CN1913994A - Sheet infiltration of powder metal parts - Google Patents

Abstract

A powder metal component infiltration method uses a stamped metal sheet as a source of infiltration metal to obtain a high strength powder metal component. The powder metal is compacted and the infiltrant blank is formed from a wrought metal sheet. The infiltrant blank is placed atop the powder metal compact, and the compact is sintered at a temperature sufficient to form a sintered compact having a matrix with pores and to melt the wrought metal such that the molten wrought metal infiltrates the pores of the matrix. Locating elements may be formed on the infiltrant blank for engaging corresponding locating elements on the compact to enhance the location of the blank on the compact. The compact may also be fired separately and then the infiltrant blank placed on top of the sintered compact. The wrought metal is then melted such that the melted wrought metal infiltrates the pores of the matrix.

Description

Sheet infiltration of powder metal parts

Related Application Cross Reference

This application claims priority to US Provisional Patent Application Serial No. 60/542,271, filed February 4,2004.

            Statement Regarding Federally Funded Research

none.

Background of the Invention

1. Field of invention

The present invention relates to the manufacture of powder metal parts and in particular to infiltrating powder metal parts with metallic materials such as copper.

2. Description of related fields

Powdered metal components are used to make many automotive parts that require mesh parts. Powder metal parts are typically produced by pressing powder metal in a die into a compact of the desired shape and then sintering the compact to increase the strength of the part.

It has been reported that conventional powder parts manufactured by pressing and sintering have poor impact and fatigue strength due to the presence of pores in the sintered part. Therefore, methods have been proposed to remove porosity and make parts close to fully densified. One way to approach full densification is to infiltrate powdered metal parts with metals like copper.例如，参见美国专利第6,676,894号，6,551,373号，6,500,384号，5,925,836号，5,574,959号，5,031,878号，4,976,778号，4,861,373号，4,836,848号，4,769,071号，4,734,968号，4,731,118号，4,606,768号，4,485,147号，4,424,953号, No. 4,412,873, No. 4,168,162, No. 4,008,051 and No. 3,829,295.

Infiltration is the process of filling the interconnected pores in a powder metal compact with a molten metal or alloy with a lower melting point ("infiltrant") by capillary action. For example, copper-infiltrated steel is produced by pressing iron or iron-based powders (with or without graphite powder) into the final shape and infiltrating the interconnected pores with the copper-based material during the sintering operation. This can be a single infiltration or a two-stage infiltration. The result is a steel-copper structure unique to powder metallurgy. Infiltration of copper improves tensile strength, fatigue strength, ductility, hardness and impact properties compared to direct sintered iron or carbon steel powder metal parts.

The copper source used in the past to infiltrate powder metal parts has been powder metal copper compacts, ie parts made from copper powder pressed together to hold its shape. However, the use of copper powder metal compacts as a source of infiltrated copper has some disadvantages. For example, (1) there will be residue after infiltration; (2) corrosion may occur on the surface of the base metal where the infiltrant enters; (3) due to certain shapes may not be compacted by conventional powder metal infiltrants (4) Breakage may occur due to the brittleness of powdered metal infiltrant compacts; (5) Positioning of powdered copper compacts may be difficult.

Therefore, there is a need for an improved method of infiltrating porous metal parts with metallic materials such as copper.

Brief description of the invention

The present invention meets the above needs by providing an alternative to powdered metal compacts as a source of infiltration. The infiltration method of the present invention uses a stamped metal sheet as a metal source for infiltration to obtain a high strength powdered metal article. In one form, the infiltration method of the present invention uses a stamped sheet of malleable copper as the source of copper for infiltration to obtain a high strength powdered iron or steel article.

In one aspect, the invention provides a method of making a metal infiltrated powder metal part. In this method, powdered metal is pressed into compacts and infiltrant blanks are formed from wrought copper sheets. placing the infiltrant blank in contact with the compact and firing the compact at a temperature sufficient to form a sintered compact having a porous matrix and sufficient to melt the malleable metal so that the molten malleable metal infiltrates the Within the pores of the matrix, a powder metal part is formed that infiltrates the metal. Placing the blank on top of the compact improves the infiltration of the wrought metal. In one embodiment, the powder metal is selected from iron and iron alloys and the malleable metal is selected from copper and copper alloys. The thickness of the malleable metal sheet is preferably less than 1 mm. Infiltrant blanks may be formed by stamping, fine blanking or abrasive water jet cutting.

In another aspect, the present invention may form locating elements on the infiltrant blank, which locating elements are adapted to engage corresponding locating elements on the compact, and the infiltrant blank may be placed in contact with the compact such that the blank The locating element of the piece engages with the corresponding locating element of the pressed block. For example, the positioning element of the blank may be a portion extending outwardly from the body of the batch. As a result, the positioning of the blank on the compact is improved.

