CN102913555A - Powder metallurgy composite oil-impregnated bearing and manufacturing method thereof - Google Patents

Abstract

The invention discloses a powder metallurgy composite oil-retaining bearing and a manufacturing method thereof. This compound oiliness bearing of powder metallurgy is bilayer structure, and concrete structure includes: one or more powder metallurgy layers positioned on the inner layer and a steel sleeve positioned on the outer layer, wherein the one or more powder metallurgy layers and the steel sleeve are sintered together. According to the technical scheme of the invention, the powder metallurgy composite oil-retaining bearing adopts a double-layer structure, so that the powder metallurgy composite oil-retaining bearing has good wear resistance and high bearing capacity, and the impact resistance is enhanced under the condition that the periphery of the powder metallurgy composite oil-retaining bearing is provided with the steel sleeve. Under the condition of installation, particularly hammering, the steel sleeve bears most external force due to compactness and high hardness, so that the inner-layer powder metallurgy oil-retaining bearing is protected from brittle fracture even under the condition of uneven stress or inclined installation.

Description

Powder metallurgy composite oil-impregnated bearing and manufacturing method thereof

technical field

The invention relates to the field of bearings, in particular to a powder metallurgy composite oil-impregnated bearing and a manufacturing method thereof.

Background technique

The bushings currently used in the field of construction machinery are mainly steel bushings, high-strength brass bushes inlaid with graphite, bimetallic bushings and powder metallurgy oil-impregnated bearings. Among them, powder metallurgy oil-impregnated bearings are more ideal. They are made of porous materials, and the inside of the body contains oil and self-lubricating. It can be used for a long time without adding butter, reducing maintenance time and costs. However, the product's bearing capacity and impact resistance are relatively poor, requiring The wear resistance and carrying capacity of the bearing are improved by means of quenching treatment.

However, since the powder metallurgy oil-impregnated bearing is made of porous materials, its carrying capacity is still limited even after quenching treatment; in addition, the bearings made of porous materials must be heat-treated to maintain good wear resistance and high wear resistance. Bearing capacity must be tempered at low temperature, which increases the brittleness of the bearing. When the outer diameter of the bearing is assembled with the interference fit of the equipment base hole, if the press-fitting equipment cannot be used, such as large-scale bearings at the production site Components cannot use press-fitting equipment or field maintenance operations, and are generally installed by hammering, making the powder metallurgy oil-impregnated bearing very easy to be brittle.

Contents of the invention

In order to solve the above technical problems, the present invention provides a powder metallurgy composite oil-impregnated bearing with good wear resistance, high bearing capacity and impact resistance and a manufacturing method thereof.

In order to achieve the above object, according to one aspect of the present invention, a powder metallurgy composite oil bearing is provided. The powder metallurgy composite oil bearing has a double-layer structure. Layered steel sleeve, one or more powder metallurgy layers are sintered with the steel sleeve.

Further, the steel sleeve is in the shape of a cylinder or a cylinder with a flange at the end, and the material used is medium-high carbon steel, or low-carbon steel subjected to carburizing treatment.

Further, the weight ratio of each component when mixing the powder metallurgy layer is: electrolytic copper powder 15%-25%, carbon powder 0.6%-1.3%, zinc stearate 0.8%-1%, and the rest is atomized iron powder; molybdenum disulfide or iron phosphide with a weight ratio of less than or equal to 2% can also be added during mixing.

Further, the wall thickness of the powder metallurgy layer is 2.5 mm or more.

According to another aspect of the present invention, a method for manufacturing the above-mentioned powder metallurgy composite oil-impregnated bearing is provided, and the specific process includes:

Step 1, mixing the materials of the powder metallurgy layer according to the weight ratio;

Step 2, powder metallurgy layer green body forming;

Step 3, processing the steel sleeve, and making the inner diameter of the steel sleeve larger than the outer diameter of the powder metallurgy layer green body;

Step 4, putting the powder metallurgy layer green body into the steel sleeve and then carrying out liquid phase sintering;

Step 5, quenching the sintered bearing and performing low-temperature tempering;

Step 6, immersing the heat-treated bearing in oil;

Step seven, processing the powder metallurgy composite oil-impregnated bearing into a finished product size.

