CA2570236A1 - Sintered metal parts and method for the manufacturing thereof - Google Patents
Sintered metal parts and method for the manufacturing thereof Download PDFInfo
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- CA2570236A1 CA2570236A1 CA002570236A CA2570236A CA2570236A1 CA 2570236 A1 CA2570236 A1 CA 2570236A1 CA 002570236 A CA002570236 A CA 002570236A CA 2570236 A CA2570236 A CA 2570236A CA 2570236 A1 CA2570236 A1 CA 2570236A1
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- 238000000034 method Methods 0.000 title claims abstract description 17
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 5
- 239000002184 metal Substances 0.000 title claims abstract description 5
- 238000004519 manufacturing process Methods 0.000 title claims description 4
- 239000000843 powder Substances 0.000 claims abstract description 42
- 238000005480 shot peening Methods 0.000 claims abstract description 22
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 17
- 238000005452 bending Methods 0.000 claims abstract description 16
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 13
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 12
- 239000011651 chromium Substances 0.000 claims abstract description 12
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 11
- 238000005245 sintering Methods 0.000 claims abstract description 11
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims abstract description 8
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 8
- 239000011733 molybdenum Substances 0.000 claims abstract description 8
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 6
- 239000010439 graphite Substances 0.000 claims abstract description 6
- 229910052742 iron Inorganic materials 0.000 claims abstract description 6
- 239000000203 mixture Substances 0.000 claims abstract description 6
- 229910000734 martensite Inorganic materials 0.000 claims description 6
- 238000005496 tempering Methods 0.000 claims description 3
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 abstract description 2
- 239000012535 impurity Substances 0.000 abstract description 2
- 229910052748 manganese Inorganic materials 0.000 abstract description 2
- 239000011572 manganese Substances 0.000 abstract description 2
- 239000000463 material Substances 0.000 description 21
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 14
- 229910052799 carbon Inorganic materials 0.000 description 13
- 238000005056 compaction Methods 0.000 description 7
- 238000001816 cooling Methods 0.000 description 7
- 229910052759 nickel Inorganic materials 0.000 description 7
- 239000011148 porous material Substances 0.000 description 6
- 229910001563 bainite Inorganic materials 0.000 description 5
- 229910000831 Steel Inorganic materials 0.000 description 3
- 239000010959 steel Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000009661 fatigue test Methods 0.000 description 2
- 238000005242 forging Methods 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 229910001562 pearlite Inorganic materials 0.000 description 2
- 238000004663 powder metallurgy Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 206010020751 Hypersensitivity Diseases 0.000 description 1
- 230000002730 additional effect Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 229910052729 chemical element Inorganic materials 0.000 description 1
- 229940000425 combination drug Drugs 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 238000000280 densification Methods 0.000 description 1
- 238000010410 dusting Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/02—Making ferrous alloys by powder metallurgy
- C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/02—Making ferrous alloys by powder metallurgy
- C22C33/0207—Using a mixture of prealloyed powders or a master alloy
- C22C33/0228—Using a mixture of prealloyed powders or a master alloy comprising other non-metallic compounds or more than 5% of graphite
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/12—Both compacting and sintering
- B22F3/16—Both compacting and sintering in successive or repeated steps
- B22F3/164—Partial deformation or calibration
- B22F2003/166—Surface calibration, blasting, burnishing, sizing, coining
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/24—After-treatment of workpieces or articles
- B22F2003/248—Thermal after-treatment
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Powder Metallurgy (AREA)
Abstract
The invention relates to a method consisting of the steps of providing a pre-alloyed iron-based metal powder comprising at least 1.3-3.5% chromium, 0.15-0.7% molybdenum, manganese and unavoidable impurities, mixing said powder with 0.1-1.0% graphite, compacting the obtained mixture at a pressure of at least 600 MPa, sintering the compacted part in a single step at a temperature above 1100~C, shot-peening the part and after sintering optionally hardening the component. The invention also relates to a powder metallurgical part and use of a low chromium prealloyed powder for preparing notched sintered parts having a bending fatigue limit of at least 340 MPa at a sintered density of 7.15 g/cm3, preferably at least 400 MPa at a sintered density of 7.3 g/cm3.
Description
I
SINTERED METAL PARTS AND METHOD FOR THE MANUFACTURING
THEREOF
FIELD OF THE INVENTION
The present invention refers to powder metallurgy and more specifically to pre-alloyed chromium powder metal parts with improved fatigue properties.
