CA2074193C - Metal-powder blend - Google Patents
Metal-powder blend Download PDFInfo
- Publication number
- CA2074193C CA2074193C CA002074193A CA2074193A CA2074193C CA 2074193 C CA2074193 C CA 2074193C CA 002074193 A CA002074193 A CA 002074193A CA 2074193 A CA2074193 A CA 2074193A CA 2074193 C CA2074193 C CA 2074193C
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- CA
- Canada
- Prior art keywords
- graphite
- content
- metal powder
- max
- powder mixture
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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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
- C22C33/0264—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements the maximum content of each alloying element not exceeding 5%
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- 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 is based on the object to provide a metal powder mixture which is simple to manufacture and makes possible the manufacture of high-strength.and wear-resistant cylinder parts with low dimensional deviations. This metal powder mixture is composed of a steel powder which is obtained by atomizing a melt and is mixed with 0.3-0.7% by wt. graphite, wherein the steel alloy powder is composed of (% by wt.) max. ~0.02 ~% C
max. ~0.03 ~% Si 0.05 - 0.25 ~~% Mn 2.5 - 5.0 ~~% Ni 0.2 - 1.5 ~~% Mo the remainder being iron and the usual impurities and the mixture contains finely particulate Cu in an amount of 0.7-1.5% with the requirement that the ratio of quantities of Cu:graphite is in the range of 1.4-2.5.
max. ~0.03 ~% Si 0.05 - 0.25 ~~% Mn 2.5 - 5.0 ~~% Ni 0.2 - 1.5 ~~% Mo the remainder being iron and the usual impurities and the mixture contains finely particulate Cu in an amount of 0.7-1.5% with the requirement that the ratio of quantities of Cu:graphite is in the range of 1.4-2.5.
Description
METHOD OF MANUFACTURING HIGH-STRENGTH
SINTERED PARTS AND METAL POWDER MIXTURE
The invention relates to a method of manufacturing high-strength sintered parts by sintering compacts which have been manufactured from a steel alloy powder containing Ni additionally comprising (in % by wt.) max. 0.02 % C
max. 0.03 % Si 0.05 - 0.25 % Mn 0.2 - 1.5 % Mo the remainder being iron and the usual impurities, wherein (i) finely particulate Cu in an amount of 0.7-1.5% and graphite in an amount of 0.3-0.7% have been added to the steel alloy powder;(ii) wherein the Ni content of the steel alloy powder which was produced by spraying a steel melt with water is greater than 2.5 to at most 5.0%; (iii) the ratio of quantities of Cu:graphite is maintained in the range of 1.4-2.5; and (iv) the sintered parts undergo martensite full hardening by being cooled in air or under a gas spray without subsequent heat treatment following sintering.
Additionally, the invention also relates to a metal powder mixture for use in the method of the present invention manufactured from a steel allay containing Ni with (in % by weight) max. 0.02 % C
max. 0.03 % Si la 0.05 - 0.25 % Mn 0.2 - 1.5 % Mo the remainder being iron and the usual impurities, with an addition of finely particulate Cu in an amount of 0.7-1.5%
and graphite in an amount of 0.3-0.7%, wherein the steel powder produced by spraying with water has an Ni content of greater than 2.5 to at most 5.0%, and wherein the ratio of quantities of Cu: graphite is maintained in the range of 1.4-2.5.
A steel alloy powder for manufacturing high-strength sintered parts is known from EP 0 136 169 B1. The steel alloy powder is composed of (% by wt.) max. 0.02 % C
max. 0.1 % Si 0.4 - 1.3 % Ni 0.2 - 0.5 % Cu 0.1 - 0.3 % Mo max. 0.3 % Mn max. 0.01 % N
the remainder being iron and the usual impurities.
2~~t~~.~
(~:f r. _ 2 _ 1 This alloy powder is to be inexpensive to 2 manufacture and to process, is to have good pressing 3 properties, and is to ensure a high strength in the 4 sintered finished part. The reference does not discuss in detail the properties of the finished 6 part with respect to the obtainable accuracy to size 7 of the finished part.
