KR20130005164A - A combined type sintered oilless bearing for a sliding bearing - Google Patents

Abstract

PURPOSE: An oil-less sliding bearing of a composite sintered structure is provided to harden iron of a sliding layer with graphite in thermal treatment, thereby improving the durability of abrasion and a load carrying capacity. CONSTITUTION: An oil-less sliding bearing of a composite sintered structure comprises a sliding layer(200), a steel support base(100), and a welded portion(300). The sliding layer is formed in an inner cylindrical part of a cylindrical combined body(500R). The sliding layer is formed into a sintered layer of Fe-Cu based alloy powder. As the sliding layer is sintered, an outer cylindrical part is welded. The outer cylindrical part is formed by the steel support base and the steel support base is made of a weldable low-carbon steel materials. The welded portion is formed in the outer cylindrical part in a longitudinal direction.

Description

Combined oilless sliding bearing {A combined type sintered oilless bearing for a sliding bearing}

The present invention relates to a bearing used in high-load low-speed sliding parts of construction and industrial machinery of various fields, more specifically, environmentally friendly, excellent wear resistance, lubricating properties, in particular where high load, high surface pressure An oilless sliding bearing suitable for supporting a moving body moved at a low speed.

In general, the sliding bearing is a device provided between the movable body and the stationary body to support the movable body to be able to move smoothly from the stationary body in a state of being in surface contact with the movable body or the stationary body. In particular, since the sliding bearings have stronger impact resistance than rolling bearings, construction machinery such as excavators and loaders that support relatively high loads, industrial machinery such as injection molding machines, and water gates used for dams in rivers and wind power It is used in various places such as new and renewable industrial machinery.

On the other hand, industrial machinery and construction machinery has a plurality of shaft rotational portion, the sliding portion is typically installed between the shaft and the shaft hole to reduce the frictional resistance between the shaft and the shaft hole is installed, usually every fixed period It is divided into the case of supplying lubricating oil separately and the case of using semi-permanently without supplying lubricating oil because it has a function to contain lubricating oil itself. In particular, the latter is referred to as an oilless sliding bearing. More specifically, one method of containing graphite into a sliding bearing by lubricating oil and using a sintered body in which sliding occurs is formed in the sintered body. It is divided into another way to contain and use lubricating oil in the pores. In addition, in the case of a bearing using a sintered body, a sintered bearing made of only a sintered body and a double structure having a form of securing strength by using an iron material outside the sintered body to compensate for the low strength of the sintered body It is divided into bearing of composite sintered structure.

The annular bearing with such a composite sintered structure is secured through an external iron material, and has a merit of lowering manufacturing costs by using an inexpensive iron material instead of an expensive sintered body, while a schedule disposed inside the external iron material In order to form a sintered body having a shape, it is difficult to manufacture the bearing size more than a certain size according to the mold size by inserting the powder into the mold and molding using a powder press, and between the top, bottom, and middle parts during the molding process. There is a disadvantage that it is difficult to uniformly form pores in the sintered body containing the lubricating oil due to the density non-uniformity of.

The annular sliding bearing according to the conventional general art, as disclosed in Korean Patent Publication No. 10-0286246, inserts a metal and a core into the mold of the molding apparatus, and inserts a metal and a core into the mold. Fill the metal mixed powder between the metals, insert the upper pressing member to the upper end of the mold, and press the upper pressing member or the lower pressing member to form the metal mixed powder. The sintering together and the process of joining to the metal if it is steel is made with its main configuration. The annular sliding bearings produced in this way have a difference in the density of the upper, lower and middle parts of the molded part in the forming step. Because of the nonuniformity, it is difficult to make a long molded body of 50 mm or more, and an annular slab having a larger specification To manufacture the bearing, a sliding bearing having a molded body having a short length of 50 mm or less is molded and sintered to manufacture a plurality of composite sliding bearings, and the two or more short length composite sliding bearings thus manufactured are welded. There is a problem to make a long product by joining.

As another conventional technique, as disclosed in Korean Patent Laid-Open Publication No. 10-2006-0056701, first, an annular molded body is formed of metal mixed powder, and then the molded body is sintered into a sintered body, and then the sintered bodies are lasered. Friction heat is generated at the contact parts by heating or frictional contact with each other to bond each other.The inner and outer surfaces of the bonded sintered joint are processed and polished, followed by hardening heat treatment, and then impregnated with oil to sinter bearing. There is a method of manufacturing the present invention, there is a problem that it is difficult to make a large diameter product due to the limited size of the mold for making a basic molded body, and the process of joining a long molded body itself is not only easy but also large Large equipment is required to frictionally contact diameter sintered bodies There is.

In this way, the sintered joint is press-fitted into the metal round bar (or shaft hole) and finally completed as a bush-type sliding sintered bearing product. The joint strength between the metal round bar and the sintered joint joined by the press is uneven. The sintered body is made of external metal round bar (steel) in order to be manufactured for the large industrial machinery with high practical load and high surface pressure. It is necessary to manufacture a sliding bearing of a composite structure supported by a back metal), which indicates that a large press apparatus having a size exceeding a range generally used in the process of pressing the sintered joint into a metal round rod is required. .