BACKGROUND OF THE INVENTION
In general, sintered products made by powder metallurgy are advantageous in cost over ingot steels obtained through forging and rolling steps and has wide utility as parts in e.g. motor vehicles. However, the sintered prod-uct has pores which are inevitably formed during the course of its fabrication. These remaining pores of the sintered powder-metallurgical materials impair the me-chanical properties of the materials, as compared with completely dense materials. This is a result of the pores acting as stress concentrations and also because the pores reduce the effective volume under stress. Thus, strength, ductility, fatigue strength, macro-hardness etc. in iron-based powder-metallurgical materials de-crease as the porosity increases.
Despite their comparatively low fatigue strength , iron-based powder-metallurgical materials are, to a certain extent, used in components requiring high fatigue strength. Distaloy HP, available from Hoganas AB , Swe-den, is a steel powder possible for use in high perform-ing purposes. In this Distaloyo-powder the base-powder is alloyed with nickel, which is an expensive alloying ele-ment. This high performing material is therefore rather costly and there is a need for less expensive materials, which have at least as good fatigue strength.
SINTERED METAL PARTS AND METHOD FOR THE MANUFACTURING
THEREOF
FIELD OF THE INVENTION
The present invention refers to powder metallurgy and more specifically to pre-alloyed chromium powder metal parts with improved fatigue properties.
BACKGROUND OF THE INVENTION
In general, sintered products made by powder metallurgy are advantageous in cost over ingot steels obtained through forging and rolling steps and has wide utility as parts in e.g. motor vehicles. However, the sintered prod-uct has pores which are inevitably formed during the course of its fabrication. These remaining pores of the sintered powder-metallurgical materials impair the me-chanical properties of the materials, as compared with completely dense materials. This is a result of the pores acting as stress concentrations and also because the pores reduce the effective volume under stress. Thus, strength, ductility, fatigue strength, macro-hardness etc. in iron-based powder-metallurgical materials de-crease as the porosity increases.
Despite their comparatively low fatigue strength , iron-based powder-metallurgical materials are, to a certain extent, used in components requiring high fatigue strength. Distaloy HP, available from Hoganas AB , Swe-den, is a steel powder possible for use in high perform-ing purposes. In this Distaloyo-powder the base-powder is alloyed with nickel, which is an expensive alloying ele-ment. This high performing material is therefore rather costly and there is a need for less expensive materials, which have at least as good fatigue strength.
One route to improve the fatigue performance of powder metallurgical steels are secondary operations. Through hardening, case hardening or shot peening (or a combina-tion) are possible processes to get highest possible fa-tigue resistance of a component. Shot peening is normally performed in order to utilize the beneficial influence of compressive residual stresses in the surface. Pores open to the surface are weak points in powder metallurgical materials. These pores are at least partly neutralized by introduction of surface compression residual stresses.
Shot peening of compacted parts is disclosed in e.g. the US patent 6 171 546. According to this patent the shot peening is followed by a final sintering step. An iron-based powder containing i. a. nickel is used as starting material. As indicated above there is an increasing de-mand for powders, which do not contain nickel, as nickel is expensive. Other disadvantages with nickel containing powders are dusting problems which may occur during the processing of the powder, and which may cause allergic reactions also in minor amounts. The use of nickel-should thus be avoided. Also the US patent application 2004/0177719 relates to a method including shot peening.
More specifically, this application discloses a method, wherein a portion of the surface of a compacted part is subjected to shot peening after sintering. According to this application a densifying process involving powder forging or sizing is necessary in order improve the prop-erties of the final compacted part.
An object of the present invention is to provide a cost effective process for the preparation of powder metallur-gical components with high fatigue strength without any steps for achieving core densification. Another object is to provide a process involving powder materials, which are free from nickel.
Shot peening of compacted parts is disclosed in e.g. the US patent 6 171 546. According to this patent the shot peening is followed by a final sintering step. An iron-based powder containing i. a. nickel is used as starting material. As indicated above there is an increasing de-mand for powders, which do not contain nickel, as nickel is expensive. Other disadvantages with nickel containing powders are dusting problems which may occur during the processing of the powder, and which may cause allergic reactions also in minor amounts. The use of nickel-should thus be avoided. Also the US patent application 2004/0177719 relates to a method including shot peening.
More specifically, this application discloses a method, wherein a portion of the surface of a compacted part is subjected to shot peening after sintering. According to this application a densifying process involving powder forging or sizing is necessary in order improve the prop-erties of the final compacted part.
An object of the present invention is to provide a cost effective process for the preparation of powder metallur-gical components with high fatigue strength without any steps for achieving core densification. Another object is to provide a process involving powder materials, which are free from nickel.