Further, in step 4, the powder metallurgy layer green body is put into the steel sleeve, and liquid phase sintering is carried out above the melting point of copper under gas protection.

According to the technical solution of the present invention, since the powder metallurgy composite oil-impregnated bearing adopts a double-layer structure, it not only has good wear resistance and high bearing capacity, but also has enhanced impact resistance when there is a steel sleeve on the outer periphery. Under the conditions of installation, especially hammering, the steel sleeve bears most of the external force due to its compactness and high hardness, thereby protecting the inner powder metallurgy oil-impregnated bearing from brittle cracks, even under the condition of uneven force or skewed installation. Not brittle.

Description of drawings

Fig. 1 is the schematic diagram of axial sectional structure without flange in the first embodiment of the powder metallurgy composite oil-impregnated bearing according to the present invention;

Fig. 2 is the schematic diagram of the axial sectional structure with a flange in the first embodiment of the powder metallurgy composite oil-impregnated bearing according to the present invention;

Fig. 3 is according to the second embodiment of the powder metallurgy composite oil-impregnated bearing of the present invention without the axial cross-sectional structure schematic diagram of flange;

Fig. 4 is a schematic diagram of the axial sectional structure with a flange in the second embodiment of the powder metallurgy composite oil-impregnated bearing according to the present invention;

Fig. 5 is a flow chart of the manufacturing method of the powder metallurgy composite oil-impregnated bearing according to the present invention.

Explanation of reference signs:

1-powder metallurgy layer, 2-steel sleeve, 21-flange.

Detailed ways

The specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

Figures 1 and 2 show the first embodiment of the present invention. As shown in Figures 1 and 2, the powder metallurgy composite oil-impregnated bearing has a double-layer structure, specifically including: a powder metallurgy layer 1 located in the inner layer and a powder metallurgy layer located in the inner layer. Outer steel sheath 2. The powder metallurgy layer 1 and the steel sleeve 2 use the principles of expansion and contraction and liquid phase diffusion to carry out liquid phase sintering above the melting point of copper, and the steel sleeve 2 is closely combined with the powder metallurgy layer 1; the two are mainly quenched martensite, The hardness is above HRC30 degrees.

Among them, the powder metallurgy layer 1 is a cylindrical structure with one section as a whole, and the weight ratio of each component during mixing is: electrolytic copper powder 15%-25%, carbon powder 0.6%-1.3%, zinc stearate 0.8% ~1%, the remainder is atomized iron powder; molybdenum disulfide, iron phosphide, etc. for improving strength or wear resistance can also be added during mixing, and the weight ratio is ≤2%. In order to obtain better self-lubricating effect and strength, the wall thickness of the powder metallurgy layer 1 is 2.5 mm or more. The hardness of the hard phase of the powder metallurgy layer 1 is HRC40 or above. The steel sleeve 2 is a cylindrical structure with a flange 21 at the end. The material of the steel sleeve 2 is medium-high carbon steel, or low-carbon steel subjected to carburizing treatment, with a hardness of HRC30 or above.

As shown in Figure 5, the manufacturing method of the powder metallurgy composite oil-impregnated bearing is:

Step 1, powder metallurgy layer mixing: mixing the materials of the powder metallurgy layer according to the weight ratio. Pour 1.6kg of electrolytic copper powder, 8.22kg of atomized iron powder, 0.1kg of carbon powder, and 0.08kg of zinc stearate into the mixer for mixing.

Step 2, powder metallurgy layer green body molding: put the mixed materials into the mold, and press it under a certain pressure to form a straight sleeve green body, the outer diameter of the straight sleeve green body is 55.84mm, and the inner diameter is 44.50mm , with a height of 50mm. The density of the green body is 6-6.8 g/cm ³ , preferably 6.3 g/cm ³ .

Step 3, steel sleeve processing: process 45# seamless steel pipe into a steel sleeve, and make the inner diameter of the steel sleeve less than 0.2 mm larger than the outer diameter of the powder metallurgy layer green body, preferably 0.01 to 0.1 mm, for example, 45 #Seamless steel pipe is processed into a steel sleeve with an outer diameter of 61.50mm, an inner diameter of 55.90mm, and a height of 50mm.