Therefore, the molding density of the molded body forming the sintered body can be provided by a simple method of uniformity of the molding density, and if the steel forming the outer cylindrical portion (housing) of the bush structure (double structure), the metal and the inner cylindrical portion are formed. It does not cause unevenness in the bonding strength of the joining interface of the sintered body, thereby increasing the substantial joining area, achieving high strength, and eliminating the need for a large press in forming a large diameter sintered bearing. There is a need for a new type of sintered bush bearing for sliding bearings and a method of manufacturing the same, which are more economical by removing excessive burdens in maintaining high molding accuracy.

The present invention is to solve the problems of the prior art, the technical problem of the present invention,

Since the sliding layer does not contain lead, which is a heavy metal, it is environmentally friendly, improves the wear resistance so that it is not easily damaged by the inflow of external foreign substances, and because the formation of internal pores and impregnation with oil does not require frequent oil injection. It is an oilless sliding bearing of composite sintered structure with excellent lubrication characteristics and load resistance that can improve the operation rate of and can be used without problems in the shaft connection of construction machinery and industrial machinery with high surface pressure of 400kgf / ㎠,

In particular, the density change of the upper, lower, and intermediate portions of the molded body forming the sintered body forming the inner cylindrical portion of the cylindrical sintered oilless sliding bearing provides a considerable level of uniformity (molding precision). If the steel forms the outer cylindrical portion (cylindrical housing) of the double structure (bush structure), it does not cause nonuniformity in the bonding strength of the bonding interface between the metal and the sintered body forming the inner cylindrical portion, resulting in an increase in the actual bonding area. This eliminates the need for large powder metallurgy presses in forming large diameter or long composite sintered oilless sliding bearings, while increasing the overload of manufacturing costs in achieving the required high molding precision. By eliminating the possibility, higher performance and economic To provide an oilless sliding bearing of a composite sintered structure.

The present invention, in order to solve the above problems, by sintering and bonding the powder containing iron, copper, and graphite on the iron sheet material to produce a double-structured iron plate member having a sintered body as one sliding layer, this round shape It is intended to provide an annular bearing made by forming a shape of the bearing of the bearing and then connecting the steel plate of the contacting portion by welding.

To this end, the present invention, in the cylindrical sintered bearing made of a double structure used in the axial rotation of the construction machinery and industrial machinery, the inner cylindrical portion to form a double-cylindrical cylindrical assembly made of iron, copper, and graphite A sliding layer formed of a sintered layer of iron-copper alloy alloy powder (a mixture of material powders forming an iron-copper alloy) is provided, and the outer cylindrical portion to be joined as the sliding layer is sintered is welded low carbon steel steel. It is provided by a steel support base made of a material, and the outer cylindrical portion is provided with an oilless sliding bearing of a composite sintered structure, characterized in that the weld is provided in the longitudinal direction.

Here, the outer cylindrical portion made of a steel material is formed primarily of a plate-shaped steel support base, the inner cylinder portion is a plate-shaped iron-copper, in which the alloy powder is sintered and joined primarily on the plate-shaped steel support base. Formed of a sliding layer of a base alloy, and

After the heterogeneous metal plate-like joined body including the plate-shaped steel support base and the sliding layer of the iron-copper-based alloy is formed into a cylindrical joined body by a subsequent press forming or rolling step, the outer cylinder is formed from the joint ends of both ends. Forming a weld along the longitudinal direction of the cylindrical joint, connecting the joint ends of both ends of the steel support base to form a part,

And a steel support base forming an outer cylindrical portion of the cylindrical joined body, and a sliding layer of an iron-copper alloy forming an inner cylindrical portion sintered and joined to the steel support base to form an annular bush structure. It is desirable to provide an oilless sliding bearing of sintered structure.

In addition, the sliding layer of the iron-copper-based alloy is 18% by weight based on the weight ratio of the total composition of any one selected from copper (Cu) or copper alloy as the iron-copper-based alloy powder on the plate-shaped steel support base To 30% by weight, graphite is contained in 0.3% to 1.0% by weight based on the weight ratio of the total composition, the remainder is formed by laminating and sintering the iron-copper-based alloy powder containing iron to the base It is preferable.

And, the welding portion is formed by welding the joint ends of the both ends of the steel support base to form a joint end of the cylindrical assembly processed into a cylinder with a welding material, the weld portion is formed by joining the joint end of the cylindrical assembly processed into a cylinder Preferably, the weld material penetrates into the wedge-shaped spaces between the inclined ends of the both ends of the steel support base to be formed, and the sintered metal structure of the sliding layer of the iron-copper alloy is treated with martensite through heat treatment. It is preferably formed.

On the other hand, as a method for manufacturing an oilless sliding bearing of cylindrical composite sintered structure according to the present invention,

① any one selected from copper (Cu) or copper alloy is contained in 18% to 30% by weight based on the weight ratio of the total composition, graphite is contained in 0.3% to 1.0% by weight based on the weight ratio of the total composition And mixing the iron-copper alloy powder containing iron as a base,

② In order to prepare a plate-shaped steel sheet on which the iron-copper alloy powder is to be laminated, to remove foreign substances from the surface thereof, and to improve adhesion to the iron-copper alloy powder, copper plating, zinc plating, tin plating, and nickel plating. Plating is carried out by either method to form a plate-shaped steel support base,

③ In order to form a sintered layer of a composite sintered structure, the mixed iron-copper-based alloy powder is powdered at a predetermined thickness on the upper surface of the plate-shaped steel support base,

④ sintering the iron-copper alloy powder in a powdery state which is 50% or less of theoretical density,

(5) In order to densify the sintered sintered layer to 65% to 85% of the theoretical density, the plate-like joined body is subjected to plastic working by one or more of rolling, pressing and drawing processes, After leveling,

⑥ Annealing heat treatment in a vacuum furnace or a continuous furnace can obtain a plate-like assembly of a composite sintered structure.

