heated at a high temperature of 1200 ° C. or higher in order to form an oxide film to the extent that it imparts an insulating property to a resistance welding jig and various electric parts, and therefore, it is not deformed or brittle during heat treatment. Is likely to occur,
There is a problem that it becomes difficult to use as an electrically insulating member that requires precision.

An object of the present invention is to provide an alloy having a protective film having a sufficient insulating property and an alloy having an oxide film having a sufficient insulating property formed on the surface of the alloy by oxidative heating at a relatively low temperature. It is to provide a manufacturing method.

[0007]

The alloy having an oxide film of the present invention is an alloy material in which an insulating oxide film is formed on the surface of a base material by oxidation treatment, and the alloy material is contained in the alloy material. It is composed of a protective film forming component and an oxidized surface layer containing an element that promotes its oxidation.

The oxidized surface layer in the present invention has a thickness of 7 to 70 m.
It is formed to have an absolute thickness of 0.5 to 50 μm in g / cm ² .

As the protective film forming component contained in the alloy material, Cr, Al, Ti, Nb, etc. can be applied, and these must be contained in the alloy base material in an amount of 7% by weight or more. . Cr-containing Fe as an alloy applicable to the present invention
The alloy is preferable in order to obtain an excellent wear resistant coating, and particularly, the Cr content of 7% by weight or more is particularly effective. As the alloy containing 7 wt% or more of Cr, Co-based stellite, Fe-based stainless steel, etc. are generally used, but in addition, it is widely applicable to sintered materials containing nichrome or chromium carbide.

As the element that promotes the oxidation of the easily oxidizable component, an element that forms a low melting point oxide such as group Ia such as K and Na or B and P is preferable, and those oxides and carbonates, The selection and amount of compounds such as nitrates and organic acid salts are determined by the material of the alloy and the conditions of use. Especially when the easily oxidizable component contained in the alloy is Cr, the group Ia element is preferable, In the case of ordinary stellite alloy or stainless steel alloy, dissolve potassium carbonate with a small amount of water to give 5 to 100 mg.
It may be applied so that it becomes / cm ² . Oxides of Group Ia metals are strong alkalis and have high hygroscopicity, so that organic acid salts are easier to handle in practice. The compound to be coated on the alloy may be added with various solvents and binders to facilitate coating. However, the thicker the coating amount of the compound, the thicker the film can be formed. However, if the coating amount is too thick, peeling or the like is likely to occur, so it is necessary to set appropriate conditions according to the application.

The heating for forming the oxide film is carried out by heating in an oxidizing atmosphere such as the atmosphere in which the partial pressure of O ₂ is about 0.2 atm to form a strong and sufficiently thick oxide film rich in insulating property. Can be formed. Further, as the temperature of the oxidation treatment is higher and the time is longer, the thickness of the oxide film increases, but
An oxide film having a sufficient insulating property can be formed at a low temperature of ℃ or below. The processing conditions for oxidation also differ depending on the type of alloy.

In general, when the easily oxidizable alloying element contained in the alloy is Cr, a sufficient amount cannot be obtained unless the oxidation temperature is increased as the amount increases. However, if the temperature is 1200 ° C. or higher, the alloy may be deformed or the characteristics of the alloy itself may be changed, which is not suitable. Oxidation is performed at a temperature of 1200 ° C. or less, preferably 600 to 1000 ° C. depending on the amount of Cr.

[0013]

[Function] Oxides of Group Ia elements such as potassium and sodium, which are applied to the surface of an alloy containing an alloy element such as Cr or Al that easily forms a protective film, are
By reacting with an oxide of an alloying element such as Al, the melting point thereof is lowered and diffusion is promoted, so that an oxide film having a sufficient thickness can be formed even at a low temperature.

The coating formed by this is Cr, A
It contains a composite oxide of an oxide of a protective film forming alloy element such as 1 and an element for promoting oxidation such as a group Ia element, and has excellent adhesion to the alloy base material, and is mainly composed of an oxide. The coating has electrical insulation and high hardness, and its wear resistance exceeds that of the alloy base metal.

When potassium is used as an element for promoting oxidation, for example, a group Ia element, a compound other than an oxide, such as potassium nitrate, can be used as the compound. In this case, potassium nitrate changes into potassium oxide during the temperature rise, and exhibits the same effect as when the oxide is applied.

