Powder metallurgy product part densification process

Abstract

The invention discloses a powder metallurgy product part densification technology, and particularly relates to the technical field of powder metallurgy, the powder metallurgy product part densification technology comprises the first step, the second step, the third step and the fourth step, a densification tool in the fourth step comprises a base, a bottom block is arranged at the top of the base, and a plurality of balls making contact with the top end of the base are fixedly arranged at the bottom end of the bottom block; two tool half dies are arranged at the top end of the bottom block, the two tool half dies are symmetrically arranged front and back, and a cavity is formed after the two tool half dies are combined. A sintered and formed gear workpiece is placed in the cavity defined by the two tool half dies, then the gear workpiece is pressed downwards through the pressing assembly, the gear workpiece can be extruded by the side wall of the cavity, materials forming the gear workpiece move inwards in the radial direction, therefore, holes in the gear workpiece are compressed, the local density of the gear workpiece is improved, and the machining precision of the gear workpiece is improved. And the strength of the gear workpiece is further improved.

Description

Technical Field

[0001] The invention relates to the technical field of powder metallurgy, and in particular to a process for densifying parts of powder metallurgy products. Background Art

[0002] Traditional gears are made of steel through a complex machining process, which has a long processing flow and high cost. The powder metallurgy process uses metal or non-metallic powder as raw material, puts the raw material into a mold, extrudes the powder to initially agglomerate, and then sinters it to make a metal workpiece.

[0003] Therefore, processing gears by powder metallurgy has the advantages of short process flow, near-net forming, high efficiency and low cost. However, the powder metallurgy process often causes pores inside the formed workpiece due to air mixing or insufficient powder mixing during the pressing process, which affects the comprehensive performance of the material.

[0004] Gears made of powder metallurgy are often used in the automotive field. Since today's automotive gear application scenarios have higher requirements for gear strength, especially higher requirements for tooth surface fatigue strength, gears manufactured by conventional powder metallurgy processes can no longer fully meet application requirements. Summary of the invention

[0005] The purpose of the present invention is to provide a process for densifying parts of powder metallurgy products. The gear workpiece is pressed down by a pressing component, and the gear workpiece is squeezed by the side wall of the cavity, so that the material constituting the gear workpiece moves radially inward, thereby compressing the pores inside the gear workpiece, increasing the local density of the gear workpiece, and further increasing the strength of the gear workpiece.

[0006] In order to achieve the above object, the present invention provides the following technical solution: a process for densifying parts of powder metallurgy products, the specific steps are as follows: Step 1: Select special materials and mix various raw material powders of special materials evenly according to the proportion. Only when the raw materials are fully mixed evenly can the pores inside the workpiece caused by uneven mixing of raw materials be effectively avoided; Step 2: Put the evenly mixed raw materials into the gear mold, and apply a pressure of 500-1000MPa to the raw material powder in the mold. According to the size, structure, application scenario and other factors of the gear, the extrusion force can be adjusted within this range to initially extrude the raw material powder into shape; Step 3: Put the extruded gear workpiece into a sintering furnace, heat it at different temperatures in different areas inside the sintering furnace, and finally sinter it into shape. Finally, take out the sintered gear workpiece and cool it. Step 4: After cooling, the gear workpiece is placed inside the densification chemical equipment and processed by the densification chemical equipment. The upper part of the workpiece presses the gear workpiece downward into the cavity of the tooling. As it is pressed down, the gear workpiece moves down to the specified position inside the tooling cavity. Then the relevant components at the bottom of the tooling cavity will push the gear workpiece upward. After processing, the gear workpiece is taken out to complete the densification process.

[0007] Furthermore, the raw materials of the special material in step 1 include Mo 0.2-1.5%, Ni 0-4%, C 0-1%, B 0-0.1% and Fe 93.6-99.8% in percentage. The above raw materials need to be made into powder before mixing to facilitate subsequent mixing work.

[0008] Furthermore, the sintering furnace in step three is divided into four areas: dewaxing area, welding preheating area, sintering area and water cooling area. During the sintering process, the gear workpiece passes through these four areas in sequence in the above order. The temperature range of the dewaxing zone is 550-715°C, the temperature range of the welding preheating zone is 980-1090°C, and the temperature range of the sintering zone is 1110-1150°C.