Here, the plastic working and leveling process of ⑤ and the annealing heat treatment of ⑥ may be further performed once more after the annealing heat treatment of ⑥ to improve the bonding strength or increase the density of the plate-like assembly of the composite sintered structure.

⑦ The plate-like joined body is a process of deforming the width direction by pressing with a press using an upper punch die and a lower die, and undergoes a first curvature forming bending process, a second U-shaped bending process, and a third circular bending process. Performing a press forming to shape the plate-like body into a cylindrical body, or forming the plate-like body into a cylindrical body through a rolling forming process,

⑧ The welding part is formed by filling a welding material in the gap between both ends of the steel support base forming the joint end of the cylindrical body processed into a cylindrical shape, and then in the same manner as the manufacturing method of the oilless sliding bearing of the general composite sintered structure. That is,

⑨ First cutting (roughing), carburizing heat treatment, impregnating oil in the heat-treated cylindrical joints, and second-cutting (finishing) of the impregnated cylindrical joints of the final cylindrical composite sintered structure Oilless sliding bearings will be manufactured.

And, in detail explaining the step of forming the plate-like joined body into a cylindrical joined body by the press forming of ⑦ described above,

A step of deforming the width direction by pressing the plate-like joined body with a press using an upper punch die and a lower die,

A primary curvature forming bending step of forming a curvature in the width direction on both sides of the plate-shaped joined body by using an upper punch mold having a convex circumferential portion at a lower end thereof and a lower die having a concave circumferential portion at an upper surface thereof;

Bending a U-shape by adding a curvature deformation to an intermediate portion using an upper punch mold having a circumferential portion convex at a lower end of the plate-shaped joined body that has undergone the first curvature forming bending process and a lower die having a bridge at both sides thereof. The second U-bending machining step, and

An upper punch mold having a round bar having a diameter corresponding to an inner diameter of a bush bearing required at the center of the plate-shaped joined body which has undergone the second U-bending processing step, and having a curvature corresponding to an outer diameter of the required bush bearing; It is desirable to provide a method for producing an oilless sliding bearing of a composite sintered structure comprising a third round bending processing step of forming the plate-like assembly into a cylindrical assembly by rotational pressing using a lower die.

As described above, the manufacturing method of the oilless sintered bearing of the sliding type according to the embodiment of the present invention may have the following effects.

According to an embodiment of the present invention, since the sliding layer does not contain lead, which is a heavy metal, it is environmentally friendly, and iron, which is a base part included in the sliding layer, is cured together with graphite during heat treatment, thereby improving abrasion resistance and load resistance. Pore formation and impregnation of oil can improve the machine's utilization rate without requiring frequent oil injection.

In addition, since wear resistance and load resistance are improved, it is not easily damaged by the inflow of external foreign matters, and is required without limitation on the size (diameter and length) of the axial rotation part of construction machinery and industrial machinery where high surface pressure of 400kgf / ㎠ or more is applied. Can be manufactured and used according to the standard.

In particular, it is possible to provide a considerable level of uniformity in a simple manner in the forming density of the molded body forming the sintered body forming the inner cylindrical portion of the cylindrical bush-type sliding bearing, and if the steel forming the outer cylindrical portion, the metal and the inner cylindrical portion It eliminates the necessity of a large press in forming large diameter or long oilless sliding bearings while achieving high strength by bringing about an increase in the actual joint area without causing unevenness in the bonding strength of the bonding interface of the sintered body to be formed. It is possible to provide an oilless sliding bearing of a sintered structure with higher performance and economy by eliminating the possibility of increasing the excessive burden of manufacturing cost in achieving the required high molding precision.

1A and 1B are flow charts illustrating a method of manufacturing an oilless sliding bearing of a composite sintered structure according to an embodiment of the present invention.
Figure 2 is a view showing a plate-like assembly first made in order to manufacture the oilless sliding bearing of the composite sintered structure according to the manufacturing method according to an embodiment of the present invention.
3 to 5 are views showing a specific progress of the press forming step of forming the plate-like assembly into a cylindrical assembly.
Fig. 6 is an enlarged view of a state machined in a cylindrical joined body and its main portion;
FIG. 7 is an enlarged view of a state in which a welding material is filled and welded to a gap between both ends of a cylindrical joined body and a welded part; FIG.
Figure 8 is a microscopic structure observation picture of the "A" part of Figure 7 as showing in detail the oilless sliding bearing of the composite sintered structure according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

1A and 1B are flowcharts illustrating a method of manufacturing an oilless sliding bearing having a composite sintered structure according to an embodiment of the present invention, and FIG. 2 is an oil of the composite sintered structure according to a manufacturing method according to an embodiment of the present invention. Figure 3 is a view showing a plate-like assembly made first to manufacture a sliding sliding bearing, Figures 3 to 5 is a view showing a specific progress state of the press forming step of forming the plate-like assembly into a cylindrical joint, Figure 6 is a cylindrical Fig. 7 shows a state in which a shape is processed into a joined body and an enlarged portion thereof, and Fig. 7 shows a state in which a bush-type sliding sintered bearing is completed by joining by filling a gap between both ends of the cylindrical joined body by forming a welded portion. It is a figure, and FIG. 8 is a microscopic observation picture of the "A" part of FIG.

