JPH0633218A - Manufacture of seal ring for floating sheet - Google Patents

Abstract

PURPOSE:To manufacture a seal ring excellent in wear resistance and having high reliability with high yield at low cost by subjecting a steel tube having specified carbon content to cold forging into seal ring stock and subjecting at least its sliding face to carbo-nitriding. CONSTITUTION:The steel tube having 0.3 to preferably about 0.1% (as the lower limit) carbon content and good in formability or the sheet obtd. by stretching the steel sheet to form its shape into a ring is subjected to cold forging and is plastically molded into the seal ring stock. At least the sliding face of this stock is subjected to carbo-nitriding. The thickness of the hardened layer formed by this method is preferably regulated to about 0.005 to 0.0l0mm. After this carbo-nitriding, preferably, the same stock is subjected to oil or water hardening to strengthen the core part of the stock, and furthermore, the surface layer part in which a part is converted into retained austenite is martensitized by sub zero treatment. Moreover, after the carbo-nitriding treatment or sub-zero treatment, preferably, the face fitted with an O ring is subjected to phosphating convertion treatment to improve the roughening of its surface and its rusting resistance.

Description

Detailed Description of the Invention

The present invention relates to a method of manufacturing a seal ring used as a floating sheet. More specifically, the present invention prevents the inflow of earth and sand from the periphery of the axle of a construction machine used in an environment in which foreign matter such as stone, metal, and plastic is mixed with earth, sand and water, or these to the internal drive unit. As described above, the present invention relates to a method for manufacturing a seal ring of a floating seat attached to the axle.

More specifically, as shown in the sectional view of FIG. 1 and the assembly view of FIG.
O-ring 1 on collar 10 fixed to non-rotating shaft 13
The floating sheet 1a is fixed to the shaft 13 in a floating state via the 2a, while the floating sheet 1b is fixed to the shaft 13 in a floating state via the O-ring 12b to the bush 11 which rotates symmetrically with the floating sheet 1a. The sliding surfaces 7a and 7b of the sheets 1a and 1b come into contact with each other with a surface pressure and relatively rotate and slide, thereby providing a sealing function and preventing infiltration of fluid from the outside or leakage of fluid from the inside. The sliding surface 7 of the seal ring used in this way is required to have high wear resistance, and in particular, a minute cutting action that occurs when hard foreign matter particles such as mud or earth and sand intervene between the friction surfaces of the sliding surface. Abrasion resistance against abrasive abrasion due to is required.

[0003]

2. Description of the Related Art Floating sheets have hitherto been manufactured by casting methods such as shell mold, green sand mold, vanishing model mold, and centrifugal casting. The reason is that the special cast iron has considerable wear resistance and that the shape in which the O-ring 12 is fitted to the outside can be easily obtained by casting.

[0004]

However, in the casting method, the yield of the product with respect to the molten raw material is low due to the riser or "burr", and the product yield is often low due to casting defects, and the reliability of the product is low. However, there is a problem in that the cost is high due to the alloying element for producing special cast iron and the mold production.

Therefore, the present inventors have conducted a study on manufacturing a floating sheet by a plastic working method such as cold forging of a steel pipe or a sheet metal plate.

[0006]

A first aspect of the present invention is to cold forge a seal ring into a steel pipe or a steel plate having a carbon content of 0.3% or less in a ring shape, and then cold forge the material. Is a method of manufacturing a seal ring characterized by carbonitriding at least the sliding surface, the second of the present invention is a manufacturing of a seal ring characterized by performing quenching after carbonitriding and subsequently performing sub-zero treatment A third method of the present invention is at least O after carbonitriding or sub-zero treatment.
A method for manufacturing a seal ring is characterized in that the ring mounting surface is subjected to a phosphate conversion treatment.

The structure of the present invention will be described below. The inventors of the present invention have made various studies on the processing method of the raw material, but the hot working method adopted the cold working method because it has an adverse effect on the raw material such as decarburization and the thin material is bent due to heating. In cold working, a steel pipe is cut to the length of a floating sheet, a mandrel is fitted inside the pipe, and the outer wall of the pipe is struck and compressed by a tool or mold toward the pipe axis to form a recess for accommodating the O-ring. To do. The outer diameter of the steel pipe is 45-60m
m, the thickness of 2 to 4 mm can be used,
It is not limited to this. Also, for example, the plate thickness is 2
It is also possible to punch a steel plate of ~ 4 mm in a ring shape by sheet metal, and then perform cold forging as described above.

The carbon content of the cold-worked material is 0.3
If it exceeds%, it becomes difficult to process it not only when it is rolled but also when it is annealed, and the wear resistance does not improve to the extent that the carbon content increases, so the carbon content of the material was limited to 0.3% or less. The lower limit of the preferable carbon content is 0.1%. Additive elements other than carbon generally reduce workability, so it is better not to add them as much as possible. Therefore, carbon steel for machine structural use is the most preferable, but alloy steel containing 1.25% or less of Cr as an alloy element is also to some extent. The workability of is secured.

