JPH0146581B2 - - Google Patents
Info
- Publication number
- JPH0146581B2 JPH0146581B2 JP5343980A JP5343980A JPH0146581B2 JP H0146581 B2 JPH0146581 B2 JP H0146581B2 JP 5343980 A JP5343980 A JP 5343980A JP 5343980 A JP5343980 A JP 5343980A JP H0146581 B2 JPH0146581 B2 JP H0146581B2
- Authority
- JP
- Japan
- Prior art keywords
- sintering
- gas
- torr
- temperature
- during
- 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
Links
- 238000005245 sintering Methods 0.000 claims description 68
- 238000000034 method Methods 0.000 claims description 42
- 229910000831 Steel Inorganic materials 0.000 claims description 17
- 230000008569 process Effects 0.000 claims description 17
- 239000010959 steel Substances 0.000 claims description 17
- 229910052804 chromium Inorganic materials 0.000 claims description 13
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 12
- 238000001816 cooling Methods 0.000 claims description 12
- 229910052720 vanadium Inorganic materials 0.000 claims description 12
- 238000004519 manufacturing process Methods 0.000 claims description 11
- 229910052710 silicon Inorganic materials 0.000 claims description 11
- 229910052748 manganese Inorganic materials 0.000 claims description 10
- 229910052782 aluminium Inorganic materials 0.000 claims description 7
- 238000010791 quenching Methods 0.000 claims description 6
- 230000000171 quenching effect Effects 0.000 claims description 6
- 229910052719 titanium Inorganic materials 0.000 claims description 6
- 229910021529 ammonia Inorganic materials 0.000 claims description 5
- 229910052796 boron Inorganic materials 0.000 claims description 5
- 238000000354 decomposition reaction Methods 0.000 claims description 5
- 229930195733 hydrocarbon Natural products 0.000 claims description 5
- 150000002430 hydrocarbons Chemical class 0.000 claims description 5
- 239000004215 Carbon black (E152) Substances 0.000 claims description 4
- 238000005255 carburizing Methods 0.000 claims description 4
- 238000005121 nitriding Methods 0.000 claims description 4
- 230000009466 transformation Effects 0.000 claims description 3
- 239000007789 gas Substances 0.000 description 49
- 238000006722 reduction reaction Methods 0.000 description 19
- 238000006243 chemical reaction Methods 0.000 description 18
- 239000000843 powder Substances 0.000 description 15
- 230000009467 reduction Effects 0.000 description 14
- 238000010438 heat treatment Methods 0.000 description 13
- 229910052760 oxygen Inorganic materials 0.000 description 10
- 239000000047 product Substances 0.000 description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 9
- 239000001301 oxygen Substances 0.000 description 9
- 230000000694 effects Effects 0.000 description 7
- 229910052799 carbon Inorganic materials 0.000 description 6
- 229910052739 hydrogen Inorganic materials 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 230000003647 oxidation Effects 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- 238000004663 powder metallurgy Methods 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 4
- 239000007795 chemical reaction product Substances 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 238000007796 conventional method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 229910044991 metal oxide Inorganic materials 0.000 description 3
- 150000004706 metal oxides Chemical class 0.000 description 3
- 229910052750 molybdenum Inorganic materials 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 238000009770 conventional sintering Methods 0.000 description 2
- 238000005261 decarburization Methods 0.000 description 2
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 230000000977 initiatory effect Effects 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 238000003754 machining Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 229910052721 tungsten Inorganic materials 0.000 description 2
- 229910002551 Fe-Mn Inorganic materials 0.000 description 1
- 229910000997 High-speed steel Inorganic materials 0.000 description 1
- 229910018106 Ni—C Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000001273 butane Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 1
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000001294 propane Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000010405 reoxidation reaction Methods 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
Description
本発明は機械的強度、靭性、耐熱性、耐摩性が
優れ且つ寸法精度、寸法安定性の高い粉末冶金製
品の焼結法に関するものである。
粉末冶金による部品の製造は非削加工と大量生
産をベースとする経済性に優れた精密部品製造技
術として近年著しい発展を遂げている技術であ
り、そのプロセスの骨子は数種の金属粉末ないし
は合金粉末を所要の形状の型に入れ、プレス成形
後、高温で焼結し所要の硬度、耐摩特性を得るも
のである。
材質および成形密度一定の場合得られる強度、
靭性、耐摩性等の焼結体特性は焼結の状態つまり
焼結法の良し悪しに左右される。
即ち焼結が不正の場合、上記の所要の特性が得
られないばかりか寸法精度的にも安安定せず、焼
結後、サイジングの如き寸法矯正のためのプレス
工程や余分な機械加工が必要となり、粉末冶金の
経済性が損なわれる結果となる。