Step 4, assembly: put the powder metallurgy layer green body into the steel sleeve, the two are clearance fit, the smaller the clearance, the better the combination of the two after sintering.

Step 5, sintering: put the assembled powder metallurgy layer green body and steel sleeve into the sintering furnace, and carry out liquid phase sintering above the melting point of copper under gas protection (the sintering temperature can be 1120 degrees).

During the sintering process, zinc stearate volatilizes, and a large number of pores will be formed in the original position; the solubility of copper in iron is 8%, and after copper enters the iron atom, the original position of copper will form individual or connected pores.

Using this material to produce full powder metallurgy oil-impregnated bearings (without outer steel sleeve), the volume will expand after sintering. Its expansion rate is generally 0.3% to 0.6%, which is much larger than the gap between the powder metallurgy layer green body and the steel sleeve, so that after sintering, the powder metallurgy layer green body and the steel sleeve can be closely combined to make the gap between the two In addition, after combined sintering, the outer diameter of the steel sleeve will shrink (making the double-layer powder metallurgy composite oil-impregnated bearing shrink in size and volume), and the shrinkage value is generally 0.1-0.3mm, which can also In addition, under the premise that the powder metallurgy layer green body and the steel sleeve shrink, the two are closely combined. Under the liquid phase sintering condition, through the liquid phase diffusion, part of the copper atoms diffuse to the In steel, a stronger bond strength can be obtained.

The dimensions of the powder metallurgy composite oil-impregnated bearing and the full powder metallurgy oil-impregnated bearing before and after sintering of the present invention are as follows:

It can be seen from the above table that the powder metallurgy composite oil-impregnated bearing will shrink after sintering; the full powder metallurgy oil-impregnated bearing will expand after sintering.

In addition, powder metallurgy composite oil-impregnated bearing "A" adopts liquid phase sintering (that is, the formed green body is matched with the steel sleeve, and the combination is sintered above the liquidus temperature of copper) and solid phase sintering (that is, the After the powder metallurgy oil-impregnated bearing has been sintered and processed, then the interference fit with the steel sleeve is carried out, and the combination is pressed and assembled below the melting point of copper, and solid-phase sintering is carried out) the powder metallurgy composite oil-impregnated bearing "B" is compared for bonding strength:

project Bond strength A 480Mpa B 236Mpa

It can be seen from the above that the bonding strength of the powder metallurgy composite oil-impregnated bearing that adopts liquid phase sintering is better than that of the powder metallurgy composite oil-impregnated bearing that is solid-phase sintered below the melting point of copper after interference press assembly. In addition, during solid phase sintering, the inner and outer layers are easily deformed, causing separation at the junction, thereby seriously reducing the strength of the bushing.

Step 6, heat treatment: Quenching the sintered bearing and tempering at low temperature, so that the steel sleeve and the powder metallurgy layer of the inner layer can obtain a martensite-based quenching structure to improve wear resistance and bearing capacity .

Step 7, oil immersion: put the heat-treated bearing into a vacuum oil immersion machine, vacuumize, and the anti-wear oil enters from the surface pores and stays inside the powder metallurgy layer to form an oil-impregnated bearing.

Step 8, processing: process the powder metallurgy composite oil-impregnated bearing into finished product size by turning and grinding.

Generally, crush strength is used to evaluate the strength of powder metallurgy oil-impregnated bearings. For example, powder metallurgy composite oil-impregnated bearings and full powder metallurgy oil-impregnated bearings are respectively processed into sizes of 50*60*50 (inner diameter*outer diameter*height) mm, and carried out The crush strength test shows that the powder metallurgy composite oil bearing is 816Mpa, and the full powder metallurgy oil bearing is 390Mpa. It can be seen that the crush strength of the powder metallurgy oil bearing is higher than that of the full powder metallurgy oil bearing. More than nearly 100%, that is, the powder metallurgy composite oil bearing with a steel sleeve on the outer periphery has much higher crush strength than the full powder metallurgy oil bearing.