Even if the material cold-worked as described above is hardened, the sealing performance sharply deteriorates during use of the seal ring. Therefore, various surface hardening methods were investigated. First, in induction hardening, the hardness of the material was Hv 450 or less, and the wear resistance was poor. Next, the hardness of the material in the carburizing process was about Hv650 or less, and good wear resistance was obtained with special cast iron even at this hardness, so good sealing performance was expected, but unexpectedly the sealing performance was unexpected. Became bad. Therefore, it has been decided to subject at least the sliding surface of the cold-worked material to carbonitriding treatment that provides higher hardness.

The carbonitriding may be carried out at the same time using a gas having carburizing and nitriding properties, or one of the treatments may be carried out and then the other treatment may be carried out. Carburization may be either solid or gas, and nitriding is performed with gas. The thickness of the surface hardened layer formed by the carbonitriding treatment is not particularly limited, but is preferably 0.005 to 0.010 mm.

After carbonitriding, it is preferable to strengthen the material core by water quenching, oil quenching or the like. But,
A part of the surface layer that has been carbonized by carburization becomes residual austenite by quenching, resulting in poor wear resistance. As a countermeasure against this, after quenching, it is preferable to carry out subzero treatment at a temperature of -70 to -50 ° C for 15 to 30 minutes to convert residual austenite to martensite.

The surface of the cold forged product has a very good surface roughness and is usually 10 s or less. However, in the oil ring mounting portion, the oil ring is slippery on the surface having high smoothness and the oil sealing property is deteriorated. If the surface roughness of the cold forged product is increased as a countermeasure against this, the forged product will not be separated from the mold, and there is a risk of the mold being destroyed. Therefore, the present invention
It provides a measure for roughening the surface roughness by subjecting a cold forged product to carbonitriding and then phosphate conversion treatment. In the phosphate conversion treatment, the phosphoric acid in the treatment liquid has an etching effect and roughens the surface of the iron base material. This gives 20
A roughness of ~ 30s is obtained.

Further, since the phosphate film of Zn, Ca, etc. formed on the surface of the iron substrate by the phosphate chemical conversion treatment has excellent rust resistance, it is used as a rust preventive treatment when earth and sand water adheres to the seal ring. Are better.

[0014]

In the first aspect of the present invention, low carbon steel is used as a material to enable cold forging, and the material shape is a steel pipe or sheet metal plate, which reduces the number of processing steps and simplifies the die. I made it. Furthermore, it was thought that the wear resistance on the mutual sliding surfaces of the seal rings would be sufficient if there was some hardness due to quenching, etc., but when actually tested, only the carbonitrided material showed sufficient wear resistance. So I chose this process.

When the retained austenite in the carbonitrided layer is converted to martensite by the subzero treatment as in the second aspect of the present invention, the wear resistance is further improved.

Since the cold forged surface has a small roughness,
The ring is easily displaced during use. Phosphate chemical conversion treatment was adopted as a countermeasure. In addition, the phosphate chemical treatment improves the rust resistance against sediment water. Hereinafter, the present invention will be described in more detail with reference to examples.

[0017]

【Example】

Example 1 A steel pipe equivalent to S25C was cold forged into a seal ring material,
This was subjected to the following processing. Carbonitriding At 930 ° C., holding for 5 hours, then at 800 ° C. for 1 hour, heat treatment was performed in a carbonitriding atmosphere of 0.15 m ³ / min of ammonia gas and 1.1% of C potential. Carbon is L
PG was decomposed into 95% butane and 5% ethylene gas, which was purified and supplied to the heat treatment furnace so that the carbon potential became 1.1%. After the heat treatment, water quenching was performed, followed by tempering at 160 ° C. for 1.5 hours. After carbonitriding + subzero carbonitriding, the material was immersed in a liquid mixture of liquid nitrogen and methanol for 1 hour. Then, it tempered at 160 degreeC for 1.5 hours. Induction hardening (comparative example) V-type oscillation, voltage -6kV, power -18KWH, time-
High-frequency heating was performed under the condition of 5.9 sec, and then water was sprayed to perform quenching. Then, it tempered at 150 degreeC for 1.5 hours. As a result, the following hardness and texture were obtained.

Carbonitriding: HmV730 (Fig. 2) Carbonitriding + Sub-zero treatment: HmV785 (Fig. 3) Induction hardening (Comparative example): HmV450 (Fig. 4)

A wear resistance test of the surface-treated material obtained by the above-mentioned treatment was carried out by a two-head type rotary wear tester shown in FIG. In the figure, 1a is a rotary seal ring, 1b is a fixed seal ring, 10 is a housing, 12 is an O-ring,
Reference numeral 13 is a rotary shaft, 15 is a housing fixing plate, 16 is an oil supply hole, 18 is earth and sand water, and 20 is a storage box.

