JP2002097593A - Machining material with high corrosion resistance for electronic device/component, electronic device/ component using the same, and method for manufacturing machining material with high corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a machining material with high corrosion resistance for an electron device/component, which has a combination of superior corrosion resistance and a machining property, to provide an electron device/component, and a method for manufacturing the machining material with the high corrosion resistance. SOLUTION: This method comprises employing a carbon steel or a low alloy steel of which the quantities of S and C are limited to a fixed range, Cr plating and Ni plating on its surface, and then heat treating it to form a Cr-Ni-Fe alloy layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high corrosion resistant C
The present invention relates to a cutting material made of carbon steel or low alloy steel having an r-Ni-Fe alloy layer formed thereon, an electronic device component using the same, and a method of manufacturing a cutting material.

[0002]

2. Description of the Related Art Precision parts such as spindles for motors of hard disk drives for personal computers, which are used in electronic devices that require high dimensional accuracy as well as corrosion resistance, are made of free-cutting stainless steel with improved machinability by adding S. It is manufactured by cutting.

Many electronic devices have Ag, Cu, A inside.
Metals such as 1 are used as constituent materials of circuits. When these metals are corroded by a sulfide gas such as hydrogen sulfide, non-conductive corrosion products are formed, and as a result, there is a problem in that current does not flow and equipment does not operate properly. For electronic equipment parts such as spindles for motors of personal computer hard disk drives manufactured from S-added free-cutting stainless steel, when heated by the heat generated inside the electronic equipment, it is added to improve machinability. Sulfide gas resulting from S is generated,
It is considered that the metal constituting the circuit is corroded to generate non-conductive corrosion products, and the conductivity of the circuit becomes poor, resulting in malfunction of the device.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks, and provides a high corrosion-resistant cutting material used for electronic equipment parts having both excellent corrosion resistance and cutting workability, an electronic equipment part using the same, and a high corrosion-resistant cutting material. An object of the present invention is to provide a method for producing a corrosion-resistant cutting material.

[0005]

In order to achieve the above object, the high corrosion resistant cutting material of the present invention has a C content of 0.005.
A Cr—Ni—Fe alloy layer having a thickness of 1.2 to 9 μm is formed on the surface of carbon steel containing up to 0.25% and 0.04% or less of S, and the Cr concentration in the alloy layer is 20-60
% Or a Cr-Ni-Fe alloy layer having a thickness of 1.2 to 9 μm on the surface of a low alloy steel containing 0.005 to 0.25% of C and 0.04% or less of S. Is formed,
In addition, the Cr concentration in the alloy layer is 20 to 60%, and further, together with the Ag foil and pure water, each is put in a closed container in a non-contact state with each other and left at 80 ° C. for 24 hours. No discoloration is observed and no sulfide gas is generated.

Further, an electronic device part according to the present invention is characterized in that any one of the above-mentioned cutting surfaces of the highly corrosion-resistant cutting material is precision-processed and then buffed.

Further, the method for producing a high corrosion resistant cutting material according to the present invention is characterized in that C is 0.005 to 0.25% and S is 0.0
A thickness of 0.2 to 1.0 on the surface of carbon steel containing 4% or less.
After forming a Cr plating layer having a thickness of 1 to 8 μm and further forming a Ni plating layer having a thickness of 1 to 8 μm on the Cr plating layer, in a non-oxidizing atmosphere or a reducing atmosphere, 500 to 600 ° C.
Heat treatment in a temperature range of 0.005 to 0.
Forming a Cr plating layer having a thickness of 0.2 to 1.0 μm on a surface of a low alloy steel containing 25% and S of 0.04% or less;
Further, after forming a Ni plating layer having a thickness of 1 to 8 μm on the Cr plating layer, heat treatment is performed in a temperature range of 500 to 600 ° C. in a non-oxidizing atmosphere or a reducing atmosphere.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is intended to replace free-cutting stainless steel which is superior in corrosion resistance but has poor machinability by adding S to machinability. Dedicated research aimed at obtaining high corrosion-resistant cutting materials used in electronic equipment parts, which do not generate corrosive gas such as material gas, have excellent cutting workability, and have excellent corrosion resistance equivalent to stainless steel As a result,
The purpose is to form a Cr-Ni-Fe alloy layer by applying Cr plating and Ni plating to the surface of carbon steel or low alloy steel carbon steel in which the amount of C and S is limited to a certain range, and then performing a heat treatment. It has been found that a high corrosion resistant cutting material can be obtained. Hereinafter, the present invention will be described in detail.