SUMMARY OF THE INVENTION
It has unexpectedly been found that components having high fatigue strength can be obtained by shot peening of sintered components prepared from iron based powders dis-tinguished by low levels of chromium and molybdenum.
DETAILED DESCRIPTION OF THE INVENTION
The powders used in the present invention are pre-alloyed iron-base powders comprising low amounts of chromium and molybdenum. A preferred amount is 1.3-3.5% by weight of chromium and 0.15-0.7% by weight of molybdenum. The pow-der may also contain small amounts, 0.09 to 0.3% by weight, of manganese and inevitable impurities. Such pow-ders are known from the US patent 6 348 080 and WO
03/106079.
The base powder is further mixed with graphite to obtain the desired strength in the material. The amount of graphite which is mixed with the iron-base powder is 0.1-1.0%, preferably 0.15-0.85%. The powder mixture is com-pacted in a die to produce a green body. The compaction pressure is at least 600 MPa, preferably at least 700 MPa and more preferably 800 MPa. The compaction can be per-formed by cold compaction or warm compaction. After the compaction the obtained green part is sintered at a sin-tering temperature above 1100 C, preferably above 1220 C.
The sintering atmosphere is preferably a mix of nitrogen and hydrogen. A normal cooling rate in the sintering process is 0.8 C/s, a range between 0.5 C/s and 1.0 C/s is preferred. The sintered density is preferably above 7.15 g/cm3, more preferably above 7.3 g/cm3. The obtained microstructure in the as-sinterd material is mainly fine-pearlitic with a lower chromium and molybdenum content and martensitic or lower bainitic for slightly higher chromium and molybdenum content.
It has now unexpectedly been found that a remarkable in-crease in the bending fatigue limit can be obtained by shot peening the sintered low chromium powder materials.
Especially remarkable increase is obtained for notched parts, where an increase of more than 50% and even more than 70% can be obtained as can be seen from the follow-ing examples. The degree of shot peening as defined by Almen A intensity, is preferably between 0.20 and 0.37 mm.
Secondary operations e.g. through hardening and case hardening, can be performed before the shot peening in order to improve the properties even more. Thus, after through hardening followed by tempering the material is mainly martensitic and the fatigue limit is raised by shotpeening. The martensite in the surface which is formed during case hardening is believed to form compres-sive stresses, which is beneficial for the fatigue limit.
Sinterhardening is an alternative process which is ap-plied in the sintering process. Sinterhardening uses forced cooling at the end of the sintering process of the components which results in a hardened structure.
The fatigue tests have been performed on notched specimen with a stress concentration factor, Kt, of 1.38 and on un-notched specimen. The tests show a greater increase in bending fatigue limit when shot peening notched specimen than when the shot peening is performed on un-notched specimen. The expression "notched" in this context refers to a specimen or component having a stress concentration factor above 1.3.
The invention is illustrated by the following non-limiting examples.
Example 1 5 Two pre-alloyed base-powders, Astaloy CrL and Astaloy CrM, and one diffusion-alloyed base powder, Distaloy HP, are included in the study. Distaloy HP is diffusion-alloyed with Ni and Cu and pre-alloyed with Mo. The three materials included in this study are shown in Table 1.
Table 1 Material Ni [ o] Cu [ o] Mo [ o] Cr [ o]
Astaloy CrL 0.2 1.5 Astaloy CrM 0.5 3.0 Distaloy HP 4.0 2.0 1.5 Detailed information on process parameters, density and carbon levels will be given below. In table 2 plane bend-ing fatigue performance of un-notched specimen is shown for different alloys which are sintered 30 min in 90/10 N2/H2 with cooling rate about 0.8C/sec. Fatigue tests on un-notched specimens are performed using 5 mm IS03928 samples with chamfered edges. The tests are made in four-point plane bending at load ratio R=-1. The staircase method is used with 13 - 18 samples in the staircase and 2 million cycles as run-out limit. Evaluation of the staircase (50% probability fatigue limit and standard de-viation) is made according to the MPIF 56 standard. Test frequency is 27 - 30 Hz.
It has unexpectedly been found that components having high fatigue strength can be obtained by shot peening of sintered components prepared from iron based powders dis-tinguished by low levels of chromium and molybdenum.
DETAILED DESCRIPTION OF THE INVENTION
The powders used in the present invention are pre-alloyed iron-base powders comprising low amounts of chromium and molybdenum. A preferred amount is 1.3-3.5% by weight of chromium and 0.15-0.7% by weight of molybdenum. The pow-der may also contain small amounts, 0.09 to 0.3% by weight, of manganese and inevitable impurities. Such pow-ders are known from the US patent 6 348 080 and WO
03/106079.