この意味で粉末冶金製品の製造において、焼結
技術は極めて重要であり、中でも温度と共に焼結
雰囲気の制御は製品品質を直接左右するので最も
重要である。
本発明はこれらの点に鑑み、優れた機械的強
度、靭性、耐熱性、耐摩性が得られ且つ経済性に
優れた新規の焼結法を提供するものである。
焼結の目的とするところは、金属粉末の溶融点
以下の温度において、粉末同志の熱的な接合およ
び異種金属粉の拡散であるが、焼結雰囲気として
の要件はまず
() 粉末同志表面の吸着ガスの除去、表面酸化
物の還元
() 焼結中の酸化、浸炭および脱炭の防止であ
る。
粉末冶金工業で現在実際に使用されている焼結
雰囲気は吸熱性変成ガス、H2、アンモニア分解
ガス、N2、真空等であるが、これら従来の雰囲
気にはそれぞれ以下のような一長一短が存在す
る。
() 吸熱性変成ガス
プロパンあるいはブタン系炭化水素ガスを空
気と混合して変成するもので、現在Fe−Cu−
Ｃ系、Fe−Ni−Ｃ系の一般焼結機械部品の焼
結雰囲気として最もポピユラーなものである
が、構成ガス中Co、H2の量はそれぞれ11％、
17％と少なくガス還元能力としては低い。
このため、Cr、Mn、Si、Ｖ等の易酸化性元
素を含合する材質の場合、酸化物．Cr2O3、
MnO、SiO2）の還元は困難であり、事実上焼
結は不可能である。
() アンモニア分解ガス
一般的なガス組成は75％H2、25％N2で
（）の吸熱性変成ガスに比べるとはるかに還
元能力は高く、露点を−50〜−60℃位に保持す
れば、高温ではCr2O3の還元も可能であるが、
MnO、SiO2の還元は事実上不可能である。
また雰囲気としては脱炭性であり、炭素を含
有する製品に適用する場合、製品のＣ量の制御
が難しい問題がある。
() 水素
MO＋H2→Ｍ＋H2O（Ｍ：金属）
の反応に基づく強い還元能力があるが、この反
応はPH2O／PH2の値によつて反応の進行が左
右される。
つまり金属酸化物の還元反応を十分起こさせ
るためにH2Oの分圧を下げる必要があり、こ
のためには焼結炉内に供給する水素の純度を上
げると共に供給量も増す必要があり、これは高
価なガスを大量に消費することになり不経済で
ある。
またアンモニア分解ガスと同様、生成された
H2Oないしはガス中に含まれているH2Oによ
り、高価で
H2O＋Ｃ→CO＋H2
の反応が起こり脱炭が進行するため精密なＣ量
の制御には問題がある。
() 窒素
N2単独またはN2ベースにH2、分解アンモニ
アガス、炭化水素等の還元性ガスを混ぜて利用
する方法で変成装置が不要のため経済的である
が、還元能力は低く、Mn、Cr、Si、Ｖ等の易
酸化性元素を含有する製品の焼結は極めて困難
である。
() 真空
真空雰囲気焼結の特徴として品物の表面の吸
着ガスが除去し易いことと雰囲気ガスとの反応
の心配がないことが特徴であるが、還元反応を
起こさせるためにはグラフアイトの如き固体還
元剤との共存が必要である。そしてこの場合、
他の雰囲気と同様精密なＣ量制御はかなり困難
である。
以上の如く、現在実用されている各種の焼結雰
囲気は還元能力の高いものは脱炭性で製品のＣ量
制御が困難であり、Ｃ量制御の可能な雰囲気は逆
に還元能力が低く、Mn、Cr、Si、Ｖ等の易酸化
性元素と含有する材質の焼結が出来ないという問
題点を有しているのが実情である。更にこれら酸
素との親和力の強い元素を含有する焼結鋼の場
合、たとえ焼結がうまく出来たとしても熱処理に
おいて、再度酸化が進み所要の強度、靭性、耐摩
性が得られないことも問題があつた。
これらの点に鑑み本発明の狙いとするところ
は、従来の焼結と熱処理技術の問題点を解決し酸
素との親和力の強いMn、Cr、Ｖ、Si、Ti、Al等
の元素を含有する焼結鋼の製造に適した新規の焼
結法、熱処理法を提供せんとするものである。そ
の骨子は
(1) 焼結
全体を１気圧以下の減圧条件下に保ちつつ、
焼結の進行に応じて、COガスを炉内に導入、
炉内のガス分圧PCO2／COのコントロールを行
うことにより、酸化物の還元と焼結を促進す
る。
(2) 熱処理
(1)の焼結に引き続きその冷却過程で焼入れ処
理を行うか、もしくは焼結後期よりN2または
分解アンモニアガス、微量の炭化水素系ガスを
導入、外気に触れさせることなく焼結で活性化
状態にある製品表面に対し短時間に精度良く窒
化ないしは浸炭処理を施そうとするものであ
る。
まず、本発明における還元性ガスの導入と分圧
コントロールの意義について述べると以下のとお
りである。
金属粉末の焼結時、起こり得る金属酸化物の還
元反応としては、焼結鋼の場合
MO＋Ｃ→Ｍ＋CO ……(1)
MO＋CO→Ｍ＋CO2 ……(2)
CO2＋Ｃ→2CO ……(3)
MO＋H2→Ｍ＋H2O ……(4)
であり、この時のこれらの反応の自由エネルギー
変化は△Ｇ＝△G゜＋RTlnKそれぞれの反応にお
けるＫは
PCO／PC、PCO2／PCO、PH2O／PH2
であるから結局(1)〜(4)の反応の進行は各反応系の
ガス分圧によつて支配されると考えられる。
つまりこれらの酸化物を還元し焼結を進行させ
るには炉内におけるこれらのガス分圧のコントロ
ールが重要と考えられる。（第３図）
例えばCrを含む系でCr2O3の還元の場合を考え
てみると起こり得る反応は
3Cr2O3＋17CO→2Cr3C2＋13CO2 ()
7Cr2O3＋33CO→2Cr7C3＋27CO2 ()
23Cr2O3＋93CO→2Cr23C6＋81CO2 ()
Cr2O3＋3CO→2Cr＋3CO2 ()
2C＋O2→2CO ()
であり、これらについてKubaschewskiらが集録
した熱力学データに基づき平衡PCO2／PCO比を求
めると第１図のようになる。
この図において全圧（PCO＋PCO2）が1atmの時
のCr2O3の還元開始温度は反応（）と（）の
各平衡分圧図線の交点(a)（1120℃）であるが、こ
れを減圧し、0.2atm（約146Torr）にした時各平
衡分圧曲線は破線で示すようにそれぞれ下方に移
動し、Cr2O3の還元開始温度は(a)′（1020℃）と
なり１気圧の時に比べて約100℃低くなる。つま
り還元反応は促進される。
これはMnO、Fe2O3ら他の酸化物の還元につ
いても同様である。既に述べた吸着ガス除去のし
易さと併せここに減圧下（真空下）で行う焼結の
意義があるのであり、これから行くと、より真空
度を上げた方が酸化物の還元、焼結の進行には有
利となる筈であるが、実際にはこのようにはなら
ない。あるレベル以上真空度を上げてもCr2O3、
MnO等の酸化物の還元はかなり困難であること
を我々は実験的に確認している。
この原因につき色々検討した結果、反応生成ガ
スの除去の問題に関連することが判明した。つま
り、真空下での焼結の場合確かに前述した吸着ガ
スの除去、還元開始温度の低下など焼結初期の反
応の促進には極めて有効であるが、中期から後期
にかけては反応生成ガスの除去が十分に行われな
いため、還元および焼結の通行が著しく遅くなる
ことが判つた。
これは真空下ではガスの平均自由工程が長くな
ること、特に粉末型押体内の細孔等からの反応生
成ガスの除去が難しくなり、結果的に細孔内の
PCO2／PCO比が高くなつて還元速度、焼結の進行
が遅くなるためと考えられる。
この問題を打開する方法が焼結過程における還
元性ガスの導入による炉内ガス分圧のコントロー
ルである。つまり焼結初期の真空排気に続く800
℃以上の温度域でCOガスを0.2〜20/min導入し
連続的に排気を行いながら圧力を0.2〜500Torr
にコントロールすることにより、前述の(1)(3)およ
び（（）〜（）の還元反応を最も効率良く行
わしめ得ることを見出したものである。これは導
入したCOガスと反応生成ガスとの間のガス拡散
により反応生成ガスの除去がスムーズに行われ部
分的に高まつていたPCO2／PCO比が下がるためと
考えられる。
これらを最も効率良く行うには、COガス導入
時期、温度、圧力、ガス流量、前後における雰囲
気圧力条件へ精密な制御が必要であり、具体的に
は以下のような条件である。
The present invention relates to a method for sintering powder metallurgy products that have excellent mechanical strength, toughness, heat resistance, and wear resistance, as well as high dimensional accuracy and dimensional stability. Manufacturing parts using powder metallurgy is a technology that has made remarkable progress in recent years as an economically efficient precision parts manufacturing technology based on non-machining and mass production. The powder is put into a mold of the desired shape, press-molded, and then sintered at high temperature to obtain the desired hardness and wear resistance. Strength obtained when material and molding density are constant,
