JPH036961B2 - - Google Patents
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- Publication number
- JPH036961B2 JPH036961B2 JP61148045A JP14804586A JPH036961B2 JP H036961 B2 JPH036961 B2 JP H036961B2 JP 61148045 A JP61148045 A JP 61148045A JP 14804586 A JP14804586 A JP 14804586A JP H036961 B2 JPH036961 B2 JP H036961B2
- Authority
- JP
- Japan
- Prior art keywords
- cooling
- powder
- reduction annealing
- reduction
- temperature
- 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
- 238000001816 cooling Methods 0.000 claims description 67
- 239000000843 powder Substances 0.000 claims description 60
- 238000000137 annealing Methods 0.000 claims description 36
- 239000002184 metal Substances 0.000 claims description 16
- 229910052751 metal Inorganic materials 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 12
- 239000002994 raw material Substances 0.000 claims description 9
- 229910052799 carbon Inorganic materials 0.000 claims description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 5
- 229910000831 Steel Inorganic materials 0.000 description 25
- 239000010959 steel Substances 0.000 description 25
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 9
- 239000007789 gas Substances 0.000 description 9
- 238000010438 heat treatment Methods 0.000 description 7
- 230000001590 oxidative effect Effects 0.000 description 6
- 230000007423 decrease Effects 0.000 description 5
- 238000004663 powder metallurgy Methods 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 239000013078 crystal Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000011049 filling Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 238000010583 slow cooling Methods 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- 238000009692 water atomization Methods 0.000 description 2
- 229910000979 O alloy Inorganic materials 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- UQLDLKMNUJERMK-UHFFFAOYSA-L di(octadecanoyloxy)lead Chemical compound [Pb+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O UQLDLKMNUJERMK-UHFFFAOYSA-L 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 238000009700 powder processing Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Landscapes