The oilless sliding bearing of the composite sintered structure according to the present invention, as shown in Figures 2 to 9, in the cylindrical sintered bearing made of a double structure used in the axial rotation of the construction machinery and industrial machinery, The inner cylindrical portion forming the cylindrical bonded body 500R is provided with a sliding layer 200 formed of a sintered layer of an alloy powder including iron, copper, and graphite, and is joined while the sliding layer 200 is sintered. The outer cylindrical portion is provided by a steel support base 100 made of a low carbon steel weldable steel, and the outer cylindrical portion is a composite sintered oil, characterized in that the weld portion 300 is provided in the length (L) direction A sliding sliding bearing is provided.

Here, the outer cylindrical portion made of a steel material is primarily formed of a plate-shaped steel support base 100, the inner cylinder portion is primarily sintered joined the alloy powder on the plate-shaped steel support base 100 It is formed of a sliding layer 200 of the plate-shaped iron-copper alloy, and

The heterogeneous metal plate-shaped assembly 500 comprising the plate-shaped steel support base 100 and the sliding layer 200 of an iron-copper alloy is formed into a cylindrical assembly 500R through a subsequent press forming or rolling step. After the processing, a welded portion 300 connecting the both ends of the steel support base 100 forming the outer cylindrical portion among the bonding ends of both ends is formed along the length L direction of the cylindrical joined body 500R. ,

The steel support base 100 forming the outer cylindrical portion of the cylindrical joined body 500R, and the sliding layer 200 of the iron-copper alloy forming the inner cylindrical portion sintered and bonded to the steel support base 100 are annular. It is desirable to provide an oilless sliding bearing of a composite sintered structure, characterized in that to form a bush structure.

In addition, the welding part 300 is formed by welding a joint end of both ends of the steel support base 100 forming a joint end of the cylindrical joined body 500R processed into a cylindrical shape with a welding material, and the welding part 300 Preferably, the weld material penetrates into the wedge-shaped spaces between the inclined ends of the both ends of the steel support base 100 forming the joint end of the cylindrical joined body 500R processed into a cylindrical shape, and the iron The sintered metal structure of the sliding layer 200 of the copper-based alloy is preferably a martensite structure is formed through heat treatment.

Here, the steel support base 100 is made of carbon steel (preferably, low carbon steel) and preferably to support the load applied to the sliding layer 200, the load applied to the sliding layer 200 It may be a load of a construction machine or an industrial machine itself in which the oilless sliding bearing of the composite sintered structure of the present invention is mounted, or an impact load generated when the construction machine or the industrial machine is operated. Ultimately, the steel support base 100 improves the strength and impact properties of the sliding layer 200.

The sliding layer 200 of the iron-copper alloy is sintered and bonded to the steel support base 100, oil is impregnated into the internal pores 201 formed by sintering, and a relative sliding member that requires sliding (not shown). ) Is in contact with the surface. In particular, when the oil is impregnated into the internal pores 201 formed in the sliding layer 200 by sintering, as shown in Figure 8 it is possible to implement an oilless (oilless) bearing, industrial machinery according to frequent oil injection It is possible to prevent the lowering of the operation rate. In addition, since iron (Fe), which is known, is hardened together with graphite (Gr) during heat treatment and is changed into a martensite structure, the wear resistance of the sliding layer 200 can be greatly improved. In addition, even if no separate lead (Pb) can be used because it can improve the lubrication characteristics through sintering and oil impregnation may be environmentally friendly. Hereinafter, the components of the sliding layer 200 of the iron-copper-based alloy will be described in detail.

The sliding layer 200 of the iron-copper alloy according to the present invention is iron-copper alloy powder laminated on the plate-shaped steel support base, based on the weight ratio of the entire composition, 18 to 30% by weight Of copper (Cu) or copper alloy, 0.3 to 1.0% by weight of graphite (Gr), and iron-copper alloy powder containing iron (Fe) as a base is preferably formed by laminating and sintering Do. In addition, the sliding layer 200 of the iron-copper-based alloy may further include 0.1 wt% to 3.0 wt% of other components, and the other components may be any one selected from nickel (Ni) or silver (Ag). It can be one or both.