Sintered body properties such as toughness and wear resistance depend on the sintering state, that is, the quality of the sintering method. In other words, if sintering is incorrect, not only will the required properties described above not be obtained, but the dimensional accuracy will also be unstable, and after sintering, a press process or extra machining is required for dimensional correction such as sizing. As a result, the economic efficiency of powder metallurgy is impaired. In this sense, sintering technology is extremely important in the production of powder metallurgy products, and control of the sintering atmosphere as well as temperature are the most important because they directly affect product quality. In view of these points, the present invention provides a novel sintering method that provides excellent mechanical strength, toughness, heat resistance, and wear resistance, and is also highly economical. The purpose of sintering is to thermally bond the powders together and to diffuse dissimilar metal powders at a temperature below the melting point of the metal powders, but the requirements for the sintering atmosphere are () Removal of adsorbed gases, reduction of surface oxides () Prevention of oxidation, carburization and decarburization during sintering. The sintering atmospheres currently used in the powder metallurgy industry include endothermic modified gas, H 2 , ammonia decomposition gas, N 2 , vacuum, etc., but each of these conventional atmospheres has the following advantages and disadvantages. do. () Endothermic metamorphosed gas Propane or butane-based hydrocarbon gas is metamorphosed by mixing it with air, and currently Fe-Cu-
This is the most popular sintering atmosphere for general sintered machine parts such as C type and Fe-Ni-C type, but the amount of Co and H2 in the constituent gases is 11%, respectively.
The gas reduction capacity is low at 17%. For this reason, in the case of materials containing easily oxidizable elements such as Cr, Mn, Si, and V, oxides. Cr2O3 ,
Reduction of MnO, SiO 2 ) is difficult, and sintering is virtually impossible. () Ammonia decomposition gas The general gas composition is 75% H 2 and 25% N 2 , and it has a much higher reducing ability than the endothermic metamorphosed gas in (), and the dew point can be maintained at around -50 to -60℃. For example, reduction of Cr 2 O 3 is possible at high temperatures;
Reduction of MnO, SiO 2 is virtually impossible. Furthermore, the atmosphere is decarburizing, and when applied to products containing carbon, there is a problem in that it is difficult to control the amount of carbon in the product. () Hydrogen It has a strong reducing ability based on the reaction MO+H 2 →M+H 2 O (M: metal), but the progress of this reaction is influenced by the value of PH 2 O/PH 2 . In other words, it is necessary to lower the partial pressure of H 2 O in order to sufficiently cause the reduction reaction of the metal oxide, and to do this, it is necessary to increase the purity of the hydrogen supplied to the sintering furnace as well as the amount of hydrogen supplied. This is uneconomical as it consumes a large amount of expensive gas. Also, similar to ammonia decomposition gas, the produced
H 2 O or H 2 O contained in the gas causes an expensive reaction of H 2 O+C→CO+H 2 to progress decarburization, which poses a problem in precisely controlling the amount of C. () Nitrogen This method uses N 2 alone or a mixture of reducing gases such as H 2 , decomposed ammonia gas, and hydrocarbons based on N 2 .It is economical because it does not require a shift converter, but its reducing ability is low and Mn It is extremely difficult to sinter products containing easily oxidizable elements such as , Cr, Si, and V. () Vacuum Vacuum atmosphere sintering is characterized by the fact that adsorbed gas on the surface of the product can be easily removed and there is no need to worry about reaction with atmospheric gas. Coexistence with a solid reducing agent is required. And in this case,
As with other atmospheres, precise control of the amount of C is quite difficult. As mentioned above, among the various sintering atmospheres currently in use, those with high reducing ability are decarburizing and it is difficult to control the amount of C in the product, while atmospheres where it is possible to control the amount of C have low reducing ability. The actual situation is that materials containing easily oxidizable elements such as Mn, Cr, Si, and V cannot be sintered. Furthermore, in the case of sintered steel containing elements that have a strong affinity for oxygen, even if sintering is successful, oxidation occurs again during heat treatment and the required strength, toughness, and wear resistance cannot be obtained. It was hot. In view of these points, the aim of the present invention is to solve the problems of conventional sintering and heat treatment techniques and to create a material containing elements such as Mn, Cr, V, Si, Ti, and Al, which have a strong affinity with oxygen. The purpose is to provide a new sintering method and heat treatment method suitable for manufacturing sintered steel. The main points are (1) Keeping the entire sintering process under reduced pressure conditions of 1 atm or less,
As sintering progresses, CO gas is introduced into the furnace.
