JP2011214129A - Sintered sliding member of configuration fixed to base metal and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sintered sliding member satisfying that no lead is contained, a long life is obtained without causing seizure under a boundary lubrication condition, a satisfactory bonding is obtained, hardness is not low and no deterioration in strength is caused, since lead exerts adverse effect on an environment although lead bronze is much used in the conventional sintered sliding member of configuration fixed to base metal.SOLUTION: The sintered sliding member has such a configuration that alloy which has a composition containing Fe of 20 to 45%, Mo of 7 to 15%, S of 0.5 to 1.5%, Cu of 35 to 65%, Sn of 3 to 8% and inevitable impurities and has a porosity of 5 to 20% is integrally fixed to the base metal of steel, copper or copper alloy.

Description

  There are many rotating parts in automobiles, industrial machines, etc., and sliding members are used for the rotating parts. In automobiles, there are bearings for receiving rotating shafts, in hydraulic machine gear pumps there are side plates for pressing the side surfaces of gears, and in piston pumps there are cylinders, swash plates, shoe parts, etc., and the present invention relates to these sliding members.

  Since many of the conventional sliding members are inexpensive and have an appropriate sliding property, lead bronze is used. These are standardized in JIS H 5120. However, when these are used and disposed of in landfills, groundwater is contaminated and lead to lead poisoning. Therefore, their use is being restricted on a global scale. Therefore, a sliding member not containing lead is strongly demanded as an urgent problem.

  In response to this, proposals have been made for bismuth instead of lead, and the same level of sliding characteristics can be obtained (see Patent Document 1). Although lead is contained, addition of graphite has been proposed (see Patent Document 2). In addition, as a method of joining to the iron alloy of the base metal, the molten lead bronze is solidified into a raw material, which is processed to the specified dimensions and then fixed by brazing if necessary, or after copper plating, It is known to use it as a moving member (see Patent Document 3).

Japanese Patent Laid-Open No. 2005-60808 JP-A-4-198440 Japanese Patent Laid-Open No. 10-1704

  As described above, lead bronze, which is a conventional sliding member, has a serious drawback that contains a large amount of lead that adversely affects the environment. In addition, the lead bronze-based sliding member has good sliding performance under use conditions in which lubricating oil is present.

  However, the alloy is extremely easy to seize and inferior in wear resistance under the severe boundary lubrication conditions where the sliding condition such as the work machine bush is high rotation and high surface pressure or the lubricating oil cannot be sufficiently supplied. However, there is a problem that sufficient sliding characteristics such as wear, peeling, and hardness are not sufficiently high, so that sufficient sliding characteristics are not obtained, such as the hardness is reduced as lead is increased. Thus, low life is an issue, and there is a demand for somehow to extend the life.

  In the case of production with lead bronze powder, it is usually the case that the lead bronze powder is placed on a steel plate at 700 to 900 ° C and sintered, then press rolled with a roller or the like, and sintered at the same temperature and used as a sliding member. However, attention has not been paid to the control of the pores in that case. In addition, when the material is manufactured by casting, there are naturally no pores.

  Further, in order to join lead bronze-based sintered materials, it is necessary to sinter at a high temperature during sintering. However, when the sintering temperature is increased, lead particles that ensure conformability in terms of sliding characteristics grow and become larger, leading to a decrease in strength of the sintered material. On the other hand, in order to finely disperse the lead particles, it must be sintered at a low temperature. However, at a low sintering temperature, there is a problem that the amount of liquid phase generated is small and the wetting is not sufficient, resulting in insufficient bonding.

  Therefore, the problem to be solved is that it does not contain lead, that it does not seize under boundary lubrication conditions and has a long life, that good bonding is obtained, that the hardness is not low, that there is no strength reduction, 5 items are the main items, and it is most important that they are actually used as sliding members and have a long life.