More specifically, the sliding layer 200 of the iron-copper-based alloy is manufactured by adding copper or a copper alloy having good toughness and sintering ability to the iron matrix (which serves to secure the strength of the sliding layer as a base). By adding pure copper (Cu), which is copper, or by adding bronze alloy (Cu-Sn) or brass alloy (Cu-Zn), which are copper alloys, to improve friction characteristics with relative sliding members (not shown), The sintering ability of the sliding layer 200 is improved to improve the strength. For example, copper and tin-bonded bronze alloys (Cu-Sn) have a low sintering temperature and thus sinter (ie, iron-copper alloy powder sintering) and joining (ie, steel support base and iron-) at low temperatures. Copper-based alloy bonding) is preferably added, and in another example, when the sliding layer 200 requires high strength, brass alloy (Cu-Zn) is preferably added. As another example, when performing a high temperature heat treatment, pure copper (Cu) may be added to the iron matrix to prevent melting from occurring at a heat treatment temperature (about 910 ° C. to 940 ° C.).

 On the other hand, according to the experiments while adjusting the composition ratio of the main components constituting the sliding layer 200, any one selected from copper (Cu) or copper alloy (Cu-Sn or Cu-Zn) is based on the entire composition 18 It was shown that it is most preferred to be composed of 30% by weight. That is, since copper (Cu) or copper alloy has a lower melting point than iron (Fe), excellent lubricity, and a large diffusion coefficient, it is easy to diffuse. When the addition amount is less than 18 wt%, the sliding layer 200 When the adhesiveness, lubricity and impact resistance are lowered, and the addition amount is more than 30% by weight, the adhesion and lubricity of the sliding layer 200 are effective, but the strength and durability of the sliding layer 200 are reduced. Therefore, according to the experimental results, while maintaining the strength and durability of the sliding layer 200 in an optimal state (Cu) (or copper alloy) to improve the bonding between the sliding layer 200 and the support base 100 ) Was added in an amount of 18% to 30% by weight.

In addition, when graphite (Gr) is added to the iron matrix of the sliding layer (200), it diffuses to the iron matrix during sintering and contributes to the hardening of the iron matrix, and the graphite remaining without diffusion is impregnated in the sliding layer (200) Apart from serving as a solid lubricant to provide additional lubricating action to the sliding layer 200, graphite (Gr) was found to be most preferably composed of 0.3% to 1.0% by weight based on the total composition. That is, graphite (Gr) is partially diffused into iron (Fe) powder during high temperature bonding to harden the powder, and some remain to act as a solid lubricant, if the addition amount is less than 0.3% by weight, iron (Fe) If it does not contribute to hardening of a powder and the addition amount is more than 1.0 weight%, the intensity | strength of the sliding layer 200 will fall. Accordingly, it is necessary to add an optimum amount of graphite (Gr) that can harden the iron (Fe) powder and improve the strength of the sliding layer 200. Therefore, according to the experimental results, the amount of graphite (Gr) that can harden the iron (Fe) powder while improving the strength of the sliding layer 200 was found to be 0.3% by weight to 1.0% by weight.

In addition, in order to improve the bonding strength with the plate-shaped steel support base 100, nickel (Ni) or silver (Ag) having excellent bonding properties may be selected and added to the iron matrix of the sliding layer 200 in order to improve the bonding strength. Other components such as nickel (Ni) or silver (Ag) may be added to the sliding layer 200 at 0.1 wt% to 3 wt% based on the weight ratio of the total composition. It was shown that the bond strength with 100) is improved. Specifically, when the addition amount of the other components is more than 3% by weight, the appearance of the liquid phase in the sliding layer (layer formed by sintering the iron-copper alloy powder) is high, so that the deformation amount is large and the processing amount increases. If the amount of the other components added was less than 0.1 wt%, the amount of liquid phase appeared in the sliding layer was too small to improve the bonding strength between the sliding layer and the support base (which is made of carbon steel) and did not contribute to the improvement of the strength of the sliding layer.

Hereinafter, referring to FIGS. 1A to 7, a method of manufacturing an oilless sliding bearing having a composite sintered structure will be described in detail.

1A and 1B are flowcharts illustrating a method of manufacturing an oilless sliding bearing having a sintered composite structure according to an embodiment of the present invention, and a method of manufacturing the oilless sliding bearing having a sintered composite shown in FIGS. 1A and 1B. According to a preferred embodiment for, firstly mixing (S110) the iron-copper-based alloy powder having a composition as described above;

Preparing a plate-shaped steel sheet (S120);

Removing foreign matter from the surface of the prepared steel plate (S130);

Plating the surface of the plate-shaped steel sheet by any one of copper plating, zinc plating, tin plating, and nickel plating to form a plate-shaped steel support base 100 (S140);

Stacking the mixed iron-copper-based alloy powder at a predetermined thickness on an upper surface of the plate-shaped steel support base (S200); And

The iron-copper alloy powder is sintered in a powdery state of 50% or less of theoretical density so that the iron-copper alloy powder becomes a sliding layer 200 on the plate-shaped steel support base 100, and at the same time, 10 to 50 minutes at a sintering temperature of 950 ° C. to 1200 ° C., such that the interface between the steel support base 100 and the iron-copper alloy powder laminated thereon is bonded to each other to form a single plate-shaped assembly 500. A simultaneous sintering step (S300) of bonding sintering in a reducing atmosphere or a vacuum atmosphere during the bonding sintering time is performed.