By controlling the gas partial pressure P CO2 /CO in the furnace, the reduction and sintering of oxides is promoted. (2) Heat treatment After the sintering in (1), quenching is performed during the cooling process, or N 2 or decomposed ammonia gas or a small amount of hydrocarbon gas is introduced from the later stage of sintering to sinter without exposing it to outside air. The purpose is to perform nitriding or carburizing treatment on the activated product surface in a short time and with high precision. First, the significance of introducing reducing gas and controlling partial pressure in the present invention will be described as follows. When metal powder is sintered, the reduction reaction of metal oxides that can occur is MO+C→M+CO in the case of sintered steel...(1) MO+CO→M+CO 2 ...(2) CO 2 +C→2CO...(3) MO＋H 2 →M＋H 2 O ...(4), and the free energy changes of these reactions at this time are △G=△G゜＋RTlnK. K in each reaction is P CO /P C , P CO2 /P CO , Since it is P H2O /P H2 , it is thought that the progress of reactions (1) to (4) is ultimately controlled by the gas partial pressure of each reaction system. In other words, it is considered important to control the partial pressure of these gases in the furnace in order to reduce these oxides and advance sintering. (Figure 3) For example, if we consider the reduction of Cr 2 O 3 in a system containing Cr, the possible reactions are 3Cr 2 O 3 +17CO→2Cr 3 C 2 +13CO 2 () 7Cr 2 O 3 +33CO→2Cr 7 C 3 +27CO 2 () 23Cr 2 O 3 +93CO→2Cr 23 C 6 +81CO 2 () Cr 2 O 3 +3CO→2Cr+3CO 2 () 2C+O 2 →2CO (), and based on the thermodynamic data collected by Kubaschewski et al. Based on this, the equilibrium P CO2 /P CO ratio is calculated as shown in Figure 1. In this figure, when the total pressure (P CO + P CO2 ) is 1 atm, the reduction initiation temperature of Cr 2 O 3 is at the intersection point (a) (1120°C) of the equilibrium partial pressure diagram lines of reactions () and (). When the pressure is reduced to 0.2 atm (approximately 146 Torr), each equilibrium partial pressure curve moves downward as shown by the broken line, and the starting temperature for reduction of Cr 2 O 3 becomes (a)′ (1020°C). The temperature is approximately 100°C lower than when the pressure is 1 atm. In other words, the reduction reaction is promoted. This also applies to the reduction of other oxides such as MnO and Fe 2 O 3 . This is the reason why sintering under reduced pressure (vacuum) is important, along with the ease of removing adsorbed gases mentioned above.From now on, it will be better to increase the degree of vacuum to reduce oxides and improve sintering. This should be advantageous for progression, but in reality it doesn't work out like this. Even if the degree of vacuum is increased beyond a certain level, Cr 2 O 3 remains.
We have experimentally confirmed that reduction of oxides such as MnO is quite difficult. As a result of various studies on the cause of this problem, it was found that it is related to the problem of removing reaction product gas. In other words, sintering under vacuum is certainly extremely effective in promoting the reactions in the early stages of sintering, such as removing the adsorbed gases mentioned above and lowering the reduction initiation temperature, but in the middle to late stages, it is extremely effective to remove the gases produced by the reaction. It was found that the reduction and sintering process was significantly slowed down due to insufficient oxidation. This is because the mean free path of the gas becomes longer under vacuum, making it particularly difficult to remove the reaction generated gas from the pores in the powder die.
This is thought to be because the reduction rate and sintering progress slow down as the P CO2 /P CO ratio increases. A method to overcome this problem is to control the gas partial pressure in the furnace by introducing reducing gas during the sintering process. In other words, 800 hours following the vacuum evacuation at the beginning of sintering
In the temperature range above ℃, introduce CO gas at 0.2 to 20/min and increase the pressure to 0.2 to 500 Torr while continuously exhausting.
It was discovered that the above-mentioned reduction reactions (1), (3) and (() to ()) can be carried out most efficiently by controlling the amount of CO gas introduced and the reaction product gas. This is thought to be due to the smooth removal of the reaction product gas due to gas diffusion during the period, which lowers the partially high P CO2 /P CO ratio. To achieve this most efficiently, the CO gas introduction timing, Precise control is required for temperature, pressure, gas flow rate, and atmospheric pressure conditions before and after, and specifically the conditions are as follows.
