WO2017043090A1 - Procédé de production de poudre d'alliage d'acier pour la métallurgie des poudres - Google Patents

Procédé de production de poudre d'alliage d'acier pour la métallurgie des poudres Download PDF

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WO2017043090A1
WO2017043090A1 PCT/JP2016/004119 JP2016004119W WO2017043090A1 WO 2017043090 A1 WO2017043090 A1 WO 2017043090A1 JP 2016004119 W JP2016004119 W JP 2016004119W WO 2017043090 A1 WO2017043090 A1 WO 2017043090A1
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powder
gas
iron
content
alloy steel
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PCT/JP2016/004119
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English (en)
Japanese (ja)
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小林　聡雄
中村　尚道
伊都也 佐藤
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Ｊｆｅスチール株式会社
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Priority to JP2016575265A priority Critical patent/JP6112277B1/ja
Priority to KR1020187002726A priority patent/KR20180022905A/ko
Publication of WO2017043090A1 publication Critical patent/WO2017043090A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/14—Treatment of metallic powder
    • B22F1/142—Thermal or thermo-mechanical treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2201/00—Treatment under specific atmosphere
    • B22F2201/01—Reducing atmosphere
    • B22F2201/013—Hydrogen
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
    • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys

Definitions

  • the present invention relates to a method for producing an alloy steel powder for powder metallurgy by reducing atomized iron base powder to produce an alloy steel powder for powder metallurgy, and in particular, the atomized iron base powder is an easily oxidizable element such as Cr and Mn
  • the present invention relates to a method for producing alloy steel powder for powder metallurgy that can effectively reduce the C (carbon) content and O (oxygen) content in the alloy steel powder.
  • Powder metallurgy technology allows parts with complex shapes to be manufactured in a shape very close to the product shape (so-called near net shape) and with high dimensional accuracy. Therefore, if a part is produced using powder metallurgy technology, the cutting cost can be greatly reduced. For this reason, powder metallurgy products to which powder metallurgy technology is applied are used in various fields as various machine parts. Recently, there has been a strong demand for improving the strength of powder metallurgy products in order to reduce the size and weight of parts. In particular, there is a demand for higher strength in iron-based powder metallurgy products (iron-based sintered bodies). Is strong.
  • an alloy element is added to the iron-based powder used in powder metallurgy.
  • the alloy element for example, Cr and Mn are used because they have a high effect of improving hardenability and are relatively inexpensive.
  • alloy powder for powder metallurgy containing the above alloy elements examples include Cr—Mo alloy steel powder (Patent Document 1) and Cr—Mn—Mo alloy steel powder (Patent Document 2, Patent Document 3). Are known.
  • heat treatment is performed to reduce the C content and O content in the iron-based powder as a raw material.
  • the heat treatment is generally carried out continuously using a moving bed furnace (moving bed furnace).
  • the iron-based powder include a crude iron-based powder that has been atomized and a roughly reduced iron obtained by roughly reducing a mill scale.
  • a crude iron-based powder such as a base powder is used.
  • at least one treatment of decarburization, deoxidation, and denitrification is performed according to the use of the powder.
  • an apparatus described in Patent Document 4 is known as an apparatus for performing the heat treatment.
  • the space in the moving bed furnace is divided into a plurality of partitions by a partition wall provided so as to be perpendicular to the traveling direction of the raw material powder.
  • the flow path for flowing atmospheric gas is provided in the upper part of each divided
  • the heat treatment is continuously performed while flowing an atmospheric gas through the channel in a direction opposite to the moving direction of the raw material powder.
  • Cr and Mn are further oxidized during the heat treatment, and the amount of oxide is increased.
  • the C content and the O content are large, the compressibility of the alloy steel powder at the time of pressure forming is lowered, so that a large amount of oxide remains is a problem.
  • Patent Document 5 and Patent Document 6 propose a method that enables decarburization and deoxidation in the production of alloy steel powder containing easily oxidizable elements such as Cr and Mn.
  • the method proposed in Patent Document 6 is a method of performing heat treatment continuously using a belt furnace and is therefore suitable for mass production.
  • it is essential to continuously measure the CO or CO 2 concentration or the oxygen potential (O 2 concentration or H 2 / H 2 O concentration ratio) in the atmospheric gas during the heat treatment, Furthermore, it is necessary to adjust the amount of water vapor injected into the furnace so that these measured values become target values.