- Powder Metallurgy (AREA)
Description
（産業上の利用分野）
本発明は、金属粉末の還元焼鈍時における冷却
方法に関するものであり、特に粉末冶金等の原料
となる金属粉末（以下は「鋼粉」の例で述べる）
を、炭素を予合金化させたアトマイズ鉄粉などを
原料とし、これを還元焼鈍することにより、低酸
素合金鋼粉などにする際の還元焼鈍後の新規な冷
却技術について提案する。
（従来の技術）
従来、金属粉末とりわけ鋼粉の還元焼鈍は、原
料鉄粉；例えば水アトマイズ法で粉化させた生粉
をベルト式ガス還元炉を使うことによつて行つて
いた。最近、こうした鋼粉等に対する要求も一段
ときびしくなり、合金成分を含有した鋼粉の製造
が望まれている。しかし、合金成分であるMnや
Cr等、易酸化性合金成分を含有する鋼粉を水ア
トマイズ法で製造した場合、MnやCrが難還元性
酸化物を形成するので、従来のベルト式ガス還元
炉を用いて還元することは不可能であつた。すな
わち、炉温を1000℃以上に保持しなければならな
いこと、および低露点低酸素雰囲気に保つことが
工業的に困難であるという理由による。
これに対して従来、特開昭52−110208号として
開示された技術があり、この技術はいわゆる減圧
雰囲気下の堅型シヤフト炉を高周波誘導加熱する
ことにより、炉内で高温原料粉末中に予合金化さ
せた酸素で粉末中の酸素を還元し焼鈍する方法で
ある。
上記従来技術は、原料鉄粉が上方から下方へ自
重により連続的に移動する形式であるから極めて
合理的で優れた方法である。しかしこの堅型シヤ
フト炉は、連続的な縦並びに結合された予熱帯、
還元焼鈍帯、冷却帯から構成されているため、原
料粉の種類が変更されたときや予熱・加熱工程で
の操業条件を変更するような場合に、予熱・加熱
条件をそれぞれの帯域で必要とする好ましい条件
のものに調整するようなことはできず、平均的な
ものに制限されるから著しいケースでは生産性の
低下を招くという欠点があつた。
（発明が解決しようとする問題点）
こうした欠点を克服するために、先に本出願人
は特願昭60−28365号として、原料鉄粉を加熱・
焼鈍することにより良質の鋼粉を製造するのに有
利な水平型３室構造の金属粉末用処理炉を提案し
た。
この提案に係る熱処理炉は、含炭素原料粉末を
予熱・乾燥するための予熱室、予熱後の原料粉末
を含有炭素の利用により脱酸し焼鈍する段階の還
元焼鈍室および還元焼鈍粉末を冷却するための冷
却室とを区画して横並びに連続配置し、それら各
室の境界にはそれぞれ可動扉を設けることにより
各室が独立した画成空間となるように構成し、か
つそれら各室にはそれぞれ減圧用排気装置を設け
た構成によつてなる金属粉末の還元焼鈍炉であ
る。
この炉の場合、品質確保のために、通常約1200
℃の還元温度から室温までを減圧下でH2ガスを
供給した非酸化性雰囲気で自然冷却を行つてい
る。
しかしながら、上記提案にかかる還元焼鈍炉を
用い、還元焼鈍後の鋼粉を冷却室中の非酸化性雰
囲気下で自然冷却すると、その冷却に長時間を必
要とし、予熱−還元焼鈍−冷却工程のうち冷却段
階が律速となり、生産性低下を招いていた。
しかも、冷却フアンを用い、還元温度から室温
までを非酸化性雰囲気ガスによる強制冷却を行う
と、冷却時間の短縮が図れると共に生産性の向上
が達成されるものの、一方では金属粉末をトレイ
に充填した際の充填層表面部と中心部の性状にバ
ラツキを生じて品質低下を招いていた。とくに、
還元温度から急冷されると、トレイに充填した金
属粉末表面部が急冷されることに伴う急冷歪が発
生し、圧縮性の低下が起るという問題点を抱えて
いた。
そこで、本発明の目的は、冷却時間の短縮を図
つて生産性を向上させると共に充填層表面部と中
心部が均一な品質になる鋼粉を製造するのに好適
な金属粉末還元焼鈍後の冷却方法を提案するとこ
ろにある。
（問題点を解説するための手段）
発明者らは、鋼粉の還元焼鈍後の冷却工程にお
いて、圧縮性に影響を及ぼす温度域について調査
した結果、800℃〜400℃の範囲内であることを確
認した。
第１図ａに、鋼粉の圧縮性を表わす圧粉密度と
冷却速度との関係を、1200℃で還元焼鈍された鋼
粉を500〜800℃の各温度まで種々の速度で冷却
し、その後は150℃／Hr以下の速度で冷却して得
られた鉄粉について調べた結果を示す。同図ａに
示すように、還元焼鈍後800℃までは全ての冷却
速度において圧粉密度の低下はないが、これより
低い700〜500℃の各温度までは300℃／Hr以上の
急冷処理において圧粉密度の低下が認められた。
また同図ｂに、1200℃で還元焼鈍された鋼粉を