In another aspect of the invention, the compact is separately sintered at a temperature sufficient to form a sintered compact comprising a porous matrix, and the infiltrant blank is formed from a sheet of wrought metal. The infiltrant blank is then placed in contact with the sintered compact and the malleable metal is melted such that the molten malleable metal infiltrates the pores of the matrix to form an infiltrated metal powder metal part.

Some of the advantages of using wrought metal sheet instead of powdered metal compacts as the infiltration material are: (1) reduced amount of residue after infiltration; (2) reduced amount of base metal compact corrosion that occurs at the point where the infiltrant enters; (3 ) the localization of selective infiltration can be improved since sheet stamping can achieve geometries not achievable with conventional powder metal infiltrant compacts, such as thin webs and areas that are easily missed; (4) due to the elimination of Improves the quality of the infiltration process by reducing breakage caused by brittle powdered metal infiltrant compacts; (5) Improved stamped sheet material due to the ability of stamping to position structures for connection or engagement with infiltrated parts Positioning of the blank.

These features, aspects and advantages of the present invention, as well as other features, aspects and advantages, can be better understood from the following detailed description, drawings and appended claims.

Brief description of the attached drawings

Figure 1 shows a top view of a copper infiltrant blank placed on an iron-based compact prior to sintering in accordance with one form of the invention.

Figure 2 shows a detailed view of the test specimen after sintering and infiltration.

Detailed description of the invention

In one exemplary method of making a metal infiltrated powder metal part of the present invention, iron or iron alloy powder is introduced into a die having the desired shape of the final part. The powdered metal is then compressed within a die into a higher density article, commonly referred to as a "green compact". Typically the iron-based green compact has a density of 6.0 g/cm3 to 7.3 g/cm3. (The theoretical density of iron is 7.88 grams per cubic centimeter.) The desired amount of wrought sheet of copper or copper alloy is then formed into the desired shape of the infiltrant blank, which is placed in contact with the green compact such that Copper can penetrate into the pores of the compact when heated.

The compact and the copper blank placed in contact with the compact are subjected to a conventional sintering process, i.e. at a predetermined temperature above the melting point of copper (eg 1100°C) in a suitable atmosphere (eg a reducing atmosphere comprising hydrogen) Lower firing for a fixed time (eg 15 minutes). Typically, the sintering process promotes bonding or dispersion between iron or iron alloy powder particles to form a sintered compact comprising a porous matrix. During sintering, molten copper flows into the pores in the matrix. Molten copper penetrates into the open pores of the matrix by surface tension, gravity and capillary action. Thus, molten copper fills the pores of the matrix, thereby increasing the density and integrity of the matrix. The amount of copper infiltration depends on the desired physical and mechanical properties in the matrix. When only partial penetration into the substrate is required, the amount of copper is reduced. The amount of copper infiltrant required can be determined by measuring the porosity of the green compact.

In another process, the compact is first subjected to conventional sintering alone to form a sintered compact comprising the matrix. In the second step, a copper infiltrant blank formed of a malleable sheet is placed in contact with a sintered compact, and the copper sheet and the sintered compact are heated at a predetermined temperature. In the second step, copper melts and flows into the pores within the pre-sintered porous matrix. The copper melts and penetrates into the open pores of the matrix by surface tension, gravity and capillary action.

Figure 1 shows examples of combinations of compacts and infiltrant blanks suitable for use in the present invention. It is shown that an annular copper infiltrant blank 10 approximately 0.032 inches (0.8128 mm) thick is placed on top 22 of a tubular iron base compact 20 prior to sintering. The top 22 of the compact 20 has recessed regions 24a, 24b, 24c and 24d for receiving tabs 14a, 14b, 14c and 14d extending outwardly from the perimeter 12 of the body of the blank 10.

Tabs 14a, 14b, 14c and 14d provide locating structures for engaging or engaging with recessed areas 24a, 24b, 24c and 24d in compact 20 to be infiltrated with copper from blank 10. In the embodiment shown, tabs 14 a , 14 b , 14 c and 14 d extend outwardly from blank 10 to engage recessed areas 24 a , 24 b , 24 c and 24 d in compact 20 . However, in other configurations, the blank may include a recess that engages an outwardly extending locating structure in the compact.

The copper infiltrant blank 10 may be formed by stamping, fine blanking or abrasive water jet cutting of a sheet of wrought copper or copper alloy. "Forgeable" means a material formed by mechanical action such as rolling, forging, extrusion or drawing. The density of malleable materials is usually greater than 99% of theoretical density. Therefore, compacted powder materials are not considered malleable materials, since the density of malleable materials is usually equal to or less than 93% of theoretical density. Exemplary malleable copper materials have a thickness of 0.001-0.250 inches (0.0254-6.35 mm). It is particularly preferred that the wrought copper material has a thickness of less than 0.039 inches (1 mm). Suitable copper alloys include brass and bronze.

