CN108097948B - A kind of high-temperature heat treatment method that metal alloy attritive powder is anti-oxidation - Google Patents
A kind of high-temperature heat treatment method that metal alloy attritive powder is anti-oxidation Download PDFInfo
- Publication number
- CN108097948B CN108097948B CN201711405807.3A CN201711405807A CN108097948B CN 108097948 B CN108097948 B CN 108097948B CN 201711405807 A CN201711405807 A CN 201711405807A CN 108097948 B CN108097948 B CN 108097948B
- Authority
- CN
- China
- Prior art keywords
- temperature
- heat treatment
- powder
- atmosphere
- furnace
- 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.)
- Active
Links
- 239000000843 powder Substances 0.000 title claims abstract description 50
- 238000010438 heat treatment Methods 0.000 title claims abstract description 48
- 238000000034 method Methods 0.000 title claims abstract description 39
- 230000003064 anti-oxidating effect Effects 0.000 title claims abstract description 13
- 229910001092 metal group alloy Inorganic materials 0.000 title claims abstract description 9
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 20
- 239000007789 gas Substances 0.000 claims description 11
- 229910052786 argon Inorganic materials 0.000 claims description 10
- 238000004321 preservation Methods 0.000 claims description 10
- 238000010792 warming Methods 0.000 claims description 10
- 238000001816 cooling Methods 0.000 claims description 7
- 230000001681 protective effect Effects 0.000 claims description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 5
- 239000001257 hydrogen Substances 0.000 claims description 5
- 229910052739 hydrogen Inorganic materials 0.000 claims description 5
- 238000006467 substitution reaction Methods 0.000 claims description 4
- 238000006073 displacement reaction Methods 0.000 claims 1
- 239000002184 metal Substances 0.000 abstract description 12
- 229910045601 alloy Inorganic materials 0.000 abstract description 9
- 239000000956 alloy Substances 0.000 abstract description 9
- 238000000137 annealing Methods 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 3
- 238000002791 soaking Methods 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 238000010146 3D printing Methods 0.000 description 1
- 229910000906 Bronze Inorganic materials 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 239000010974 bronze Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- KUNSUQLRTQLHQQ-UHFFFAOYSA-N copper tin Chemical compound [Cu].[Sn] KUNSUQLRTQLHQQ-UHFFFAOYSA-N 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
Classifications
-
- 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
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/14—Treatment of metallic powder
- B22F1/142—Thermal or thermo-mechanical treatment
Abstract
A kind of high-temperature heat treatment method that metal alloy attritive powder is anti-oxidation, related powder are average diameter in 150 μm of superfine spherical metal powders below, and provided anti-oxidation high-temperature heat treatment method is simple, at low cost, are suitable for producing in enormous quantities.Micro-alloy powder to be processed is placed in atmosphere rotary furnace, in temperature-rise period, powder is kept the temperature at different temperature, carry out vacuum outgas, then it is raised to required heat treatment temperature, carries out specified heat treatment process, the heat treatment temperature being applicable in is 950 DEG C or less.
Description
Technical field
The present invention relates to refining metallic powders, the anti-oxidation processing side of metal powder especially in high-temperature heat treatment process
Method.
Background technique
Metal powder is that have widely applied raw material in a kind of engineering field.In spraying, laser melting coating and 3D printing
In required powder have the characteristics that small size, large specific surface area, good fluidity, but be different application direction to powder
Performance has different requirements, such as size distribution requirements, sphericity requirement and hardness requirement etc..
Dusty material requires processing before carrying out according to application conditions before use in many cases,.Make as
With preceding needing that powder is dried, this processing is relatively simple, pertains only to temperature and soaking time.But at certain
The application of a little particular/special requirements needs to carry out high-temperature heat treatment to metal powder, to obtain compared with coarse grain or other specific groups
It knits and performance, as soft annealing is handled.And metal powder generally existing high-temperature oxydation phenomenon in high-temperature heat treatment process, it is original
Oxygen content in power is generally in 300 ppm hereinafter, and the oxygen content of powder can then be increased to 1000 after the completion of high-temperature heat treatment
Ppm or more, or even 4000 ppm can be met or exceeded.Therefore, seek suitable processing method to solve metal powder in high temperature
Anti-oxidation problem in heat treatment process has important practical significance.
Summary of the invention
It is an object of the invention to be directed to the above problem present in the heat treatment of existing metal superfine alloyed spherical powder,
Simple process and low cost is provided, a kind of anti-oxidation high-temperature heat treatment method for the metal powder produced in enormous quantities is suitable for.It needs
It is noted that the temperature of anti-oxidation high-temperature heat treatment method of the present invention specifically refers at 950 DEG C of high warms below
Reason.
