JPH0790475A - Production of seal ring for floating seat - Google Patents

Abstract

PURPOSE:To produce a seal ring usable as cast and excellent in wear resistance by using alloy cast iron having a limited compsn. and executing metal mold centrifugal casting. CONSTITUTION:The compsn. of alloy cast iron to be used is constituted of the one contg., by weight, 2.4 to 3.8% C, 0.5 to 1.5% Si, 0.2 to 1.5% Mn, 10 to 20% Cr, and Mo, V, Nb, W and Ti independently or in total by 1.0 to 10%, and the balance Fe with inevitable impurities. Instead of Mo, V, Nb, W and Ti in the compsn. or together with them, <=2% B may be added. Moreover, 0.2 to 5% Ni is added according to necessary. Molten metal obtd. by subjecting the cast iron to melting and deoxidation is cast into a centrifugal casting metal mold. As for the centrifugal casting conditions, the value (G) obtd. by dividing acceleration due to the centrifugal force of the molten metal by gravitational acceleration is regulated to the range of 70 to 85.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a seal ring used as a floating sheet, and more specifically, it will be used in an environment in which foreign matter such as earth and sand, earth and sand water, stone, metal, plastic, etc. is mixed. And a method for manufacturing a seal ring of a floating seat, which is attached to an axle for a construction machine so as to prevent dirt and sand from flowing into the drive portion of the axle from the periphery thereof.

More specifically, as shown in the assembly diagram of FIG. 1, the floating sheets 2a and 2b are floated on the shaft 6 via O-rings 3a and 3b on a collar 4 fixed to a shaft 6 which does not rotate. The sliding surfaces 1a and 1b of the floating sheets 2a and 2b come into contact with each other with a surface pressure and rotate relative to each other and slide to perform a sealing action, and intrusion of earth and sand and liquid from the outside and from the inside Prevent fluid leakage. The sliding surfaces of the seal rings 2a and 2b used for such a purpose are required to have high wear resistance.

[0003]

2. Description of the Related Art Most conventional seal rings for floating sheets (hereinafter referred to as "floating sheets") are high Cr cast iron castings made by shell molding or sand casting. The castings produced by these manufacturing methods need to be machined in order to improve the dimensional accuracy, and need to be heat-treated because they lack wear resistance in the as-cast condition. Therefore, the conventional shell mold and sand casting must be made into products having the above-mentioned characteristics through the steps of softening annealing, lace processing, and quenching.

[0004]

As described above, due to the problem of dimensional accuracy and the requirement of the metal structure, the softening heat treatment is once performed for the machining, and then the hardening heat treatment is performed to improve the wear resistance. Therefore, the cost of the conventional floating sheet is high.

The present invention realizes the functions required for a floating sheet by densifying and refining the metal structure by the rapid cooling effect of the centrifugal casting mold, and by polishing the sliding surface in the as-cast state. An object of the present invention is to provide a method for manufacturing a floating sheet that can obtain the required dimensional accuracy.

[0006] Conventionally, materials containing a large amount of Cr generated oxides violently in the air and had a large amount of oxygen in the molten metal, and casting defects such as pinholes and oxide entrainment were likely to occur. In sand casting, etc., it is possible to adopt a method of collecting impurities in the feeder while allowing some contamination of the molten metal, but since there is no feeder, runner, etc. in the centrifugal casting method, before casting The gas component contained in the molten metal directly leads to the occurrence of casting defects such as product pinholes and oxide inclusion. For this reason, the centrifugally cast floating sheet has a high defect rate, and in order to prevent this, a pure raw material with less gas components and rust must be used as the raw material for melting, and the cost is high. Therefore, it is another object of the present invention to provide a method of manufacturing a floating sheet that can solve these problems.

[0007]

Means and Actions for Solving the Problems The first aspect of the present invention is C: 2.4 to 3.8% by weight, Si: 0.5 to 1.5.
% By weight, Mn: 0.2 to 1.5% by weight, Cr: 10 to 2
0 wt%, Mo, V, Nb, W, and Ti: 1.0 to 10 wt% each alone or in total, the balance: Fe
And a method of manufacturing a floating sheet, which comprises casting a molten metal composed of unavoidable impurities into a mold by a centrifugal casting method. First, the reasons for limiting the composition of the molten metal of the present invention will be described below.