The base powder is further mixed with graphite to obtain the desired strength in the material. The amount of graphite which is mixed with the iron-base powder is 0.1-1.0%, preferably 0.15-0.85%. The powder mixture is com-pacted in a die to produce a green body. The compaction pressure is at least 600 MPa, preferably at least 700 MPa and more preferably 800 MPa. The compaction can be per-formed by cold compaction or warm compaction. After the compaction the obtained green part is sintered at a sin-tering temperature above 1100 C, preferably above 1220 C.
The sintering atmosphere is preferably a mix of nitrogen and hydrogen. A normal cooling rate in the sintering process is 0.8 C/s, a range between 0.5 C/s and 1.0 C/s is preferred. The sintered density is preferably above 7.15 g/cm3, more preferably above 7.3 g/cm3. The obtained microstructure in the as-sinterd material is mainly fine-pearlitic with a lower chromium and molybdenum content and martensitic or lower bainitic for slightly higher chromium and molybdenum content.
It has now unexpectedly been found that a remarkable in-crease in the bending fatigue limit can be obtained by shot peening the sintered low chromium powder materials.
Especially remarkable increase is obtained for notched parts, where an increase of more than 50% and even more than 70% can be obtained as can be seen from the follow-ing examples. The degree of shot peening as defined by Almen A intensity, is preferably between 0.20 and 0.37 mm.
Secondary operations e.g. through hardening and case hardening, can be performed before the shot peening in order to improve the properties even more. Thus, after through hardening followed by tempering the material is mainly martensitic and the fatigue limit is raised by shotpeening. The martensite in the surface which is formed during case hardening is believed to form compres-sive stresses, which is beneficial for the fatigue limit.
Sinterhardening is an alternative process which is ap-plied in the sintering process. Sinterhardening uses forced cooling at the end of the sintering process of the components which results in a hardened structure.
The fatigue tests have been performed on notched specimen with a stress concentration factor, Kt, of 1.38 and on un-notched specimen. The tests show a greater increase in bending fatigue limit when shot peening notched specimen than when the shot peening is performed on un-notched specimen. The expression "notched" in this context refers to a specimen or component having a stress concentration factor above 1.3.
The invention is illustrated by the following non-limiting examples.
Example 1 5 Two pre-alloyed base-powders, Astaloy CrL and Astaloy CrM, and one diffusion-alloyed base powder, Distaloy HP, are included in the study. Distaloy HP is diffusion-alloyed with Ni and Cu and pre-alloyed with Mo. The three materials included in this study are shown in Table 1.
Table 1 Material Ni [ o] Cu [ o] Mo [ o] Cr [ o]
Astaloy CrL 0.2 1.5 Astaloy CrM 0.5 3.0 Distaloy HP 4.0 2.0 1.5 Detailed information on process parameters, density and carbon levels will be given below. In table 2 plane bend-ing fatigue performance of un-notched specimen is shown for different alloys which are sintered 30 min in 90/10 N2/H2 with cooling rate about 0.8C/sec. Fatigue tests on un-notched specimens are performed using 5 mm IS03928 samples with chamfered edges. The tests are made in four-point plane bending at load ratio R=-1. The staircase method is used with 13 - 18 samples in the staircase and 2 million cycles as run-out limit. Evaluation of the staircase (50% probability fatigue limit and standard de-viation) is made according to the MPIF 56 standard. Test frequency is 27 - 30 Hz.
Table 2 Powder Density Carbon 6A,50% Std Dev 6A,90 [g/cm3] As-Sint [%] [MPa] [MPa] [MPa]
AstaloyCrL 7.17 0.60 244 7 234 7.16 0.80 267 5 260 AstaloyCrM 7.06 0.35 284 7.0 274 7.04 0.56 316 8.4 300 Distaloy HP 7.13 0.65 295 22.5 261 7.13 0.85 330 <5 >322 The microstructure of Astaloy CrL with sintered carbon below 0.6% and cooling rate about 0.8 C/s is upper bain-ite. Increased carbon above 0.74% changes the microstruc-ture to fine pearlite.
Microstructure analysis of 1120 C sintered Astaloy CrM
materials and cooling rate 0.8 C/s and with sintered car-bon levels between 0.32% and 0.49% show a dense upper bainitic microstructure. Dense upper bainite has the same characteristics as regular upper bainite, i.e. an irregu-lar mix of ferrite and cementite. The differences are the smaller distances between carbides and sizes of the car-bides. Increased sintered carbon shifts the microstruc-ture to a mix of martensite and lower bainite.