Evaluation Method A wear test was carried out using a two-head type rotary wear tester. Abrasion test conditions 1) Abrasion tester 2-head rotary abrasion tester 2) Peripheral speed: 1 m / s (peripheral speed at the outermost diameter of the floating sheet) 3) Pressure: Atmospheric pressure 4) Seal liquid: Outside 5 wt% slurry Sediment water (JIS Z8901-8 type) Inner engine oil # 30 is sealed up to the shaft core 5) Sliding surface pressing: 31.1 kgf / cm ² (surface pressure conversion 4.9 kgf / cm ² ) Attaching force 6) Time: 100 hr Continuous

For both the fixed side seal ring 1b and the rotary side seal ring 1b of the abrasion tester, carbonitrided products of 1.2 to 2.5 μm and carbonitrided + zab zero treated products of 0.5 to 2.5 μm were used. Induction hardened products 2.0 to
The amount of wear was 3.0 μm.

Example 2 The carbonitriding + zab-zero treated product of Example 1 was subjected to the following surface treatment. (A) Phosphate conversion treatment Degreasing (Degreasing agent: Nippon Parkerizing Co., Ltd. product name Fine Cleaner 4360, 20 g / L solution, temperature 60
℃, 5 minutes immersion); water washing (ground water, 0.5 minutes spray);
10% hydrochloric acid pickling (0.5 min spray); water washing (0.5 min spray); phosphoric acid conversion treatment (Nippon Parkerizing Co., Ltd., product name Parphos M / A; total acid concentration 30-35 points; temperature 93- 96 ° C; 10 minutes immersion); water washing; hot water washing;
Each treatment of air blow drying was sequentially performed.

FIG. 7 shows the roughness of the oil ring mounting portion of the material before the phosphate chemical conversion treatment, and FIG. 8 shows the roughness after the treatment. From these figures, it is apparent that the phosphate chemical conversion treatment increases both the average roughness Ra and the maximum roughness Rmax.

(B) Homo treatment (preparation of a thin film of Fe ₃ O ₄ ) (c) Black dyeing treatment (treatment of black iron oxide, a black thin film of Fe ₃ O ₄ is formed to a thickness of 1 to 2 μm with an alkaline solution) ) Anti-rust oil coating (Yushiro Chemical Non-Raster PS-2
(Uses 5 times diluted solution of (brand name))

The seal ring which has been subjected to these treatments has a humidity of 7
It was exposed to 0% outdoors and the generation of rust was observed. The results are shown below. The criteria for judgment were as follows. ○: No abnormality △: Beginning of rust ×: 1.5% or more of the whole is rusted

Surface treatment 1 week 2 weeks 3 weeks 1 month 2 months 3 months 4 months Homo treatment ○ ○ ○ △ × × × × Phosphate treatment ○ ○ ○ ○ ○ △ △ Black dyeing treatment ○ ○ ○ ○ × × × Prevention Rust oil coating ○ ○ △ × × × × From the above results, it is understood that the phosphate treatment is excellent as the rust preventive treatment for the carbonitrided material.

[0027]

As described above, according to the present invention, a seal ring having no problem in practical performance can be manufactured by cold forging, and carbonitriding treatment, subzero treatment or phosphate chemical treatment is adopted. However, all of these are suitable for mass production, and there is no factor of yield reduction compared with the processes such as melting, mold manufacturing, and mold release required in the conventional casting method, and the lead time is also reduced. , Industrially advantageous.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a seal ring.

FIG. 2 is a metallographic photograph (magnification: 400 times) of the carbonitrided material surface.

FIG. 3 is a metallographic photograph (magnification: 400 times) of the surface of the material that has been subjected to sub-zero treatment after carbonitriding.

FIG. 4 is a metallographic photograph (magnification: 400 times) of the surface of the material that has been induction hardened.

FIG. 5 is an explanatory diagram of a usage state of a seal ring.

FIG. 6 is an explanatory diagram of a seal ring tester.

FIG. 7 is a diagram showing the surface roughness of the carbonitrided cold forging material.

FIG. 8 is a diagram showing the surface roughness of a cold forging material that has been subjected to a phosphate chemical conversion treatment after carbonitriding.

[Explanation of symbols]

 1 Floating seat 7 Sliding surface 13 Shaft 10 Collar 11 Bushing 12 O-ring

Claims (3)

[Claims] 1. A method of manufacturing a seal ring for a floating sheet, wherein a steel pipe or a steel plate having a carbon content of 0.3% or less is formed into a ring shape by cold forging, and then the seal ring material is formed. A method for manufacturing a seal ring for a floating sheet, which comprises carbonitriding at least a sliding surface of a material. 2. The method for manufacturing a seal ring for a floating sheet according to claim 1, wherein the carbonitriding is followed by quenching and then sub-zero treatment. 3. The method for producing a seal ring for a floating sheet according to claim 1, wherein at least the O-ring mounting surface is subjected to a phosphate conversion treatment after the carbonitriding or the subzero treatment.