  • the sensor part is soiled and the gas intake port is clogged, making it impossible to perform measurement normally. There's a problem. Therefore, when the method of Patent Document 6 is continuously performed, maintenance of the analyzer is a heavy burden.
  • the present invention has been made in view of the above circumstances, and is a method for producing alloy steel powder for powder metallurgy using a moving bed furnace, without requiring gas analysis that requires complicated maintenance management, It aims at providing the manufacturing method of the alloy steel powder for powder metallurgy which can heat-process the iron-base powder containing Cr and Mn, and can reduce C content and O content stably.
  • the gist configuration of the present invention is as follows.
  • alloy steel powder containing Cr and Mn which are easily oxidizable elements
  • the content and the O content can be stably reduced.
  • alloy steel powder that is low in cost and excellent in compressibility during pressure forming.
  • sintered parts produced using the alloy steel powder for powder metallurgy obtained by the production method of the present invention have excellent mechanical properties such as strength, toughness and fatigue properties. Applications of powders and sintered bodies can be expanded.
  • FIG. 1 It is side sectional drawing which shows the example of the heat processing apparatus which can be used in one Embodiment of this invention. It is a figure which shows the example of the temperature pattern in the heat processing apparatus described in patent document 4. FIG.
  • alloy steel powder for powder metallurgy (hereinafter sometimes simply referred to as “alloy steel powder”) is produced by heat-treating atomized iron-based powder as a raw material using a moving bed furnace.
  • the production method of the present invention includes the following treatments; (1) Prepare atomized iron-based powder. (2) supplying the atomized iron-based powder into a moving bed furnace so as to form a packed bed having a thickness of d (mm); (3) By supplying hydrogen-containing gas into the moving bed furnace so as to have an average gas flow velocity v (mm / s), and (4) by heat-treating the atomized iron-based powder in the moving bed furnace. Reduce to alloy steel powder for powder metallurgy.
  • Each of the above processes can be performed independently at an arbitrary timing, and a plurality of processes can be performed simultaneously.
  • atomized iron-based powder is used as a raw material.
  • the manufacturing method of the atomized iron-based powder is not particularly limited, and can be manufactured according to a conventional method.
  • “Atomized iron-based powder” means an iron-based powder produced by the atomizing method.
  • the “iron-based powder” means a powder containing 50% by mass or more of Fe.
  • the atomized iron-based powder either a gas atomized iron-based powder obtained by a gas atomizing method or a water atomized iron-based powder obtained by a water atomizing method can be used.
  • the gas atomization method it is preferable to use an inert gas such as nitrogen or argon.
  • gas since gas is inferior in cooling capacity compared to water, it is necessary to use a large amount of gas when producing iron-based powder by the gas atomization method. Therefore, it is preferable to use the water atomization method from the viewpoint of mass productivity and manufacturing cost.
  • the water atomization method is normally performed in an atmosphere in which air is mixed, the iron-based powder is more easily oxidized in the production process than the gas atomization method. Therefore, the method of the present invention is particularly effective when a water atomized iron-based powder is used.
  • C and O are elements to be reduced by a heat treatment described later. And from the viewpoint of improving the compressibility of the finally obtained alloy steel powder for powder metallurgy, it is desirable to reduce the C content and O content of the alloy steel powder as much as possible, specifically, C: 0.1% or less, O: 0.28% or less are preferable. In order to achieve these appropriate amounts of C and O, the amount that can be reduced by the heat treatment according to the present invention is anticipated, and the appropriate ranges of the C content and O content of the atomized iron-based powder are determined as follows.
  • C 0.8% or less C is present in the atomized iron-based powder mainly as a precipitate such as cementite or in a solid solution state.
  • the C content in the atomized iron-based powder exceeds 0.8%, it becomes difficult to lower the C content to 0.1% or less in the heat treatment of the present invention, and an alloy powder having excellent compressibility is obtained. I can't. Therefore, the C content of the atomized iron-based powder is set to 0.8% or less.
  • the lower the C content the easier the reduction (decarburization) of the C content during heat treatment. Therefore, the lower limit of the C content is not particularly limited, and may be 0% or industrially greater than 0%.
  • O 1.0% or less O is present on the surface of the iron-based powder mainly as Cr oxide or Fe oxide. If the O content in the atomized iron-based powder exceeds 1.0%, it becomes difficult to reduce the O content to 0.28% or less during heat treatment, and an alloy powder having excellent compressibility cannot be obtained. Therefore, the O content of the atomized iron-based powder is set to 1.0% or less. The O content is preferably 0.9% or less. On the other hand, the lower the O content, the easier the reduction (deoxidation) of the O content during heat treatment. Therefore, the lower limit of the O content is not particularly limited, but excessive reduction leads to an increase in manufacturing cost, so the O content is preferably 0.4% or more.