Table 3 shows influence of compaction pressure and carbon level for cold compacted Astaloy CrL. All materials were sintered at 1120 C for 30 min. in 90/10 N2/H2. In table 3 a summary of plane bending fatigue performance of Astaloy CrL at two compaction pressures and two levels of addi-tional graphite. Std.dev. <5 indicates that the scatter is small and the MPIF standard 56 evaluation of standard deviation cannot be applied. The specimen in table 3 are un-notched.
Table 3 Material Graphite Compacting Density Carbon oA,50% Std aA,9o C-UF4 Pressure As-sint As- Dev [%] [MPa] [g/cm3] sint [MPa] [MPa] [MPa]
[%]
AstaloyCrL 0,6 600 6,94 0,56 224 11.6 205 1120 C, 0,8 600 6,93 0,75 233 9.5 218 30min, 0,6 800 7,13 0,55 236 8.5 222 90/10 N2/HZ 0,8 800 7, 09 0, 74 252 <5 0.8 C/s >244 Influence of sintering temperature on the fatigue per-formance with un-notched specimen is shown in Table 4.
The microstructures of the materials in table 4 are char-acterized by mainly upper bainite (1120 C 0.58%C) and fine pearlite (1120 C, 0.77%C and 1250 C, 0.74oC).
Table 4 Powder Sint. Density Carbon 6A, 50% StdDev 6A, 90%
teTnp As-Sint As-Sint [MPa] [MPa] [MPa]
[g/cm3] 1%]
AstaloyCrL 1120 C 7.10 0.58 220 11 203 1120 C 7.08 0.77 236 9.7 222 1250 C 7.02 0.74 290 18 264 Example 2 Influence of shot peening and the combination of heat treatment and shot peening has been investigated on Asta-loy CrL 3 mm edge-notched specimens. The notch is in-cluded in the press tool and no machining is performed.
The stress concentration factor in bending is obtained by FEM to Kt=1.38. Test frequency is 27-30 Hz.
The materials are sintered at 1280 C for 30 min in H2.
Cooling rate is 0.8 C/s.
The shot peening is performed to obtain an Almen A inten-sity of 0.32 mm.
AstaloyCrL 7.17 0.60 244 7 234 7.16 0.80 267 5 260 AstaloyCrM 7.06 0.35 284 7.0 274 7.04 0.56 316 8.4 300 Distaloy HP 7.13 0.65 295 22.5 261 7.13 0.85 330 <5 >322 The microstructure of Astaloy CrL with sintered carbon below 0.6% and cooling rate about 0.8 C/s is upper bain-ite. Increased carbon above 0.74% changes the microstruc-ture to fine pearlite.
Microstructure analysis of 1120 C sintered Astaloy CrM
materials and cooling rate 0.8 C/s and with sintered car-bon levels between 0.32% and 0.49% show a dense upper bainitic microstructure. Dense upper bainite has the same characteristics as regular upper bainite, i.e. an irregu-lar mix of ferrite and cementite. The differences are the smaller distances between carbides and sizes of the car-bides. Increased sintered carbon shifts the microstruc-ture to a mix of martensite and lower bainite.
Table 3 shows influence of compaction pressure and carbon level for cold compacted Astaloy CrL. All materials were sintered at 1120 C for 30 min. in 90/10 N2/H2. In table 3 a summary of plane bending fatigue performance of Astaloy CrL at two compaction pressures and two levels of addi-tional graphite. Std.dev. <5 indicates that the scatter is small and the MPIF standard 56 evaluation of standard deviation cannot be applied. The specimen in table 3 are un-notched.
Table 3 Material Graphite Compacting Density Carbon oA,50% Std aA,9o C-UF4 Pressure As-sint As- Dev [%] [MPa] [g/cm3] sint [MPa] [MPa] [MPa]
[%]
AstaloyCrL 0,6 600 6,94 0,56 224 11.6 205 1120 C, 0,8 600 6,93 0,75 233 9.5 218 30min, 0,6 800 7,13 0,55 236 8.5 222 90/10 N2/HZ 0,8 800 7, 09 0, 74 252 <5 0.8 C/s >244 Influence of sintering temperature on the fatigue per-formance with un-notched specimen is shown in Table 4.
The microstructures of the materials in table 4 are char-acterized by mainly upper bainite (1120 C 0.58%C) and fine pearlite (1120 C, 0.77%C and 1250 C, 0.74oC).