8 When a compact manufactured of steel 9 powder is sintered, its geometry usually changes.
This is called shrinkage due to sintering. This 11 effect is counteracted by martensitic hardening 12 essentially because of the attendant increase in 13 volume due to structural transformation. Of course, 14 a volumetric change of the finished part compared to the compact used for sintering can also be taken 16 into consideration when dimensioning the pressing 17 die, i.e., it is attempted to anticipate the 18 dimensional deviations and to compensate the 19 deviations by changing the dimensions of the compact from the beginning. However, this was only very z1 incompletely achieved in the past, not only because 22 the relative dimensional deviations depend on the 23 respective wall thicknesses of the compact, but also 24 because the relative dimensional deviations are significantly influenced by the density obtained in 26 the compact which is subject to significant 27 variations within the same compact and also between 28 individual compacts which are otherwise the same.
29 Consequently, the efforts for obtaining a dimensional constancy in the sintered finished part 31 of finished alloy materials have in the past only 32 resulted in a reproducible limitation of the 33 dimensional deviations in the most favorable case to 34 values of approximately 0.1%. Such deviations are no longer tolerable for many parts. For this 36 reason, sintered parts are frequently subjected to 37 a final calibration procedure which is very 38 expensive. However, this calibration procedure 39 cannot even be carried out in hardened parts because of the hardness of the sintered parts.
G:\MJM\3245158P.PAT
r.:.
,. . ., -2A-1 A sinter alloy in which the Ni content is at most 2 2.5% is known from EP 0 042 654. This content is of 3 significance in connection with the Mo content for 4 the possibility of air hardening. However, the highest limit of 0.7% Mo disclosed in this reference 6 cannot be carried out. In this alloy, the improved 7 strength is obtained by a special heat treatment 8 after sintering.
G:\MJM\3245158P.PAT
It is the object of the invention to provide a metal powder mixture which is as simple as possible to manufacture and permits the manufacture of high-strength and wear-resistant sintered parts whose dimensional deviations can be kept within a tolerance range having a width of at most tD.05% without requiring additional structural measures in the pressing tool for the manufacture of compacts to be sintered. Accordingly, it should be a property of the metal powder not to result in significant shrinkage or growth when compacts manufactured by conventional compacting are sintered.
This object is met by a method and a metal powder mixture having the features recited above. Advantageous further developments of this mixture are the preferred Mn content of the mixture is 0.10 to 0.20%, the preferred Ni content of the mixture ~is 3.0 to 4.0%, the preferred Mo content of the mixture is 0.5 to 1.0%, the preferred graphite content is 0.5 to 0.6% and the preferred ratio of Cu:graphite is 2.
Contrary to the steel alloy powder known from EP 0 136 169 B1, the present invention provides that the Cu content is not already introduced in the alloy used for atomizing, but is admixed in finely distributed form to the steel powder. In addition, in accordance with the invention, the quantitative contents of the individual alloy elements are maintained within different limits than in the known steel powder. It is 25~ particularly important that the ratio of the Cu content relative to the graphite content which is also introduced into the metal powder mixture in powder form as carbon is maintained in the range of 1.4-2.5, preferably 2Ø When observing all requirements of the invention, it is surprisingly possible to manufacture compacts by using the usual compressing procedures of powder metallurgy which, again under the usual sintering 3a conditions, have almost complete dimensional constancy independently of the wall thicknesses of the compacts. The dimensional deviations are less than ~0.05.
. .
... ;
When the sintered parts are cooled in air or by means of a gas shower (for example, inert gas supplied under pressure) arranged in the cooling zone of a sintering =urnace, a completely martensitic structure is obtained in the sintered parts which imparts a high-strength (more than 750 N/mmZ) to the parts without requiring a subsequent heat treatment.
The invention shall be described in more detail with the aid of the following example.
A steel powder having the following composition (% by wt.) was produced by water atomizing of a melt.
0.01 % C
0.02 % Si 0.10 % Mn 4.0 % Ni 0.5 % Mo 0.020 % P
0.010 % S
the remainder being iron and the usual impurities.