800℃まで急冷後150℃／Hr以下の速度でそれぞ
れ700、600、500及び400℃まで冷却し、再び種々
の速度で冷却した際の同図ａと同様の関係を示
す。同図ｂに示すように、400℃をこえる温度か
ら急冷を開始すると圧粉密度が低下することがわ
かる。
したがつて同図ａ及びｂから、800℃〜400℃を
除く温度域では急冷処理を施しても鋼粉の圧縮性
に悪影響を与えたいことが判明した。なお上記の
実験に供した鋼粉の成分組成は、1wt％Cr−
0.7wt％Mr−0.018wt％Ｃ−Bal.Feである。
そこで、本発明では、冷却に影響される圧縮性
を支配するのは鋼粉内の結晶粒の大きさであり、
この結晶粒を粗大化させれば、結晶粒界の周長が
大となつて粉末冶金法による塑性変形を起し易く
なり、その結果として圧縮性の良好な鋼粉を得る
ことができるということを知見した。このような
知見をもとに更に研究を進め、800℃〜400℃の範
囲内における冷却速度について適正な冷却速度を
求めたところ、第２図に示したように、付記した
成分の還元焼鈍後の鋼粉について冷却室内の減圧
量との関係において、圧力20トール以下の減圧状
態下のもとに250℃／Hr以下の冷却速度で冷却す
れば、充填層表面部、中央部とも均一なしかも管
理基準値を満たすような品質の鋼粉が得られるこ
とが判つた。
このような知見をもとに、本発明では、生産性
を向上させるために、金属粉末を還元焼鈍後冷却
する際に、粉末冶金法によつて成形する際の圧縮
性に影響を及ぼさない温度域では急冷処理を行
い、圧縮性に影響を及ぼす温度域の800〜400℃間
では20メートル以下の減圧状態に保持して金属粉
末充填及び器具を炉体との間で断熱状態にする一
方、圧力を調整することにより250℃／Hr以下の
遅い冷却速度にして鋼粉充填中心部から表面部へ
熱の拡散を充分に行わせ、鋼粉全体の温度の均一
化と表面急冷部の急冷歪除去を図るようにした。
（実施例）
第３図のａ，ｂ，ｃは、この実施例で用いる還
元焼鈍炉であり、原料となる金属粉末（鋼粉）
は、第３図ｂ，ｃに示すトレイ７、受皿８に充填
されたあと、入口扉４から入れ、予熱室１で600
〜900℃の温度で予熱・乾燥する。次いで、可動
扉５を開とし、次の還元焼鈍室２に移送し、950
〜1250℃の温度および１メートルの減圧状態の付
活性雰囲気下で還元焼鈍を行う。次いで可動扉６
を開とし、冷却室３で本発明に従つて冷却する。
この場合、還元焼鈍温度800℃以上の高温で行わ
れる場合と、800℃以下の比較的低い温度で行わ
れる場合について区別して説明する。
第４図は、このうち、800℃以上の高温で還元
焼鈍が行われた場合の冷却室３における冷却方法
を示すものである。
先ず、1200℃で還元焼鈍された鋼粉は、H2ガ
スを供給した非酸化性雰囲気下で圧縮性に影響を
及ぼさない800℃までの温度域についてはやゝ大
気圧より高い状態で冷却室３内に設置されている
フアンを回転させて急冷を行う。次に、同じ非酸
化性雰囲気で20トール以下まで真空ポンプによる
減圧を行い、400℃までの間は250℃／Hr以下の
冷却速度で徐冷を行つた。次いで圧縮性に影響を
及ぼさない400℃〜室温までは、同じく大気圧以
上の状態にして非酸化性雰囲気で再度冷却室３の
フアンを回転させて急冷処理を行つた例である。
第５図は、還元焼鈍温度が800℃以下の低い温
度の例について行なつた場合の冷却方法を示すも
ので、還元温度以下を20トール以下の減圧状態で
250℃／Hr以下の冷却速度で400℃まで徐冷し、
400℃〜室温までは大気圧以上に戻してフアン回
転に急冷を行つた場合である。
なお、前記実施例では、急冷を行うのに、フア
ン回転を用いたが、H2ガスや、N2ガスを供給す
ることで急冷してもよく、何れにしてもできるだ
け速い冷却速度で急冷するのが生産性向上の面か
ら好ましい結果を示した。
以下、次に示す成分組成の鋼粉を還元焼鈍した
結果を説明する。
(1) 1wt％Cr、0.7wt％Mn、0.018wt％Ｃ、Bal.
Fe
(2) 3wt％Cr、0.3wt％Mn、0.018wt％Ｃ、Bal.
Fe
この実施例は、第１表に示すような条件下で、
第４図に示すような冷却を行つたところ、第２
表、第３表に示す如き結果が得られた。
(Industrial Application Field) The present invention relates to a method for cooling metal powder during reduction annealing, and in particular to metal powder that is a raw material for powder metallurgy (the following will be described using the example of "steel powder").