First, as the steel material used for the cutting material of the present invention, C is 0.005 to 0.25% and S is 0.04%.
% Or less of carbon steel or 0.005 to 0.2% of C
An annealed material of a low alloy steel containing 5% and S of 0.04% or less is used. As the low-alloy steel, one or more of Mn, Ni, Cr, and Mo in addition to C and S in the above ranges may be used.
n: 2.0% or less, Ni: 4.0% or less, Cr: 2.0
% And Mo: 0.6% or less.

In the above carbon steel and low alloy steel, C
If the amount is less than 0.005%, the required strength cannot be obtained when molded into an electronic device part, while if it exceeds 0.25%, the final shape of the electronic device component intended for these steel materials is used. Cr and Ni plating are performed after being cut into almost the same shape as Cr, and then, when heat treatment is performed, Cr is combined with C by thermal diffusion, the amount of formed Cr carbide increases, and Ni, which has an effect on corrosion resistance, is formed. And the amount of the solid solution or compound of Fe and C is reduced, and the corrosion resistance is deteriorated.

On the other hand, if the S content exceeds 0.04%, when molded into electronic device parts and used, the electronic device parts will be heated by prolonged use, and sulfide gas will be generated, resulting in the generation of sulfide gas. A circuit formed of a metal such as Ag, Cu, or Al inside the device is undesirably corroded.

[0012] After annealed carbon and low-alloy steel containing C and S in the above-mentioned range, the surface of the electronic component is cut into almost the same shape as the final shape of the electronic device component, and then the surface is subjected to corrosion resistance. Cr plating and Ni
Apply plating. First, after performing the degreasing treatment and the pickling treatment on the member subjected to the above cutting, the thickness is 0.2 to 1.0 μm by using a surge bath or the like by a barrel plating method.
Cr plating is applied to a thickness of m. Plating thickness 0.2μm
If the thickness is less than 1, sufficient corrosion resistance cannot be obtained even if Ni plating is performed on the Cr plating layer and then heat treatment is performed to form a Cr—Ni—Fe alloy layer, while the plating thickness is 1 μm.
If the thickness exceeds m, the effect of improving the corrosion resistance saturates and becomes economical, which is not preferable. A more preferred Cr plating thickness is 0.3 to 0.6 μm.

Next, Ni plating is further performed on the Cr-plated upper layer using a barrel plating method in the same manner as Cr plating. PH of commonly used watt bath etc. is 3 ~
When a plating bath of No. 5 is used, a strong Cr oxide film is formed on the Cr plating surface which is difficult to remove even in a very short time when the process shifts from Cr plating to Ni plating. And plating. But,
Since the strike Ni plating bath has a low Ni deposition efficiency,
After short-time strike plating using this bath, it is economically preferable to deposit most of the Ni plating layer using a Ni plating bath such as a Watt bath or a sulfamic acid bath. The thickness of the Ni plating is 1 to 8 μm, preferably 2 to 4 μm. As will be described later, when heat treatment is performed after Ni plating, as the amount of Ni plating increases, a face-centered cubic lattice structure similar to that of austenitic stainless steel changes from a body-centered cubic lattice structure similar to ferritic stainless steel. And the corrosion resistance is improved. When the thickness of the Ni plating is less than 1 μm, it is impossible to prevent the lower Cr from diffusing to the surface layer of the Ni plating and discoloring when a heat treatment described later is performed. Further, even if the thickness exceeds 8 μm, the effect of improving corrosion resistance saturates, the production cost increases, and it is not economical.