  As a result of diligent research on the characteristics that have a reduction in friction coefficient, a reduction in wear rate, high strength, and high hardness with a composition that does not contain lead, the present inventor has found that these problems that must be solved. Except for the substantial part) Fe: 20-45%, Mo: 7-15%, S: 0.5-1.5%, Cu: 35-65%, Sn: 3-8%, and composition of inevitable impurities Thus, an alloy having a porosity of 5 to 20% was found.

  This makes it possible to obtain a high-performance sintered sliding member that has a friction coefficient that is incomparable to conventional products, a reduced wear rate, and high strength. (Lubrication) environment, the friction coefficient does not increase much, and it can be firmly fixed and integrated with steel, copper, or copper alloy base metal during sintering. It led to the invention of being able to. The reasons for limiting the composition of the product of the present invention are described below.

Fe content:
Fe combines with Mo and S to give the material itself a self-lubricating property. When the content is less than 19%, the effect of imparting self-lubricating properties to the material is small. (The shape of FeS does not contribute to self-lubricating properties.) If it is more than 46%, the strength of the material is lowered. Therefore, the Fe content is preferably 20 to 45%.

Mo content:
Mo is combined with S to give the material a self-lubricating property. If it is less than 6%, the effect of imparting self-lubricating properties to the material is small. If it is as large as 16% or more, the formation of sulfide is saturated, and no further improvement in the lubricating performance is recognized. In addition, the amount of shrinkage during sintering becomes too large, further reducing the strength of the material. Therefore, the Mo content is preferably 7 to 15%.

S content:
S forms sulfides and provides self-lubricating properties. Improves non-seizure and wear resistance in boundary lubrication and non-lubrication areas. When the content is as low as 0.4% or less, the formation of sulfide is less imparted and the effect of imparting self-lubricity is less. If it is as large as 1.6% or more, sulfide generation that does not contribute to solid lubrication increases, and the strength of the material decreases. Therefore, the S content is preferably 0.5 to 1.5%.

Cu content:
Cu acts as a binding material for the material, and improves the strength and acts to adhere to the base metal. If it is as low as 34% or less, the effect of the adhesive action with the base metal is small and the film is easily peeled off. If it is as large as 66% or more, the lubrication characteristics are reduced, and seizure tends to occur. Therefore, the Cu content is preferably 35 to 65%.

Sn content:
Sn reinforces the Cu binder. If it is as low as 2% or less, the Cu matrix is not sufficiently strengthened, and the sinterability is also deteriorated. When it is more than 9%, the sinterability is improved, but the Cu—Sn compound is formed and becomes brittle, and the heat resistance is also reduced. In addition, since other components are relatively reduced, the lubrication characteristics are also reduced. Therefore, the Sn content is preferably 3 to 8%.

Porosity:
When the sliding condition is high rotation and high surface pressure, boundary lubrication or depletion lubrication occurs, but by including pores, the lubrication characteristics of the material can be used to prevent depletion lubrication and increase the friction coefficient. Reduce. If the amount is less than 4%, the effect of assisting lubrication characteristics is small. When the content is as high as 21% or more, the strength of the material is reduced (one of the causes of peeling). Therefore, the pore content is preferably 5 to 20%.

Next, a method for producing alloys of these inventive compositions will be described. Each powder of Fe, Mo, S, Cu, and Sn is weighed into a blend composition by an ordinary powder metallurgy method, and then stirred and mixed with a coarse machine. As for the particle size of the powder, Fe, Mo, and S desirably have a particle size that passes through a 100 μm sieve, and Cu and Sn desirably have a permeability of 5 to 15 μm.

  As the lubricant, zinc stearate or the like is used. Each of these mixed powders is put into a mold and pressed at 200 to 700 MPa to produce a green compact. Each powder may be an alloy of two or more of them.

Next, the green compact is sintered together with the base metal in a non-oxidizing atmosphere such as vacuum, Ar, or N ₂ at a temperature in the range of 800 to 1100 ° C. and lower than the melting point of the base metal, and is integrally sintered. Get a member. Here, the porosity can be controlled by the sintering temperature and its holding time. That is, the higher the sintering temperature and the longer the holding time, the smaller the porosity.