After water atomizing of the melt, the steel powder was dried and subjected at approximately 1,000°C to reduction annealing in an Hz atmosphere. After cooling, the resulting agglomerate was ground into fine particles. The residual oxygen content of the steel powder was approximately 0.15% and its apparent density was approximately 3 g/cm3.
Subsequently, added to this steel powder were 0.60% graphite powder and 1.0% finely G:\MJM\3245158P.PAT
._, particulate Cu as well as about 1% conventional lubricants. After these components were uniformly mixed, compacts were produced by cold pressing in the conventional manner, wherein the density of the compacts was approximately 7 g/em3.
After the compacts were sintered at approximately 1,120°C, the finished parts had dimensional deviations of less than ~0.03% relative to the dimensions of the compact. When cooled under a nitrogen shower after sintering, the parts were completely martensitically hardened and had a tensile strength of more than 820 N/mm2 with a hardness of approximately 400 HB.
In another test with the metal powder mixture according to the invention, the compacts were subjected to a two-fold pressing and sintering procedure with temperature stages of 800°C and 1,120°C. Again, the two sintering procedures resulted in dimensional deviations of less than 0.03%. The tensile strength was approximately 900 N/mm2, and the hardness approximately 450 HB.
The advantages of the metal powder mixture according to the invention are to be seen particularly in the fact that dimensionally constant sintered parts can be manufactured which do not require any complicated mechanical, deforming, or thermal after-treatment after sintering, and wherein the steel powder can be manufactured inexpensively.
This is because the selected alloy according to the invention can be water atomized with subsequent reduction under H2 atmosphere. Expensive vacuum annealing, as it is required in other finished-G:\MJM\324515$P.PAT
,:-r..; . , 1 alloy, water-atomized metal powders for the same 2 use, is not required. Also, in addition to the 3 inexpensive manufacture, the metal powder mixture 4 results in excellent strength and wear properties.
G:\MJM\3245158P.PAT
SINTERED PARTS AND METAL POWDER MIXTURE
The invention relates to a method of manufacturing high-strength sintered parts by sintering compacts which have been manufactured from a steel alloy powder containing Ni additionally comprising (in % by wt.) max. 0.02 % C
max. 0.03 % Si 0.05 - 0.25 % Mn 0.2 - 1.5 % Mo the remainder being iron and the usual impurities, wherein (i) finely particulate Cu in an amount of 0.7-1.5% and graphite in an amount of 0.3-0.7% have been added to the steel alloy powder;(ii) wherein the Ni content of the steel alloy powder which was produced by spraying a steel melt with water is greater than 2.5 to at most 5.0%; (iii) the ratio of quantities of Cu:graphite is maintained in the range of 1.4-2.5; and (iv) the sintered parts undergo martensite full hardening by being cooled in air or under a gas spray without subsequent heat treatment following sintering.
Additionally, the invention also relates to a metal powder mixture for use in the method of the present invention manufactured from a steel allay containing Ni with (in % by weight) max. 0.02 % C
max. 0.03 % Si la 0.05 - 0.25 % Mn 0.2 - 1.5 % Mo the remainder being iron and the usual impurities, with an addition of finely particulate Cu in an amount of 0.7-1.5%
and graphite in an amount of 0.3-0.7%, wherein the steel powder produced by spraying with water has an Ni content of greater than 2.5 to at most 5.0%, and wherein the ratio of quantities of Cu: graphite is maintained in the range of 1.4-2.5.
A steel alloy powder for manufacturing high-strength sintered parts is known from EP 0 136 169 B1. The steel alloy powder is composed of (% by wt.) max. 0.02 % C
max. 0.1 % Si 0.4 - 1.3 % Ni 0.2 - 0.5 % Cu 0.1 - 0.3 % Mo max. 0.3 % Mn max. 0.01 % N
the remainder being iron and the usual impurities.
2~~t~~.~
(~:f r. _ 2 _ 1 This alloy powder is to be inexpensive to 2 manufacture and to process, is to have good pressing 3 properties, and is to ensure a high strength in the 4 sintered finished part. The reference does not discuss in detail the properties of the finished 6 part with respect to the obtainable accuracy to size 7 of the finished part.
