JPS5840672B2 - Gear pump side plate - Google Patents

Description

[Detailed Description of the Invention] The side plate of a gear pump needs to have a high degree of wear resistance against sliding contact with the gear, and conventionally the material thereof has been cast lead bronze such as LBC4 or a sintered alloy with a similar composition. is used.

All of these utilize the solid lubricating effect of lead, which contains approximately 8 to 16% lead, but because the melting point of lead is lower than other components, it tends to segregate during casting or sintering, and the uniform distribution of lead makes it resistant to wear. It was difficult to obtain a side plate with stable properties.

This invention first creates a sintered base material that does not contain lead, and by infiltrating lead into the pores to distribute it uniformly, and by appropriately selecting the composition of the sintered base material, it has better wear resistance than before. This provides a pump side plate with excellent properties.

When customizing the base material, it is first necessary to have high self-lubricating and oil-retaining properties, and materials that meet these requirements include cast iron containing free graphite.

However, as will be explained later, both sintered materials made from cast iron powder and materials infiltrated with lead do not show good results.

That is, as the second condition, the strength and sintering density of the base that holds free graphite are important.

As a result of various studies, the inventors found that carbon was 1.5 to 3% by weight.
, copper 1-5%, tin 0.1-2%, phosphorus 0.1-0.3%
and iron remainder, with a sintered density of 6.1 to 6.797
It has been found that a sintered alloy of - is suitable as a base material, and that a member obtained by infiltrating this base material with lead has the desired wear resistance.

Hereinafter, this invention will be described in detail with respect to one embodiment thereof.

First, atomized iron powder with a particle size of 80 mesh or less, natural graphite powder with a particle size of 200 mesh or less, and bronze powder with a tin content of 10% and a particle size of 200 mesh or less are prepared as raw material powders, and after mixing them in a predetermined ratio, stearin is used as a lubricant. After adding and mixing 0.5% zinc acid, it was molded under a pressure of 4.5 kg/-.
A large number of green compacts having a predetermined shape and a density of 6.4 g/- were prepared.

Next, these green compacts are decomposed in an ammonia gas furnace at a temperature of 1
After sintering at 000°C for 30 minutes, the sintered density was 6.4 g.
/c111 and the alloy composition is 2% carbon by weight.

A sintered base material containing 4.5% copper, 0.5% tin, 0.2% phosphorus and balance iron was obtained.

Next, lead was infiltrated into the pores of this base material under conditions of 5700C and 27 atmospheres to prepare a sample of the present invention, and the sample was subjected to an abrasion resistance test.

In addition to the above-mentioned inventive samples, the test samples include, for comparison, the inventive base material impregnated with Teflon instead of lead, the inventive base material as it is, LBC4, sintered cast iron powder, and Six types of lead-infiltrated materials were targeted.

Figure 1 shows the test method for abrasion resistance, in which a test sample 2 is attached and fixed to a suitable backing metal 1, and a 40φ×
A rotor (material: SCM21) having an annular projection of 35φ was pressed against a load of 16.7 at 9/-, and the rotor was rotated at 750 revolutions per minute, 1
The wear marks produced by dry friction for 50 seconds are measured, and the wear resistance is evaluated based on the depth.

The abrasion resistance test results for each of the above samples are shown in FIG.

Cast iron in the figure is a sintered material made from cast iron powder, but it is significantly inferior to LBC type 4 regardless of whether it is infiltrated with lead or not.

The wear resistance of the base material of the present invention is slightly better than LBC type 4 before infiltration with lead, and it does not improve much even if it is impregnated with Teflon.

However, when the base material of the present invention is infiltrated with lead, the wear resistance is significantly improved as shown in the figure.

This is considered to be due to the effect of the combination of the base material and the infiltrant.

The composition of the base material according to the present invention will be explained below.

In this base material, a carbon content of 1.5% or more is required in order to disperse free graphite in the base and utilize its solid lubricating effect, and if it is less than this, the wear resistance will deteriorate rapidly as shown in Figure 3. decreases to

Moreover, even if it is added in an amount of 3% or more, the abrasion resistance does not improve, and on the contrary, the moldability of the powder decreases, which is not preferable in terms of work.

Copper and tin are preferably added in the form of bronze powder, and the ratio of the two can be arbitrarily determined within the above range by using bronze powder of an appropriate composition.

However, if the copper content exceeds 5%, the amount of expansion during sintering increases, and the dimensional accuracy of the sintered body decreases.

Moreover, if the tin content exceeds 2%, the base material will become brittle, so excessive blending is not preferable.

On the other hand, if the amount is too small, the required strength and wear resistance cannot be obtained.

Phosphorus forms a ternary alloy of Fe--C--P in the matrix and increases wear resistance, but if the amount added exceeds 0.3%, machinability decreases and finishing efficiency decreases.

On the other hand, below 0.1%, the amount of ternary alloy phase produced is small;
It hardly contributes to improving wear resistance.

The raw material powder is formed and sintered using the usual powder metallurgy method, but a carburizing gas should be selected for the furnace atmosphere to avoid decarburization during sintering.

Furthermore, since sintering at a high temperature promotes carbon diffusion, the sintering temperature is preferably 1100°C or less, preferably around 1000°C.

Regarding the density of the sintered base material, if it is lower than the above range, the strength of the base material will be insufficient, and if it is higher, the amount of lead infiltration will decrease.
Both reduce wear resistance.

As a result of tests conducted so far, it has been confirmed that the pump side plate according to the present invention can be applied to a gear pump with a discharge pressure of 180 kg/-.

[Brief explanation of the drawing]

Figure 1 is a drawing explaining the abrasion resistance test method, Figure 2 is a graph comparing the abrasion resistance of various materials, and Figure 3 is a graph showing the relationship between the amount of graphite and the abrasion resistance in the present invention. It is.

Claims (1)

[Claims] 1 Lead is infiltrated into the pores, the sintered density is 6.1 to 6,
7 g/=, its composition is 1.5-3% carbon by weight
, copper 1-5%, tin 0.1-2%, phosphorus, i-0.3%
, the side plate of a gear pump made of iron-based sintered alloy with the remaining iron.