Example

The present invention is further illustrated by the following examples, but does not limit the present invention.

1. Test method

The three infiltrated techniques were compared to a non-infiltrated reference test. Use a standard test ring with a nominal outer diameter of 2.0 inches (50.8 mm) x inner diameter of 0.75 inches (19.05 mm) x length of 1.125 inches (28.575 mm), which is made to meet the requirements of the Metal Powder Industries Federation (MPIF) 35 FC- 0208 material. MPIF Std 35 FC-0208 is as follows: elemental iron powder 93.2-97.9% by weight: elemental copper powder 1.5-3.9% by weight: carbon (graphite powder) 0.6-0.9% by weight and other elements up to 2.0% by weight.

The base compact was pressed to a density of 6.95 g/cc. Make 18 test rings for infiltration.

The three infiltration techniques studied were: (1) non-infiltration (reference) tests based on MPIF Std 35 FC-0208; (2) standard powder metal copper infiltration as described in MPIF Std 35 (FX series), That is, using a powdered copper infiltrant material, pressed into a shape suitable for placement on top of a pressed iron or iron-based powdered metal article for subsequent infiltration of copper during sintering; (3) the double addition method, in which, Mix copper powder with MPIF STD 35 FC-0208 material, then lower the die head, fill with copper infiltrated material for the second time and press; (4) use 0.032 inches (0.8128 mm) thick copper stamping material for infiltration, use iron sheet The shears cut the stamped material into a shaped copper source of the same area as the test ring.

All the test pieces were sintered in a 24-inch high-temperature oven under conventional sintering conditions. The sintering conditions were 2050°F (1121°C) for 15 minutes in an atmosphere of 90% nitrogen-10% hydrogen.

Figure 2 shows a detail of the test piece after sintering/infiltration. The top row is the specimens for the double addition method. The second row from the top is the standard ring with pressed powder copper compact rings placed on top. The second row from the bottom is a standard ring with a prefabricated stamped copper piece on top. The bottom row is the standard rings. Note the amount of crust remaining on the top two rows. Prefabricated stampings leave no crust.

2. Test results

Density tests were carried out and the results are shown in Table 1.

Table 1 method Density (g/cm3) (1) Non-infiltrated reference basic method 6.88 (2) Conventional copper infiltration method using copper powder compact 7.57 (3) Double added material 7.57 (4) Infiltration through copper stamping parts 7.62

Infiltration of copper stampings according to the invention yields maximum density and is therefore suitable for use in place of powdered metal infiltration. Wrought sheet materials other than copper may also be used as a source of infiltrated material.

Corrosion/cleanliness was tested and listed in Table 2.

Table 2 method note (1) Non-infiltrated reference basic method direct sintering (2) Conventional copper infiltration method using copper powder compact The method has general residue and corrosion (3) Double added material Double addition produces more corrosion than conventional copper infiltration (2) (4) Infiltration through copper stamping parts Reduced corrosion with minimal residue compared to conventional copper infiltration methods(2)

3. Summary

Dual feed materials are not a suitable method for infiltration of powdered metal articles.

Conventional copper infiltration produces significant residue and corrosion. Uneven infiltration due to difficulty in aligning pressed strips of copper infiltrant. Due to the brittle green strength of the pressed infiltrant material, there is a lot of rejects due to handling breakage when the infiltrant strips are thin.

Infiltration through copper stampings is a unique method that has the following advantages: (1) the method is an infiltration method that produces low corrosion; (2) the method is an infiltration method that produces low residue; Stamping shapes that cannot be achieved with conventional powder metal infiltrant strips, such as thin meshes and areas that are easily missed, this method is a selective infiltration method; (4) This method uses thin gauge copper material, eliminating the need for infiltration with powder metal (5) This method can use stamped positioning structures such as "ears", "flanges" or "tips" or other easily stamped orientation structure.

Accordingly, the present invention provides a powdered metal compact as an alternative source of infiltration. One infiltration method of the present invention uses a stamped metal (eg copper) sheet as a source of metal (eg copper) for infiltration to obtain high strength powdered metal (eg iron or steel) parts.

Although the present invention has been described in detail in conjunction with some embodiments, those skilled in the art will understand that the present invention can be implemented in other ways than the described embodiments, and the described embodiments are only used to illustrate the present invention, not to limit it. Therefore, the scope of the appended claims should not be limited by the embodiments contained herein.

Industrial Applicability

The present invention relates to the manufacture of stronger, denser powder metal parts with improved surface texture.