We propose a new cooling technology after reduction annealing to produce low-oxygen alloy steel powder by using atomized iron powder, which is prealloyed with carbon, as a raw material and subjecting it to reduction annealing. (Prior Art) Conventionally, reduction annealing of metal powders, particularly steel powders, has been carried out using raw iron powders, such as raw powders pulverized by water atomization, using a belt-type gas reduction furnace. Recently, the requirements for such steel powders have become even more severe, and it is desired to produce steel powders containing alloy components. However, Mn, which is an alloy component,
When steel powder containing easily oxidizable alloy components such as Cr is produced using the water atomization method, it is impossible to reduce it using a conventional belt-type gas reduction furnace because Mn and Cr form refractory oxides. It was impossible. That is, the reason is that the furnace temperature must be maintained at 1000° C. or higher, and that it is industrially difficult to maintain a low dew point and low oxygen atmosphere. To solve this problem, there is a technology disclosed in Japanese Patent Application Laid-Open No. 52-110208, which uses high-frequency induction heating in a vertical shaft furnace under a so-called reduced pressure atmosphere. This is a method in which oxygen in the powder is reduced and annealed using alloyed oxygen. The above-mentioned conventional technique is an extremely rational and excellent method because the raw iron powder moves continuously from above to below by its own weight. However, this vertical shaft furnace has a continuous vertically arranged pre-heating zone,
It consists of a reduction annealing zone and a cooling zone, so when the type of raw material powder is changed or the operating conditions in the preheating/heating process are changed, the preheating/heating conditions are required in each zone. Since it is not possible to adjust the conditions to the desired conditions, and the conditions are limited to average conditions, there is a drawback that in severe cases, productivity is reduced. (Problems to be Solved by the Invention) In order to overcome these drawbacks, the present applicant previously filed a patent application No. 60-28365 by heating and heating the raw material iron powder.
We proposed a horizontal three-chamber metal powder processing furnace that is advantageous for producing high-quality steel powder through annealing. The heat treatment furnace according to this proposal includes a preheating chamber for preheating and drying carbon-containing raw material powder, a reduction annealing chamber in which the raw material powder after preheating is deoxidized and annealed by using carbon, and a reduction annealing chamber for cooling the reduction annealing powder. Cooling chambers are divided and arranged side by side in series, and movable doors are provided at the boundaries of each chamber, so that each chamber becomes an independent defined space. This is a reduction annealing furnace for metal powder, each of which is equipped with an exhaust device for depressurization. For this furnace, approximately 1200
Natural cooling is performed from the reduction temperature of °C to room temperature in a non-oxidizing atmosphere supplied with H 2 gas under reduced pressure. However, when the reduction annealing furnace according to the above proposal is used to naturally cool the steel powder after reduction annealing in a non-oxidizing atmosphere in a cooling chamber, a long time is required for cooling, and the process of preheating, reduction annealing, and cooling is required. The cooling stage was rate-limiting, causing a drop in productivity. Furthermore, by using a cooling fan to perform forced cooling from the reduction temperature to room temperature with a non-oxidizing atmospheric gas, the cooling time can be shortened and productivity can be improved. When this was done, the properties of the surface and center of the packed bed varied, resulting in a decline in quality. especially,
When the metal powder is rapidly cooled from the reduction temperature, a problem arises in that the surface portion of the metal powder filled in the tray is rapidly cooled, resulting in rapid cooling distortion, resulting in a decrease in compressibility. Therefore, an object of the present invention is to provide a method for cooling after metal powder reduction annealing, which is suitable for shortening the cooling time and improving productivity, as well as producing steel powder with uniform quality on the surface and center of the packed bed. This is where we propose a method. (Means for explaining the problem) The inventors investigated the temperature range that affects compressibility in the cooling process after reduction annealing of steel powder, and found that it is within the range of 800°C to 400°C. It was confirmed. Figure 1a shows the relationship between the green powder density, which represents the compressibility of steel powder, and the cooling rate. shows the results of investigating iron powder obtained by cooling at a rate of 150°C/Hr or less. As shown in Figure a, there is no decrease in green density at all cooling rates up to 800℃ after reduction annealing, but at lower temperatures of 700 to 500℃, rapid cooling at 300℃/Hr or higher A decrease in green density was observed. Figure b also shows steel powder that has been reduction annealed at 1200℃.