【表】【table】
【表】
本発明において、COガスの導入に先立ち、
まず800〜900℃以下の焼結昇温過程で
10-1Torr以下に排気する理由は既に述べた如
く吸着ガス成分の除去と酸化物還元反応を提供
することが狙いである。
超硬合金の焼結法としてCOガス導入に先立
ち800〜1200℃以下の温度H2ガスを導入する方
法が既に提案されているが、本発明の狙いとす
るところはＷ、Co等よりはるかに酸素との親
和力の強いMn、Cr、Ｖ、Si等の酸化物の還元
まで行うことであり、このためにはCOガス導
入に先立つ雰囲気、圧力条件は上に述べたよう
な条件でなければならない。
つまりH2雰囲気で処理した場合
MO＋H2→Ｍ＋H2O（MO：金属酸化物）
により生成したH2Oにより酸素との親和力の
強いMn、Cr、Ｖ、Si等の酸化が却つて進み、
全体の反応が著しく低下するからである。
（我々の実験では本発明の方法に比べFe−Mn
−Cr−Ｃ系の場合で10倍程度遅くなることを
確認している。）
次に800℃以上の温度になると前述の反応(1)、
(2)、(3)に基づくCO反応がより活発に行われる
ようになるから、これらの反応を効率良く連続
的に行わしめるために、外部よりCOガスを導
入し炉内ガス分圧（PCO2／PCO）のコントロー
ルと反応生成ガスの除去を行うことが必要にな
る。
この場合基本的に二つの方法がある。
一つは800℃以上の温度より焼結終了まで圧
力0.2〜100Torrに保つ方法(A)、もう一つは焼
結温度に達するまでCOの圧力を100〜500Torr
まで上げ、焼結は10-2Torr以下の真空に保つ
方法(B)である。
どちらでも同様の効果を得ることが出来る
が、蒸気圧の高い元素（例えばCr、Al、Cu…
…）を含有するような場合は(B)の方法は蒸発に
よるロスが問題となるので(A)の方法を採用する
のが好ましい。圧力範囲を0.2〜500Torrに限
定する理由は第２図に示す如く、この範囲で焼
結後の酸素量が最も低くなり、かつ焼結後の特
性が優れるためである。
（0.2Torr以下では、CO減圧の効果少なく
500Torr以上となつても効果変わらず、Ｃの析
出が多くなつてバラツキが大きくなる。）
焼結終了後の冷却は、通常は以下に述べる方
法で行うことが望ましい。即ち、冷却時の雰囲
気ガスとしては、H2、ArあるいはN2のいずれ
でも良いが、経済性の点からはN2の方が望ま
しい。
冷却時の圧力については、得ようとする焼結
体を硬さを考えて選択することが可能である。
圧力が高い程、得られる焼結体の硬さは高くな
るが1500Torrを越えてもその効果はあまり変
わらない。従つて、圧力の上限は1500Torrと
した。
一方、圧力の下限については圧力が低くなる
程冷却時間が長くなるため、処理時間の経済性
を考慮すると300Torr以上が望ましい。但し次
項に述べる焼結後に引続いて焼入れを行うた
め、焼結温度からA1変態点以下の750℃まで下
げるという様な場合には、過冷却を防止するた
め冷却速度をコントロールする必要がある。こ
のような場合には、圧力は0.3〜300Torrの範
囲にあることが望ましい。
(2) 熱処理[Table] In the present invention, prior to introducing CO gas,
First, in the sintering temperature raising process below 800-900℃.
As mentioned above, the reason for evacuation to below 10 -1 Torr is to remove adsorbed gas components and provide oxide reduction reactions. As a method for sintering cemented carbide, a method has already been proposed in which H2 gas at a temperature of 800 to 1200°C or less is introduced prior to introducing CO gas, but the aim of the present invention is to The purpose is to reduce oxides such as Mn, Cr, V, and Si, which have a strong affinity with oxygen, and for this purpose, the atmosphere and pressure conditions prior to introducing CO gas must be as described above. . In other words, when treated in an H 2 atmosphere, the H 2 O generated by MO + H 2 → M + H 2 O (MO: metal oxide) accelerates the oxidation of Mn, Cr, V, Si, etc., which have a strong affinity for oxygen.
This is because the overall reaction is significantly reduced.
(In our experiments, compared to the method of the present invention, Fe−Mn
- It has been confirmed that the speed is about 10 times slower in the case of the Cr-C system. ) Next, when the temperature reaches 800℃ or higher, the above reaction (1),
Since the CO reactions based on (2) and (3) will take place more actively, in order to efficiently and continuously carry out these reactions, CO gas is introduced from the outside to increase the gas partial pressure (P It is necessary to control CO2 /P CO ) and remove reaction product gas. There are basically two methods in this case. One method is to maintain the pressure at 0.2 to 100 Torr from a temperature of 800℃ or higher until the end of sintering (A), and the other method is to maintain the CO pressure at 100 to 500 Torr until the sintering temperature is reached.
Method (B) is to raise the temperature to 10 -2 Torr or less during sintering. The same effect can be obtained with either, but elements with high vapor pressure (e.g. Cr, Al, Cu...
...), it is preferable to use method (A) since method (B) causes loss due to evaporation. The reason why the pressure range is limited to 0.2 to 500 Torr is that, as shown in FIG. 2, the amount of oxygen after sintering is the lowest in this range and the properties after sintering are excellent. (Below 0.2 Torr, the effect of CO depressurization is less.
Even if the temperature exceeds 500 Torr, the effect remains the same, but the amount of C precipitated increases and the variation becomes large. ) Cooling after completion of sintering is usually preferably carried out by the method described below. That is, the atmospheric gas during cooling may be any of H 2 , Ar, or N 2 , but N 2 is more desirable from the economic point of view. Regarding the pressure during cooling, it is possible to select the pressure in consideration of the hardness of the sintered body to be obtained.