The present invention provides a kind of high-temperature heat treatment methods that metal alloy attritive powder is anti-oxidation, it is characterised in that including
Following steps:
(1) metal powder to be processed is placed in atmosphere rotary furnace, enclosed furnace rear substitution furnace atmosphere is finally kept
Ultimate vacuum state；
(2) rotary furnace is warming up to heat preservation in the progress of the first temperature 2 hours or more, and keeps ultimate vacuum state；
(3) rotary furnace is warming up to heat preservation in second temperature progress 1 hour or more, and keeps ultimate vacuum state；
(4) it is filled with protective atmosphere after step (3) are kept the temperature, carries out further heat treatment process；The wherein guarantor
Protecting atmosphere is high-purity argon gas and high-purity hydrogen.
Advantageously, in step (1), furnace atmosphere is replaced using high-purity argon gas.
Advantageously, second temperature is greater than 300 DEG C of first temperature or more.
Advantageously, the first temperature is between 100-200 DEG C.
Advantageously, second temperature is between 500-600 DEG C.
Advantageously, control rotary furnace rotation in step (1).
Advantageously, the high-temperature heat treatment in step (4) is soft annealing processing.
Advantageously, further heat treatment process in step (4) specifically: rotary furnace is to slowly warm up to 700-950 DEG C
Between some temperature spot and keep the temperature 15 hours within, furnace is as cold as room temperature after then dropping to 600 DEG C with certain cooling rate, will
Powder is come out of the stove.
Advantageously, further heat treatment process in step (4) specifically: rotary furnace is to slowly warm up to 860 DEG C and is protected
13-15 hours warm, furnace is as cold as room temperature after then dropping to 600 DEG C with 10 DEG C per hour of cooling rate, and powder is come out of the stove.
According to a further aspect of the invention, a kind of high-temperature heat treatment side that metal alloy attritive powder is anti-oxidation is additionally provided
Method, the specific steps of which are as follows:
(1) metal powder to be processed is placed in atmosphere rotary furnace, (number can root for enclosed furnace rear substitution furnace atmosphere
Determine according to needing), finally keep ultimate vacuum state；
(2) equipment is warming up to heat preservation in the progress of the temperature spot between 100-200 DEG C 2 hours or more, and keeps the limit true
Dummy status；
(3) equipment is warming up to heat preservation in the progress of the temperature spot between 500-600 DEG C 1 hour or more, and keeps the limit true
Dummy status；
(4) it is filled with protective atmosphere after step (3) are kept the temperature, carries out corresponding heat treatment process.
In step (1), the equipment uses specific atmosphere rotary furnace, and protective atmosphere is high-purity argon gas.
It is heat-treated using the program, the temperature of heat treatment can be at 950 DEG C hereinafter, the soaking time of heat treatment can be
Within 15 hours (such as 860 DEG C or more).Advantageously, knot is controlled by the exact gradient to the micro-alloy powder temperature
Control climate processing is closed, thoroughly solves problem of oxidation of the alloy powder in high-temperature heat treatment process.
Specific embodiment
Embodiment 1
The present invention provides a kind of high-temperature heat treatment methods that metal alloy attritive powder is anti-oxidation.This method includes as follows
Step:
(1) metal powder to be processed is placed in atmosphere rotary furnace, enclosed furnace rear substitution furnace atmosphere is finally kept
Ultimate vacuum state；
(2) rotary furnace is warming up to heat preservation in the progress of the first temperature 2 hours or more, and keeps ultimate vacuum state；
(3) rotary furnace is warming up to heat preservation in second temperature progress 1 hour or more, and keeps ultimate vacuum state；
(4) it is filled with protective atmosphere after step (3) are kept the temperature, carries out further heat treatment process；The wherein guarantor
Protecting atmosphere is high-purity argon gas and high-purity hydrogen.
Advantageously, in step (1), furnace atmosphere is replaced using high-purity argon gas.
Advantageously, second temperature is greater than 300 DEG C of first temperature or more.
Advantageously, the first temperature is between 100-200 DEG C.
Advantageously, second temperature is between 500-600 DEG C.
Advantageously, control rotary furnace rotation in step (1).
Advantageously, the high-temperature heat treatment in step (4) is soft annealing processing.