  • the contents of Mn, Cr, Mo, S, and P are not changed by the heat treatment of the present invention. Therefore, these elements contained in the atomized iron-based powder remain as they are in the alloy steel powder for powder metallurgy after the heat treatment. Based on this, the contents of these elements in the atomized iron-based powder are respectively defined as follows.
  • Mn 0.08% or less Mn is an element having an action of improving the strength of the sintered body by improving hardenability, solid solution strengthening, and the like. However, if the Mn content is higher than 0.08%, the amount of Mn oxide produced increases and the compressibility of the alloy steel powder decreases. Further, the Mn oxide serves as a starting point for destruction inside the sintered body, and reduces fatigue strength and toughness. Therefore, the Mn content is set to 0.08% or less. The Mn content is preferably 0.07% or less.
  • the lower limit of the Mn content is not particularly limited and may be 0%, but from the viewpoint of improving the strength of the sintered body, it is preferably 0.01% or more, 0.05% More preferably.
  • Cr 0.3-3.5%
  • Cr is an element that has the effect of improving hardenability and improving the tensile strength and fatigue strength of the sintered body. Further, Cr has the effect of increasing the hardness after heat treatment such as quenching and tempering of the sintered body and improving the wear resistance. In order to obtain these effects, the Cr content is set to 0.3% or more. On the other hand, when the Cr content exceeds 3.5%, the amount of Cr oxide generated increases. Since the Cr oxide serves as a starting point for fatigue failure inside the sintered body, the fatigue strength of the sintered body is reduced. Therefore, the Cr content is 3.5% or less.
  • Mo 0.1-2%
  • Mo is an element having an action of improving the strength of the sintered body by improving hardenability, solid solution strengthening, precipitation strengthening, and the like. In order to acquire the said effect, Mo content shall be 0.1% or more. On the other hand, when the content of Mo exceeds 2%, the toughness of the sintered body decreases. Therefore, the Mo content is 2% or less.
  • the Mn content in the atomized iron-based powder is set to 0.08% or less. Therefore, among S contained in the atomized iron-based powder, the amount present as MnS decreases, and the amount present as solute S increases. If the S content of the finally obtained alloy steel powder exceeds 0.01%, the solid solution S increases and the grain boundary strength decreases. Therefore, the S content at the stage of atomized iron-based powder is set to 0.01% or less. On the other hand, the lower the S content, the better because the solid solution S decreases. Therefore, the lower limit of the S content is not particularly limited, and may be 0%, but industrially it may be more than 0%. However, since excessive reduction leads to an increase in manufacturing cost, the S content is preferably 0.0005% or more.
  • the content of P does not affect the toughness, but the Mn content of the alloy steel powder is 0.08% or less and the S content is 0.00.
  • the content is 01% or less, the grain boundary strength is increased and the toughness is improved by setting the P content to 0.01% or less. Therefore, the P content at the stage of atomized iron-based powder is set to 0.01% or less.
  • the lower limit of the P content is not particularly limited and may be 0%, but industrially it may be more than 0%. However, excessive reduction leads to an increase in manufacturing cost, so the P content is preferably 0.0005% or more.
  • the component composition of the atomized iron-based powder in the present invention is composed of the above elements, the remainder Fe and inevitable impurities.
  • the average particle size of the atomized iron-based powder is not particularly limited, and any particle size can be used as long as it is an iron-based powder obtained by the atomization method.
  • the average particle size of the atomized iron-based powder is less than 30 ⁇ m, the fluidity of the atomized iron-based powder is lowered, and it may be difficult to supply to the moving bed furnace using a hopper or the like.
  • the average particle size of the atomized iron-based powder is less than 30 ⁇ m, the fluidity of the alloy steel powder after heat treatment also decreases, so the work efficiency of filling the mold when the alloy steel powder is press-formed decreases. There is a case.
  • the average particle size of the atomized iron-based powder is preferably 30 ⁇ m or more, more preferably 40 ⁇ m or more, and even more preferably 50 ⁇ m or more.
  • the average particle size of the atomized iron-based powder is preferably 120 ⁇ m or more, more preferably 100 ⁇ m or less, and even more preferably 90 ⁇ m or less.