8 When a compact manufactured of steel 9 powder is sintered, its geometry usually changes.
This is called shrinkage due to sintering. This 11 effect is counteracted by martensitic hardening 12 essentially because of the attendant increase in 13 volume due to structural transformation. Of course, 14 a volumetric change of the finished part compared to the compact used for sintering can also be taken 16 into consideration when dimensioning the pressing 17 die, i.e., it is attempted to anticipate the 18 dimensional deviations and to compensate the 19 deviations by changing the dimensions of the compact from the beginning. However, this was only very z1 incompletely achieved in the past, not only because 22 the relative dimensional deviations depend on the 23 respective wall thicknesses of the compact, but also 24 because the relative dimensional deviations are significantly influenced by the density obtained in 26 the compact which is subject to significant 27 variations within the same compact and also between 28 individual compacts which are otherwise the same.
29 Consequently, the efforts for obtaining a dimensional constancy in the sintered finished part 31 of finished alloy materials have in the past only 32 resulted in a reproducible limitation of the 33 dimensional deviations in the most favorable case to 34 values of approximately 0.1%. Such deviations are no longer tolerable for many parts. For this 36 reason, sintered parts are frequently subjected to 37 a final calibration procedure which is very 38 expensive. However, this calibration procedure 39 cannot even be carried out in hardened parts because of the hardness of the sintered parts.
G:\MJM\3245158P.PAT
r.:.
,. . ., -2A-1 A sinter alloy in which the Ni content is at most 2 2.5% is known from EP 0 042 654. This content is of 3 significance in connection with the Mo content for 4 the possibility of air hardening. However, the highest limit of 0.7% Mo disclosed in this reference 6 cannot be carried out. In this alloy, the improved 7 strength is obtained by a special heat treatment 8 after sintering.
G:\MJM\3245158P.PAT
It is the object of the invention to provide a metal powder mixture which is as simple as possible to manufacture and permits the manufacture of high-strength and wear-resistant sintered parts whose dimensional deviations can be kept within a tolerance range having a width of at most tD.05% without requiring additional structural measures in the pressing tool for the manufacture of compacts to be sintered. Accordingly, it should be a property of the metal powder not to result in significant shrinkage or growth when compacts manufactured by conventional compacting are sintered.
This object is met by a method and a metal powder mixture having the features recited above. Advantageous further developments of this mixture are the preferred Mn content of the mixture is 0.10 to 0.20%, the preferred Ni content of the mixture ~is 3.0 to 4.0%, the preferred Mo content of the mixture is 0.5 to 1.0%, the preferred graphite content is 0.5 to 0.6% and the preferred ratio of Cu:graphite is 2.
Contrary to the steel alloy powder known from EP 0 136 169 B1, the present invention provides that the Cu content is not already introduced in the alloy used for atomizing, but is admixed in finely distributed form to the steel powder. In addition, in accordance with the invention, the quantitative contents of the individual alloy elements are maintained within different limits than in the known steel powder. It is 25~ particularly important that the ratio of the Cu content relative to the graphite content which is also introduced into the metal powder mixture in powder form as carbon is maintained in the range of 1.4-2.5, preferably 2Ø When observing all requirements of the invention, it is surprisingly possible to manufacture compacts by using the usual compressing procedures of powder metallurgy which, again under the usual sintering 3a conditions, have almost complete dimensional constancy independently of the wall thicknesses of the compacts. The dimensional deviations are less than ~0.05.
. .
... ;
When the sintered parts are cooled in air or by means of a gas shower (for example, inert gas supplied under pressure) arranged in the cooling zone of a sintering =urnace, a completely martensitic structure is obtained in the sintered parts which imparts a high-strength (more than 750 N/mmZ) to the parts without requiring a subsequent heat treatment.
The invention shall be described in more detail with the aid of the following example.
A steel powder having the following composition (% by wt.) was produced by water atomizing of a melt.
0.01 % C
0.02 % Si 0.10 % Mn 4.0 % Ni 0.5 % Mo 0.020 % P
0.010 % S
the remainder being iron and the usual impurities.