After rapid cooling to 800°C, the samples were cooled to 700, 600, 500 and 400°C at a rate of 150°C/Hr or less, respectively, and then cooled again at various rates, showing the same relationship as in Figure a. As shown in Figure b, it can be seen that the green density decreases when rapid cooling is started from a temperature exceeding 400°C. Therefore, from a and b of the same figure, it has been found that in a temperature range other than 800°C to 400°C, even if the rapid cooling treatment is performed, the compressibility of the steel powder is likely to be adversely affected. The composition of the steel powder used in the above experiment was 1wt%Cr-
0.7wt%Mr-0.018wt%C-Bal.Fe. Therefore, in the present invention, it is the size of the crystal grains in the steel powder that governs the compressibility that is affected by cooling.
If these crystal grains are made coarser, the circumference of the grain boundaries becomes larger, making it easier to cause plastic deformation by powder metallurgy, and as a result, it is possible to obtain steel powder with good compressibility. I found out. Based on this knowledge, we conducted further research and determined the appropriate cooling rate within the range of 800°C to 400°C.As shown in Figure 2, we found that after reduction annealing of the listed components, Regarding steel powder, if it is cooled at a cooling rate of 250°C/Hr or less under a reduced pressure of 20 Torr or less, the surface and center of the packed bed may not be uniform. It was found that steel powder of quality that met the control standard values could be obtained. Based on this knowledge, in the present invention, in order to improve productivity, when metal powder is cooled after reduction annealing, a temperature that does not affect the compressibility when molded by powder metallurgy is set. In the temperature range of 800 to 400 degrees Celsius, which affects compressibility, rapid cooling is performed, and the pressure is kept at a vacuum of 20 meters or less to insulate the metal powder filling and equipment from the furnace body. By adjusting the pressure, a slow cooling rate of 250℃/Hr or less is achieved, allowing sufficient heat to diffuse from the center of the steel powder filling to the surface, making the temperature of the entire steel powder uniform, and reducing quench distortion in the surface quench area. I tried to remove it. (Example) A, b, and c in Fig. 3 are reduction annealing furnaces used in this example, in which metal powder (steel powder) is used as a raw material.
After the trays 7 and saucers 8 shown in Fig. 3b and c are filled, they are put in through the entrance door 4 and heated in the preheating chamber 1 for 600 minutes.
Preheat and dry at a temperature of ~900℃. Next, the movable door 5 is opened, and it is transferred to the next reduction annealing chamber 2, and the temperature is reduced to 950.
Reduction annealing is carried out under an activated atmosphere at a temperature of ~1250°C and a vacuum of 1 meter. Next, movable door 6
is opened and cooled according to the invention in the cooling chamber 3.
In this case, the case where the reduction annealing is performed at a high temperature of 800°C or higher and the case where the reduction annealing is performed at a relatively low temperature of 800°C or lower will be distinguished and explained. FIG. 4 shows a cooling method in the cooling chamber 3 when reduction annealing is performed at a high temperature of 800° C. or higher. First, steel powder that has been reduction annealed at 1,200℃ is stored in a cooling chamber at a temperature higher than atmospheric pressure in a non-oxidizing atmosphere supplied with H2 gas, at temperatures up to 800℃ that do not affect compressibility. Rapid cooling is performed by rotating the fan installed inside 3. Next, in the same non-oxidizing atmosphere, the pressure was reduced to 20 Torr or less using a vacuum pump, and slow cooling was performed at a cooling rate of 250°C/Hr or less until 400°C. Next, from 400 DEG C. to room temperature, which does not affect compressibility, the cooling chamber 3 was rapidly cooled by rotating the fan again in a non-oxidizing atmosphere under atmospheric pressure or higher. Figure 5 shows the cooling method when the reduction annealing temperature is low, 800°C or less.