[0009] Furthermore, the densification chemical equipment in step four includes a base, a bottom block is provided on the top of the base, a plurality of ball bearings in contact with the top of the base are fixedly provided on the bottom end of the bottom block, two tooling half-molds are provided on the top of the bottom block, the two tooling half-molds are symmetrically arranged front to back, and the two tooling half-molds are merged to form a cavity, which is located between the two tooling half-molds. The cavity is funnel-shaped, with a large opening at the upper end and a small bottom end. The taper of the cavity is 0.1-0.6, and the side extrusion amount of the gear workpiece is 0.1-0.5mm.

[0010] Furthermore, two columns are fixedly provided at the top of the base, the tooling half-mold and the bottom block are located between the two columns, and a fixed beam is fixedly provided on the side of the column facing the tooling half-mold, and a pressing assembly is provided at the bottom end of one of the fixed beams; The pressing assembly comprises a pressurized hydraulic cylinder fixedly arranged at the bottom end of the fixed crossbeam, a pressurized plate is fixedly arranged at the bottom end of the pressurized hydraulic cylinder, and the pressurized hydraulic cylinder can push the pressurized plate downward and squeeze the gear workpiece downward.

[0011] Furthermore, a spray pipe is fixedly provided at the bottom end of another fixed crossbeam, a plurality of atomizing nozzles are fixedly provided at the bottom end of the spray pipe, and an oil delivery pipe is fixedly provided at the outer end of the spray pipe for delivering lubricating oil to the inside of the spray pipe.

[0012] Furthermore, two linear motors are fixedly provided at the top of the base, and connecting plates are fixedly provided at the tops of the movers of the two linear motors. Two clamping plates are provided at one end of the connecting plate facing the bottom block through bolts, and the clamping plates are fixed at the outer end of the bottom block, so that the linear motor can drive the bottom block to move left and right.

[0013] Furthermore, a support block is provided at the top of the connecting plate through bolts, and a detachable side hydraulic cylinder is provided at the top of the support block. An arc-shaped push plate is fixedly provided at one end of the piston rod of the side hydraulic cylinder. The two arc-shaped push plates are respectively arranged at the outer ends of the two tooling half-molds. The extension and retraction of the side hydraulic cylinder can drive the tooling half-molds to merge or separate.

[0014] Furthermore, a demoulding assembly is provided at the top of the bottom block, and the demoulding assembly is arranged inside the cavity. The demoulding assembly includes a spring fixed at the top of the bottom block, and a lifting plate is fixed at the top of the spring. The elastic force of the spring can push the lifting plate to lift the gear workpiece upward.

[0015] In the above technical solution, the technical effects and advantages provided by the present invention are: 1. By placing the sintered gear workpiece in a cavity surrounded by two half-molds, and then pressing the gear workpiece down by a pressing assembly, the gear workpiece will be squeezed by the side wall of the cavity, so that the material constituting the gear workpiece moves radially inward, thereby compressing the pores inside the gear workpiece, increasing the local density of the gear workpiece, and thus improving the strength of the gear workpiece; 2. The lubricating oil is sprayed out through the atomizing nozzle and adheres to the inner wall of the cavity. In the subsequent densification process, the lubricating oil reduces the friction between the outer end of the gear workpiece and the inner wall of the cavity, making the outer end of the gear workpiece less worn. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0017] Figure 1 This is the overall structure diagram of the compact chemical equipment of the present invention; Figure 2 It is a schematic diagram of the separation state of the tooling half-mold of the compact chemical tooling of the present invention; Figure 3 It is a cross-sectional view of a half-mold of a compact chemical equipment of the present invention; Figure 4 It is a bottom view of the structure of the pressing assembly of the compact chemical equipment of the present invention; Figure 5 This is a bottom-up structural diagram of the spraying pipeline and atomizing nozzle of the compact chemical equipment of the present invention.

