JPH0219199B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a metal gasket, and more particularly, to a method for manufacturing a metal gasket in which the sealing edge of the gasket itself is difficult to creep even when used at high temperatures for a long period of time, and the valve seat is also unlikely to be damaged. As a metal gasket, one shown in FIG. 1 is generally known. In Fig. 1, 1 is a valve stem, 2 is a valve gasket housing, 3 is a valve gasket (metal gasket), 4 is a gasket support ring, 5 is a valve seat, and 6
1 is a hydraulic cylinder, 7 is a metal bellows, 8 is a hydraulic cylinder support base, and 9 and 10 are flanges. The hydraulic cylinder 6 presses the valve gasket 3 against the valve seat 5 and performs a roll between X and Y. The above valve gasket 3 is as shown in FIG.
Usually, stainless steel 3' is coated with copper sulfate plating 3 through Ni plating 3'', and the stainless steel 3' has a spring action and the copper sulfate plating 3 has a sealing action.It is a disc spring-like gasket with a sealing edge. The Ni plating 3'' is very likely to peel off if copper plating is applied directly to the stainless steel 3', so it is interposed between the stainless steel 3' and the copper sulfate plating 3. This serves to ensure adhesion. If the metal gasket described above is used at high temperatures for a long period of time with the valve closed (a state in which a load is applied to the valve and a seal is formed), the seal edge E will undergo creep deformation, as shown in Figure 3. like,
There is a drawback that the stainless steel 3' comes into direct contact with the valve seat 5, making it impossible to seal. As a countermeasure to this problem, applying hard copper plating may be considered, but such plating requires a high load to seal, which may cause damage to the valve seat. The present invention provides a method for manufacturing a metal gasket in which the seal edge E is less likely to creep and the valve seat is less likely to be damaged even if the gasket is used in the valve seat state at high temperatures for a long period of time. That is, the present invention provides the following advantages: (1) Nickel plating is applied to a stainless steel base material to a thickness of about 2 to 6 μm using a nickel chloride bath, and then nickel plating is applied to a thickness of about 1 to 6 μm using a copper pyrophosphate bath containing a sulfur compound-containing additive. Approximately 3mm, hardness Hv180~220
(2) After applying the copper plating according to the above (1), a method for manufacturing a metal gasket is characterized in that: (2) After applying the copper plating according to the above (1), a softening heat treatment is performed to make the hardness of the copper plating 100 to 180 Hv. It is related to. The above-mentioned nickel bath plating has the effect of improving the adhesion between the base material and the copper plating, so theoretically the presence of single molecule crystals of nickel is sufficient, but under actual working conditions In terms of control, it is easy to set the lower limit to 2 μm, but on the other hand, if it is too thick, it will not improve the adhesion and will be economically disadvantageous, so it is practical to set the upper limit to 6 μm. . In addition, the thickness of copper plating on nickel bath plating is
In order to fully achieve the sealing mechanism which is the objective of the present invention, 1.
A range of 3 mm to 3 mm is usually appropriate. In other words, if the copper plating thickness is less than 1 mm, the life will be short, and
This is because if it exceeds mm, buckling deformation occurs and performance tends to deteriorate. In the present invention, the stainless steel base material is
For example, austenitic stainless steels such as SUS304, 316, and 326 can be used, and these solution-treated materials (hardness Hv150 to 160) or work-hardened materials such as cold rolling or shot peening are applied to the solution-treated materials. (hardness Hv165-180) can be used. In the present invention, nickel plating is first applied to the base material, but this has the disadvantage that if copper plating is applied directly to stainless steel, it will peel off easily, whereas nickel plating is between stainless steel and copper plating. This is because it has the effect of improving the adhesion between the two. Next, copper plating is applied on the nickel plating using a copper pyrophosphate bath. In this case, additives containing sulfur compounds (for example,
By adding a mercaptan additive, it is possible to make the crystals of the deposited copper metal finer, impart luster, and produce effects as shown in the Examples described below. The thickness of the copper plating is several mm, preferably about 1 to 3 mm, because if the thickness of the copper plating is too thick, the crystals of the plating layer will become coarse, which will not only change the properties but also cause them to peel off easily and be uneconomical. Hereinafter, the present invention will be specifically explained with reference to Examples. Example 1 The surface of a SUS304 round bar was polished with emery paper #600,
After that, it was buffed to a mirror surface, and then cleaned by degreasing, pickling, washing with water, etc. in the usual way. Add this to nickel chloride bath 240g/hydrochloric acid 120g/
Ni plating was applied using electrolyte solution (25℃),
After washing with water, it was treated under the following conditions () or () so that the copper plating thickness was approximately 2 mm. () Copper sulfate bath Copper sulfate: 250g/Sulfuric acid: 50g/Mercaptan additive: None, 0.3ml/Ah ⁽ Note ⁾ Cathode current density: 2A/dm ² liquid Temperature: 25℃ (Note) 1 ampere for 1 hour This means that it was added at a rate of 0.3 ml/per energization. () Copper pyrophosphate bath Copper pyrophosphate: 90g/ Potassium pyrophosphate: 350
g/ Total pyrophosphoric acid: 230g/ 28% Ammonia: 1-6
ml/Mercaptan additive: None, 0.1~3ml/Cathode current density: 1~5A/
dm ² liquid Temperature: 30 to 60°C In addition, in the copper pyrophosphate bath, the amount of ammonia and mercaptan additives added, the cathode current density, and the liquid crystal are varied within a considerable range, but the commercially available sulfur copper bath All of these, including the presence or absence of additives, are intended to change the hardness of the electrodeposited plating layer. Table 1 shows the results of measuring the hardness of the copper plating layer obtained using a micro-Vickers.