After forming the Cr plating and the Ni plating on the cutting member as described above, a heat treatment is performed. Ni
In order to prevent the oxidation of the plating layer and the plating pinhole portion, the heat treatment is generally performed in a non-oxidizing atmosphere such as N ₂ gas or Ar gas, or reduction of vacuum, H ₂ gas, H ₂ -N ₂ mixed gas or the like. Perform in an atmosphere. The composition and thickness of the Cr-Ni-Fe alloy layer formed on the steel sheet surface by interdiffusion of Cr, Ni, and Fe depending on the size of the above-mentioned cutting member, the thickness of Cr plating and Ni plating, and the heat treatment conditions. Is determined. Lower Cr exceeds upper Ni plating layer 2
If it diffuses to the surface of the layer plating layer, it forms Cr oxide and discolors, which is not preferable. Therefore, it is necessary to minimize the diffusion of Cr in the lower plating layer. Also C
If r remains without being alloyed, when a large force acts during use, cracks occur in the hard Cr plating layer, deteriorating the corrosion resistance and the plating adhesion, so that it is necessary to diffuse all the plated Cr. Further, if Cr diffuses too deeply into the steel material as the plating base, the Cr concentration of the Cr—Ni—Fe alloy layer becomes too low, and the effect of improving corrosion resistance is lost. From the above viewpoints, the Cr concentration in the Cr-Ni-Fe alloy layer is preferably 20 to 60%.
Regarding the Cr concentration in the alloy layer, a small piece was cut out from the machined member on which the Cr-Ni-Fe alloy layer was formed, and a high voltage was applied between the small piece and the counter electrode (anode) using the cut piece as a cathode to generate a gap between the electrodes Luminescence analysis of constituent atoms generated by sputtering the alloy layer surface by glow discharge,
The peak area of each element was measured using a glow discharge optical emission spectrometer (hereinafter referred to as GDS), and C
It can be determined by calculating the ratio of the peak area of r.

[0015] Fe has a larger diffusion coefficient in the α region where the temperature is lower than in the γ region where the temperature is higher. In addition, when Fe is cooled after being heated to the γ region, it undergoes phase transformation. In the case of steel, the heat treatment is preferably performed not in the γ region but in the α region because deformation occurs cheaply and the diffusion may proceed rapidly at the grain boundaries. Preferably, the heat treatment is performed in a temperature range of 500 to 600 ° C. When the heat treatment temperature is lower than 500 ° C., even in the α region where the diffusion coefficient is large, the diffusion speed is slow, so that a long time is required for the diffusion and the productivity is poor. On the other hand, when the temperature exceeds 600 ° C., deformation occurs or the structure of the steel itself becomes coarse grains,
The mechanical properties deteriorate. The processing time is preferably 7 to 10 hours, although it depends on the size of the cutting member and the thickness of the Cr-Ni-Fe alloy layer to be formed.

The Cr—Ni— formed as described above
The total thickness of the Fe alloy layer is preferably 1.2 to 9 μm. When the thickness of the alloy layer is less than 1.2 μm, the corrosion resistance is poor. On the other hand, when the thickness exceeds 9 μm, the effect of improving the corrosion resistance is saturated and is not economical. Cr-Ni-Fe
The thickness of the alloy layer was determined by using GDS, etching the alloy layer by argon sputtering under certain conditions, measuring the time until the base material steel (Fe) was exposed, and using a known thickness of the alloy layer under the same conditions. Can be obtained by performing a comparison conversion with the time required until Fe is exposed when argon sputtering is performed.

As described above, the surface is made of Cr-Ni-F
After the formation of the e-alloy layer, the surface of the machined member is further subjected to precision processing and / or buffing to finish the final shape of the target electronic device component. In this way,
The electronic device component of the present invention is obtained.

[0018]

The present invention will be described in more detail with reference to the following examples. (Example 1) A steel ingot prepared from 12 types of carbon steel and low alloy steel shown in Table 1 was hot-rolled to a thickness of 10 mm, annealed, cut out into a size of 30 mm x 30 mm, and used for cutting. It was a member.