[0018] Description of reference numerals: 1. Base; 2. Linear motor; 3. Column; 4. Fixed beam; 5. Tooling half mold; 6. Bottom block; 7. Side hydraulic cylinder; 8. Spray pipe; 9. Demolding assembly; 901. Spring; 902. Lifting plate; 10. Clamp; 11. Arc push plate; 12. Support block; 13. Connecting plate; 14. Pressing assembly; 1401. Pressurized hydraulic cylinder; 1402. Pressing plate; 15. Atomizing nozzle. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0020] The present invention provides a process for densifying powder metallurgy product parts, and the specific steps are as follows: Step 1: Select special materials and mix various raw material powders of special materials evenly according to the proportion. The raw materials of special materials include Mo 0.2-1.5%, Ni 0-4%, C 0-1%, B 0-0.1% and Fe 93.6-99.8% in percentage. The above raw materials need to be made into powder before mixing to facilitate the subsequent mixing work. Only when the raw materials are fully mixed evenly can the pores inside the workpiece caused by uneven mixing of raw materials be effectively avoided; Step 2: Put the evenly mixed raw materials into the gear mold, and apply a pressure of 500-1000MPa to the raw material powder in the mold. According to the size, structure, application scenario and other factors of the gear, the extrusion force can be adjusted within this range to initially extrude the raw material powder into shape; Step 3: Put the extruded gear workpiece into a sintering furnace, heat it at different temperatures in different areas inside the sintering furnace, and finally sinter it into shape. Finally, take out the sintered gear workpiece and cool it. The sintering furnace is divided into four areas: dewaxing area, welding preheating area, sintering area and water cooling area. During the sintering process, the gear workpiece passes through these four areas in the above order. The temperature range of the dewaxing area is 550-715°C, the temperature range of the welding preheating area is 980-1090°C, and the temperature range of the sintering area is 1110-1150°C. Step 4: After cooling, the gear workpiece is placed inside the densification chemical equipment and processed by the densification chemical equipment. The upper part of the workpiece presses the gear workpiece downward into the cavity of the tooling. As it is pressed down, the gear workpiece moves down to the specified position inside the tooling cavity. Then the relevant components at the bottom of the tooling cavity will push the gear workpiece upward. After processing, the gear workpiece is taken out to complete the densification process.

[0021] The density that can be obtained by conventional processes is usually 6.8~7.2g / cm 3The product densified by the above process has higher tooth shape accuracy and the overall density is increased to 7.4g / cm 3 At the same time, the density near the surface is greatly increased to 7.7g / cm 3 The above can achieve fatigue performance close to that of steel and meet functional requirements.

[0022] like Figure 1-5 As shown, the densification chemical equipment in step 4 includes a base 1, a bottom block 6 is provided on the top of the base 1, a plurality of balls in contact with the top of the base 1 are fixedly provided at the bottom end of the bottom block 6, two tooling half-molds 5 are provided on the top of the bottom block 6, the two tooling half-molds 5 are symmetrically arranged front to back, and the two tooling half-molds 5 are combined to form a cavity, which is located between the two tooling half-molds 5, and the cavity is funnel-shaped, with a large opening at the upper end and a small bottom end. The taper of the cavity is 0.1-0.6, and the side extrusion amount of the gear workpiece is 0.1-0.5mm.

[0023] Two columns 3 are fixedly provided at the top of the base 1, and the tooling half mold 5 and the bottom block 6 are located between the two columns 3. A fixed beam 4 is fixedly provided on the side of the column 3 facing the tooling half mold 5, and a pressing component 14 is provided at the bottom end of one of the fixed beams 4; The pressing assembly 14 includes a pressurized hydraulic cylinder 1401 fixedly disposed at the bottom end of the fixed crossbeam 4 , and a pressurized plate 1402 is fixedly disposed at the bottom end of the pressurized hydraulic cylinder 1401 . The pressurized hydraulic cylinder 1401 can push the pressurized plate 1402 downward and squeeze the gear workpiece downward.

[0024] The two tooling half-molds 5 are tightly merged together to form a cavity. During the densification process, the sintered gear tooling is placed in the cavity between the two tooling half-molds 5. The cavity then drives the gear workpiece to move to just below the down-pressing assembly 14. The piston rod of the pressurized hydraulic cylinder 1401 then pushes the down-pressing plate 1402 downward. After the down-pressing plate 1402 moves down, it enters the cavity and contacts the top of the gear workpiece. The down-pressing plate 1402 then further squeezes the gear workpiece downward. Due to the special funnel-shaped structure of the cavity, the gear workpiece squeezed downward will be squeezed by the side walls of the cavity, causing the material constituting the gear workpiece to move radially inward, thereby compressing the pores inside the gear workpiece, increasing the local density of the gear workpiece, and thereby increasing the strength of the gear workpiece.