The higher the pressure, the harder the obtained sintered body becomes, but even if the pressure exceeds 1500 Torr, the effect does not change much. Therefore, the upper limit of the pressure was set to 1500 Torr. On the other hand, the lower limit of the pressure is preferably 300 Torr or more, considering the economical efficiency of processing time, since the lower the pressure, the longer the cooling time will be. However, as described in the next section, sintering is followed by quenching, so if the sintering temperature is lowered to 750℃, which is below the A1 transformation point, the cooling rate must be controlled to prevent overcooling. . In such cases, the pressure is preferably in the range of 0.3 to 300 Torr. (2) Heat treatment
【表】
焼結に引き続き焼き入れを行う場合は、一旦
焼結温度よりA1変態点以下に温度を下げ、再
び900℃以上の温度に上げてから焼き入れる。
その後焼き入れの方法としては、N2ガス圧を
500Torr以上とするか、または油冷によつて焼
結体を冷却することによつて可能である。
また、窒化または浸炭の場合は、焼結後期よ
りN2あるいはアンモニア分解ガスまたはCH4
またはC3H8等の如く炭化水素ガスを導入する
ことによつて行われる。そしてその圧力は常圧
以下、望ましくは0.3〜300Torrの間で炉内圧
力をコントロールすることによつて行う。
このように焼結に引き続き、製品を外気にさ
らすことなく、直後焼入れまたは熱処理まで持
つていくことにより、従来Mn、Cr、Ｖ、Ｂ、
Si、Al、Ti等を含む焼結鋼で大きな問題であ
つた熱処理時の酸化が防止でき、かつ焼結直後
の高い活性化状態で、浸炭、窒化等の処理が出
来るため、精度の高い熱処理が可能である。
つまり本発明の目的とする酸素との親和力の
強いCr、Mn、Ｂ、Si、Ｖ、Al、Tiの元素を合
金要素として含有する焼結鋼において、焼結−
熱処理で優れた機械的性質、耐摩性等を得るに
は上に述べた焼結から直接熱処理を行う方法が
必要である。
本願のは、本願焼結鋼にさらにNi、Mo、
Co、Ｗよりなる群より１種または２種以上の
合金元素を0.1〜13％の範囲で含有したものに
ついても本願同様の効果を得ることができる。
さらに詳細には、Mn：0.5〜2.5％、Cr：0.3〜
1.5％、Mo：0.1〜1.5％、Ｃ：0.1〜2.5％残部が
鉄である焼入性に優れた高強度焼結鋼や、また
Cr：3.5〜5.5％、Ｖ：4.0〜6.0％、Ｗ：10〜13
％、Co：４〜６％、Mo：２〜８％、Ｃ：0.5
〜20％と残部が鉄よりなる高強度焼結鋼におい
ても同様の効果を得ることができる。
以下実施例にて詳細に説明する。
実施例 １
含有酸素量の異なる２種類のMn−Cr鋼粉（第
１表）にグラフアイト0.4％を加え７t/cm2で圧粉
成形後、第２表に示すような種々の条件で焼結
し、機械的性質その他の評価を行つた。（第３表）[Table] When performing quenching after sintering, first lower the temperature below the sintering temperature to below the A1 transformation point, then raise the temperature again to 900°C or higher before quenching.
After that, the quenching method is to use N2 gas pressure.
This is possible by setting the temperature to 500 Torr or more or by cooling the sintered body by oil cooling. In addition, in the case of nitriding or carburizing, N 2 or ammonia decomposition gas or CH 4 is used from the later stage of sintering.
Alternatively, it is carried out by introducing a hydrocarbon gas such as C 3 H 8 or the like. The pressure in the furnace is controlled to be below normal pressure, preferably between 0.3 and 300 Torr. In this way, following sintering, the product is immediately quenched or heat treated without exposing it to the outside air, allowing conventional Mn, Cr, V, B,
Oxidation during heat treatment, which was a big problem with sintered steel containing Si, Al, Ti, etc., can be prevented, and processes such as carburizing and nitriding can be performed in a highly activated state immediately after sintering, resulting in highly accurate heat treatment. is possible. In other words, in the sintered steel containing Cr, Mn, B, Si, V, Al, and Ti elements as alloying elements, which have a strong affinity for oxygen, which is the object of the present invention,
In order to obtain excellent mechanical properties, wear resistance, etc. through heat treatment, it is necessary to use the method described above in which heat treatment is performed directly from sintering. In addition to the sintered steel of the present application, Ni, Mo,
The same effect as the present invention can also be obtained with a material containing one or more alloying elements from the group consisting of Co and W in a range of 0.1 to 13%.
More specifically, Mn: 0.5~2.5%, Cr: 0.3~
1.5%, Mo: 0.1~1.5%, C: 0.1~2.5%, the balance being iron, high strength sintered steel with excellent hardenability, and
Cr: 3.5-5.5%, V: 4.0-6.0%, W: 10-13
%, Co: 4-6%, Mo: 2-8%, C: 0.5
A similar effect can be obtained with high-strength sintered steel in which the balance is ~20% iron. This will be explained in detail in Examples below. Example 1 0.4% graphite was added to two types of Mn-Cr steel powders with different oxygen contents (Table 1), and the powder was compacted at 7t/cm 2 and then sintered under various conditions as shown in Table 2. The mechanical properties and other properties were evaluated. (Table 3)
【表】【table】
【表】【table】
【表】【table】
【表】【table】
【表】
第３表からも明らかなように従来焼結法焼結で
の酸素量を0.08％以下にすることは困難であつた
が、本発明の方法では0.03％のレベルまで下げる
ことが出来た。この結果焼結状態での強度、靭性
は従来法に比べ60〜80％改善された。
またこの実験で靭性値を得るためには原料粉末
として予め含有酸素量の低い粉末を選択すること
が必要であることも判明した。
実施例 ２
実施例１におけるMn−Cr鋼粉を用い、本発
明の焼結と熱処理を連続して行う方法(A)と焼結の
み本発明(B)、焼結も熟処理も従来法(C)の三つの方
法（第４表）について得られる機械的性質につい
て比較を行つた。（第５表）[Table] As is clear from Table 3, it was difficult to reduce the oxygen content to 0.08% or less in the conventional sintering method, but with the method of the present invention, it was possible to reduce it to a level of 0.03%. Ta. As a result, the strength and toughness in the sintered state were improved by 60 to 80% compared to conventional methods. It was also found in this experiment that in order to obtain a toughness value, it was necessary to select a powder with a low oxygen content as the raw material powder in advance. Example 2 Using Mn-Cr steel powder in Example 1, sintering and heat treatment of the present invention were carried out continuously (A), sintering only was carried out according to the present invention (B), and both sintering and heat treatment were carried out using the conventional method ( A comparison was made regarding the mechanical properties obtained by the three methods (Table 4) of C). (Table 5)
【表】【table】
【表】【table】
【表】
Ａの方法が最も強度、靭性が得られることが判
る。これは熱処理で外気に触れることなく、直接
焼結に引き続いて行われるため、熱処理のとき起
る再酸化が完全に防止できるためと思われる。
実施例 ３
実施例１における粉末をＢ、Ｄ、Ｇの焼結体
を熱間鍜造100％の密度にしたものにつき機械的
性質を調べた結果は第６表のとおりである。[Table] It can be seen that method A provides the highest strength and toughness. This is thought to be because the heat treatment is performed directly following sintering without exposure to the outside air, so reoxidation that occurs during heat treatment can be completely prevented. Example 3 Table 6 shows the results of examining the mechanical properties of the powders in Example 1 prepared by hot-melting sintered bodies of B, D, and G to a density of 100%.