Cr as an element for forming a protective film in the alloy base material
In the case of using potassium carbonate as a coating material, 2Cr ₂ O ₃ + 4K ₂ CO ₃ + 3O ₂ → 4K ₂ CrO ₄
It reacts directly with the oxide of Cr like + 2CO ₂ .

[0017]

EXAMPLES C as an alloying element for forming a protective film in an alloy base material
An example of using an alloy containing r and using potassium in the group Ia as an element for promoting the oxidation will be described below.

Example 1 Sintered stellite alloy (Co-13Cr-30Cr ₃ C ₂
-12W) with a 30% aqueous solution of potassium carbonate with a brush
After coating at a rate of 00 cc / m ³ , it was heated in the atmosphere at 1000 ° C. for 1 hour to be oxidized. Since excess potassium oxide remains on the film on the surface of the alloy after cooling, it was washed with water and removed, and then the insulation resistance (ρ) and the film thickness (t) were measured. Next, a disk-shaped sample was prepared by the same method, and the abrasion resistance of the coating was examined by a pin-disk abrasion test. The wear resistance test condition is that the tip of the pin has a surface of 3 mm × 0.5 mm and a load of 4.9 N is applied,
The time (T) until the insulation was broken was measured at a peripheral speed of 0.4 m / s. Similarly, create a guide pin for welding nuts,
The actual number of times the nut can be welded and welded (n)
Was measured.

Example 2 Stainless alloy SUS304 (Fe-18Cr-8N)
For i), a 30% aqueous solution of potassium carbonate is applied with a brush to 500c
After coating at a ratio of c / m ³ , an oxidation treatment was performed by heating at 700 ° C. for 1 hour in the atmosphere, and then the same test as in Example 1 was performed.

Comparative Example 1 Tool steel SK4 (Fe-1C) was coated with an aqueous solution of potassium carbonate with a brush and then oxidized in the air at 600 ° C. for 1 hour. The test was performed in the same manner as in Example 1 below.

Comparative Example 2 Sintered stellite alloy (Co-13Cr-30Cr ₃ C ₂
Nothing was applied to (-12 W), and oxidation treatment was performed in the atmosphere at 1000 ° C. for 1 hour. The test was performed in the same manner as in Example 1 below.

Comparative Example 3 Stainless alloy SUS3O4 (Fe-18Cr-8N)
No coating was applied to i), and oxidation treatment was performed in the atmosphere at 1200 ° C. for 1 hour. The test was performed in the same manner as in Example 1 below.

The test results are shown in Table 1.

[0024]

[Table 1] In the case of Examples 1 and 2, the insulation resistance and wear resistance were superior to those of Comparative Examples 1 to 3, and when the guide pin was actually manufactured and the welding test was performed, the dielectric breakdown occurred. The life until the occurrence of was long. Further, in Comparative Example 3, there was a sample in which the welding test was hindered due to the deformation of the alloy.

Regarding the corrosion resistance and the like, the corrosion resistance of the surface-treated alloy of the present invention is equal to or higher than that of the alloy before the treatment, although it depends on the test method.

[0026]

The present invention has the following effects.

(1) It is possible to obtain an alloy having an electrically sufficient insulating function while maintaining the characteristics of the alloy base material.

(2) A coating having an electrically sufficient insulating function can be formed by oxidation heating at a relatively low temperature.

(3) A sufficiently strong oxide film can be formed relatively easily on an alloy excellent in corrosion resistance, weather resistance, wear resistance and the like.

Claims (2)

[Claims] 1. Oxidation of an oxide of a protective film forming component contained in the alloy material containing 7% by weight or more of a protective film forming component and an element which promotes oxidation of the protective film forming component contained in the alloy material. An alloy having an oxide film provided with a surface layer having a thickness of 0.5 to 50 μm containing a complex oxide with a substance. 2. A compound which accelerates the oxidation of the protective film forming component contained in the alloy material is formed as a surface layer on the surface of the alloy material containing the protective film forming component in an amount of 7% by weight or more. A method for producing an alloy having an oxide film, which comprises heating a material in an oxidizing atmosphere at 1200 ° C or lower.