C: 2.4 to 3.8% by weight C is an element which mainly combines with Fe, Cr and other carbide forming elements to form carbides, but 2.4% by weight or less is sufficient. Since the amount of carbide cannot be obtained and the wear resistance is insufficient, the lower limit was set to 2.4% by weight. Further, if it exceeds 3.8% by weight, the carbide becomes coarse and becomes brittle, and cracks easily occur during casting under the rapid cooling conditions of centrifugal casting, and there is a problem of cracking or chipping when polishing the sliding surface in the as-cast condition. Therefore, the upper limit was set to 3.8% by weight.

Si: 0.5 to 1.5 wt% Si is an element that affects the flow of molten metal during casting, is a deoxidizing agent, and, like C, is an element related to cracking and chipping. If it is less than 0.5% by weight, sufficient fluidity cannot be obtained, and if the fluidity is tried to be increased, the melting temperature naturally rises, and the life of the furnace body of the melting furnace or the die of the casting apparatus is shortened, and also in terms of cost. Since it is disadvantageous, the lower limit is set to 0.5% by weight. Further, if it exceeds 1.5% by weight, problems such as casting cracking and chipping are likely to occur under the rapid cooling conditions of centrifugal casting, so the upper limit is 1.5.
It was set to% by weight.

Mn: 0.2-1.5% by weight Mn is a carbide-forming and austenite-forming element,
Further, it is an element used as a deoxidizing material in the production of steel and cast iron, which are the main raw materials for melting, and having a deoxidizing effect even when melting the casting raw material. When Mn is 0.2% by weight or less, these actions are insufficient, and the selection of the melting raw material is limited, resulting in high cost and impracticality. Therefore, the lower limit is set to 0.2% by weight. On the other hand, if it exceeds 1.5% by weight, the number of gas defects increases and the amount of retained austenite increases and the hardness becomes unstable, so the upper limit was made 1.5% by weight.

Cr: 10 to 20% by weight Cr is the most important element among the carbide-forming elements, and has the effect of forming a composite carbide together with elements such as Fe and improving wear resistance. If the amount of Cr is small, white pig iron is inhibited and the amount of carbides becomes insufficient, so that sufficient hardness cannot be obtained, so the lower limit was made 10% by weight. On the other hand, if it exceeds 20% by weight, the amount of oxides generated during melting increases, the material becomes brittle, the fluidity of the molten metal decreases, and the hardness hardly increases, so the upper limit was made 20% by weight.

Mo, V, Nb, W, Ti: Alone or in total 1.0 to 10% by weight Mo, V, Nb, W and / or Ti are carbide forming elements and have a matrix hardening ability superior to Cr. The wear resistance is improved by adding these alone or in combination. Furthermore, these elements are elements that improve the corrosion resistance due to earth and sand water, which is one of the necessary characteristics of the floating sheet.
As a result of various experiments, it was found that the effect is remarkable when these are contained in an amount of 1.0% by weight or more, and no more effect is observed even when the amount exceeds 10% by weight. Further, since these elements are expensive and it is disadvantageous in practice to contain a large amount of them, the range of 1.0 to 10% by weight is set.

The O-rings 3a, 3
It is poured into a gap between a tubular mold having a concave portion for receiving b (see FIG. 2) and a cylindrical core, and casting is performed while applying a centrifugal force.

The second aspect of the present invention is the above-mentioned Mo, V, Nb, W,
And / or B in place of or together with Ti, with an upper limit of 2% being added. B: Upper limit 2.0 wt% B is a boride-forming element, but it has the effect of further refining the carbide, and the addition of a trace amount further improves the wear resistance, but 2.0 wt% Even if added in excess, the effect does not change, so in consideration of economic efficiency, the upper limit was made 2.0% by weight.

A third aspect of the present invention is characterized in that Ni is further added to the above chemical composition with an upper limit of 5.0% by weight. Ni: 0.2 to 5.0 wt% Ni is an austenite stabilizing element and a hardening ability improving element. Under the cooling conditions of centrifugal casting, Ni has the effect of improving the toughness by increasing the amount of retained austenite in the matrix and further ensuring the necessary hardness even if there is a delay in cooling during casting. In particular, when it is not desired to preheat the die, it is effective to add Ni in order to prevent cracking during casting. When Ni is added in an amount of 5.0% by weight or more, the amount of austenite in the matrix increases, the hardness decreases too much, and the wear resistance decreases, so the upper limit was limited to 5.0% by weight. If it is less than 0.2% by weight, N
Since there is no effect of i addition, the lower limit was limited to 0.2% by weight.