Here, the iron-copper-based alloy powder powdered to the steel support base 100 is bonded in a reducing atmosphere or a vacuum atmosphere so as to be one bonded body in the simultaneous sintering step (S300). In particular, maintaining a reducing atmosphere or a vacuum atmosphere during bonding is to reduce the oxide layer that may be formed on the surface of the steel support base 100 or the surface of the alloy powder to activate the bonding and sintering well. In addition, simultaneously with bonding, the iron-copper alloy powder is sintered on the steel support base 100 to become the sliding layer 200. Bonding sintering temperature for the above bonding and sintering in a vacuum atmosphere or reducing atmosphere is 950 ° C to 1200 ° C, which is the liquid phase appearance temperature of the copper (or copper alloy) powder serving as a bonding material, Bonding sintering time to build depends on the thickness of the steel support base 100 but takes approximately 10 to 50 minutes.

Then, in the simultaneous sintering step (S300), the sliding layer 200 sintered in a powdered state in which the density becomes 50% or less of the theoretical density is pressed after sintering, thereby densifying the density of the sliding layer 200 by the theoretical density. Plasticizing the plate-like assembly 500 in one or more of rolling, pressing and drawing processes to densify from 65% to 85% of the , Performing a secondary plastic sintering step (S400) of annealing heat treatment in a vacuum furnace or a continuous furnace. Through the second plastic sintering step (S400), the sliding layer 200 is densified to 65% to 85% of the theoretical density to achieve an improvement in strength as well as to contain oil, that is, a space containing internal pores ( 201) can also be achieved at the same time.

This secondary plastic sintering step (S400) is preferably carried out including the following more specific steps as shown in Figure 1a specifically.

-First plastic working step (S410) provided by a cold working method in order to roll primarily to improve the density of the sliding layer 200 of the plate-shaped joined body 500 passed through the simultaneous sintering step (S300) Is carried out. Here, the rolling is densified to 4.96 to 5.2 g / cm 3, which is about 80% of 6.2 to 6.5 g / cm 3, which is the final target sintered density of the sliding layer 200 of the oilless sliding bearing of the composite sintered structure to be the final product. For example, in the rolling process, which is repeatedly carried out in several stages divided into several stages, a single reduction ratio is suitably about 5% (0.5 mm reduction based on the initial powder stack height of 10 mm) based on the reduction ratio of the cross section. This is because when the reduction ratio is 5% or more based on the reduction ratio of the cross section, there is a high possibility of cracking in the sintered body. In this case, when the rolling process (first plastic working) is performed on the plate-like joined body, the height c of the sliding layer 200 having a height of about 10 mm at the time of completion of the first sintering, for example, in the case of the experimental example, is the total litigation process. Assuming that the height (c) of the sliding layer 200 in the final state of completing all the above is 4.0mm, it is reduced to 5.2mm while passing through the first plastic working step (S410). That is, when the height is reduced by 4.8 mm, which is 80% of 6 mm which is the difference between 10 mm and 4 mm, the height difference exceeds 4.8 mm in the actual first plastic working step, namely, If the reduction proceeds to more than 80% of the total reduction, cracking occurs in the sintered body during the firing process or causes excessive bending of the plate, thereby increasing the possibility of cracking in the sintered body in the next step, the leveling process. ② Next, the plate-like assembly 500 which has undergone the first plastic working step S410 is subjected to a first leveling step S415 to improve the flatness. The main purpose of this leveling is to It is possible to facilitate the charging of the annealing heat treatment (which may be referred to as secondary sintering) to be carried out to improve the productivity, and to provide a second plastic processing (rolling) step (S420) to be performed next. It is to give smooth rolling reduction rate by preventing cracks by increasing flatness. It is preferable that the plane tolerance of the plate-shaped joined body which passed this leveling step shall be 5 mm or less.

(3) Further, the plate-like assembly which has passed through the first plastic working step (S410) and the first leveling step (S415) has an increased dislocation density, so that decomposition and cracking of the bonded powder may be generated when further plastic working is performed. In order to lower the dislocation density and increase the bonding force between powders, the first annealing heat treatment step S420 is performed as a secondary sintering process of heating and slow cooling in a vacuum furnace or a continuous furnace, which is performed in a vacuum furnace and a continuous furnace. Any is possible, and usually, annealing heat treatment (secondary sintering) is performed at a temperature of about 1,100 ° C. or more and a time condition of about 50 to 100 minutes.

④ Next, in order to improve the density of the first plastic working (rolled) sintered compact, a second plastic working step (S430) provided by a cold working method for the second plastic working (rolling) is performed. The density during the primary rolling in the plastic working step (S410) was 4.96 to 5.2 g / cm3, which is about 80% of the final sintered density, but the secondary rolling in the second plastic working step (S430) is the remaining 20 % To ensure that the sliding layer 200 of the plate-like assembly 500 has a sintered density of 6.2 to 6.5 g / cm 3, for example, a single reduction ratio in a rolling process that is repeatedly carried out many times in several steps. Silver is about 3% (0.3mm reduction based on the initial sintered layer height of 10mm) on the basis of the reduction rate of the cross section.If the single reduction rate is 3% or more on the basis of the reduction ratio of the cross section, cracks are likely to occur in the sintered body and the surface flatness Because the road is bad. When the secondary rolling process (second plastic working) is performed on the plate-shaped joined body 500 as described above, the height of the sliding layer (sintered layer), which has been reduced to 5.2 mm through the first firing process (S410), is again increased. It will be reduced to 4.0mm. That is, the reduction of the remaining 20% of the total reduction ratio of the entire firing process is to proceed.