[Table] (Note): Observation using an optical microscope has confirmed that the harder the plating layer is, the finer the metal particles are.
No. 4 from the copper-plated stainless steel round bar above.
The test piece shown in the figure was processed. This test piece tip a
The shape is as shown in FIG. 5, and is the same as the shape of the seal portion of the valve gasket shown in FIG. In addition,
In Figure 4, 3' is stainless steel, 3'' is Ni plating,
3 indicates copper plating. Using these test pieces (copper plated with different hardnesses), the amount of settling of the tip (seal edge) (in Fig. 5, The amount indicated by H) and the appearance of the valve seat after the test were visually observed. Among these, the test results regarding the relationship between the test time and the amount of settling of the tip were as shown in FIG. In FIG. 6, the symbols of the straight lines correspond to the numbers in Table 1, and the Ho line indicates the amount of sag of the seal edge until the stainless steel of the valve gasket directly contacts the valve seat. The following is clear from FIG. In other words, plating layers obtained not only from copper sulfate baths but also from copper pyrophosphate baths without mercaptan additives are generally very soft.
While the deformation of the allowable amount (the amount of settling Ho of the seal edge until the stainless steel of the valve gasket directly contacts the valve seat) occurred at test time t ₁ or t ₃ ,
The plating layer obtained from the bath with the addition of mercapotane additives has a high hardness, so the amount of sagging is small. In particular, the hard plating layer obtained from the copper pyrophosphate bath exhibits even less settling and exhibits excellent sealing performance over a long period of time. However, with a very hard plating layer, when looking at the contact surface of the valve seat after the test, scratches (more precisely, recesses) were observed, which is not desirable from the standpoint of sealing performance. From the above tests, it has become clear that although it is important to obtain a hard copper plating layer in the present invention, it is necessary to have an appropriate hardness because if it is too hard, it will cause scratches on the valve seat. It was confirmed that the microvits hardness was 180 to 220. Since the hardness of the valve seat is between 165 and 180, a copper plating with a hardness slightly harder than this indicates good performance. Next, the valve gasket shown in FIG.
A plating layer with a hardness of 220 was obtained using the following copper pyrophosphate bath containing a mercaptan additive, and a sealing test was conducted under the above test conditions at room temperature and 150°C. As a result, it was confirmed that good sealing properties were exhibited even under this temperature condition. Copper pyrophosphate bath Copper pyrophosphate: 90g/ Potassium pyrophosphate: 350
g/ Total pyrophosphoric acid: 230g/ 28% Ammonia: 3.3-3.4
ml/Mercaptan additive: 0.5
~1.5ml/ Cathode current density: 3A/dm ^Two liquids Temperature: 53℃±1℃ As is clear from the above results, in order to manufacture the gasket targeted by the present invention, the first step is to select the type of plating bath. is important, and then the amount of various chemicals added to the plating bath is determined and determined based on the Bitkers hardness.
It is extremely important to obtain a plating layer of 180 to 220, and the object of the present invention cannot be achieved simply by adding additives. Example 2 In Example 1, when a valve seat material with a Vickers hardness of 165 to 180 is used, it is clear that a copper plating layer with a hardness of 180 to 220 exhibits the best sealing properties. However, here, an experiment was conducted on the hardness of the copper plating layer when the hardness of the valve seat material was softer than that in Example 1. Using the same processing method as in Experimental Example 1 using a SUS304 round bar, processing was performed under the following conditions () or () so that the plating thickness was approximately 2 mm. () Copper sulfate bath Copper sulfate: 250g/Sulfuric acid: 50g/Mercaptan additive: 0.3
ml/Ah Cathode current density: 2A/dm ² liquid temperature: 25℃ () Copper pyrophosphate bath: Copper pyrophosphate: 90g/
Potassium pyrophosphate: 350
g/ Total pyrophosphoric acid: 230g/ 28% ammonia water: 3.3-3.4
ml/Mercaptan additive: 0.5
~1.5ml/ Cathode current density: 3A/dm ^Two liquids Temperature: 53℃±1℃ The microvits hardness of the plating layer obtained by this treatment is 100 ~
120, and that of the copper pyrophosphate bath in () was within the range of 190-200. From these copper-plated stainless steel bars, the fourth
The test piece shown in the figure was processed and the sealing performance was examined by the same method and under the same conditions as in Example 1, by observing the amount of sagging at the tip (seal edge) and the appearance of the valve seat after the test. The hardness of this valve seat was 150 to 160 microbits hardness. As a result of the above, even in this test, the amount of settling of the plating layer obtained from copper pyrophosphate was smaller than that of copper sulfate, and was better. However, when looking at the valve seat after the test, scratches were observed on the abutment surface of the tip, and if the valve seat is soft, the copper plating layer with a hardness of 180 to 220 would have demonstrated sufficient performance. It turned out that I couldn't say it. Therefore, the plating layer made of copper pyrophosphate was subjected to the following heat treatment to soften it. (1) After being left in an environment of 250℃ for 20 minutes, it was processed into the test piece shown in Figure 4. (2) After being left in an environment of 250℃ for 4 minutes, it was processed into the test piece shown in Figure 4. Processed into the test piece shown in Figure 4 after being left in an environment for 1 hour at 250℃ (4) Processed into the test piece shown in Figure 4 after being left in an environment of 250°C for 3 hours The hardness of the layer was measured as follows. (1) 160-170 (2) 130-150 (3) 103-110 (4) 95-105 Test pieces of plating layers subjected to the above four types of heat treatment and test pieces of plating layers obtained from copper sulfate baths (hardness 100 to 120), the sealing properties were investigated under the same conditions as the above method. The results are shown in Table 2, and the hardness of the valve seat is
When the hardness is 150 to 160, it has been found that the sealing properties can be improved by using a plating layer obtained from copper pyrophosphate that has a hardness of 180 to 220 and is softened by heat treatment. The microbit scales in the range of 103 to 170 showed excellent performance. Even in this case, it has become clear that if the softening is excessive, the amount of sagging at the tip is large, and that even copper plating of the same hardness obtained from a copper sulfate bath has poor sealing properties. In addition, by increasing the heat treatment temperature to 270℃, it is possible to adjust the plating hardness to the specified level within a short period of time.
As long as the hardness was within the range of ~170, excellent sealing properties were exhibited regardless of the heat treatment conditions.