Slowly cool down to 400℃ at a cooling rate of 250℃/Hr or less,
The range from 400°C to room temperature is when the temperature is returned to above atmospheric pressure and rapid cooling is performed by fan rotation. In the above embodiment, fan rotation was used to perform the rapid cooling, but the cooling may also be performed by supplying H 2 gas or N 2 gas, and in either case, the rapid cooling is performed at the fastest possible cooling rate. showed favorable results in terms of productivity improvement. Hereinafter, the results of reduction annealing of steel powder having the following chemical composition will be explained. (1) 1wt%Cr, 0.7wt%Mn, 0.018wt%C, Bal.
Fe (2) 3wt%Cr, 0.3wt%Mn, 0.018wt%C, Bal.
Fe In this example, under the conditions shown in Table 1,
When cooling was performed as shown in Figure 4, the second
The results shown in Table 3 were obtained.
【表】
第２表、第３表には、比較例Ａ：H2ガスを供
給しフアンの回転による1.5Hrの急冷処理、Ｂ：
H2ガスを9.1Nm3供給し、フアンを回転させずに
減圧下で自然冷却、を併記した。[Table] Tables 2 and 3 show Comparative Example A: Rapid cooling treatment for 1.5 hours by supplying H 2 gas and rotating a fan; B:
9.1 Nm 3 of H 2 gas was supplied and natural cooling was performed under reduced pressure without rotating the fan.
【表】【table】
【表】
第２表、第３表から判るように、圧縮性の指標
となる圧粉密度（ｇ／cm3）（金属粉末に潤滑剤と
してステアリン酸鉛を１％混粉後、7t／cm2の圧力
にて直径11.3mm、高さ11〜12mmの円柱状に圧粉し
たときの圧粉体の体積（cm3）と重量（ｇ）の比か
ら表される密度比）で示すと、
Ａの急冷処理では、表面層と中心部で差が生じ
ると共に、Ｂの自然冷却やＣの本発明による冷却
法よりも表面層、中心部ともに圧粉密度が小さ
く、いわゆる圧縮性が悪いということがわかる。
一方、Ｃの本発明では、Ｂのような長時間をか
けた自然冷却の場合と同様の品質のものが得られ
ていることがわかる。これは還元焼鈍温度が800
℃以下の場合に本冷却法を適用した場合にも同様
の結果が得られた。
なお、前記実施例では、含Crの鋼粉を還元焼
鈍後冷却する方法について述べた他の合金元素を
含むもの或いは一般の金属粉末の冷却にも適用で
きることが推測される。
（発明の効果）
以上説明したように本発明によれば、圧縮性に
影響を及ぼさないような冷却速度を採用したから
生産性の向上をはかりつゝ長時間の自然冷却処理
したと同様の均一で圧縮性にも良好な品質の金属
粉末を得ることができるようになつた。従つて、
粉末冶金法によつて粉末を成形する際に、圧縮性
の極めて良好な成形体を得ることができる。[Table] As can be seen from Tables 2 and 3, green density (g/cm 3 ), which is an index of compressibility (7 t/cm after mixing 1% lead stearate as a lubricant with metal powder) When the powder is compacted into a cylinder with a diameter of 11.3 mm and a height of 11-12 mm at a pressure of 2 , the density ratio is expressed as the ratio of the volume (cm 3 ) and weight (g) of the compact In the rapid cooling treatment of A, there is a difference between the surface layer and the center, and the density of the green powder is lower in both the surface layer and the center than in the natural cooling of B or the cooling method of the present invention in C, resulting in poor compressibility. I understand. On the other hand, it can be seen that in the present invention of C, the same quality as in the case of natural cooling over a long period of time as in B is obtained. This has a reduction annealing temperature of 800
Similar results were obtained when this cooling method was applied to temperatures below ℃. In addition, it is presumed that the above-mentioned example can also be applied to the cooling of powders containing other alloying elements or general metal powders, as described in relation to the method of cooling Cr-containing steel powder after reduction annealing. (Effects of the Invention) As explained above, according to the present invention, since a cooling rate that does not affect compressibility is adopted, productivity is improved and uniformity similar to that achieved by long-term natural cooling treatment is achieved. It has become possible to obtain metal powder with good quality and compressibility. Therefore,
When molding powder by powder metallurgy, a molded body with extremely good compressibility can be obtained.
第１図ａ及びｂは、圧粉密度と冷却速度との関
係を示すグラフ、第２図は、冷却速度が圧縮性に
及ぼす影響を示すグラフ、第３図ａ，ｂ，ｃは、
本発明法で用いる還元焼鈍炉ａと受皿ｂおよびト
レイについて示す略線図、第４図は、還元温度が
800℃以上の鋼粉の本発明冷却方法の説明図、第
５図は、還元温度が800℃以下の鋼粉の本発明冷
却方法の説明図である。
１……予熱室、２……還元焼鈍室、３……冷却
室、４……入口扉、５，６……可動扉、７……ト
レイ、８……受皿。
Figures 1 a and b are graphs showing the relationship between green powder density and cooling rate, Figure 2 is a graph showing the influence of cooling rate on compressibility, and Figure 3 a, b, and c are graphs showing the relationship between green powder density and cooling rate.
FIG. 4 is a schematic diagram showing the reduction annealing furnace a, the saucer b, and the tray used in the method of the present invention.
FIG. 5 is an explanatory diagram of the cooling method of the present invention for steel powder having a reduction temperature of 800°C or higher. FIG. 1... Preheating chamber, 2... Reduction annealing chamber, 3... Cooling room, 4... Entrance door, 5, 6... Movable door, 7... Tray, 8... Receiver.
Claims (1)
いて冷却することにより還元粉末を得る方法にお
いて、還元温度が800℃を超えるものについての
還元焼鈍を終えた還元粉末の冷却に際し、還元温
度から800℃までの間を急冷し、800〜400℃まで
の間を250℃／Hr以下の速度で徐冷し、そして
400℃以下を再び急冷することを特徴とする金属
粉末の還元焼鈍時における冷却方法。 ２ 含炭素原料粉末を予熱し、還元焼鈍し、冷却
することにより還元粉末を得る方法において、還
元温度が800℃以下のものについての還元焼鈍を
終えた還元粉末の冷却に際し、還元温度から400
℃までの間を250℃／Hrの速度で徐冷し、そして
400℃以下を再び急冷することを特徴とする金属
粉末の還元焼鈍時における冷却方法。[Claims] 1. A method for obtaining a reduced powder by preheating a carbon-containing raw material powder, subjecting it to reduction annealing, and then cooling it, wherein the reduced powder has undergone reduction annealing and has a reduction temperature exceeding 800°C. When cooling, it is rapidly cooled from the reduction temperature to 800℃, slowly cooled from 800 to 400℃ at a rate of 250℃/Hr or less, and
A cooling method during reduction annealing of metal powder, characterized by rapid cooling again to 400°C or less. 2. In a method of obtaining reduced powder by preheating carbon-containing raw material powder, subjecting it to reduction annealing, and cooling it, when cooling the reduced powder after reduction annealing for those whose reduction temperature is 800°C or less,
℃ at a rate of 250℃/Hr, and
A cooling method during reduction annealing of metal powder, characterized by rapid cooling again to 400°C or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61148045A JPS637301A (en) | 1986-06-26 | 1986-06-26 | Cooling method for metallic powder at reduction annealing thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61148045A JPS637301A (en) | 1986-06-26 | 1986-06-26 | Cooling method for metallic powder at reduction annealing thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS637301A JPS637301A (en) | 1988-01-13 |
| JPH036961B2 true JPH036961B2 (en) | 1991-01-31 |
Family
ID=15443903
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP61148045A Granted JPS637301A (en) | 1986-06-26 | 1986-06-26 | Cooling method for metallic powder at reduction annealing thereof |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS637301A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0417640A (en) * | 1990-05-09 | 1992-01-22 | Kobe Steel Ltd | Manufacture of powder tool steel |
-
1986
- 1986-06-26 JP JP61148045A patent/JPS637301A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS637301A (en) | 1988-01-13 |
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