[0019]

[Table 1]

Next, after 12 kinds of cutting members shown in Table 1 were subjected to alkali degreasing and pickling, Cr was plated by barrel plating under the following conditions using a surge bath under the following conditions. Plated. Next, the sample was washed with water, strike-plated Ni by barrel plating using a Ni strike plating bath and a Watt bath under the following conditions, and then Ni-plated to have a plating thickness shown in Table 2 to obtain a sample. Each plating amount was measured using a fluorescent X-ray method. [Sergent bath composition] Chromic anhydride 250 g / l Sulfuric acid 25 g / l Sodium silicate 3 g / l [Electrolysis conditions] Bath temperature 50 ° C Current density 40 A / dm ² [Ni strike plating bath composition] Nickel sulfate 240 g / l Nickel chloride 45 g / l boric acid 30 g / l sulfuric acid 10 g / l [electrolysis conditions] pH <1 bath temperature 50 ° C. current density 5 A / dm ² [Ni plating bath composition] nickel sulfate 240 g / l nickel chloride 45 g / l boric acid 30 g / l [electrolysis Conditions] pH 3.5-4.5 Bath temperature 50 ° C. Current density 5 A / dm ²

[0021]

[Table 2]

Next, the samples shown in Table 2 were heat-treated under the conditions shown in Table 3 to form Cr-Ni-Fe alloy layers having the thicknesses shown in Table 3. The thickness of the alloy layer is GDS (manufactured by Shimadzu Corporation:
The alloy layer was etched by argon sputtering using a Shimadzu glow discharge emission spectrometer: GDLS-5017). Regarding the Cr concentration of the obtained alloy layer, the same GD
Using S, the peak area of each element was measured and determined. Table 3 shows the results.

[0023]

[Table 3]

(Characteristic evaluation) For samples Nos. 1 to 20 shown in Tables 2 and 3, and a free-cutting stainless steel (SUS430F: S content 0.17%) as a comparative material, the strength, the crystal structure of the alloy layer, The degree of surface discoloration due to diffusion, corrosion resistance, cutting workability, and sulfide gas generation were evaluated as follows. [Strength] A No. 5 test piece based on JIS Z 2201 was prepared, tensile strength was measured, and strength was evaluated according to the following criteria. ：: 150 N / mm ² or more, ×: less than 150 N / mm ² [Crystal structure of alloy layer] It was determined by X-ray diffraction using Cu-Kα ray as a radiation source. [Surface Discoloration Degree] The sample surface was visually observed, and the discoloration degree was evaluated based on the following criteria. ：: good, △: slightly discolored, ×: discolored [Corrosion resistance] JIS Z 237 after buffing the sample surface
A salt spray test based on No. 1 was performed, and an area ratio at which red rust was generated after 72 hours was measured and evaluated according to the following criteria.
◎: 0 to 0.1%, ：: 0.1 to 0.5%,
Δ: 0.5 to 2.5%, ×: 2.5% or more [Machinability] A round bar having the same composition as steel numbers A to L and having a diameter of 20 mm, and a free-cutting stainless steel having the same diameter (SUS430F)
Is cut using a lathe equipped with a cutting tool made of carbide tool (JIS K-10) under the following conditions, and the time until the blank wear amount of the cutting tool becomes 1 mm is obtained. The cutting workability was evaluated based on the standard. <Processing conditions> Cutting speed: 200 mm / min Biting feed speed: 0.15 mm / rev Cutting depth: 1.0 mm Cutting oil: None ◎: 100 minutes or more, ○: 50 to 100 minutes, △:
10 to 50 minutes, ×: 10 minutes or less [Sulfide gas generation] A sample was prepared with a thickness of 20 μm and a thickness of 30 mm.
Sealed in a container having an internal volume of 250 cm ³ together with Ag foil having a size of × 30 mm and 0.5 ml of pure water;
After standing at 24 ° C. for 24 hours, the surface of the Ag foil was visually observed,
The degree of blackening was classified by the following symbols, and the sulfide gas generation was evaluated. A smaller degree of blackening indicates better sulfide gas generation. ◎: no blackening was observed at all; o: slightly darkened color was observed; Δ: darkened color was observed;
×: Blackening is observed. Table 4 shows the results of the property evaluation.