Advantageously, further heat treatment process in step (4) specifically: rotary furnace is to slowly warm up to 700-950 DEG C
Between some temperature spot and keep the temperature 15 hours within, furnace is as cold as room temperature after then dropping to 600 DEG C with certain cooling rate, will
Powder is come out of the stove.
Advantageously, further heat treatment process in step (4) specifically: rotary furnace is to slowly warm up to 860 DEG C and is protected
13-15 hours warm, furnace is as cold as room temperature after then dropping to 600 DEG C with 10 DEG C per hour of cooling rate, and powder is come out of the stove.High-purity argon
The ratio of gas and high-purity hydrogen is preferably ratio 9:1.It is filled with a pressure preferably slightly below atmospheric pressure for protective atmosphere.
Advantageously, the soaking time in step (3) is 1 hour or more.It is understood that powder involved in the present invention
End is average diameter in 150 μm of superfine spherical metal powders below, provided anti-oxidation high-temperature heat treatment method letter
It is single, it is at low cost, it is suitable for producing in enormous quantities, the heat treatment temperature being applicable in is 950 DEG C or less.
Embodiment 2(with H13 powder, average diameter in 100 μm of spherical powders below, for)
150 kg of powder is taken, is placed in atmosphere rotary furnace, enclosed furnace is first evacuated to ultimate vacuum, is then charged with high-purity argon
Gas is to atmospheric pressure, then is evacuated to ultimate vacuum, and two to three times repeatedly, finally keeps ultimate vacuum state.
It rotates equipment with certain revolving speed, equipment is warming up to 150 DEG C of heat preservations 3-5 hours, and keep ultimate vacuum state；After
It is continuous that equipment is warming up to 500 DEG C and carries out heat preservation in 1 hour, holding ultimate vacuum state during this.It is filled when closing to an end wait keep the temperature
Enter high-purity argon gas and high-purity hydrogen (ratio 9:1) to a slightly below atmospheric pressure.
Equipment is to slowly warm up to 860 DEG C and keeps the temperature 13-15 hours, is then dropped to 10 DEG C per hour of cooling rate
Furnace is as cold as room temperature after 600 DEG C, and powder is come out of the stove.
The high-temperature heat treatment is that the soft annealing of H13 material is handled, and finally the powder hardness of H13 can be reduced to HV 180
Up and down.
It is understood that the present invention is being heated up by the way that micro-alloy powder to be processed to be placed in atmosphere rotary furnace
In the process, powder is kept the temperature at different temperature, carries out vacuum outgas, is then raised to required heat treatment temperature, carried out
Specified heat treatment process, the heat treatment temperature being applicable in are 950 DEG C or less.By to the accurate of the micro-alloy powder temperature
Gradient control combines control climate to handle, and thoroughly solves problem of oxidation of the alloy powder in high-temperature heat treatment process.More into
One step can also thoroughly solve to close by the precise controlling of temperature and rotation to the micro-alloy powder and manipulative
Agglomeration problems of the bronze end in high-temperature heat treatment process improve performance parameter (such as the size distribution, spherical shape of alloy powder
Degree, hardness), it can be achieved that being precisely controlled to alloy powder performance.
Claims (7)
1. a kind of high-temperature heat treatment method that metal alloy attritive powder is anti-oxidation, the high temperature is 950 DEG C of temperature below,
It is characterized in that including the following steps:
(1) metal alloy attritive powder to be processed is placed in atmosphere rotary furnace, enclosed furnace rear substitution furnace atmosphere, finally
Keep ultimate vacuum state；
(2) atmosphere rotary furnace is warming up to heat preservation in the progress of the first temperature 2 hours or more, and keeps ultimate vacuum state；
(3) atmosphere rotary furnace is warming up to heat preservation in second temperature progress 1 hour or more, and keeps ultimate vacuum state；
(4) it is filled with protective atmosphere after step (3) are kept the temperature, carries out further heat treatment process；The wherein protection gas
Atmosphere is high-purity argon gas and high-purity hydrogen；
The average diameter of the metal alloy attritive powder is at 150 μm hereinafter, the first temperature is the second temperature between 100-200 DEG C
Degree is greater than 300 DEG C of first temperature or more.
2. high-temperature heat treatment method as described in claim 1, it is characterised in that in step (1), using high-purity argon gas displacement furnace
Interior atmosphere.
3. high-temperature heat treatment method as described in claim 1, it is characterised in that second temperature is between 500-600 DEG C.
4. high-temperature heat treatment method as claimed in claim 1 or 2, it is characterised in that control atmosphere rotary furnace turns in step (1)
It is dynamic.