【表】
本発明Ｂと他の方法では特に靭性に大きな差が
認められた。
実施例 ４
下記組成の粉末
１） Fe−5Cr−5Mo−6W−2V−0.9C（高速度
鋼）
２） Fe−17Cr−0.5Al−2.5C
を圧粉成形後、第７表に示す条件で焼結を行い機
械的性質、耐摩性の評価を行つた結果は第８表に
示すとおりである。[Table] A large difference in toughness was observed between Invention B and other methods. Example 4 Powder with the following composition 1) Fe-5Cr-5Mo-6W-2V-0.9C (high-speed steel) 2) Fe-17Cr-0.5Al-2.5C was compacted under the conditions shown in Table 7. The results of sintering and evaluation of mechanical properties and wear resistance are shown in Table 8.
【表】【table】
【表】
従来法に比べ焼結後の炭素量のバラツキが約1/
２に減少、この結果表面硬さの安定性が増し、更
に焼結中に入つて来る窒素の効果で耐ピツチング
性が著しく改善された。
実施例 ５
硬質相として20〜80μのMn−30Cr、Ni−
50Mn、Mn−20Si粉末を含有する下記組成の材
質
１） Fe−7Mn−3Cr−1C
２） Fe−5Mn−5Ni−1C
３） Fe−8Mn−1.6Si−1C
を第９表の条件で焼結し、強度と耐摩性の評価を
行つた結果を第10表に示す。[Table] Compared to the conventional method, the variation in carbon amount after sintering is approximately 1/1
As a result, the stability of the surface hardness was increased, and the pitting resistance was significantly improved due to the effect of nitrogen introduced during sintering. Example 5 20-80μ Mn-30Cr, Ni- as hard phase
Materials with the following composition containing 50Mn and Mn-20Si powder 1) Fe-7Mn-3Cr-1C 2) Fe-5Mn-5Ni-1C 3) Fe-8Mn-1.6Si-1C are sintered under the conditions shown in Table 9. Table 10 shows the results of evaluating strength and wear resistance.
【表】【table】
【表】
従来の水素雰囲気焼結に比べ強度、耐摩性が改
善され、かつ硬さ、寸法、バラツキが1/2に減少
した。
実施例 ６
Fe−7Mn−3Cr−1Cの組成を有する鋼粉末を
10φ×5mmtに圧粉成形後、以下の条件で焼結し
た。
室温→800℃ 真空 ２×10-2Torr
800℃→1200℃ CO 30Torr
（CO導入量 ２/min）
1200℃×１時間 真空 ２×10-2Torr
1200℃→900℃ CH3 500Torr
（１時間）
900℃→室温 N2 700Torr
（30分）
得られた焼結体の断面の硬度を調べた結果、表
面から0.5mmまで浸炭していることがわかつた。[Table] Compared to conventional hydrogen atmosphere sintering, strength and wear resistance are improved, and hardness, dimensions, and variations are reduced by half. Example 6 Steel powder with a composition of Fe-7Mn-3Cr-1C was
After compacting to 10φ x 5mmt, it was sintered under the following conditions. Room temperature→800℃ Vacuum 2×10 -2 Torr 800℃→1200℃ CO 30Torr (CO introduction rate 2/min) 1200℃×1 hour Vacuum 2×10 -2 Torr 1200℃→900℃ CH 3 500Torr (1 hour) 900℃ → Room temperature N 2 700Torr (30 minutes) As a result of examining the hardness of the cross section of the obtained sintered body, it was found that it was carburized up to 0.5 mm from the surface.
第１図は明細書第９〜10頁の（）、（）、
（）、（）、（）の各反応の平衡PCO2／PCO比の
温度との関係図、第２図はCO2ガス導入炉内圧力
と焼結体O2量との関係図、第３図は酸化物の標
準生成自由エネルギーと温度との関係図である。
Figure 1 shows (), (), on pages 9-10 of the specification.
Figure 2 is a diagram of the relationship between the equilibrium P CO2 /P CO ratio and temperature for each reaction (), (), and ( ). Figure 3 is a diagram showing the relationship between the standard free energy of formation of oxides and temperature.