[0025]

[Table 4]

As shown in Table 4, since the high corrosion resistant cutting material of the present invention is made of carbon steel or low alloy steel whose bulk is small in C content and S content, sulfide gas is generated even when heated. And excellent cutting workability with less wear of the tool during cutting. Further, since an alloy layer having a crystal structure equivalent to that of austenitic stainless steel is formed on the surface, it has excellent corrosion resistance equivalent to that of stainless steel.

Example 2 Next, Sample Nos. 6, 12,
And 16 were precision-machined and then buffed, finished into a spindle having the cross-sectional shape shown in FIG. 1, assembled into a hard disk drive, and placed in a constant temperature and high humidity chamber at a temperature of 70 ° C. and a relative humidity of 90%. , 20,000 RPM
No corrosion was observed on the exposed portion of the electric circuit after continuously rotating for 40 days.

[0028]

The cutting material with high corrosion resistance according to the present invention has a thickness of 1% on the surface of carbon steel or low alloy steel containing 0.005 to 0.25% of C and 0.04% or less of S. .2-9μ
m-Cr-Ni-Fe alloy layer is formed, and the Cr concentration in the alloy layer is 20 to 60%, and this cutting material is sealed together with Ag foil and pure water in a non-contact state with each other. After being placed in a container and allowed to stand at 80 ° C. for 24 hours, it is a highly corrosion-resistant cutting material characterized by no discoloration of the Ag foil surface and no generation of sulfide gas. No gas is generated, and excellent cutting workability with little tool wear during cutting. Further, since an alloy layer having a crystal structure equivalent to that of austenitic stainless steel is formed on the surface, it exhibits excellent corrosion resistance equivalent to that of stainless steel.

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[Procedure amendment]

[Submission date] October 30, 2000 (2000.10.
30)

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an electronic device component (spindle) of the present invention.

Claims (6)

[Claims] 1. A carbon steel containing 0.005 to 0.25% by weight of C (hereinafter simply referred to as%) and 0.04% or less of S is formed on a surface of a carbon steel having a thickness of 1.2 to 9 μm. Ni-Fe
An alloy layer is formed, and the Cr concentration in the alloy layer is 20
High corrosion resistant cutting material of up to 60%. 2. C is 0.005 to 0.25%, and S is 0.1 to 0.2%.
The thickness of the low alloy steel containing less than
A highly corrosion-resistant cutting material in which a 9 μm Cr—Ni—Fe alloy layer is formed and the Cr concentration in the alloy layer is 20 to 60%. 3. An Ag foil and pure water are placed in a closed container in a non-contact state with each other, and the mixture is placed at 80 ° C. for 24 hours.
The highly corrosion-resistant cutting material according to claim 1 or 2, wherein no discoloration is observed on the surface of the Ag foil after leaving for a time, and no sulfide gas is generated. 4. An electronic device component obtained by precision-cutting a highly corrosion-resistant cutting material according to claim 1 and buffing the cut surface. 5. C is 0.005 to 0.25%, and S is 0.1 to 0.2%.
On the surface of carbon steel containing not more than 0.4%, a thickness of 0.2 to 1.
After forming a Cr plating layer of 0 μm and further forming a Ni plating layer having a thickness of 1 to 8 μm on the Cr plating layer, 500 to 600 μm in a non-oxidizing atmosphere or a reducing atmosphere.
A method for producing a highly corrosion-resistant cutting material, comprising heat-treating in a temperature range of ° C. 6. The content of C is 0.005 to 0.25% and the content of S is 0.1 to 0.2%.
0.4% or less on the surface of low alloy steel containing
After forming a 1.0 μm Cr plating layer, and further forming a 1-8 μm thick Ni plating layer on the Cr plating layer, 500-500 μm in a non-oxidizing atmosphere or a reducing atmosphere.
A method for producing a highly corrosion-resistant cutting material, comprising heat-treating in a temperature range of 600 ° C.