[Table] (Note): (1) to (4) were obtained from a copper pyrophosphate bath and were obtained under different heat treatment conditions.
of
(5) was obtained from copper sulfate bath

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of a general metal gasket, Figure 2
The figure is an enlarged schematic diagram of the metal gasket 3 shown in Figure 1, Figure 3 is an enlarged schematic diagram showing the state of the metal gasket 3 after long-term use, and Figure 4 is a test piece prepared in an example of the present invention. FIG. 5 is an enlarged view of part a in FIG. 4, and FIG. 6 is a chart showing the results obtained in an example of the present invention.

Claims (1)

[Scope of Claims] 1 Nickel plating is applied to a thickness of about 2 to 6 μm on a stainless steel base material using a nickel chloride bath, and then nickel plating is applied to a thickness of about 1 to 3 mm using a pyrophosphate steel bath containing an additive containing a sulfur compound. A method for manufacturing a metal gasket, characterized by applying copper plating to a degree and hardness of Hv180 to Hv220. 2. Apply nickel plating to a thickness of about 2 to 6 μm on a stainless steel base material using a nickel chloride bath, and then apply nickel plating to a thickness of about 1 to 3 mm and a hardness of Hv180 to Hv180 using a pyrophosphate steel bath containing additives containing sulfur compounds. 220 copper plating is applied, and the hardness of the copper plating is further increased.
A method for producing a metal gasket, characterized by heat treatment at 250° C. for 20 minutes to 3 hours at Hv 100 to 180.