A fourth aspect of the present invention is characterized in that a raw material having the above chemical composition is burned down in a melting furnace, a deoxidizer is added, and then centrifugal casting is performed. The amount of the deoxidizer added is preferably 1.0% by weight for Al and 1.0% by weight for Ca-Si. The chemical composition of the present invention is Mn,
The addition of Si has a deoxidizing effect and makes it difficult for casting defects due to oxygen absorption to occur even with a high Cr composition, but by further deoxidizing before casting, casting defects can be further reduced. . Deoxidation is preferably performed immediately before casting by furnace deoxidation or ladle deoxidation.

In a fifth aspect of the present invention, a value G (hereinafter simply referred to as "G") obtained by dividing the acceleration due to the centrifugal force of a rotating die by the gravitational acceleration is 70. ~ 85
It is characterized by being cast in. The present inventors have found that G added to the molten metal having the above-described chemical composition was changed, and the relationship between G and the casting cavity was investigated.
It was found that ~ 85 is an appropriate range where the number of casting cavities is the smallest. G acts as a pressing force for the molten metal against the metal in centrifugal casting, and serves as a point for producing a sound casting. If it exceeds the range of 70 to 85, air entrapment due to turbulent flow during casting occurs.
And the range.

By using the above-mentioned method, it is possible to manufacture a floating sheet by a mold centrifugal casting method, and a dense metal structure can be obtained.

[0019]

EXAMPLES The present invention will be described below based on specific examples. Example 1 A floating sheet casting mold having an inner diameter of 73 mm was manufactured, and as shown in Table 1, the composition of the comparative example containing no Mo, V, W, Ti, Ni, and B and the composition of the example were subjected to centrifugal casting. Carried out. For melting the raw materials, a high-frequency melting furnace with a melting output of 300 kw was used, and the mold centrifugal casting conditions were G = 40,
Mold preheating temperature 320 ℃, molten metal casting temperature 1420 ± 10
C., and the pouring amount was 170 ± 5 g. In addition, deoxidation of the molten metal was carried out immediately after the material burned out by 0.5% by weight of rod-shaped Al and Ca-S.
i (50%) 1.0 wt% was added.

[0020]

[Table 1] Element Comparative material This developed material A B C D E F G H I C 3.45 3.35 2.95 3.25 3.47 3.35 2.65 3.33 3.32 3.31 Si 0.98 1.05 1.10 1.02 0.52 1.03 1.45 0.87 0.89 0.79 Mn 0.87 0.95 0.55 1.01 0.32 0.89 0.25 1.42 1.12 1.10 Cr 15.5 15.2 19.6 19.5 10.5 15.6 19.8 16.2 15.9 15.2 Mo-2.51 2.11 1.02--3.51 2.05 2.09 2.20 V-0.65 1.05---0.78 0.65 0.66 0.67 Nb--0.52 1.02--1.05---W--0.70 0.80 2.51- 0.23---Ti---0.45 0.56-0.25---Ni--------1.23 4.21 B-----1.5-0.5-- Fe Bal Bal Bal Bal Bal Bal Bal Bal Bal

A wear test was performed on these samples under the following conditions. 1) Abrasion tester Two-head abrasion tester (see Fig. 2) 2) Peripheral speed: 1 m / s (peripheral speed at the outermost diameter of the floating seat) 3) Pressure: Atmospheric pressure 4) Seal liquid: 5% by weight outside Soil and sand water 3
0 (JIS Z 8901-8 type) Inner engine oil # 30 Sealing oil up to the shaft core 5) Sliding surface: 31.1 kgf / cm2 (surface pressure conversion 4.9)
kgf / cm2) Pressing force 6) Time: 200Hr In addition, in FIG. 2, 31 is a shaft, 32 and 33 are shaft sealing covers, 3
4 is an oil inlet. The test results are shown in Table 2.