Sintering with the base metal in a non-oxidizing atmosphere such as vacuum, Ar, or N ₂ at 800-1100 ° C., which is higher than the conventional product, is due to the sintering of the sliding member and the sliding member and the base metal. This is because it is preferable to perform the bonding simultaneously.

  The base metal is made of steel, copper, or copper alloy because it can be firmly bonded to the sliding member and strength is required. The steel material does not contain carbon, for example, a general structural rolled steel material is preferable because it has good adhesive strength and is difficult to deform at the sintering temperature, but is not limited thereto. Sintering at a high temperature also means excellent heat resistance.

  According to the present invention, it is a problem that it does not contain lead, that it does not seize under boundary lubrication conditions and has a long life, that good bonding is obtained, that the hardness is not low, and that there is no decrease in strength, It is clear and can provide a sliding member that does not contain lead, which has been strongly required to be replaced. Particularly, the sliding member can be provided under severe conditions, and the industrial contribution is great.

  Here, examples and comparative examples according to the manufacturing method of the present invention will be described.

  The product of the present invention and the comparative product are prepared in accordance with a normal powder metallurgy method, and the powder is molded at a pressure of 200 MPa using a mold to form a green compact. The green compact is sintered in a vacuum. Thus, sintered bodies having a length of 24 × 8 × 4 mm based on the cemented carbide tool association standard CIS 026 (1983) were produced as bonded to a single body and a general structural rolled steel material. In addition, what was adhere | attached was taken as the thickness of the sliding member part 0.5mm and the steel material part 3.5mm.

  Using a single specimen, the bending strength and Vickers hardness were measured. Further, the bonding strength was measured with the bonded test pieces. This was done by performing a three-point bending test at a speed of 0.1 mm / s, unloading after reaching the maximum pressure, and observing the joint surface at 120 to 150 ° to determine whether there was any peeling.

  Furthermore, a cylindrical test piece having a diameter of 9 mm and a length of 15 mm was also prepared, and a pin-on-disk friction test was performed using the bottom surface as a friction surface using a set of three pieces. The minimum PV value (product of pressure and velocity) that occurred was measured respectively. In the pin-on-disk friction test, martensitic stainless steel SUS440C is used as the mating material disk, and ester oil is applied to the mating material disk at a sliding speed of 0.4 m / s and a load of 98 to 2352 N. Conducted at medium room temperature.

  These results are shown in Table 1. 1 and 2 show the state of the test piece after the measurement of the bonding strength. The total composition is not 100% because of inevitable impurities.

  A sliding material for pressing the side surface of the gear of the gear pump for a hydraulic machine was manufactured with the product of the present invention (corresponding to the test piece shown in 2 of Table 1), incorporated in the gear pump, and the pump performance and the performance as the sliding material were measured. As a result, in an accelerated test that reproduced the actual machine conditions, the performance was equivalent to or better than that of a conventional gear pump using lead bronze.

It is a mode of the test piece after measurement of the joint strength of the product of the present invention (2 in Table 1). It is a mode of the test piece after the measurement of the joint strength of the comparative example (8 in Table 1).

Claims (2)

  The mass percentage (about the substantial part excluding pores) is Fe: 20 to 45%, Mo: 7 to 15%, S: 0.5 to 1.5%, Cu: 35 to 65%, Sn: 3 to 8%, A sintered sliding member characterized in that an alloy having a composition of inevitable impurities and a porosity of 5 to 20% is fixed to and integrated with a base metal of steel, copper, or a copper alloy.   Each powder having a mass percentage of Fe: 20 to 45%, Mo: 7 to 15%, S: 0.5 to 1.5%, Cu: 35 to 65%, Sn: 3 to 8%, and composition of inevitable impurities After pressing, the green compact is sintered together with a steel, copper, or copper alloy base metal in a non-oxidizing atmosphere at a temperature in the range of 800 to 1100 ° C. and lower than the melting point of the base metal. Then, a method for manufacturing a sintered sliding member by integrating them.

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