Table 4 Powder Sint. Density Carbon 6A, 50% StdDev 6A, 90%
teTnp As-Sint As-Sint [MPa] [MPa] [MPa]
[g/cm3] 1%]
AstaloyCrL 1120 C 7.10 0.58 220 11 203 1120 C 7.08 0.77 236 9.7 222 1250 C 7.02 0.74 290 18 264 Example 2 Influence of shot peening and the combination of heat treatment and shot peening has been investigated on Asta-loy CrL 3 mm edge-notched specimens. The notch is in-cluded in the press tool and no machining is performed.
The stress concentration factor in bending is obtained by FEM to Kt=1.38. Test frequency is 27-30 Hz.
The materials are sintered at 1280 C for 30 min in H2.
Cooling rate is 0.8 C/s.
The shot peening is performed to obtain an Almen A inten-sity of 0.32 mm.
Estimated plane bending fatigue performance of as sin-tered and as-sintered plus shot peened samples is shown in table 5.
Table 5 Powder Carbon Density Secondary op- Bending Fa- Increase As-Sint As-Sint eration tigue Limit after shot [%] [g/cm3] Shot peening [MPa] peening AstaloyCrL 0.70 7.30 NO 235 notched YES 420 +79%
AstaloyCrL 0.85 7.30 NO 340 un-notched YES 450 +32%
In table 6 an estimated plane bending fatigue performance of through hardened tempered and shot peened samples is shown. Through hardening is performed with an austeniti-zation temperature at 880 C. The cooling rate after aus-tenitization is made at 8 C/s. Finally the specimen are tempered at 250 C for 1 hour Table 6 Powder Carbon Density Secondary operations Bending Increase As- As-Sint Fatigue after Sint [g/cm3] Limit shot Through Tempering Shot [ ] hardenin.g 250 C lh peening [MPa] peening AstaloyCrL 0.50 7.30 YES YES NO 285 notch 0.50 7.30 YES YES YES 490 +73%
AstaloyCrL 0.50 7.30 YES YES NO 370 un-notch 0.50 7.30 YES YES YES 520 +41%
From the tables 5 and 6 it can be found that by shot peening the materials containing chromium and molybdenum a great increase of the bending fatigue limit is achieved.
Table 5 Powder Carbon Density Secondary op- Bending Fa- Increase As-Sint As-Sint eration tigue Limit after shot [%] [g/cm3] Shot peening [MPa] peening AstaloyCrL 0.70 7.30 NO 235 notched YES 420 +79%
AstaloyCrL 0.85 7.30 NO 340 un-notched YES 450 +32%
In table 6 an estimated plane bending fatigue performance of through hardened tempered and shot peened samples is shown. Through hardening is performed with an austeniti-zation temperature at 880 C. The cooling rate after aus-tenitization is made at 8 C/s. Finally the specimen are tempered at 250 C for 1 hour Table 6 Powder Carbon Density Secondary operations Bending Increase As- As-Sint Fatigue after Sint [g/cm3] Limit shot Through Tempering Shot [ ] hardenin.g 250 C lh peening [MPa] peening AstaloyCrL 0.50 7.30 YES YES NO 285 notch 0.50 7.30 YES YES YES 490 +73%
AstaloyCrL 0.50 7.30 YES YES NO 370 un-notch 0.50 7.30 YES YES YES 520 +41%
From the tables 5 and 6 it can be found that by shot peening the materials containing chromium and molybdenum a great increase of the bending fatigue limit is achieved.
Claims (12)
1. A method for producing powder metallurgical parts with improved fatigue strength comprising the steps of:
- providing a pre-alloyed iron-based metal powder comprising at least 1.3-3.5%
by weight of chromium, 0.15-0.7% by weight of molybdenum, - mixing said powder with 0.1-1.0% by weight of graphite, - compacting the obtained mixture at a pressure of at least 600 MPa, - sintering the compacted part in a single step at a temperature above 1100°C, and - shot-peening the part.
- providing a pre-alloyed iron-based metal powder comprising at least 1.3-3.5%
by weight of chromium, 0.15-0.7% by weight of molybdenum, - mixing said powder with 0.1-1.0% by weight of graphite, - compacting the obtained mixture at a pressure of at least 600 MPa, - sintering the compacted part in a single step at a temperature above 1100°C, and - shot-peening the part.
2. The method according to claim 1 wherein the increase of the fatigue strength is at least 50%.
3. The method according to claim 1 or 2, wherein the compacted and sintered part is subjected to hardening and tempering prior to shot peening.