⑤ Next, the plate-like assembly 500 which has undergone the second plastic working step S430 is also subjected to a second leveling step S435 to improve flatness. The purpose is also to facilitate the productivity of the annealing heat treatment (which may be referred to as tertiary sintering), which will be carried out in the future, to improve productivity, as well as the flatness of the plate-like assembly 500 provided in the press forming step (S500) to be performed next. This is to minimize the later turning (cutting) by increasing the precision by increasing the. It is preferable that the planar tolerance of the plate joined body 500 which has undergone such a leveling step is 1 mm or less.

⑥ Further, a second annealing heat treatment as a tertiary sintering process of heating and slow cooling in a vacuum furnace or a continuous furnace in order to lower the dislocation density of the plate-shaped assembly 500 which has undergone the second leveling step S435 and increase the bonding force between powders. In step S440, the second annealing heat treatment (tertiary sintering) may be performed using any one of a vacuum furnace and a continuous furnace. Annealing heat treatment (third sintering) and slow cooling in the austenite region under time conditions.

As described above, the plate-shaped assembly 500 which has passed through the respective steps S410, S415, S4120, S430, S435, and S440 of the secondary plastic sintering performing step S400 has a plate shape as shown in FIG. 2. It has a shape of a plate-like assembly 500 consisting of a steel support base 100 and a sliding layer 200 made of a sintered body of an iron-copper alloy bonded thereto, to form an oilless sliding bearing having a sintered structure. This requires the following subsequent steps as shown in FIG. 1A.

That is, as the step of pressing the plate-like joined body 500 with a press using an upper punch die and a lower die to deform the width (W) direction, the first curvature forming bending process, the second U-shaped bending process, and A press forming step (S500) of forming the plate-shaped assembly 500 into a cylindrical assembly 500R through a third round bending process;

Forming a weld by filling a welding material in a gap between both ends of the steel support base (100) forming a joint end of the cylindrical joined body (500R) processed into a cylinder (S600);

Performing a first cutting (roughing) process on the welded cylindrical joined body 500R (S700);

Carburizing heat-treating the cylindrical assembly 500R (S800);

Impregnating oil into the heat-treated cylindrical assembly (500R) (S900); And

The oil-impregnated cylindrical joint 500R is subjected to a second cutting (finishing) process (S1000).

Meanwhile, the plate-shaped steel support base 100 has a modified cross section of FIG. 6 in which the width W of the surface on which the iron-copper alloy powder is to be laminated is larger than the width of the rear surface of the opposite surface. Using the one having a flat end portion 110 (indicated by the thickness 'b' in FIG. 2) and the inclined end portion 111 on the side surface (indicated by the thickness 'a' in FIG. 2) to have a cylindrical assembly processed into a cylindrical shape The wedge-shaped space portion is formed between the inclined end portions 111 of both ends of the steel support base 100 forming the bonded end of 500R, and thus, the wedge-shaped space portion is formed in step S600. It is easy to infiltrate the weld material into and thus may act more advantageously to induce a tighter bond between the two ends.

The above process will be described in more detail with reference to the accompanying drawings.

First, as shown in FIGS. 1B and 3 to 6, the plate-shaped assembly 500 is pressed into a press using upper punch molds 410u, 420u, 430u and lower dice 410b, 420b, 430b. As a process of pressing to deform the width (W) direction, a press forming step (S500) of forming the plate-shaped joined body 500 into a cylindrical joined body 500R is performed. More specifically, as shown in FIG. 3, the plate-shaped joined body 500 using the upper punch mold 410u having the convex circumference at the bottom and the lower die 410b having the concave circumference at the upper surface thereof. The first curvature forming bending processing step (S510) to form a curvature in the width (W) direction on both sides () of reference numeral '①' and '②' of FIG. 3), and as shown in FIG. Curvature deformation in the middle portion using the upper punch mold 420u having a circumferential portion at the lower end of the plate-shaped assembly 500 which has undergone the difference curvature forming bending process, and the lower die 420b having a bridge at both sides. The inner diameter of the cylindrical bearing required at the center of the plate-like joined body through the second U-shaped bending processing step (S520) and the second U-shaped bending processing step as shown in FIG. Diameter corresponding to the final product The upper punch mold 430u and the lower die 430b having a curvature corresponding to the outer diameter of the cylindrical bearing required by inserting a round bar 430r having a diameter of about 2 mm) in consideration of the cutting allowance before the system; By using the rotary press to form the plate-shaped assembly 500 is subjected to the third round bending processing step (S530) to shape the cylindrical assembly 500R as shown in FIG.

 Then, as shown in FIG. 7, the welding part is formed by filling a gap between both ends of the steel support base 100 that forms the joint end of the cylindrical bonded body 500R processed in a cylindrical shape ( Proceeding to S600, the step of forming the weld portion is a wedge-shaped space between the inclined end portions 111 of both ends of the steel support base 100 to form a joint end of the cylindrical assembly 500R processed into a cylindrical shape Weld, but only to the depth of the spaced apart at least 1mm from the boundary surface of the steel support base 100 and the sliding layer 200 from the outside so that the welding material does not penetrate into the flat end portion 110 of both ends of the steel support base 100 By welding, the welding layer 200 is prevented from reaching the sliding layer 200 by the welding heat influence part 111a indicated by reference numeral 111a in the enlarged portion of FIG. 7. That in order to prevent and protect from being damaged it is preferable in.