5. high-temperature heat treatment method as claimed in claim 1 or 2, it is characterised in that the heat treatment in step (4) is that softening is moved back
Fire processing.
6. high-temperature heat treatment method as claimed in claim 1 or 2, it is characterised in that further heat treated in step (4)
Journey specifically: within being to slowly warm up to some temperature spot between 700-950 DEG C by atmosphere rotary furnace and keep the temperature 15 hours, then
Furnace is as cold as room temperature after dropping to 600 DEG C with certain cooling rate, and powder is come out of the stove.
7. high-temperature heat treatment method as claimed in claim 4, it is characterised in that further heat treatment process tool in step (4)
Body are as follows: atmosphere rotary furnace is to slowly warm up to 860 DEG C and keeps the temperature 13-15 hours, is then dropped with 10 DEG C per hour of cooling rate
Furnace is as cold as room temperature after to 600 DEG C, and powder is come out of the stove.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201711405807.3A CN108097948B (en) | 2017-12-22 | 2017-12-22 | A kind of high-temperature heat treatment method that metal alloy attritive powder is anti-oxidation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201711405807.3A CN108097948B (en) | 2017-12-22 | 2017-12-22 | A kind of high-temperature heat treatment method that metal alloy attritive powder is anti-oxidation |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN108097948A CN108097948A (en) | 2018-06-01 |
| CN108097948B true CN108097948B (en) | 2019-11-05 |
Family
ID=62212323
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201711405807.3A Active CN108097948B (en) | 2017-12-22 | 2017-12-22 | A kind of high-temperature heat treatment method that metal alloy attritive powder is anti-oxidation |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN108097948B (en) |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5120720A (en) * | 1974-08-13 | 1976-02-19 | Matsushita Electric Ind Co Ltd | |
| EP0281444A1 (en) * | 1987-02-05 | 1988-09-07 | Sumitomo Electric Industries Limited | Process for manufacturing a superconducting wire of compound oxide-type ceramic |
| CN1449879A (en) * | 2003-04-30 | 2003-10-22 | 北京科技大学 | Method for processing microtantalum and/or niobium powder and powder made by said method |
| CN103008658A (en) * | 2011-09-28 | 2013-04-03 | 宝山钢铁股份有限公司 | Manufacturing method of high-temperature alloy blanks in large-size single crystal structures |
| CN104550984A (en) * | 2014-12-15 | 2015-04-29 | 中国航空工业集团公司北京航空材料研究院 | Preparation method of nickel-based high-temperature alloy powder for 3D (Three Dimensional) printing |
| CN105562681A (en) * | 2016-02-02 | 2016-05-11 | 集美大学 | High-temperature heat treatment method for metal powder |
| CN106480277A (en) * | 2016-11-11 | 2017-03-08 | 哈尔滨工业大学 | A kind of twin-stage heat treatment method of FeCo2V 0.25Nb magnetically soft alloy |
-
2017
- 2017-12-22 CN CN201711405807.3A patent/CN108097948B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5120720A (en) * | 1974-08-13 | 1976-02-19 | Matsushita Electric Ind Co Ltd | |
| EP0281444A1 (en) * | 1987-02-05 | 1988-09-07 | Sumitomo Electric Industries Limited | Process for manufacturing a superconducting wire of compound oxide-type ceramic |
| CN1449879A (en) * | 2003-04-30 | 2003-10-22 | 北京科技大学 | Method for processing microtantalum and/or niobium powder and powder made by said method |
| CN103008658A (en) * | 2011-09-28 | 2013-04-03 | 宝山钢铁股份有限公司 | Manufacturing method of high-temperature alloy blanks in large-size single crystal structures |
| CN104550984A (en) * | 2014-12-15 | 2015-04-29 | 中国航空工业集团公司北京航空材料研究院 | Preparation method of nickel-based high-temperature alloy powder for 3D (Three Dimensional) printing |
| CN105562681A (en) * | 2016-02-02 | 2016-05-11 | 集美大学 | High-temperature heat treatment method for metal powder |
| CN106480277A (en) * | 2016-11-11 | 2017-03-08 | 哈尔滨工业大学 | A kind of twin-stage heat treatment method of FeCo2V 0.25Nb magnetically soft alloy |
Also Published As
| Publication number | Publication date |
|---|---|
| CN108097948A (en) | 2018-06-01 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN103752836B (en) | A kind of method preparing fine grain spherical niobium titanium base alloy powder | |
| EP2616563B1 (en) | Processing routes for titanium and titanium alloys | |
| TW201439333A (en) | Methods for processing titanium alloys | |