[0022]

[Table 2] Abrasion amount (μm) Comparative example ABCD EFGH I 1.4 0.8 0.7 0.5 0.7 0.3 0.7 0.6 0.8 0.9 〜 〜 〜〜〜〜〜〜〜〜〜 1.9 1.2 1.1 1.4 1.0 0.8 1.2 0.8 1.2 1.3

All of the centrifugal cast materials A to I of the present invention showed less wear than the centrifugal cast materials of the comparative examples and showed good results. In particular, the centrifugally cast materials E and G of the present invention to which B (boron) was added had the least amount of wear and the best performance.

Example 2 An experiment was conducted in which a floating sheet having an inner diameter of 73 mm was centrifugally cast with a molten metal having the chemical composition shown in Table 2 in the same manner as in Example 1 by changing the deoxidizing method and confirming the effect.

[0025]

[Table 3] Element A-1 A-2 A-3 A-4 B-1 B-2 B-3 C 3.40 3.35 3.36 3.37 3.45 3.42 3.39 Si 0.92 0.98 1.02 1.10 0.98 0.95 0.96 Mn 0.56 0.75 0.56 0.52 0.45 0.62 0.55 Cr 15.52 19.42 15.98 15.97 16.58 17.52 19.02 Mo 2.65 2.54 2.53 2.56 2.65 2.63 2.65 V 0.65 0.78 0.88 0.85 0.56 0.58 0.98 Fe Bal Bal Bal Bal Bal Bal Deoxidation treatment Note 1 Note 2 Note 2 Note 3 None None None None

Note 1: Al: 1.0 wt% Note 2: Al: 0.5 wt% + Ca-Si (50%) 1.
0% by weight Note 3: Al: 2.0% by weight

Each test was repeated 10 times, and the results of comparing the number of times of oxide entrapment and gas defect generation are shown in Table 4.

[0028]

[Table 4] With deoxidation Without deoxidation A-1 A-2 A-3 A-4 B-1 B-2 B-3 N number 10 10 10 10 10 10 10 Entrapment of oxides 0 0 0 2 5 8 6 Gas defect 0 0 0 1 6 8 6

The deoxidized product has a significantly lower defect occurrence rate than the undeoxidized product, and its effect is clear. On the contrary, when Al deoxidation was increased to 2.0% by weight, defects tended to increase, and it was found that about 1.0% by weight is suitable for Al alone.

Example 3 A floating sheet having an inner diameter of 73 mm was cast in a mold without preheating a molten metal having the chemical composition shown in Table 5, and the effect of Ni was confirmed.

[0031]

[Table 5] Element A-1 A-2 A-3 A-4 B-1 B-2 B-3 C 3.43 3.32 3.45 3.57 3.45 3.42 4.29 Si 0.96 0.96 1.12 1.10 0.98 0.95 1.95 Mn 0.56 0.78 0.58 0.52 0.45 0.63 0.54 Cr 16.52 19.52 14.98 12.57 17.58 17.62 18.02 Mo 3.62 2.04 3.13 2.66 2.65 2.63 2.65 V 1.64 0.68 0.88 2.85 1.56 0.69 0.98 Ni 0.25 2.50 5.10 6.01---Fe Bal Bal Bal Bal Bal Bal N number 20 20 20 20 20 20 20 crack Number 0 0 0 0 4 2 3

All the Ni-added compositions cast in the molds which were not preheated had no cracks, whereas all the Ni-free compositions had 10% or more cracks.

Example 4 When a wear test was carried out on the compositions A-1, A-2, A-3 and A-4 of Example 3, the wear amount was 0.
8 to 1.2 μm, 0.7 to 1.2 μm, 0.8 to 1.5
μm, 1.2 to 1.6 μm, and it was found that the wear resistance deteriorates when the Ni content exceeds 5%. In the hardness measurement results, HRC = 68, 68, 67, 64 in order,
A decrease in hardness was observed due to the addition of Ni.

Example 5 In order to compare the production method of the present invention with other production methods, a comparative product was prepared by a sand casting method which has been conventionally used and compared with the results of the abrasion test of Example 1. Table 6 shows the chemical composition of the sand casting.

[0035]

[Table 6] Element C 3.45 3.56 Si 0.98 0.97 Mn 0.95 0.96 Cr 16.52 15.78 Mo 2.52 1.02 V 0.96 1.26 Fe Bal Bal

Sand-cast products were produced through the steps of casting, softening annealing, lace processing, and quenching, and the hardness was HRC68 and HRC67, respectively. The product of the present invention has the same composition as in Table 6 and is manufactured in the same manner as in Example 1. The results were as follows.