4. A powder metallurgical part manufactured according to any one of the claims 1-3 having a mainly pearlitic microstructure.
5. The powder metallurgical part manufactured according to any one of the claims 1-3 having a mainly fine pearlitic microstructure.
6. The powder metallurgical part manufactured according to any one of the claims 1-3 having a martensitic and lower bainitic microstructure.
7 The powder metallurgical part manufactured according to any one of the claim 1-3 having a mainly tempered martensitic microstructure.
8 The powder metallurgical part according to any one of the claims 1-7 having a bending fatigue limit of at least 340 MPa at a sintered density of 7.15 g/cm3.
9. The powder metallurgical part according to any one of the claims 1-7 having a bending fatigue limit of at least 400 MPa at a sintered density of 7.3 g/cm3.
10. Use of a low chromium prealloyed powder for preparing notched sintered parts having a bending fatigue limit of at least 340 MPa at a sintered density of 7.15 g/cm3, wherein said powder is compacted, sintered and optionally tempered and annealed and is subjected to shot peening.
11. Use of a low chromium prealloyed powder for preparing notched sintered parts according to claim 10 wherein said parts have a bending fatigue limit of at least 400 MPa at a sintered density of 7.3 g/cm3.
12. Use of the powder metallurgical part according to claim 10, wherein said parts have a stress concentration factor above 1.3.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE0401535A SE0401535D0 (en) | 2004-06-14 | 2004-06-14 | Sintered metal parts and method of manufacturing thereof |
| SE0401535-0 | 2004-06-14 | ||
| PCT/SE2005/000908 WO2005120749A1 (en) | 2004-06-14 | 2005-06-13 | Sintered metal parts and method for the manufacturing thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2570236A1 true CA2570236A1 (en) | 2005-12-22 |
Family
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002570236A Abandoned CA2570236A1 (en) | 2004-06-14 | 2005-06-13 | Sintered metal parts and method for the manufacturing thereof |
Country Status (13)
| Country | Link |
|---|---|
| EP (1) | EP1771268A1 (en) |
| JP (1) | JP4825200B2 (en) |
| CN (1) | CN100475389C (en) |
| AU (1) | AU2005252150B2 (en) |
| BR (1) | BRPI0512041A (en) |
| CA (1) | CA2570236A1 (en) |
| MX (1) | MXPA06014234A (en) |
| RU (1) | RU2345867C2 (en) |
| SE (1) | SE0401535D0 (en) |
| TW (1) | TWI290073B (en) |
| UA (1) | UA85245C2 (en) |
| WO (1) | WO2005120749A1 (en) |
| ZA (1) | ZA200610348B (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4789837B2 (en) * | 2007-03-22 | 2011-10-12 | トヨタ自動車株式会社 | Iron-based sintered body and manufacturing method thereof |
| AT505699B1 (en) | 2007-09-03 | 2010-10-15 | Miba Sinter Austria Gmbh | METHOD FOR PRODUCING A SINTERED CERTAIN COMPONENT |
| RU2455116C1 (en) * | 2010-12-03 | 2012-07-10 | Общество с Ограниченной Ответственностью "Научно-производственное предприятие "Вакууммаш" | Abrasive turbine gland element |
| RU2454473C1 (en) * | 2010-12-03 | 2012-06-27 | Общество с ограниченной ответственностью "Научно-производственное предприятие Вакууммаш" | Worn-out seal of turbomachine |
| CA2823267C (en) * | 2010-12-30 | 2019-07-02 | Anna Larsson | Iron based powders for powder injection molding |
| TWI626099B (en) * | 2012-01-05 | 2018-06-11 | 好根那公司 | New metal powder and use thereof |
| JP5636605B2 (en) * | 2012-10-15 | 2014-12-10 | 住友電工焼結合金株式会社 | Method for manufacturing sintered parts |
| CN103008648B (en) * | 2012-12-28 | 2015-04-15 | 杭州东华链条集团有限公司 | Novel manufacturing method of maintenance-free chain |
| DE102013212528A1 (en) | 2013-06-27 | 2014-12-31 | Robert Bosch Gmbh | Process for producing a steel shaped body |