Claims (1)
り１種または２種以上の元素を含む焼結鋼の製造
において、焼結の昇温過程で800〜900℃までは
10-1Torr以下の真空雰囲気とし、800〜900℃以
上の焼結の昇温、焼結過程で、その一部または全
部にCOガスを導入しつつ連続的に排気を行いな
がら炉内圧力を0.2〜500Torrとし、N20.3〜
1500Torrの圧力下で冷却することを特徴とする
焼結鋼の製造法。 ２ Mn、Cr、Ｖ、Ｂ、Si、Al、Tiよりなる群よ
り１種または２種以上の元素を含む焼結鋼の製造
において、焼結の昇温過程で800〜900℃までは
10-1Torr以下の真空雰囲気とし、800〜900℃以
上の焼結の昇温、焼結過程で、その一部または全
部にCOガスを導入しつつ連続的に排気を行いな
がら炉内圧力を0.2〜500Torrとし、焼結後一た
んA1変態点以下の温度に下げた後、再び900℃以
上に上げてから冷却のN2ガス圧を500Torr以上
とするか、もしくは油冷することにより焼結の冷
却過程で焼入れ処理をすることを特徴とする焼結
鋼の製造法。 ３ Mn、Cr、Ｖ、Ｂ、Si、Al、Tiよりなる群よ
り１種または２種以上の元素を含む焼結鋼の製造
において、焼結の昇温過程で800〜900℃までは
10-1Torr以下の真空雰囲気とし、800〜900℃以
上の焼結の昇温、焼結過程で、その一部または全
部にCOガスを導入しつつ連続的に排気を行いな
がら炉内圧力を0.5〜500Torrとし、焼結過程の
後期より、アンモニア分解ガス、もしくはCH4、
C3H8の如き炭化水素系ガスを導入し、焼結に引
き続き、窒化または浸炭処理を施すことを特徴と
する焼結鋼の製造法。[Claims] 1. In the production of sintered steel containing one or more elements from the group consisting of Mn, Cr, V, B, Si, Al, and Ti, up to 900℃
A vacuum atmosphere of 10 -1 Torr or less is created, and during the sintering process, the temperature is raised to 800 to 900℃ or higher, and during the sintering process, CO gas is introduced into part or all of the atmosphere and the pressure inside the furnace is maintained while exhausting continuously. 0.2~500Torr, N2 0.3~
A method for producing sintered steel characterized by cooling under a pressure of 1500Torr. 2. In the production of sintered steel containing one or more elements from the group consisting of Mn, Cr, V, B, Si, Al, and Ti, temperatures up to 800 to 900°C in the sintering temperature raising process are
A vacuum atmosphere of 10 -1 Torr or less is created, and during the sintering process, the temperature is raised to 800 to 900℃ or higher, and during the sintering process, CO gas is introduced into part or all of the atmosphere and the pressure inside the furnace is maintained while exhausting continuously. 0.2 to 500 Torr, and after sintering, lower the temperature to below the A1 transformation point, raise it again to 900℃ or higher, and then increase the cooling N2 gas pressure to 500 Torr or higher, or sinter by cooling with oil. A method for producing sintered steel characterized by quenching during the cooling process. 3. In the production of sintered steel containing one or more elements from the group consisting of Mn, Cr, V, B, Si, Al, and Ti, temperatures up to 800 to 900°C in the sintering temperature raising process are
A vacuum atmosphere of 10 -1 Torr or less is created, and during the sintering process, the temperature is raised to 800 to 900℃ or higher, and during the sintering process, CO gas is introduced into part or all of the atmosphere and the pressure inside the furnace is maintained while exhausting continuously. 0.5 to 500 Torr, and from the latter stage of the sintering process, ammonia decomposition gas or CH 4 ,
A method for producing sintered steel, which comprises introducing a hydrocarbon gas such as C 3 H 8 and performing nitriding or carburizing treatment following sintering.
Priority Applications (7)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5343980A JPS56150154A (en) | 1980-04-21 | 1980-04-21 | Preparation of sintered steel |
| CA000375600A CA1190418A (en) | 1980-04-21 | 1981-04-15 | Process for producing sintered ferrous alloys |
| ES501493A ES8203980A1 (en) | 1980-04-21 | 1981-04-20 | Process for producing sintered ferrous alloys. |
| EP81103021A EP0038558B1 (en) | 1980-04-21 | 1981-04-21 | Process for producing sintered ferrous alloys |
| DE8181103021T DE3173421D1 (en) | 1980-04-21 | 1981-04-21 | Process for producing sintered ferrous alloys |
| AU69678/81A AU535454B2 (en) | 1980-04-21 | 1981-04-21 | Producing sintered ferrous alloys |
| US06/805,413 US4614638A (en) | 1980-04-21 | 1985-12-06 | Process for producing sintered ferrous alloys |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5343980A JPS56150154A (en) | 1980-04-21 | 1980-04-21 | Preparation of sintered steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS56150154A JPS56150154A (en) | 1981-11-20 |
| JPH0146581B2 true JPH0146581B2 (en) | 1989-10-09 |
Family
ID=12942875
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP5343980A Granted JPS56150154A (en) | 1980-04-21 | 1980-04-21 | Preparation of sintered steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS56150154A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS56150155A (en) * | 1980-04-22 | 1981-11-20 | Sumitomo Electric Ind Ltd | Preparation of ferrous sintered material |
-
1980
- 1980-04-21 JP JP5343980A patent/JPS56150154A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS56150154A (en) | 1981-11-20 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4614638A (en) | Process for producing sintered ferrous alloys | |
| US4722826A (en) | Production of water atomized powder metallurgy products | |
| US3966454A (en) | Method for producing iron or iron alloy powders having a low oxygen content | |
| US2342799A (en) | Process of manufacturing shaped bodies from iron powders | |
| JP5421617B2 (en) | Method for producing porous metal body | |
| US2489839A (en) | Process for carburizing compacted iron articles | |
| US4236942A (en) | Method for the gaseous nitriding of ferrous-based components | |
| US4436696A (en) | Process for providing a uniform carbon distribution in ferrous compacts at high temperatures | |
| JPH0146581B2 (en) | ||
| US2284638A (en) | Metallurgy of ferrous metals | |
| US5441579A (en) | Method of recycling scrap metal | |
| JPH07113121B2 (en) | Method for producing low alloy steel powder for powder metallurgy with low C and low O | |
| US5162099A (en) | Process for producing a sintered compact from steel powder | |
| JPS6249345B2 (en) | ||
| JPH0995701A (en) | Production of partially alloyed steel powder | |
| JPS58107469A (en) | Preparation of high strength sintered machine parts | |
| dePoutiloff et al. | Sintering of stainless steels | |
| JPH02221354A (en) | Sintered hard alloy for wear-resistant tool and its manufacture | |
| JPH0471962B2 (en) | ||
| JPH0346524B2 (en) | ||
| JPH0379427B2 (en) | ||
| RU2068320C1 (en) | Method of obtaining powder-like high-melting tungsten carbide based compositions | |
| JPS6227121B2 (en) | ||
| JPH0257661A (en) | Manufacture of high-nitrogen stainless steel sintered body | |
| JPH10121106A (en) | Production of c-containing sintered body |