Claims (22)

1. a kind of method that the powder metal component of metal is penetrated into manufacture, this method comprises:

Powdered-metal is pressed into pressing block；

It is formed by wrought metal sheet material and penetrates into agent blank；

Infiltration agent blank is placed in the top of pressing block；

Pressing block is fired at a certain temperature, which is enough to form the pressing block with the sintering containing pore matrix, and is enough to melt wrought metal, so that the wrought metal of melting penetrates into the hole of matrix.

2. the method as described in claim 1, which is characterized in that

The powdered-metal is selected from iron, ferroalloy and its mixture；

The wrought metal is selected from copper and copper alloy.

3. method according to claim 2, which is characterized in that

The thickness of the wrought metal sheet material is less than 1 millimeter.

4. the method as described in claim 1, which is characterized in that

The agent blank that penetrates into can be formed by the method selected from punching press, fine-edge blanking and abrasive water jet cutting.

5. the method as described in claim 1, this method further include:

It is formed on penetrating into agent blank and is adapted to the setting element that setting element corresponding on pressing block is meshed；

Agent blank will be penetrated into place in contact with pressing block, so that the setting element of blank is meshed with setting element corresponding on pressing block.

6. method as claimed in claim 5, it is characterised in that:

The setting element of the blank is a part from the outwardly extending blank of main body of the blank.

7. a kind of method that the powder metal component of metal is penetrated into manufacture, this method comprises:

Powdered-metal is pressed into pressing block；

Be enough to be formed with the sintered compact containing pore matrix at a temperature of be sintered the pressing block；

It is formed by wrought metal sheet material and penetrates into agent blank；

Infiltration agent blank is placed in the top of the pressing block of sintering；

Melt wrought metal, so that the wrought metal of melting penetrates into the hole of matrix.

8. the method for claim 7, which is characterized in that

The powdered-metal is selected from iron and ferroalloy and its mixture；

The wrought metal is selected from copper and copper alloy.

9. method according to claim 8, it is characterised in that:

The thickness of the wrought metal sheet material is less than 1 millimeter.

10. the method for claim 7, it is characterised in that:

The agent blank that penetrates into can be formed by the method selected from punching press, fine-edge blanking and laser cutting.

11. the method for claim 7, this method further include:

It is formed on penetrating into agent blank and is adapted to the setting element that setting element corresponding on pressing block is meshed；

Agent blank will be penetrated into place in contact with pressing block, so that the setting element of blank is meshed with setting element corresponding on pressing block.

12. the method for claim 7, it is characterised in that:

The setting element of the blank is a part from the outwardly extending blank of main body of the blank.

13. a kind of method that the powder metal component of metal is penetrated into manufacture, this method comprises:

Powdered-metal is suppressed to form pressing block；

It is formed by wrought metal sheet material and penetrates into agent blank, the blank, which has, is adapted to the setting element that setting element corresponding on pressing block is meshed；

Agent blank will be penetrated into place in contact with pressing block, so that the setting element of blank is meshed with setting element corresponding on pressing block；

It is sintered the pressing block in certain temperature, which, which is enough to be formed, has the sintered compact containing pore matrix, and is enough to melt wrought metal, so that the wrought metal of melting penetrates into hole.

14. method as claimed in claim 13, which is characterized in that

The powdered-metal is selected from iron and ferroalloy and its mixture；

The wrought metal is selected from copper and copper alloy.

15. method as claimed in claim 14, it is characterised in that:

The thickness of the wrought metal sheet material is less than 1 millimeter.

16. method as claimed in claim 13, it is characterised in that:

The agent blank that penetrates into can be formed by the method selected from punching press, fine-edge blanking and laser cutting.

17. method as claimed in claim 13, it is characterised in that:

The setting element of the blank is a part from the outwardly extending blank of main body of the blank.

18. a kind of method that the powder metal component of metal is penetrated into manufacture, this method comprises:

Powdered-metal is suppressed to form pressing block；

Be enough to be formed with the sintered compact containing pore matrix at a temperature of be sintered the pressing block；

It is formed by wrought metal sheet material and penetrates into agent blank, the blank has the setting element being adapted to corresponding setting element is meshed on the pressing block of sintering；

Agent blank will be penetrated into place in contact with sintered compact, so that the setting element of blank is meshed with setting element corresponding in sintered compact；

Wrought metal is melted, so that the wrought metal of melting penetrates into the hole of the pressing block of sintering.

19. method as claimed in claim 18, which is characterized in that

The powdered-metal is selected from iron and ferroalloy and its mixture；

The wrought metal is selected from copper and copper alloy.

20. method as claimed in claim 19, it is characterised in that:

The thickness of the wrought metal sheet material is less than 1 millimeter.

21. method as claimed in claim 18, it is characterised in that:

The agent blank that penetrates into can be formed by the method selected from punching press, fine-edge blanking and laser cutting.

22. method as claimed in claim 18, it is characterised in that:

The setting element of the blank is a part from the outwardly extending blank of main body of the blank.