When the welding unit 300 is completed as described above, the step S600 is completed, and the primary cutting process (S700) of the welded cylindrical joint is performed, and then the steel support base 100 and the sliding layer ( At the same time to cure (200) to heat treatment to improve the strength and wear resistance (S800). Heat treatment methods include high frequency, carburization, quenching, and nitriding heat treatment. The heat treatment is performed by selecting an optimal heat treatment method according to the use and function. In particular, after the heat treatment, the iron particles in the sliding layer 200 is hardened to show martensite structure (see FIG. 8), which serves to improve strength and wear resistance.

When the heat treatment operation described above is completed, the internal pores 201 of the sliding layer 200 is impregnated with oil (S900), and finally subjected to secondary cutting to match the shape of the product (S1000).

The oilless sliding bearing of the composite sintered structure according to the preferred embodiment of the present invention described above may have the following effects.

According to an embodiment of the present invention, since the sliding layer does not contain lead, which is a heavy metal, it is environmentally friendly, and iron, which is a base part included in the sliding layer, is cured together with graphite during heat treatment, thereby improving abrasion resistance and load resistance. Pore formation and impregnation of oil can improve the machine's utilization rate without requiring frequent oil injection.

In addition, since the wear resistance and load resistance are improved, it is not easily damaged by the inflow of external foreign matters, and the specifications required without limitation on the size (diameter and length) of the shaft rotating parts of construction machinery and industrial machinery that apply high surface pressure of 400kgf / ㎠ or more. Can be manufactured and used according to

In particular, it is possible to provide a considerable level of precision in a simple manner in the forming density of the molded body forming the sintered body forming the sliding layer of the inner cylindrical portion of the cylindrical bush-type sliding bearing, and if the steel forming the cylindrical housing, the metal and the inner cylinder It does not cause unevenness in the bonding strength of the joining interface of the sintered body forming the part, thereby increasing the substantial joining area while achieving high strength, while eliminating the need for a large press in forming a large diameter or long oilless sliding bearing, In addition, it is possible to provide an oilless sliding bearing of a multi-sintered structure having higher performance and economy by eliminating the possibility of increasing excessive burden of manufacturing cost in achieving the required high molding precision.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

100: steel support base
200: sliding layer
201: internal pores 300: weld
500: plate joined 500R: cylindrical joined

Claims (5)

In the double-cylindrical cylindrical sintered bearing used in the axial rotation part of construction machinery and industrial machinery, the inner cylindrical portion forming the double-cylindrical cylindrical assembly 500R includes iron, copper, and graphite. A sliding layer 200 formed of a sintered layer of the alloy powder is provided, and the outer cylindrical portion to be joined while the sliding layer 200 is sintered is provided by a steel support base 100 made of a low carbon steel steel material that can be welded. And, The outer cylindrical portion is oilless sliding bearing of the composite sintered structure characterized in that the welding portion 300 is provided in the length (L) direction. According to claim 1, wherein the outer cylindrical portion made of a steel sheet material plated by any one of copper plating, zinc plating, tin plating, and nickel plating is formed of a plate-shaped steel support base 100, The inner cylindrical portion is formed primarily of the sliding layer 200 of the plate-shaped iron-copper-based alloy in which the iron-copper-based alloy powder is sintered and bonded on the plate-shaped steel support base 100, and
The heterogeneous metal plate-shaped assembly 500 comprising the plate-shaped steel support base 100 and the sliding layer 200 of an iron-copper alloy is formed into a cylindrical assembly 500R through a subsequent press forming or rolling step. After the processing, a welded portion 300 connecting the both ends of the steel support base 100 forming the outer cylindrical portion among the bonding ends of both ends is formed along the length L direction of the cylindrical joined body 500R. ,
The steel support base 100 forming the outer cylindrical portion of the cylindrical joined body 500R, and the sliding layer 200 of the iron-copper alloy forming the inner cylindrical portion sintered and bonded to the steel support base 100 are annular. Oilless sliding bearing of the composite sintered structure, characterized in that to form a bush structure of. According to claim 1 or claim 2, wherein the iron-copper-based alloy powder, any one selected from copper (Cu) or copper alloy is contained in 18 to 30% by weight based on the weight ratio of the total composition, graphite 0.3 to 1.0% by weight based on the weight ratio of the total composition, the rest of the oilless sliding bearing of the composite sintered structure, characterized in that the iron is included in the base. According to claim 1 or 2, wherein the welding portion 300 is welded to the joint ends of both ends of the steel support base 100 forming a joint end of the cylindrical joined body 500R processed into a cylindrical shape by welding material Although the welding part 300 is formed, the welding material penetrates into the wedge-shaped spaces between the inclined end portions 111 of both ends of the steel support base 100 forming the joint end of the cylindrical joined body 500R processed into a cylindrical shape. Oilless sliding bearing of the composite sintered structure characterized in that it is formed. The oilless sliding bearing of claim 1 or 2, wherein the sintered metal structure of the sliding layer (200) is formed of martensite structure through heat treatment.

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