[0025] During the pressing process, the gear workpiece will move axially inside the cavity. In order to reduce friction, Figure 1 , 5 As shown, a spray pipe 8 is fixedly provided at the bottom end of another fixed crossbeam 4 , a plurality of atomizing nozzles 15 are fixedly provided at the bottom end of the spray pipe 8 , and an oil delivery pipe is fixedly provided at the outer end of the spray pipe 8 for delivering lubricating oil to the inside of the spray pipe 8 .

[0026] Before placing the gear workpiece inside the cavity for processing, the tooling half mold 5 is first moved to another fixed beam 4 and the spray pipe 8 is located directly above the cavity. Lubricating oil is input into the spray pipe 8 through the oil pipe. The lubricating oil entering the spray pipe 8 is finally sprayed out through the atomizing nozzle 15 and adheres to the inner wall of the cavity. In the subsequent densification process, the lubricating oil reduces the friction between the outer end of the gear workpiece and the inner wall of the cavity, so that the wear of the outer end of the gear workpiece is smaller.

[0027] During the densification process, the tooling half mold 5 needs to move back and forth between the pressing assembly 14 and the spraying pipe 8, such as Figure 1-3 As shown, two linear motors 2 are fixedly provided at the top of the base 1, and connecting plates 13 are fixedly provided at the tops of the movers of the two linear motors 2. Two clamping plates 10 are provided at one end of the connecting plate 13 facing the bottom block 6 through bolts, and the clamping plates 10 are fixed at the outer end of the bottom block 6, so that the linear motor 2 can drive the bottom block 6 to move left and right.

[0028] A support block 12 is provided at the top of the connecting plate 13 through bolts, and a detachable side hydraulic cylinder 7 is provided at the top of the support block 12. An arc-shaped push plate 11 is fixedly provided at one end of the piston rod of the side hydraulic cylinder 7. Two arc-shaped push plates 11 are respectively arranged at the outer ends of the two tooling half-molds 5. The extension and retraction of the side hydraulic cylinder 7 can drive the tooling half-molds 5 to merge or separate.

[0029] The mover of the linear motor 2 is connected to the bottom block 6 through the connecting plate 13 and the clamping plate 10, so that the linear motor 2 can drive the bottom block 6 to move left and right, and the movement of the connecting plate 13 can drive the support block 12, the side hydraulic cylinder 7 and the tooling half mold 5 to move, thereby enabling the entire cavity to move left and right; At the same time, the side hydraulic cylinder 7 is connected to the tooling half-mold 5 through the arc-shaped push plate 11. The extension and retraction of the side hydraulic cylinder 7 can drive the tooling half-mold 5 through the arc-shaped push plate 11, so that the two tooling half-molds 5 are merged or separated. The two tooling half-molds 5 are merged to form a cavity. If the gear workpiece is stuck inside the cavity after densification processing, the side hydraulic cylinder 7 can control the separation of the two tooling half-molds 5, thereby opening the cavity to take out the gear workpiece. Moreover, after the cavity is opened, it can also be more convenient to carry out inspection and maintenance.

[0030] In order to facilitate the removal of the gear workpiece and to avoid damage to the gear workpiece during the pressing process, Figure 2 , 3 As shown, a demolding assembly 9 is provided at the top of the bottom block 6. The demolding assembly 9 is arranged inside the cavity. The demolding assembly 9 includes a spring 901 fixed at the top of the bottom block 6. A lifting plate 902 is fixed at the top of the spring 901. The elastic force of the spring 901 can push the lifting plate 902 to lift the gear workpiece upward.

[0031] When not in use, the demolding assembly 9 is located inside the cavity and the spring 901 is naturally stretched. When the gear workpiece is located inside the cavity and is pressed down by the pressing assembly 14, the spring 901 contracts. The elastic force of the spring 901 pushes the lifting plate 902 upward to make close contact with the bottom end of the gear workpiece, thereby lifting the gear workpiece upward and supporting the gear workpiece to prevent the gear workpiece from being damaged by pressure. At the same time, after the pressing assembly 14 has completed the pressing, the gear workpiece that has lost the downward pressure can also be separated from the inner wall of the cavity under the upward thrust of the demolding assembly 9 so as to be taken out.