[0037]

[Table 7] Chemical composition Chemical composition Sand type product of the present invention Sand type product of the present invention Wear amount (μm) 1.4 to 2.1 0.8 to 1.2 1.3 to 2.2 0.9 to 1.1

It can be seen that the centrifugal cast product according to the present invention is superior in wear resistance as compared with the sand cast product of the comparative example.
Further, FIG. 3 shows a structural photograph of the cast product of the present invention (chemical component), and FIG. 4 shows a structural photograph of the sand casting product. From these comparisons, it was confirmed that the structure of the present invention has fine carbides and that the structure is superior.

Example 6 By using the molten metal having the chemical composition of Example 5 and changing G, the presence or absence of casting defects and the dimensions of the cast product were confirmed. In this experiment, casting was performed using a relatively large-diameter product having an inner diameter of 300 mm, which is easily deformed. The dimension (mm) measurement and casting defects are shown in Table 8.

[0040]

[Table 8]G Site requirement 20 30 40 50 60 70 80 90 100accuracy Inner diameter ± 1.0-± 1.2 ± 1.1 ± 1.0 ± 0.9 ± 0.50 ± 0.50 ± 0.50 ± 0.50 Height ± 0.3-± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.2 Outer diameter ± 0.6-± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.2 Collar diameter ± 0.8-± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.2 Neck diameter ± 0.3-± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.2 Casting shape Inner diameter Inner diameter Inner diameter Good Good Good Good Good Inner diameter Imperfections Contraction Contraction Blow Without

When G = 50, shrinkage occurs on the inner diameter side, and G =
In No. 100, blowholes were generated on the inner diameter side due to the inclusion of air. Further, in terms of size, G has a smaller variation in inner diameter than 60, and the dimensional accuracy required for the product is secured.

[0042]

EFFECTS OF THE INVENTION According to the first and second aspects of the present invention, a high Cr cast iron to which an appropriate amount of a carbide forming element and an austenite forming element are added is provided with a desired performance in an as-cast state, and a sand casting or a shell mode casting is provided. A floating sheet that is less expensive to manufacture but has excellent abrasion resistance is provided.

According to the third aspect of the present invention, the susceptibility of centrifugal casting to cracking due to quenching can be reduced to prevent product defects and / or to increase the cooling rate.

According to the fourth aspect of the present invention, it is possible to prevent a casting defect that tends to occur when casting a high Cr composition after melting it in the atmosphere by centrifugal casting which does not use hot water or the like.

According to the fifth aspect of the present invention, casting defects such as shrinkage cavities can be prevented.

[Brief description of drawings]

FIG. 1 is a sectional view of a floating sheet.

FIG. 2 is a diagram of an abrasion tester.

FIG. 3 is a photograph of a metal structure of a centrifugally cast product according to the present invention (magnification: 100 times).

FIG. 4 is a photograph of a metal structure of a sand casting (magnification: 100
Times).

[Explanation of symbols]

 1 Sliding surface 2 Floating sheet 3 O-ring 4 Color

Claims (5)

[Claims] 1. C: 2.4 to 3.8% by weight, Si: 0.
5 to 1.5% by weight, Mn: 0.2 to 1.5% by weight, C
r: 10 to 20% by weight, Mo, V, Nb, W and Ti:
Containing 1.0 to 10% by weight of each, alone or in total,
Remainder: A method for producing a seal ring for a floating sheet, which comprises casting a molten metal composed of Fe and unavoidable impurities into a mold by a centrifugal casting method. 2. A floating sheet for a floating sheet according to claim 1, wherein a molten metal containing 2% by weight or less of B is cast in a mold instead of or together with Mo, V, Nb, W and Ti. Seal ring manufacturing method. 3. The method for producing a seal ring for a floating sheet according to claim 1, further comprising casting a molten metal containing 0.2 to 5% by weight of Ni into a mold. 4. The seal for a floating sheet according to claim 1, wherein the deoxidized molten metal is cast into a mold after the molten material has melted down in the melting furnace. Ring manufacturing method. 5. The centrifugal casting is carried out under the condition that a value (G) obtained by dividing the acceleration due to the centrifugal force of the rotating mold by the gravitational acceleration is within a range of 70 to 85.
5. A method for manufacturing a seal ring for a floating sheet according to any one of 1 to 4.