| CN111945089A (en) | Additive manufacturing titanium part and heat treatment process thereof | |
| CN109440023A (en) | A kind of high magnetic strength nitrogen coupling Fe-based amorphous nanocrystalline alloy and preparation method thereof | |
| CN103938005A (en) | Method for preparing ultra-fine grained titanium and titanium alloy from jet-milled titanium hydride powder | |
| CN105513733B (en) | A kind of preparation method of sintering type Nd iron boron permanent magnetic material | |
| CN108097948B (en) | A kind of high-temperature heat treatment method that metal alloy attritive powder is anti-oxidation | |
| CN105386041A (en) | Method for preparing modified composite Hf-Ta metal coating through laser cladding | |
| CN112475304B (en) | 12Cr stainless steel surface strengthening method based on spark plasma sintering | |
| CN108273989A (en) | A kind of high-temperature heat treatment method of metal alloy attritive powder anti-caking | |
| CN110819781B (en) | High-speed steel wire circulation heat treatment method | |
| CN113399779A (en) | Device and method for austenitic stainless steel additive manufacturing | |
| CN104746000B (en) | A kind of method of non-crystaline amorphous metal surface treatment | |
| CN105063540A (en) | Method for preparing Ni-WC coating on surface of low-carbon steel piece | |
| CN102382963A (en) | Heat treatment method for improving room-temperature ductility of high-silicon electrical steel | |
| CN106637015B (en) | A kind of heat treatment process for refining Ti-5Al-2.5Sn ELI alloy casting structures | |
| CN106756811A (en) | A kind of preparation method of alloy coating at high temperature | |
| CN112064011B (en) | Method for preparing multi-nano-phase reinforced ferrite alloy with complex shape | |
| US11938542B2 (en) | Method for finishing a workpiece made by additive manufacturing | |
| CN105483626B (en) | A kind of production method of fine grain planar molybdenum target material | |
| CN105780000B (en) | A kind of preparation method of engine chamber surface recombination silicide coating | |
| CN114075665A (en) | NiSiAlY coating on surface of titanium alloy and preparation method thereof | |
| CN103658651A (en) | Surface slot blasting sealing method of dewaxed powder metallurgy green ware body | |
| CN102978551A (en) | Heat treatment method for preventing Li removal and oxidization of Mg-Li based magnesium alloy surface |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| TR01 | Transfer of patent right | ||
| TR01 | Transfer of patent right |
Effective date of registration: 20211020 Address after: 450001 100m North West of the intersection of Chemical Road and Xiangpu Road, high tech Zone, Zhengzhou City, Henan Province Patentee after: China Machinery New Material Research Institute (Zhengzhou) Co.,Ltd. Address before: 100083 No. 18 clear road, Haidian District, Beijing Patentee before: BEIJING NATIONAL INNOVATION INSTITUTE OF LIGHTWEIGHT Ltd. |
|
| PE01 | Entry into force of the registration of the contract for pledge of patent right |
Denomination of invention: A high temperature heat treatment method for oxidation prevention of metal alloy fine powder Effective date of registration: 20220628 Granted publication date: 20191105 Pledgee: Bank of China Zhengzhou branch of Limited by Share Ltd. culture Pledgor: China Machinery New Material Research Institute (Zhengzhou) Co.,Ltd. Registration number: Y2022980009271 |
|
| PE01 | Entry into force of the registration of the contract for pledge of patent right | ||
| PC01 | Cancellation of the registration of the contract for pledge of patent right |
Date of cancellation: 20230728 Granted publication date: 20191105 Pledgee: Bank of China Zhengzhou branch of Limited by Share Ltd. culture Pledgor: China Machinery New Material Research Institute (Zhengzhou) Co.,Ltd. Registration number: Y2022980009271 |
|
| PC01 | Cancellation of the registration of the contract for pledge of patent right | ||
| PE01 | Entry into force of the registration of the contract for pledge of patent right |
Denomination of invention: A high-temperature heat treatment method for preventing oxidation of metal alloy fine powder Effective date of registration: 20230807 Granted publication date: 20191105 Pledgee: Bank of China Zhengzhou branch of Limited by Share Ltd. culture Pledgor: China Machinery New Material Research Institute (Zhengzhou) Co.,Ltd. Registration number: Y2023980050871 |
|
| PE01 | Entry into force of the registration of the contract for pledge of patent right |