After water atomizing of the melt, the steel powder was dried and subjected at approximately 1,000°C to reduction annealing in an Hz atmosphere. After cooling, the resulting agglomerate was ground into fine particles. The residual oxygen content of the steel powder was approximately 0.15% and its apparent density was approximately 3 g/cm3.
Subsequently, added to this steel powder were 0.60% graphite powder and 1.0% finely G:\MJM\3245158P.PAT
._, particulate Cu as well as about 1% conventional lubricants. After these components were uniformly mixed, compacts were produced by cold pressing in the conventional manner, wherein the density of the compacts was approximately 7 g/em3.
After the compacts were sintered at approximately 1,120°C, the finished parts had dimensional deviations of less than ~0.03% relative to the dimensions of the compact. When cooled under a nitrogen shower after sintering, the parts were completely martensitically hardened and had a tensile strength of more than 820 N/mm2 with a hardness of approximately 400 HB.
In another test with the metal powder mixture according to the invention, the compacts were subjected to a two-fold pressing and sintering procedure with temperature stages of 800°C and 1,120°C. Again, the two sintering procedures resulted in dimensional deviations of less than 0.03%. The tensile strength was approximately 900 N/mm2, and the hardness approximately 450 HB.
The advantages of the metal powder mixture according to the invention are to be seen particularly in the fact that dimensionally constant sintered parts can be manufactured which do not require any complicated mechanical, deforming, or thermal after-treatment after sintering, and wherein the steel powder can be manufactured inexpensively.
This is because the selected alloy according to the invention can be water atomized with subsequent reduction under H2 atmosphere. Expensive vacuum annealing, as it is required in other finished-G:\MJM\324515$P.PAT
,:-r..; . , 1 alloy, water-atomized metal powders for the same 2 use, is not required. Also, in addition to the 3 inexpensive manufacture, the metal powder mixture 4 results in excellent strength and wear properties.
G:\MJM\3245158P.PAT
Claims (8)
1. A method of manufacturing high-strength sintered parts by sintering compacts which have been manufactured from steel alloy powder containing Ni additionally comprising (in % by wt.) max. 0.02 % C
max. 0.03 % Si 0.05 - 0.25 % Mn 0.2 - 1.5 % Mo the remainder being iron and the usual impurities wherein (i) finely particulate Cu in an amount of 0.7-1.5% and graphite in an amount of 0.3-0.7% have been added to the steel alloy powder; (ii) the Ni content of the steel alloy powder which was produced by spraying a steel melt with water is greater than 2.5 to at most 5.0%; (iii) the ratio of quantities of Cu:graphite is maintained in the range of 1.4-2.5; and (iv) the sintered parts undergo martensite full hardening by being cooled in air or under a gas spray without subsequent heat treatment following sintering.
max. 0.03 % Si 0.05 - 0.25 % Mn 0.2 - 1.5 % Mo the remainder being iron and the usual impurities wherein (i) finely particulate Cu in an amount of 0.7-1.5% and graphite in an amount of 0.3-0.7% have been added to the steel alloy powder; (ii) the Ni content of the steel alloy powder which was produced by spraying a steel melt with water is greater than 2.5 to at most 5.0%; (iii) the ratio of quantities of Cu:graphite is maintained in the range of 1.4-2.5; and (iv) the sintered parts undergo martensite full hardening by being cooled in air or under a gas spray without subsequent heat treatment following sintering.
2. A method according to claim 1, wherein the Ni content is maintained in the range of 3.0-4.0%.
3. A metal powder mixture for use in the method according to claim 1, manufactured from a steel alloy containing Ni with (in % by wt.) max. 0.02 % C
max. 0.03 % Si 0.05 - 0.25 % Mn 0.2 - 1.5 % Mo the remainder being iron and the usual impurities, with an addition of finely particulate Cu in an amount of 0.7-1.5%
and graphite in an amount of 0.3-0.7%, wherein the steel powder produced by spraying with water has an Ni content of greater than 2.5 to at most 5.0%, and wherein the ratio of quantities of Cu:graphite is maintained in the range of 1.4-2.5.
max. 0.03 % Si 0.05 - 0.25 % Mn 0.2 - 1.5 % Mo the remainder being iron and the usual impurities, with an addition of finely particulate Cu in an amount of 0.7-1.5%
and graphite in an amount of 0.3-0.7%, wherein the steel powder produced by spraying with water has an Ni content of greater than 2.5 to at most 5.0%, and wherein the ratio of quantities of Cu:graphite is maintained in the range of 1.4-2.5.