This kind of powder metallurgy composite oil-impregnated bearing not only has good wear resistance and high bearing capacity, but also has enhanced impact resistance when there is a steel sleeve on the outer periphery. Under the condition of installation, especially hammering, the steel sleeve is dense and It has high hardness and can bear most of the external force, so as to protect the inner powder metallurgy oil-impregnated bearing from brittle cracking, even in the case of uneven force or skewed installation, it will not be brittle.

What Fig. 3 and Fig. 4 show is the second embodiment of the present invention, as shown in Fig. 3 and Fig. 4, the difference between the second embodiment and the first embodiment lies in: the cylindrical powder metallurgical Layer 1 is multi-stage (two stages in the figure), and there are gaps between multi-stage powder metallurgy layers 1. Processing engineering is also as in the first embodiment.

Nowadays, large-scale oil cylinders and large-scale engineering machinery and equipment are developing rapidly. Due to the weak compressive capacity of powder metallurgy bushings, steel sleeves or copper sleeves are mostly used for large-scale bushings. Although the compressive capacity of powder metallurgy composite oil-impregnated bearings has improved, due to The molding process of the bearing is upper and lower compression molding, which inevitably causes uneven density distribution. With the loss of pressure, the density at the upper and lower ends is high, and the density in the middle is low. The higher the density, the higher the strength but the lower the oil content. , the self-lubricating effect is poor, and vice versa; even if the strength of the upper and lower ends of the bearing is high but the oil content is low, this uneven density distribution is very unfavorable for bearings that need both high-load bushing strength and self-lubricating ability , The uneven distribution of strength and oil content can easily lead to brittle cracks in the bearing during use.

However, when the cylindrical powder metallurgy layer 1 inside the steel sleeve 2 is multi-stage, the strength and oil content are distributed at intervals along the axial direction, so that the density deviation of the bearing is small, the strength and oil content are evenly distributed, and at the same time, it has a relatively high bearing density. High strength and good self-lubricating ability.

The above disclosures are only specific embodiments of the present invention, however, the present invention is not limited thereto, and any changes conceivable by those skilled in the art shall fall within the protection scope of the present invention.

Claims (6)

1. compound oil-impregnated bearing of powder metallurgy, it is characterized in that, the compound oil-impregnated bearing of this powder metallurgy is double layer construction, and concrete structure comprises: be positioned at one or more snippets powder metallurgy layer of internal layer and be positioned at outer field steel bushing, described one or more snippets powder metallurgy layer and steel bushing are sintered together.

2. the compound oil-impregnated bearing of powder metallurgy according to claim 1 is characterized in that, described steel bushing is cylindric or cylindric with flange plate of end, and the material of employing is middle, high-carbon, perhaps for carrying out the low carbon steel of Carburization Treatment.

3. the compound oil-impregnated bearing of powder metallurgy according to claim 1, it is characterized in that, each the composition weight proportioning during described powder metallurgy layer batch mixing is: electrolytic copper powder 15%～25%, carbon dust 0.6%～1.3%, zine stearate 0.8%～1%, all the other are atomized iron powder; Can also add weight proportion during batch mixing less than or equal to 2% molybdenum disulfide or iron phosphide.

4. the compound oil-impregnated bearing of powder metallurgy according to claim 1 is characterized in that, the wall thickness of described powder metallurgy layer is 2.5mm or more than the 2.5mm.

5. the manufacture method such as the compound oil-impregnated bearing of each described powder metallurgy in the claim 1 to 4 is characterized in that, idiographic flow comprises:

Step 1 is carried out batch mixing with the material of powder metallurgy layer according to part by weight;

Step 2, the moulding of powder metallurgy layer green compact;

Step 3, steel bushing processing, and make the steel bushing internal diameter size larger than powder metallurgy layer green compact outside dimension;

Step 4 is packed powder metallurgy layer green compact into and is carried out sintering behind the steel bushing;

Step 5 is carried out Quenching Treatment with the bearing that sinters, and carries out low-temperature tempering;

Step 6 is with this heat treated bearing immersion oil;

Step 7 is processed into finished size with the compound oil-impregnated bearing of this powder metallurgy.

6. the compound oil-impregnated bearing of powder metallurgy according to claim 5 is characterized in that, is carrying out liquid-phase sintering under the air protection behind the steel bushing of in the described step 4 powder metallurgy layer green compact being packed into more than the fusing point of copper.

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