[0032] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A process for densification of powder metallurgy product parts, characterized in that: The specific steps are as follows: Step 1: Select special materials and mix various raw material powders of the special materials evenly according to the proportion; Step 2: Put the evenly mixed raw materials into the gear mold, and apply a pressure of 500-1000MPa to the raw material powder in the mold to preliminarily extrude the raw material powder into shape; Step 3: Put the extruded gear workpiece into a sintering furnace, heat it at different temperatures in different areas inside the sintering furnace, and finally sinter it into shape. Finally, take out the sintered gear workpiece and cool it. Step 4: After cooling, the gear workpiece is placed inside a densification chemical device and processed by the densification chemical device. After processing, the gear workpiece is taken out to complete the densification process.

2. A process for densifying powder metallurgy product parts according to claim 1, characterized in that: The raw materials of the special material in step 1 include Mo 0.2-1.5%, Ni 0-4%, C 0-1%, B 0-0.1% and Fe 93.6-99.8% in percentage.

3. The process for densifying powder metallurgy product parts according to claim 1, characterized in that: The sintering furnace in step three is divided into four areas: dewaxing area, welding preheating area, sintering area and water cooling area. The temperature range of the dewaxing area is 550-715°C, the temperature range of the welding preheating area is 980-1090°C, and the temperature range of the sintering area is 1110-1150°C.

4. The process for densifying powder metallurgy product parts according to claim 1, characterized in that: The densification equipment in step 4 comprises a base (1), a bottom block (6) is provided on the top of the base (1), two tooling half-molds (5) are provided on the top of the bottom block (6), the two tooling half-molds (5) are symmetrically arranged front and back, and the two tooling half-molds (5) are combined to form a cavity, and the cavity is located between the two tooling half-molds (5).

5. A process for densifying powder metallurgy product parts according to claim 4, characterized in that: Two columns (3) are fixedly provided on the top of the base (1), the tooling half-mold (5) and the bottom block (6) are located between the two columns (3), and a fixed crossbeam (4) is fixedly provided on the side of the column (3) facing the tooling half-mold (5), wherein a pressing assembly (14) is provided at the bottom end of one of the fixed crossbeams (4); The pressing assembly (14) comprises a pressurizing hydraulic cylinder (1401) fixedly arranged at the bottom end of the fixed crossbeam (4), and a pressing plate (1402) is fixedly arranged at the bottom end of the pressurizing hydraulic cylinder (1401).

6. A process for densifying powder metallurgy product parts according to claim 5, characterized in that: A spraying pipe (8) is fixedly provided at the bottom end of the other fixed crossbeam (4), a plurality of atomizing nozzles (15) are fixedly provided at the bottom end of the spraying pipe (8), and an oil delivery pipe is fixedly provided at the outer end of the spraying pipe (8).

7. The process for densifying powder metallurgy product parts according to claim 4, characterized in that: Two linear motors (2) are fixedly provided at the top of the base (1), and connecting plates (13) are fixedly provided at the tops of the movers of the two linear motors (2). Two clamping plates (10) are provided at one end of the connecting plate (13) facing the bottom block (6), and the clamping plates (10) are fixedly provided at the outer end of the bottom block (6).

8. The process for densifying powder metallurgy product parts according to claim 7, characterized in that: A support block (12) is provided at the top of the connecting plate (13), a detachable side hydraulic cylinder (7) is provided at the top of the support block (12), an arc-shaped push plate (11) is fixedly provided at one end of the piston rod of the side hydraulic cylinder (7), and two arc-shaped push plates (11) are respectively provided at the outer ends of the two tooling half-molds (5).

9. The process for densifying powder metallurgy product parts according to claim 4, characterized in that: A demoulding assembly (9) is provided at the top of the bottom block (6), and the demoulding assembly (9) is arranged inside the cavity. The demoulding assembly (9) comprises a spring (901) fixedly arranged at the top of the bottom block (6), and a lifting plate (902) is fixedly arranged at the top of the spring (901).

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