| RU2588979C1 (en) * | 2015-03-16 | 2016-07-10 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Кубанский государственный технологический университет" (ФГБОУ ВПО "КубГТУ") | Method of producing high-density powder chromium containing material based on iron |
| RU2734850C2 (en) * | 2016-03-23 | 2020-10-23 | Хеганес Аб (Пабл) | Iron-based powder |
| JP6431012B2 (en) * | 2016-09-16 | 2018-11-28 | トヨタ自動車株式会社 | Method for producing wear-resistant iron-based sintered alloy and wear-resistant iron-based sintered alloy |
| RU2703669C1 (en) * | 2018-10-16 | 2019-10-21 | Общество с ограниченной ответственностью Научно-технический центр "Уралавиаспецтехнология" | Abradable insert of turbine seal |
| US11668298B2 (en) | 2018-11-07 | 2023-06-06 | Hyundai Motor Company | Slide of variable oil pump for vehicle and method of manufacturing the same |
| US20230350103A1 (en) | 2019-10-17 | 2023-11-02 | Nippon Sheet Glass Company, Limited | Glass body |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03130349A (en) * | 1989-06-24 | 1991-06-04 | Sumitomo Electric Ind Ltd | Ferrous sintered parts material excellent in fatigue strength and its production |
| WO1994014991A1 (en) * | 1992-12-21 | 1994-07-07 | Stackpole Limited | As sintered coining process |
| ES2149195T3 (en) * | 1992-12-21 | 2000-11-01 | Stackpole Ltd | METHOD AND TREATMENT TO PRODUCE SINTERED ARTICLES AND PRODUCTS THEREOF. |
| JP3346139B2 (en) * | 1995-12-28 | 2002-11-18 | 三菱マテリアル株式会社 | Iron-based sintered alloy connecting rod with a mechanically fractured surface between the rod and cap |
| SE9602376D0 (en) * | 1996-06-14 | 1996-06-14 | Hoeganaes Ab | Compact body |
| SE9800154D0 (en) * | 1998-01-21 | 1998-01-21 | Hoeganaes Ab | Steel powder for the preparation of sintered products |
| JP3736838B2 (en) * | 2000-11-30 | 2006-01-18 | 日立粉末冶金株式会社 | Mechanical fuse and manufacturing method thereof |
| SE0201824D0 (en) * | 2002-06-14 | 2002-06-14 | Hoeganaes Ab | Pre-alloyed iron based powder |
| JP2004115868A (en) * | 2002-09-26 | 2004-04-15 | Toyota Motor Corp | Method for manufacturing sintered member |
| US7416696B2 (en) * | 2003-10-03 | 2008-08-26 | Keystone Investment Corporation | Powder metal materials and parts and methods of making the same |
-
2004
- 2004-06-14 SE SE0401535A patent/SE0401535D0/en unknown
-
2005
- 2005-06-13 WO PCT/SE2005/000908 patent/WO2005120749A1/en active Application Filing
- 2005-06-13 CN CNB2005800193408A patent/CN100475389C/en not_active Expired - Fee Related
- 2005-06-13 AU AU2005252150A patent/AU2005252150B2/en not_active Ceased
- 2005-06-13 EP EP05752520A patent/EP1771268A1/en not_active Withdrawn
- 2005-06-13 MX MXPA06014234A patent/MXPA06014234A/en active IP Right Grant
- 2005-06-13 UA UAA200700314A patent/UA85245C2/en unknown
- 2005-06-13 CA CA002570236A patent/CA2570236A1/en not_active Abandoned
- 2005-06-13 BR BRPI0512041-1A patent/BRPI0512041A/en not_active Application Discontinuation
- 2005-06-13 RU RU2007101313/02A patent/RU2345867C2/en not_active IP Right Cessation
- 2005-06-13 JP JP2007516433A patent/JP4825200B2/en not_active Expired - Fee Related
- 2005-06-13 ZA ZA200610348A patent/ZA200610348B/en unknown
- 2005-06-14 TW TW94119717A patent/TWI290073B/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| RU2345867C2 (en) | 2009-02-10 |
| TW200610599A (en) | 2006-04-01 |
| ZA200610348B (en) | 2008-06-25 |
| MXPA06014234A (en) | 2007-02-14 |
| AU2005252150A1 (en) | 2005-12-22 |
| WO2005120749A1 (en) | 2005-12-22 |
| AU2005252150B2 (en) | 2009-01-08 |
| UA85245C2 (en) | 2009-01-12 |
| RU2007101313A (en) | 2008-08-10 |
| CN100475389C (en) | 2009-04-08 |
| SE0401535D0 (en) | 2004-06-14 |
| JP2008502803A (en) | 2008-01-31 |
| EP1771268A1 (en) | 2007-04-11 |
| BRPI0512041A (en) | 2008-02-06 |
| CN1968775A (en) | 2007-05-23 |
| JP4825200B2 (en) | 2011-11-30 |
| TWI290073B (en) | 2007-11-21 |
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