4. A metal powder mixture according to claim 3, wherein the Mn content is limited to values of 0.10 to 0.20%.
5. A metal powder mixture according to claim 3 or 4, wherein the Ni content is limited to 3.0-4.0%.
6. A metal powder mixture according to any one of claims 3-5, wherein the Mo content is limited to values of 0.5-1.0%.
7. A metal powder mixture according to any one of claims 3-6, wherein the graphite addition is limited to 0.5-0.6%.
8. A metal powder mixture according to any one of claims 3-7, wherein the ratio of Cu:graphite is 2.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4001900A DE4001900A1 (en) | 1990-01-19 | 1990-01-19 | METAL POWDER MIXING |
| DEP4001900.4 | 1990-01-19 | ||
| PCT/DE1990/000751 WO1991010753A1 (en) | 1990-01-19 | 1990-09-28 | Metal-powder blend |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2074193A1 CA2074193A1 (en) | 1991-07-20 |
| CA2074193C true CA2074193C (en) | 2003-09-16 |
Family
ID=6398606
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002074193A Expired - Fee Related CA2074193C (en) | 1990-01-19 | 1990-09-28 | Metal-powder blend |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0597832B1 (en) |
| JP (1) | JP2908018B2 (en) |
| AT (1) | ATE124467T1 (en) |
| CA (1) | CA2074193C (en) |
| DE (2) | DE4001900A1 (en) |
| WO (1) | WO1991010753A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE0203135D0 (en) * | 2002-10-23 | 2002-10-23 | Hoeganaes Ab | Dimensional control |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1298614A (en) * | 1961-08-08 | 1962-07-13 | Mannesmann Ag | Process for the production of sintered pressed bodies |
| DE1207634B (en) * | 1961-11-30 | 1965-12-23 | Birmingham Small Arms Co Ltd | Powder mixture for the production of steel objects according to known powder metallurgical processes |
| GB1162702A (en) * | 1965-09-14 | 1969-08-27 | Hoganas Billesholms Ab | Low Alloy Iron Powder and process of preparing the same |
| GB1305608A (en) * | 1970-03-18 | 1973-02-07 | ||
| US4170474A (en) * | 1978-10-23 | 1979-10-09 | Pitney-Bowes | Powder metal composition |
| JPS6075501A (en) * | 1983-09-29 | 1985-04-27 | Kawasaki Steel Corp | Alloy steel powder for high strength sintered parts |
-
1990
- 1990-01-19 DE DE4001900A patent/DE4001900A1/en not_active Withdrawn
- 1990-09-28 CA CA002074193A patent/CA2074193C/en not_active Expired - Fee Related
- 1990-09-28 WO PCT/DE1990/000751 patent/WO1991010753A1/en active IP Right Grant
- 1990-09-28 DE DE59009358T patent/DE59009358D1/en not_active Expired - Lifetime
- 1990-09-28 AT AT90914132T patent/ATE124467T1/en not_active IP Right Cessation
- 1990-09-28 EP EP90914132A patent/EP0597832B1/en not_active Expired - Lifetime
- 1990-09-28 JP JP2513227A patent/JP2908018B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2074193A1 (en) | 1991-07-20 |
| EP0597832B1 (en) | 1995-06-28 |
| JPH05503318A (en) | 1993-06-03 |
| ATE124467T1 (en) | 1995-07-15 |
| JP2908018B2 (en) | 1999-06-21 |
| EP0597832A1 (en) | 1994-05-25 |
| WO1991010753A1 (en) | 1991-07-25 |
| DE59009358D1 (en) | 1995-08-03 |
| DE4001900A1 (en) | 1991-07-25 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |