JP3576578B2 - Atomized iron powder for sinter forging and method for producing the same - Google Patents

Description

【００４２】
すなわち、市販のスクラップを電気炉で溶解し、ＣａＯ −ＣａＦ_２−Ａｌ_２Ｏ_３ −ＳｉＯ_２のもとでＯ_２ガスを吹き込んで酸化精錬し除さい（滓）した後、ＣａＯ −ＣａＦ_２−Ａｌ_２Ｏ_３ −ＳｉＯ_２−Ｃのスラグを形成しつつ１７００℃に昇温して還元精錬した。次に、電気炉及び取鍋にＦｅＣｒ、ＦｅＭｎ、ＦｅＳｉ、Ａｌ、Ｍｇ、Ｚｒ、Ｃを投入してそれらの化学成分を調整するとともに、Ｃｕ、Ｆｅ−Ｎｉ又は金属Ｎｉ、Ｆｅ−Ｍｏ又はＭｏＯ_３又は金属Ｍｏ、Ｆｅ−Ｃｏ又は金属Ｃｏ、Ｆｅ−Ｗ及びＦｅＳ 等を投入して合金成分を調整し、図１、図２及び図３に示したそれぞれの方法で水アトマイズした。つづいて、脱水、乾燥、還元焼鈍及び解砕して水アトマイズ鉄粉を製造した。
【００４３】
ここで、図１に示した従来法では、取鍋から水アトマイズするまでの雰囲気は大気である。これに対し、図２及び図３に示したこの発明の方法では、取鍋から水アトマイズするまでの雰囲気はＡｒで、そのＯ_２濃度は０．１ｖｏｌ％であった。また、水アトマイズした鉄粉はフィルターで減圧脱水し、次いでＮ_２雰囲気中、２００ ℃で乾燥し、さらにＨ_２雰囲気中、９５０ ℃にて還元焼鈍した後、ハンマーミルで解砕し、１８０ μｍ ふるいの通過粉とした。
これらの還元焼鈍した水アトマイズ鉄粉の化学組成を表２、表３に、また酸化物系介在物量としてヨウ素−メタノール溶液で抽出した値を表４、表５に示す。
【００４４】
【表２】

【００４５】
【表３】

【００４６】
【表４】

【００４７】
【表５】

【００４８】
次に、これらの還元焼鈍した水アトマイズ鉄粉に天然黒鉛粉を０．６ ％及びステアリン酸亜鉛粉を１％添加して混合し、直径６０ｍｍ、長さ３０ｍｍのタブレットを圧粉密度：６．８０ｇ／ｃｍ^３ と一定にして成形した。
【００４９】
次に、このタブレットをＮ_２−１０ ｖｏｌ％Ｈ_２雰囲気中で１１３０℃で３０分間保持して焼結し、いったん室温に冷却した。次いで、この焼結タブレットをＡｒ−４ ｖｏｌ％Ｈ_２雰囲気中で１１００℃に加熱し、メカニカルプレスを用いて金型内で５．９ ＭＮの荷重をかけて鍛造し、直ちに油冷した。得られた焼鈍鍛造材はＡｒ中で９２０ ℃に加熱して６０℃の焼入油で焼入し、Ａｒ中で５８０ ℃に加熱して焼戻した。
【００５０】
次に、この鍛造タブレットの中央部から、幅１０ｍｍ、高さ１０ｍｍ、長さ５５ｍｍのＵノッチ付シャルピー衝撃試験片、平行部の長さ１５．４ｍｍ、直径８ｍｍの小野式回転曲げ疲労試験片及び平行部の長さ１５ｍｍ、直径５ｍｍの小型丸棒引張試験片を作成した。油焼入・焼戻し熱処理した焼結鍛造材の全Ｏ量、シャルピー衝撃値及び耐久限度比（耐久疲れ強さ／引張強さ）を表６に示す。
【００５１】
なお、ヨウ素−メタノール溶液法は、１５％ヨウ素−メタノール溶液で鉄粉を溶解し、０．２ μｍ のフィルターでろ過した残さをフィルターごと大気中で８００ ℃で焼いて灰化し、Ｎａ_２Ｂ_４Ｏ_７ ：Ｋ_２ＣＯ_３ ：Ｎａ_２ＣＯ_３が４：３：３の混合物を加えて融解し、５０ ｖｏｌ％温塩酸で抽出して、原子吸光法でＣｒ， Ｍｎ， Ａｌ， Ｍｇ， Ｃａの濃度を分析し、吸光光度法でＳｉ， Ｔｉ， Ｚｒの濃度を分析したものである。
また、０量分析は５ｍｍ角の試料を黒鉛ルツボに入れＡｒ気流中で加熱溶融してＣＯガスとし、赤外線の吸収量を測定して算出した。
【００５２】
【表６】

【００５３】
表６の結果から明らかなように、図１に示す大気雰囲気中で溶鋼処理し、大気雰囲気中で水アトマイズする従来法では、還元焼鈍処理したアトマイズ鉄粉の酸化物系非金属介在物量は０．１０％を超えていて、これらの焼結鍛造材の全０量も０．０１０ ％より多いため、そのシャルピー衝撃値は３０Ｊより低く、耐久限度比も０．４０より低い。これに対し、図２及び図３に示す溶鋼のＡｒガスバブリングを行い、Ａｒ雰囲気中で溶鋼処理及び水アトマイズを行うこの発明の方法では、還元焼鈍処理したアトマイズ鉄粉の酸化物系非金属介在物量は０．１０％以下となり、それらの焼結鍛造材の全０量も０．０１０ ％以下と低く、著しく清浄化しているために、そのシャルピー衝撃値は３０Ｊより高く、耐久限度比も０．４０より高い。
【００５４】
なかでも、図３に示すタンディッシュ内の堰の孔をくぐらせた溶鋼を水アトマイズしたこの発明の鉄粉は、さらに清浄化していて、焼結鍛造材は衝撃強度と疲労強度が向上する。また、この発明の方法で水アトマイズしたＣｕ：１０．０％以下、Ｎｉ：２０．０％以下、Ｍｏ：１０．０％以下、Ｃｏ：２０．０％以下、Ｗ：１０．０％以下及びＳ：１．０ ％以下から選ばれる１種以上を含む合金鋼粉についても、還元焼鈍処理した水アトマイズ鉄粉の酸化物系非金属介在物量が０．１０％以下で、それらの焼結鍛造材の全０量は０．０１０ ％以下と低く、そのシャルピー衝撃値は３０Ｊより高く、耐久限度比も０．４０より高い。
【００５５】
【発明の効果】
この発明は、溶鋼をＡｒ等の不活性ガスでバブリングし、Ａｒ等の不活性雰囲気中で溶鋼処理し、Ａｒ等の不活性雰囲気中でアトマイズするから、溶鋼処理工程で溶鋼自体を酸化させることがない。また、Ｃｒ、Ｍｎ、Ｓｉ、Ｔｉ、Ａｌ、Ｍｇ、Ｚｒ及びＣａといった強制脱酸剤を使用して溶鋼を脱酸でき、取鍋内ででもタンディッシュ内ででも非金属介在物を浮上分離できる。このため、非金属介在物量が極めて低い、清浄性に優れた、高品質のアトマイズ鉄粉を得ることができる。
【００５６】
また、この発明は、ヨウ素−メタノール溶液法で分析したときのＣｒ_２Ｏ_３ 、ＭｎＯ 、ＳｉＯ_２、ＴｉＯ_２、Ａｌ_２Ｏ_３ 、ＭｇＯ 、ＺｒＯ_２及びＣａＯ の分析値の総量が０．１０％以下であるといった極めて低い介在物量のアトマイズ鉄粉にしたので、これを原料にした焼結鍛造材はじん性及び疲労強さをともに向上できる。
【００５７】
さらに、ヨウ素−メタノール溶液法でアトマイズ鉄粉のＦｅＯ 以外の酸化物系介在物量を分析することにより、焼結鍛造材に残留する全０量を予測できるから、アトマイズ鉄粉の品質管理に適用できるという効果もある。
【図面の簡単な説明】
【図１】大気雰囲気中で溶鋼処理し、大気雰囲気中で水アトマイズする、従来の溶鋼注入法を示すアトマイズの工程説明図である。
【図２】溶鋼を非酸化性ガスでバブリングし、非酸化性ガス雰囲気中で溶鋼処理し、非酸化性ガス雰囲気中で水アトマイズする、この発明の溶鋼注入法の例を示すアトマイズの工程説明図である。
【図３】溶鋼を非酸化性ガスでバブリングし、非酸化性ガス雰囲気中で溶鋼処理し、非酸化性ガス雰囲気中で水アトマイズする、この発明の溶鋼注入法の例を示すアトマイズの工程説明図である。
【符号の説明】
１ 電気炉
２ 溶鋼
３ スラグ
４ 取鍋
５ タンディッシュ
６ タンディッシュノズル
７ 水ノズル
８ 水ジェット
９ アトマイズ生粉
１０ 噴霧槽
１１ スラグ
１２ 筒体
１３ スラグ
１４ ポーラスプラグ
１５ 導管
１６ 気泡
１７ 蓋
１８ 注湯管
１９ 排気
２０ 噴霧雰囲気圧調整器
２１ ポーラスプラグ
２２ 堰
２３ 孔[0001]
[Industrial applications]
The present invention relates to a raw iron powder suitable for producing a gear such as an automobile, a clutch ring, and a connecting rod by using a sintering forging method, which is particularly excellent in toughness and fatigue strength. Specifically, it is manufactured by spraying with liquid or gas represented by water,₂O₃  , MnO 2, SiO₂, TiO₂, Al₂O₃, MgO, ZrO₂And high cleanliness atomized iron powder in which the amount of CaO 2 and CaO 2 is reduced as much as possible, and a method for producing the same. The atomized iron powder referred to in the present invention includes not only pure iron powder but also alloy steel powder containing at least one selected from Ni, Mo, W, Cu, Co and S.
[0002]
[Prior art]
Generally, the steps of manufacturing gears, clutch rings, connecting rods and the like for automobiles and the like by the sintering forging method include (1) a main raw material (atomized iron powder), a lubricant (metal soap powder, etc.), and a mechanical strength enhancer (graphite). Powder, Cu powder, Ni powder, Mo powder, etc.) and a cutting improver (MnS powder, etc.) mixing process, (2) cold mold forming process, (3) propane modified gas,ammoniaCracked gas, N₂-10 vol% H₂Gas, N₂It consists of the steps of sintering the molded body in a gas or vacuum atmosphere, (4) preheating the sintered body, and (5) die forging the preheated sintered body.
[0003]
Here, when pure iron powder is used as a raw material, the mixed composition of the compact is, for example, Fe-2 wt% Cu-0.65 wt% graphite, Fe-2 wt% Cu-0.65 wt% graphite-0.3 wt%. MnS, Fe-2wt% Ni-0.5wt% Mo-0.65wt% graphite and the like are used. When the alloy steel powder of Cu, Ni, Mo, Co, W, and S is used as a raw material, at least one of Cu, Ni, Mo, Co, W, and S is used up to about 0.1 to 10 wt%. An alloy steel powder containing 0.2 to 0.9 wt% of graphite powder is used. The sintering temperature of these compacts is 1100 to 1250 ° C, and the forging heating temperature of the sintered compacts is 1000 to 1100 ° C.
[0004]
Incidentally, atomized iron powder as a main raw material usually contains a large amount of various kinds of oxides. This oxide has caused a remarkable decrease in toughness and fatigue strength of the sintered forged material as a final product.
[0005]
Oxide system of sintered forgings made from iron powderNon-metalRegarding the relationship between the amount of inclusions and toughness, see "New Perspectives in Powder Metallurgy, vol. 8, Power Metallurgy for D.F.R.D.R.", published by Metal Powder Industries Federation (1987). 449 to 464, the oxygen of a sintered forged material having a composition of Fe-2 wt% Ni-0.5 wt% Mo-0.4 wt% C obtained by mixing graphite powder with a perfect alloy steel powder having a water atomizing AISI 4600 composition. The relationship between the content and the Charpy impact value is shown graphically in FIG. 4, but this is only an example for the sample, and the relationship between the O content and the Charpy impact value in various sintered forgings was quantified. It is not universally described.
[0006]
Further, in Powder Metallurgy, vol. 17, No. 33, (1974), pp. 157 to 177, Table I shows the composition of a complete alloy steel powder having a water atomized AISI 4600 composition, an En16 composition containing Si or Al, a Conalloy composition, and a W4 / 2 composition. Fe-2wt% Ni-0.5wt% Mo-0.4wt% C mixed with powder, Fe-1.4wt% Mn-0.25wt% Cr-0.35wt% Mo-0.4wt% C, Fe-0.6 wt% Mn-0.5 wt% Ni-0.3 wt% Cr-0.45 wt% Mo-0.4 wt% C and Fe-0.4 wt% Mn-0.3 For a sintered forged material having a composition such as wt% Cr-0.3 wt% Mo-0.4 wt% C, the number of inclusions of 5 μm or more and the durability limit ratio (ratio between fatigue strength and tensile strength) Of FIG. 21. The water atomized fully alloyed steel powder used in this experiment was H₂As shown by Loss, the amount of O (oxygen) is 0.10 wt% or more, and the number of inclusions in the obtained sintered forged material is as shown in FIG. As shown in FIGS. 6 (a) and (b), 2.5 pieces / mm²It turns out that it is above.
[0007]
However, in this document, no experiment has been conducted on a sample in which the O content of the water atomized perfect alloy steel powder is lower than 0.10 wt%, and thus the durability limit of the sintered forged material using the iron powder lower than 0.10 wt%. No ratio is given. Also, H₂The O content of the water atomized perfect alloy steel powder indicated by Loss is not distinguished between the Fe, Ni, and Mo oxides reduced in the sintering and forging process and the unreduced Cr, Mn, Si, and Al oxide amounts. . Further, the number of inclusions in the sintered forging material is measured by Quantitative Television Microscope, but the number of inclusions has a completely different value depending on the measurement method and apparatus.
[0008]
In Japanese Patent Publication No. 54-10935, C, Si, Mn, P, S, Cu, Ni, Cr, and O are treated as impurity components for lowering the green density. A water atomized iron powder having 15 wt%, Cu + Ni + Cr: 0.03 to 0.10 wt%, O: 0.3 wt% or less, and a total of other impurities of 0.1 wt% or less is described. In this prior art, the oxidation of Fe, Ni, and Mo reduced in the sintering and sintering forging processes cannot be distinguished from the amount of unreduced oxides such as Cr, Mn, Si, and Al. In some cases could not be achieved.
[0009]
Furthermore, Japanese Patent Publication No. 58-48603 discloses that in order to reduce the amount of nonmetallic inclusions as much as possible, the temperature of the reduction period in an electric furnace is set to 1700 to 1750 ° C and the molten steel is transferred to a ladle. Tundish without forced deoxidizerSlugA method is described in which molten steel is poured into a tundish through a tubular body set up in a tundish so as not to flow into the tundish. In this prior art, oxidation of molten steel transferred into the ladle and tundish is prevented only by the slag on the surface, and therefore, oxidation of molten steel during the process of refining, dispensing, transferring and pouring molten steel is performed. However, no measures have been taken to actively remove generated oxides, slag which is likely to be involved in molten steel, or eroded refractories from molten steel.
[0010]
[Problems to be solved by the invention]
According to the study of the inventors, among the oxides contained in the atomized iron powder, oxides of Fe, Cu, Ni, Mo, Co and W are mixed graphite powder and H during sintering.₂In a sintering step or a preheating step before forging, the reducing gas is sufficiently reduced to a metal. Since S is not present as a simple oxide in the atomized iron powder, but is a solid solution of S, MnS or manganese oxysulfide, it can be used as a machinability improving component.
[0011]
On the other hand, of the oxides contained in the atomized iron powder,₂O₃  , MnO 2, SiO₂, TiO₂, Al₂O₃, MgO, ZrO₂Since CaO 2 and CaO 2 are not reduced even by graphite powder or reducing gas, they remain as oxide-based nonmetallic inclusions in the sintered forging.
[0012]
As described above, although the oxides contained in the atomized iron powder include oxides that do not remain in the product sintered forging and oxides that remain, conventionally, as described above, atomized iron powder is used. The toughness and fatigue strength of the sintered forged material used as raw materials were evaluated using the total oxygen content and the number of inclusions in the sintered forged material as parameters. The amount of inclusions remaining without being reduced in the process was not evaluated in a quantitative manner.
[0013]
Therefore, it was not possible to grasp the relationship between the amount of 0 for the sintering forging and the number of inclusions based only on the zero amount of the atomized iron powder and the analysis value of the inclusions, which had been conventionally performed. The amount of inclusions of atomized iron powder required to improve the strength has not been elucidated. For this reason, even in the process of treating molten steel until atomization, a method for preventing the formation of inclusions and a method for removing the inclusions sufficient to improve the toughness and fatigue strength of the sintered forged material are well established. Did not.
[0014]
The present invention advantageously solves the above-mentioned problems. The amount of 0 of a sintered forging material preheated before sintering and forging at 1100 to 1150 ° C. becomes 0.01 wt% or less, and dust of the sintered forging material is reduced. It is an object of the present invention to propose an atomized iron powder having a low amount of inclusions, which can significantly improve the properties and fatigue strength, together with its advantageous production method.
[0015]
[Means for Solving the Problems]
The present invention provides an analysis of iron powder inclusions and sintered forgings using an iodine-alcohol dissolution extraction separation method, that is, an oxide-based inclusion in atomized iron powder and a sintered forging with an iodine-alcohol solution. Extract the residue (residue) and extract FeO 2, Cr₂O₃, MnO 2, SiO₂, TiO₂, Al₂O₃, MgO, ZrO₂As a result of quantitative analysis of CaO 2 and CaO 2, the process of sintering and sinter-forging FeO 2 in iron powder₂Reduced by gas atmosphere or mixed graphite,₂O₃, MnO 2, SiO₂, TiO₂, Al₂O₃, ZrO₂It is based on the finding that CaO and CaO remain in the sintered forged material, and the amount of the residue well corresponds to the toughness and fatigue strength of the sintered forged material using this as a raw material.
[0016]
In other words, according to the present invention, when the content of Cr, Mn, Si, Ti, Al, Mg, Zr and Ca in the atomized iron powder increases, the Cr remaining in the sintered forged material using this as a raw material₂O₃, MnO 2, SiO₂, TiO₂, Al₂O₃, MgO, ZrO₂When the total amount of these oxides exceeds a certain limit, the toughness and fatigue strength of the sintered forged material are remarkably reduced, and Cu: 10.0 wt% as an alloy component. Hereafter, even if Ni: 20.0 wt% or less, Mo: 10.0 wt% or less, Co: 20.0 wt% or less, W: 10.0 wt% or less, these oxides can be used to produce atomized iron powder. Process, sintering process and sintering forging process₂It is sufficiently reduced in a gas atmosphere or mixed graphite to act to improve the strength of a sintered forged material, and S is within a range of 1.0 wt% or less and Cr₂O₃, MnO 2, SiO₂, TiO₂, Al₂O₃, MgO, ZrO₂And that the toughness and fatigue strength of the sintered forged material are not significantly reduced if the total amount of CaO 2 is within the limits.
[0017]
In addition, the present invention dispenses molten steel from a steelmaking furnace to a ladle, transfers the molten steel to a tundish, pours the molten steel into a spray tank, and atomizes the molten steel in the ladle or tundish. By bubbling with a non-oxidizing gas, sealing the molten steel surface with a non-oxidizing gas, or providing a weir in a tundish and passing the molten steel through the weir hole, actively preventing the generation of oxides and It is based on the knowledge that the floating of inclusions can be promoted and high-quality atomized iron powder for sintering forging with few nonmetallic inclusions can be produced.
[0018]
That is, the gist configuration of the atomized iron powder for sintering forging of the present invention is as follows.
(1) The contents of Si, Mn, Cr, Ti, Al, Mg, Zr, and Ca are respectively: Si: 0.05 wt% or less, Mn: 0.35 wt% or less, Cr: 0.35 wt% or less, Ti: 0 0.06 wt% or less, Al: 0.04 wt% or less, Mg: 0.03 wt% or less, Zr: 0.08 wt% or less, and Ca: 0.03 wt% or less, with the balance being Fe and unavoidable impurities. ,Oxide remaining in the sintered forged material without being reduced in the sintering process or preheating process before forgingSiO₂, MnO, Cr₂O₃  , TiO₂, Al₂O₃  , MgO, ZrO₂And an atomized iron powder for a sintered forging material having a total amount of CaO 2 of 0.10 wt% or less.
[0019]
(2) The contents of Si, Mn, Cr, Ti, Al, Mg, Zr and Ca are respectively 0.05% by weight or less for Si, 0.35% by weight or less for Mn, 0.35% by weight or less for Cr, and 0% for Ti. 0.06 wt% or less, Al: 0.04 wt% or less, Mg: 0.03 wt% or less, Zr: 0.08 wt% or less, and Ca: 0.03 wt% or less, and Ni: 20.0 wt% or less. Mo: at least one selected from the group consisting of 10.0 wt% or less, W: 10.0 wt% or less, Cu: 10.0 wt% or less, and Co: 20.0 wt% or less, with the balance being Fe and unavoidable impurities. Consisting ofOxide remaining in the sintered forged material without being reduced in the sintering process or preheating process before forgingSiO₂, MnO, Cr₂O₃  , TiO₂, Al₂O₃  , MgO, ZrO₂And an atomized iron powder for a sintered forging material having a total amount of CaO 2 of 0.10 wt% or less.
Atomized iron powder for sinter forging.
[0020]
(3) The contents of Si, Mn, Cr, Ti, Al, Mg, Zr and Ca are respectively 0.05% by weight or less for Si, 0.35% by weight or less for Mn, 0.35% by weight or less for Cr, and 0% for Ti. 0.06 wt% or less, Al: 0.04 wt% or less, Mg: 0.03 wt% or less, Zr: 0.08 wt% or less, and Ca: 0.03 wt% or less, and S: 1.0 wt% or less. Contain, the balance consists of Fe and inevitable impurities,Oxide remaining in the sintered forged material without being reduced in the sintering process or preheating process before forgingSiO₂, MnO, Cr₂O₃  , TiO₂, Al₂O₃  , MgO, ZrO₂And an atomized iron powder for a sintered forging material having a total amount of CaO 2 of 0.10 wt% or less.
[0021]
(4) The contents of Si, Mn, Cr, Ti, Al, Mg, Zr, and Ca are respectively 0.05% by weight or less for Si, 0.35% by weight or less for Mn, 0.35% by weight or less for Cr, and 0% for Ti. 0.06 wt% or less, Al: 0.04 wt% or less, Mg: 0.03 wt% or less, Zr: 0.08 wt% or less, and Ca: 0.03 wt% or less, and Ni: 20.0 wt% or less. Mo: at least one selected from the group consisting of 10.0 wt% or less, W: 10.0 wt% or less, Cu: 10.0 wt% or less, and Co: 20.0 wt% or less, and S: 1.0 wt% With the balance comprising Fe and inevitable impurities,Oxide remaining in the sintered forged material without being reduced in the sintering process or preheating process before forgingSiO₂, MnO, Cr₂O₃  , TiO₂, Al₂O₃  , MgO, ZrO₂And an atomized iron powder for a sintered forging material having a total amount of CaO 2 of 0.10 wt% or less.
[0023]
The gist configuration of the method for producing atomized iron powder for sintering forging of the present invention is as follows.
(I)After melting the raw molten steel for atomized iron powder in a melting furnace, dispensing it into a ladle, then pouring it through a tundish into a spray tank and atomizing it.,the above (1) ~ (4) For sintered forged material according to any one of the aboveManufacturing atomized iron powderOn the occasion,Add a deoxidizer containing at least one selected from Si, Mn, Cr, Ti, Al, Mg, Zr and Ca in at least one of the melting furnace, ladle and tundishAfter doingThe surface of the molten steel and the sizing agent in the ladle, tundish and spray tank are sealed with an inert gas, and a non-oxidizing gas is blown into one or both steel baths of the ladle and the tundish for bubbling.thingA method for producing atomized iron powder for sintered forging, characterized by the following.
[0024]
(Ii)  After melting the raw molten steel for atomized iron powder in a melting furnace, dispensing it into a ladle, then pouring it through a tundish into a spray tank and atomizing it.,the above (1) ~ (4) For sintered forged material according to any one of the aboveManufacturing atomized iron powderOn the occasion,Add a deoxidizer containing at least one selected from Si, Mn, Cr, Ti, Al, Mg, Zr and Ca in at least one of the melting furnace, ladle and tundishAfter doingLadle, the surface of the molten steel and the sizing agent in the tundish and the spray tank are sealed with an inert gas, and a non-oxidizing gas is blown into one or both steel baths of the ladle and the tundish for bubbling,And,Set up a weir in the tundish and let the molten steel in the tundish pass through the hole of this weirthingA method for producing atomized iron powder for sintered forging, characterized by the following.
[0025]
[Action]
From the residue obtained by extracting the atomized iron powder with an iodine-alcohol solution,₂O₃, MnO 2, SiO₂, TiO₂, Al₂O₃, MgO, ZrO₂And the total amount analyzed as CaO 2 is the amount of Cr remaining in the sintered forged material.₂O₃, MnO 2, SiO₂, TiO₂, Al₂O₃, MgO, ZrO₂There is a positive correlation with the analytical value of 0 indicating the total amount of non-metallic inclusions composed of Ca and CaO 2, and there is a good correspondence between the toughness (Charpy impact value) of the sintered forged material and the rotational bending fatigue strength. Therefore, in the atomized iron powder of the present invention, Si, Mn, Cr, Ti, Al, Mg, Zr, and Ca which form a solid solution by being added as a deoxidizing agent or are mixed from scrap during melting in an electric furnace. The content of Cr in the atomized iron powder is controlled within a predetermined range.₂O₃, MnO 2, SiO₂, TiO₂, Al₂O₃, MgO, ZrO₂And the total amount of CaO 2 is suppressed to 0.10 wt% or less by a value quantitatively analyzed by an iodine-alcohol dissolution extraction separation method, thereby improving the toughness and fatigue strength of a sintered forged material using this iron powder. It can be done.
[0026]
Further, as a device for obtaining such atomized iron powder, in the present invention, the molten steel is bubbled with a non-oxidizing gas during the molten steel treatment process until atomization, and the molten steel surface is passed through a hole of a weir provided in a tundish. By sealing with a non-oxidizing gas or using a pouring pipe made of a refractory material, it was possible to positively prevent the formation of oxides and promote the floating of inclusions. For this reason, Cr, Mn, Si, Ti, Al, Mg, Zr and Ca, which are easily oxidized during molten steel processing and water atomization, can be contained in a large amount, and the mechanical strength, particularly the tensile strength, of the sintered forged material can be improved. There is also an effect.
Such a contrivance in the manufacturing process is particularly effective when applied to a water atomization method in which iron powder is easily oxidized among the atomization methods.
[0027]
Hereinafter, the present invention will be described more specifically.
(A) About the component composition of atomized iron powder:
Si: 0.05wt % (Hereinafter simply indicated as%)Hereinafter, Mn: 0.35% or less, Cr: 0.35% or less, Ti: 0.06% or less, Al: 0.04% or less, Mg: 0.03% or less, Zr: 0.08% or less, and Ca: 0.03% or less
Although Si, Mn, Cr, Ti, Al, Mg, Zr and Ca are generally used as components for strengthening steel materials, they are more easily oxidizable elements than Fe, and therefore are particularly used as deoxidizing agents for molten steel in the present invention. I do. Since these oxides are harder to reduce than Fe oxides, their contents are set to 0.05% or less for Si: 0.35% or less for Mn, 0.35% or less for Cr, and 0.06% or less for Ti. % Or less, Al: 0.04% or less, Mg: 0.03% or less, Zr: 0.08% or less, and Ca: 0.03% or less, SiO2, MnO2, Cr2O3, TiO2, Al2O3, MgO , ZrO2 and CaO 2 can produce atomized iron powder having a total amount of 0.10% or less, and the toughness and fatigue strength of the sintered forged material are remarkably improved.
[0028]
(B)Oxide remaining in the sintered forged material without being reduced in the sintering process or preheating process before forgingSiO₂, MnO, Cr₂O₃  , TiO₂, Al₂O₃  , MgO, ZrO₂And the total amount of CaO 2 is 0.10 wt% or less
As already mentioned, SiO present in iron powder₂, MnO, Cr₂O₃  , TiO₂, Al₂O₃  , MgO, ZrO₂Since the amounts of Ca and CaO have a positive correlation with the toughness and bending fatigue strength of the sintered forged material, in order to improve the toughness and bending fatigue strength of the sintered forged material, the total amount thereof is set to 0.1. It must be 10% or less. More preferably, it is at most 0.085%.
[0029]
(C) Ni: 20.0% or less, Mo: 10.0% or less, W: 10.0% or less, Cu: 10.0% or less, Co: 20.0% or less
Cu, Ni, Mo, Co, and W can be solid-solution-strengthened because their oxides are more easily reduced than Fe oxides and do not remain as oxides in the atomized iron powder and its sintered forgings. It is a component that can be made.
However, due to an increase in the amount of Cu precipitated when Cu exceeds 10.0%, and FeNi that precipitates when Ni exceeds 20.0%.₃FeMo or carbide ([Fe.Mo]) that precipitates due to an increase in the amount or when Mo exceeds 10.0%₃  C, [Fe.Mo]₇  C₃, [Fe ・ Mo]₂₃C₆  Etc.) and coarsening, an increase in the Fe / Co phase which precipitates when Co exceeds 20.0%, and an increase in the amount of Fe which precipitates when W exceeds 10.0%.₂  Both increase and coarsening of W and carbide significantly reduce the toughness and fatigue strength of the sintered forged material.
In addition, the minimum contents for solid solution strengthening in the present invention are, respectively, about 0.10% of Ni: about 0.10% of Mo, about 0.20% of W, about 0.20% of Cu, Co: about 0.10%.
[0030]
(D) S: 1.0% or less
S is a component that improves machinability, but when S exceeds 1.0%, SiO is removed from the residue extracted with the iodine-alcohol solution.₂, MnO, Cr₂O₃, TiO₂, Al₂O₃, MgO, ZrO₂Even if the total amount analyzed quantitatively as 0.10% or less as Fe and Mn-OS (iron and manganese oxysulfide), FeS, CuS, MoS and CoS in the sintered forged material. , Which significantly reduces the toughness and fatigue strength of the sintered forged material.
[0031]
(E) SiO₂, MnO, Cr₂O₃, TiO₂, Al₂O₃, MgO, ZrO₂And the total amount of CaO 2 as a value determined by iodine-alcohol solution extraction separation analysis
Methods for investigating the amount of nonmetallic inclusions in steel include iodine-alcohol solution extraction / separation, bromine-alcohol solution extraction / separation, and acid dissolution using hydrochloric acid, sulfuric acid or nitric acid. The alcohol method has a trapping rate of about 0 to 40% of the total amount of iron powder (oxide amount), and the acid dissolution method has₂, Al₂O₃, ZrO₂, TiO₂In this invention, it is desirable to use a value measured by an iodine-alcohol solution extraction separation analysis method, since only the trapping can be performed.
[0032]
(F) Manufacturing method of atomized iron powder
In order to produce the atomized iron powder having the above-mentioned components, a deoxidizer containing at least one selected from Si, Mn, Cr, Ti, Al, Mg, Zr and Ca is added to at least one of the melting furnace and the ladle. After deoxidation, the surface of the molten steel and the sizing agent in the ladle, tundish, and spray tank are sealed with an inert gas, and non-oxidized in one or both ladle and tundish steel baths. Bubbling is performed by blowing inactive gas, or a weir is provided in the tundish, and molten steel in the tundish is passed through the hole of the weir. Hereinafter, description will be made with reference to the drawings.
[0033]
FIG. 1 is an explanatory view of a manufacturing process of atomized iron powder by a conventional method. This method is a method of preventing a boiling phenomenon at the time of tapping without adding a forced deoxidizing agent to a ladle, and preventing mixing of nonmetallic inclusions caused by the forced deoxidizing agent.
FIG. 2 and FIG. 3 are explanatory views of the production process of the atomized iron powder according to the present invention. That is, as a molten steel composition, Si: 0.05% or less, Mn: 0.35% or less, Cr: 0.35% or less, Ti: 0.06% or less, Al: 0.04% or less, Mg: 0.03% % Or less, Zr: 0.08% or less and Ca: 0.03% or less, a forced deoxidizer can be added in a molten steel processing step such as a ladle or a tundish, and oxide-based nonmetallic inclusions can be reduced. A method for producing atomized iron powder that is lower than before, such as bubbling by blowing non-oxidizing gas into molten steel, sealing molten steel with non-oxidizing gas, and allowing molten steel to pass through holes in weirs provided in tundishes. It is a way to do it.
[0034]
The conventional method shown in FIG. 1 and the method of the present invention shown in FIGS. 2 and 3 will be described more specifically in comparison with each other.
In the conventional method shown in FIG. 1, molten steel 2 smelted in a melting furnace, for example, an electric furnace 1 is subjected to slag 3 to reduce impurities in the furnace, and then temporarily transferred to a ladle 4, and then to a tundish 5. While being dropped from the tundish nozzle 6, high-pressure water 8 is sprayed from the water nozzle 7 to atomize the molten steel 2 into powder 9, and the powder is collected by cooling in the spray tank 10. Here, the slag 11 is floated on the surface of the molten steel in the tundish 5 to prevent oxidation by an air atmosphere and keep heat, and the cylinder 12 is immersed in a steel bath in the tundish 5 to stand upright. By injecting the molten steel 2 so that the slag 11 does not flow into the cylindrical body 12, mixing of nonmetallic inclusions due to entrainment of the slag 11 is prevented as much as possible. However, in such a conventional method, the molten steel 2 cannot escape air oxidation through the slags 11 and 13 in the tundish 5 and the ladle 4. Further, when a forced deoxidizing agent (reducing agent) is added to the molten steel 2 in the ladle 4 or the tundish 5, an increase in the amount of nonmetallic inclusions in the steel due to the addition cannot be prevented, and as a result, cleaning of the atomized iron powder is not possible. There is a limit to the conversion to SiO2 from the residue extracted with the iodine-alcohol solution.₂, MnO, Cr₂O₃, TiO₂, Al₂O₃  , MgO, ZrO₂Thus, iron powder having a total amount of 0.10% or less quantitatively analyzed as CaO 2 could not be produced.
[0035]
On the other hand, according to the present invention, in the example of FIG. 2, a porous plug 14 is attached to the bottom of the ladle 4, and Ar, N from a conduit 15 connected to a non-oxidizing gas supply device.₂, He, H₂And a non-oxidizing gas such as a mixed gas thereof is injected into the molten steel 2 to form bubbles 16 in the steel bath, bubbling the slag 13 and the oxide of the forced deoxidizing agent and the molten deoxidizer. Actively levitates damaged refractories. In addition, a lid 17 is attached to the ladle 4 to expel air in the ladle by bubbling gas, while a pouring pipe 18 is provided between the ladle 4 and the tundish 5 and connected to a non-oxidizing gas supply device. The conduit 15 is connected above the steel bath of the tundish 5, and the non-oxidizing gas is led to the tundish 5 and exhausted 19 from the pouring pipe 18, so that the molten steel 2 in the tundish 5 can be connected with the non-oxidizing gas. Slug11To prevent oxidation of molten steel flowing down in the pouring pipe 18. Further, the water nozzle 7 is surrounded by an outer shell and integrated with the spray tank 10, and a conduit 15 from a non-oxidizing gas supply device is connected to the outer shell of the water nozzle 7 and the spray tank 10 to connect the non-oxidizing gas. Is discharged from the vicinity of the tundish nozzle 6 and exhausted while adjusting the air pressure by the spray atmosphere pressure regulator 20, so that air is discharged between the tundish 5 and the spray tank 10 and into the spray tank 10. Intrusion is prevented to prevent oxidation of the molten steel 2.
[0036]
The embodiment of the present invention shown in FIG. 3 differs from the embodiment of FIG. 2 in that a porous plug 21 is attached to the bottom of the tundish 5 so as to float nonmetallic inclusions in the steel bath, and a hole is formed in the tundish 5. By providing the weir 22 with 23, the slag involved in the molten steel 211Nonmetallic inclusions such as oxides of forced deoxidizers and erosion-resistant refractories can be further separated.
[0037]
According to the method of the present invention shown in FIGS. 2 and 3, Si: 0.05% or less, Mn: 0.35% or less, Cr: 0.35% or less, Ti: 0.06% or less, Al: 0. 04% or less, Mg: 0.03% or less, Zr: 0.08% or less, and Ca: 0.03% or less, SiO2 is extracted from the residue extracted with the iodine-alcohol solution.₂, MnO, Cr₂O₃  , TiO₂, Al₂O₃  , MgO, ZrO₂And iron powder having a total amount of 0.10% or less quantitatively analyzed as CaO 2 can be suitably produced. Further, when containing at least one selected from the group consisting of Ni, Mo, W, Cu and Co, the oxides of Cu, Ni, Mo, Co and W are more easily reduced than the oxides of Fe. Therefore, it can be reduced by the forced deoxidizer of Cr, Mn, Si, Ti, Al, Mg, Zr and Ca added to the molten steel, and does not adversely affect the toughness and fatigue strength of the sintered forged material. When oxidized in molten steel, S becomes SO₂And escapes from the molten steel, so that it does not remain in the water atomized iron powder as oxide-based inclusions.
[0038]
In addition, the bubbling of the inert gas to the molten steel in the ladle and the tundish as shown in FIGS. 2 and 3 is performed by providing a porous plug on a side wall below the molten steel surface of the ladle and the tundish, and performing a process from the side wall. The same effect can be obtained by blowing with an injection nozzle immersed in a steel bath instead of a porous plug.
[0039]
In addition, FIG. 2 shows an example in which bubbling is performed only with a ladle, and FIG. 3 shows an example in which bubbling is performed with both a ladle and a tundish. Or both.
[0040]
【Example】
Regarding the effects of the method of the present invention described above and the atomized iron powder for sintering forging of the present invention, analysis values of oxide nonmetallic inclusions of iron powder, total 0-quantity analysis values of sintered forging and mechanical strength Will be described in comparison with those manufactured by a conventional method.
Table 1 shows the chemical composition of the molten steel and the molten steel processing conditions in each of the steps of electric furnace, ladle, tundish, and water atomization.
[0041]
[Table 1]

[0042]
That is, a commercially available scrap is melted in an electric furnace, and CaO—CaF₂-Al₂O₃  -SiO₂O under₂After gas is blown and oxidized and refined to remove (slag), CaO-CaF₂-Al₂O₃  -SiO₂While forming a slag of -C, the temperature was raised to 1700 ° C to carry out reduction smelting. Next, FeCr, FeMn, FeSi, Al, Mg, Zr, and C are charged into an electric furnace and a ladle to adjust their chemical components, and Cu, Fe—Ni or metallic Ni, Fe—Mo or MoO is added.₃Alternatively, metal Mo, Fe-Co or metal Co, Fe-W, FeS or the like was charged to adjust the alloy components, and water atomized by the respective methods shown in FIGS. 1, 2 and 3. Subsequently, dewatering, drying, reduction annealing and crushing were performed to produce water atomized iron powder.
[0043]
Here, in the conventional method shown in FIG. 1, the atmosphere from the ladle to the water atomization is the atmosphere. On the other hand, in the method of the present invention shown in FIGS. 2 and 3, the atmosphere from the ladle to the water atomization is Ar, and the atmosphere is Ar.₂The concentration was 0.1 vol%. The water atomized iron powder is dehydrated under reduced pressure with a filter,₂After drying at 200 ° C. in an atmosphere,₂After reduction annealing at 950 ° C. in an atmosphere, the mixture was pulverized with a hammer mill to obtain a powder passing through a 180 μm sieve.
Tables 2 and 3 show the chemical compositions of these reduced and annealed water atomized iron powders, and Tables 4 and 5 show the values of oxide inclusions extracted with an iodine-methanol solution.
[0044]
[Table 2]

[0045]
[Table 3]

[0046]
[Table 4]

[0047]
[Table 5]

[0048]
Next, 0.6% of natural graphite powder and 1% of zinc stearate powder were added to these reduced and annealed water atomized iron powders and mixed, and a tablet having a diameter of 60 mm and a length of 30 mm was pressed into a green compact having a density of 6. 80g / cm³And molded.
[0049]
Next, this tablet is₂-10 vol% H₂Sintering was carried out at 1130 ° C. for 30 minutes in an atmosphere, and once cooled to room temperature. Next, this sintered tablet was mixed with Ar-4 vol% H.₂It was heated to 1100 ° C. in an atmosphere, forged with a load of 5.9 MN in a mold using a mechanical press, and immediately cooled with oil. The obtained annealed forged material was heated to 920 ° C. in Ar, quenched with a quenching oil at 60 ° C., and tempered by heating to 580 ° C. in Ar.
[0050]
Next, a Charpy impact test specimen with a U notch having a width of 10 mm, a height of 10 mm and a length of 55 mm, an Ono-type rotary bending fatigue test specimen having a parallel part length of 15.4 mm and a diameter of 8 mm was obtained from the center of the forged tablet. Small size with parallel part length 15mm and diameter 5mmRound barA tensile test piece was prepared. Table 6 shows the total O amount, the Charpy impact value, and the durability limit ratio (durable fatigue strength / tensile strength) of the sintered forged material subjected to the oil quenching and tempering heat treatment.
[0051]
In the iodine-methanol solution method, iron powder is dissolved in a 15% iodine-methanol solution, and the residue obtained by filtration through a 0.2 μm filter is baked at 800 ° C. in the air together with the filter, and incinerated.₂B₄O₇: K₂CO₃: Na₂CO₃The mixture was melted by adding a 4: 3: 3 mixture, extracted with 50 vol% hot hydrochloric acid, analyzed for the concentrations of Cr, Mn, Al, Mg, and Ca by atomic absorption spectrometry, and analyzed for Si and Ti by spectrophotometry. , Zr were analyzed.
In addition, the zero-quantity analysis was performed by placing a 5 mm square sample in a graphite crucible, heating and melting it in an Ar gas stream to obtain CO gas, and measuring the amount of infrared absorption.
[0052]
[Table 6]

[0053]
As is clear from the results in Table 6, in the conventional method in which molten steel treatment is performed in the air atmosphere shown in FIG. 1 and water atomization is performed in the air atmosphere, the amount of the oxide-based nonmetallic inclusions in the atomized reduction-annealed iron powder is 0. Since it exceeds 0.10% and the total amount of these sintered forgings is also greater than 0.010%, its Charpy impact value is lower than 30 J and the durability limit ratio is lower than 0.40. On the other hand, in the method of the present invention in which the molten steel shown in FIGS. 2 and 3 is subjected to Ar gas bubbling, and the molten steel treatment and the water atomization are performed in an Ar atmosphere, the oxide-based nonmetallic intermediate of the atomized iron powder subjected to the reduction annealing treatment is performed. The physical amount is 0.10% or less, and the total amount of the sintered forged material is as low as 0.010% or less. Since the material is extremely clean, its Charpy impact value is higher than 30 J and the durability limit ratio is 0. Higher than .40.
[0054]
Above all, the iron powder of the present invention obtained by water atomizing molten steel passing through a weir hole in a tundish shown in FIG. 3 is further purified, and the sintered forged material has improved impact strength and fatigue strength. Further, water atomized by the method of the present invention: Cu: 10.0% or less, Ni: 20.0% or less, Mo: 10.0%Less than, Co: 20.0%Less than, W: not more than 10.0% and S: not more than 1.0% selected from the group consisting of alloy steel powder containing 1.0% or less, the amount of oxide nonmetallic inclusions in the reduction-annealed water atomized iron powder is 0.10. % Or less, the total amount of the sintered forgings is as low as 0.010% or less, and its Charpy impact value is higher than 30 J;Endurance limitThe ratio is also higher than 0.40.
[0055]
【The invention's effect】
According to the present invention, since molten steel is bubbled with an inert gas such as Ar, the molten steel is treated in an inert atmosphere such as Ar, and atomized in an inert atmosphere such as Ar, the molten steel itself is oxidized in the molten steel treatment step. There is no. In addition, molten steel can be deoxidized using a forced deoxidizer such as Cr, Mn, Si, Ti, Al, Mg, Zr and Ca, and nonmetallic inclusions can be floated and separated in a ladle or a tundish. . Therefore, it is possible to obtain a high-quality atomized iron powder having an extremely low amount of nonmetallic inclusions and excellent cleanliness.
[0056]
Further, the present invention provides a method for analyzing Cr₂O₃  , MnO 2, SiO₂, TiO₂, Al₂O₃  , MgO, ZrO₂Since the atomized iron powder having an extremely low inclusion amount such that the total amount of analyzed values of CaO 2 and CaO 2 is 0.10% or less is used, a sintered forged material using this as a raw material can improve both toughness and fatigue strength.
[0057]
Further, by analyzing the amount of oxide-based inclusions other than FeO 2 in the atomized iron powder by the iodine-methanol solution method, it is possible to predict the total amount of 0 remaining in the sintered forged material, so that it can be applied to quality control of the atomized iron powder. There is also an effect.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an atomizing process showing a conventional molten steel injection method in which molten steel processing is performed in an air atmosphere and water atomization is performed in the air atmosphere.
FIG. 2 is an explanation of an atomizing process showing an example of the molten steel injection method of the present invention, in which molten steel is bubbled with a non-oxidizing gas, subjected to molten steel treatment in a non-oxidizing gas atmosphere, and water-atomized in a non-oxidizing gas atmosphere. FIG.
FIG. 3 is an explanation of an atomizing process showing an example of the molten steel injection method of the present invention in which molten steel is bubbled with a non-oxidizing gas, subjected to molten steel treatment in a non-oxidizing gas atmosphere, and water-atomized in a non-oxidizing gas atmosphere. FIG.
[Explanation of symbols]
1 Electric furnace
2 molten steel
3 slug
4 Ladle
5 Tundish
6 Tundish nozzle
7 Water nozzle
8 water jet
9 Atomized raw flour
10 Spray tank
11 Slug
12 cylinder
13 Slug
14 Porous plug
15 conduit
16 bubbles
17 Lid
18 Pouring pipe
19 Exhaust
20 Spray atmosphere pressure regulator
21 Porous plug
22 Weir
23 holes

Claims (6)

The content of Si, Mn, Cr, Ti, Al, Mg, Zr and Ca is set to Si: 0.05 wt% or less, respectively.
Mn: 0.35 wt% or less,
Cr: 0.35 wt% or less,
Ti: 0.06 wt% or less,
Al: 0.04 wt% or less,
Mg: 0.03 wt% or less,
Zr: 0.08% by weight or less and Ca: 0.03% by weight or less, the balance being Fe and unavoidable impurities , which are not reduced in the sintering process or the preheating process before forging to form a sintered forged material. Atomized iron powder for sintering forging, wherein the total amount of remaining oxides, SiO ₂ , MnO, Cr ₂ O ₃ , TiO ₂ , Al ₂ O ₃ , MgO, ZrO ₂ and CaO, is 0.10 wt% or less. The content of Si, Mn, Cr, Ti, Al, Mg, Zr and Ca is set to Si: 0.05 wt% or less, respectively.
Mn: 0.35 wt% or less,
Cr: 0.35 wt% or less,
Ti: 0.06 wt% or less,
Al: 0.04 wt% or less,
Mg: 0.03 wt% or less,
Zr: 0.08 wt% or less and Ca: 0.03 wt% or less,
And Ni: 20.0 wt% or less,
Mo: 10.0 wt% or less,
W: 10.0 wt% or less,
Contains at least one selected from the group consisting of Cu: 10.0 wt% or less and Co: 20.0 wt% or less, with the balance being Fe and unavoidable impurities , which are reduced in a sintering step or a preheating step before forging. _{SiO 2, MnO, Cr 2 O} 3, TiO 2, Al 2 O 3, MgO, the total amount of ZrO ₂ and CaO is less 0.10 wt% sintering forging an oxide remaining in the sintered forging without Atomized iron powder for wood. The content of Si, Mn, Cr, Ti, Al, Mg, Zr and Ca is set to Si: 0.05 wt% or less, respectively.
Mn: 0.35 wt% or less,
Cr: 0.35 wt% or less,
Ti: 0.06 wt% or less,
Al: 0.04 wt% or less,
Mg: 0.03 wt% or less,
Zr: 0.08 wt% or less and Ca: 0.03 wt% or less,
And S: 1.0 wt% or less, the balance being Fe and unavoidable impurities , remaining in the sintered forged material without being reduced in the sintering step or the preheating step before forging. _{SiO 2, MnO, Cr 2 O} 3, TiO 2, Al 2 O 3, MgO, sintered forging for atomized iron powder total ZrO ₂ and CaO is less than 0.10 wt% is an oxide. The content of Si, Mn, Cr, Ti, Al, Mg, Zr and Ca is set to Si: 0.05 wt% or less, respectively.
Mn: 0.35 wt% or less,
Cr: 0.35 wt% or less,
Ti: 0.06 wt% or less,
Al: 0.04 wt% or less,
Mg: 0.03 wt% or less,
Zr: 0.08 wt% or less and Ca: 0.03 wt% or less,
And Ni: 20.0 wt% or less,
Mo: 10.0 wt% or less,
W: 10.0 wt% or less,
Cu: contains at least one member selected from the group consisting of 10.0 wt% or less and Co: 20.0 wt% or less, further contains S: 1.0 wt% or less, and the balance consists of Fe and inevitable impurities. , SiO _2, MnO without being reduced during the sintering process or forging prior to the preheating step is an oxide remaining in the sintered _{forging, Cr 2 O 3, TiO 2} , Al 2 O 3, MgO, ZrO 2 and Atomized iron powder for sintered forgings having a total amount of CaO 2 of 0.10 wt% or less. After dissolving the starting material molten steel for atomized iron powder in a melting furnace, ladle dispensed, followed by atomization and poured into spray tank through the tundish, any one of claims 1 to 4 In producing atomized iron powder for sinter forging ,
After adding a deoxidizer containing at least one selected from Si, Mn, Cr, Ti, Al, Mg, Zr and Ca in at least one of a melting furnace, a ladle and a tundish , the ladle, the tundish and the surface of the molten steel and forming again agents in the spray tank together with sealed by an inert gas, sintering forging, characterized in that the bubbling by blowing a non-oxidizing gas into one or both of the steel bath ladle and tundish Production method of atomized iron powder for materials. After dissolving the starting material molten steel for atomized iron powder in a melting furnace, ladle dispensed, followed by atomization and poured into spray tank through the tundish, any one of claims 1 to 4 In producing atomized iron powder for sintered forgings , at least one of a melting furnace, a ladle and a tundish contains at least one selected from Si, Mn, Cr, Ti, Al, Mg, Zr and Ca. After adding a deoxidizing agent, the surface of the molten steel and the sizing agent in the ladle, tundish and spray tank are sealed with an inert gas, and non-oxidized in one or both of the ladle and tundish steel bath. bubbling by blowing sex gas, and, by a weir provided in the tundish, the production method of the sintered forging for atomized iron powder of the tundish molten steel, characterized in that to preferably under the hole of the weir.

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