  • the average particle diameter means a median diameter (so-called d50, volume basis).
  • the apparent density of the atomized iron-based powder is not particularly limited, but is preferably 2.0 to 3.5 Mg / m 3, and more preferably 2.4 to 3.2 Mg / m 3 .
  • Atomized iron-based powder having the above component composition is supplied to a moving bed furnace, and a packed bed having a thickness d (mm) is formed on the moving bed of the moving bed furnace.
  • a moving bed furnace any one can be used as long as it can heat treat the atomized iron-based powder, but a moving bed furnace (hereinafter referred to as a “belt type moving bed furnace” or “ It is preferable to use a belt furnace).
  • a moving bed furnace hereinafter referred to as a “belt type moving bed furnace” or “ It is preferable to use a belt furnace).
  • an atomized iron-based powder can be supplied onto the belt to form a packed bed.
  • the atomized iron-based powder can be supplied by any method, but it is preferable to use a hopper.
  • the conveyance direction of the atomized iron-based powder in the moving bed furnace is not particularly limited, but it is generally conveyed linearly from the inlet side to the outlet side of the moving bed furnace. The thickness of the fill
  • the heating system of the moving bed furnace is not particularly limited, and any system can be used as long as it can heat the atomized iron-based powder.
  • the indirect heating system is used. It is preferable to use heating using a radiant tube.
  • a muffle furnace can also be suitably used as an indirect heating furnace.
  • the moving bed furnace is supplied with a hydrogen-containing gas.
  • the hydrogen-containing gas any gas can be used as long as it contains hydrogen.
  • the hydrogen-containing gas include pure H 2 gas and a mixed gas of H 2 gas and inert gas.
  • the mixed gas it is preferable to use a mixed gas of H 2 gas and N 2 gas.
  • a mixed gas of H 2 gas and N 2 gas obtained by decomposing ammonia can also be used.
  • the H 2 content of the hydrogen-containing gas is preferably 75% or more, and 90 vol% or more. it is more preferable, and even more preferably to a 100 vol% (H 2 gas).
  • the hydrogen-containing gas is supplied into the moving bed furnace so as to have an average gas flow velocity v (mm / s) during the heat treatment of the atomized iron-based powder in the moving bed furnace.
  • the hydrogen-containing gas is preferably flowed in the moving bed furnace in a direction opposite to the moving direction of the raw material powder.
  • a conveying means such as a belt
  • the hydrogen-containing gas is introduced from the other end (downstream side) and exhausted from the one end (upstream side). Therefore, it is preferable that the moving bed furnace is provided with an atomized iron-based powder supply port and an atmospheric gas discharge port at one end, and a discharge port for treated powder (alloy steel powder) and a hydrogen-containing gas supply port at the other end.
  • both the thickness d (mm) of the packed bed and the average gas flow velocity v (mm / s) are controlled so as to satisfy the following expression (1).
  • the heat treatment By performing the heat treatment under the above-mentioned conditions, it is possible to stably reduce C and O contained in the atomized iron-based powder even though the atomized iron-based powder contains Cr and Mn which are easily oxidizable elements. .
  • the C content and the O content in the alloy steel powder after the heat treatment can be set to extremely low values such as C ⁇ 0.1% and O ⁇ 0.28%. The reason will be described below.
  • the dew point of the atmospheric gas in the furnace is always set higher than the equilibrium dew point determined by the equilibrium reaction of the above equations (2) to (4). Need to keep low. Therefore, it is necessary to reduce the amount of generated H 2 O gas so that the dew point of the atmospheric gas is not increased too much by the H 2 O gas generated by the reaction.
  • the packed bed thickness it is conceivable to suppress the amount of iron-based powder charged into the moving bed furnace, that is, the packed bed thickness. It is also conceivable to reduce the H 2 O gas concentration by removing the H 2 O gas generated by the above reaction or diluting with a hydrogen-containing gas introduced into the moving bed furnace. Therefore, in the present invention, the packed bed thickness d and the average gas flow velocity v in the furnace when the hydrogen-containing gas is introduced into the furnace are controlled so as to satisfy the above equation (1).
  • a velocity boundary layer of flowing hydrogen-containing gas is formed in the space above the surface of the packed bed. It is derived from the theory regarding the boundary layer that the thickness of the velocity boundary layer is inversely proportional to ⁇ v. In addition, since the diffusion rate of hydrogen before the reduction reaction and water vapor generated by the reduction reaction is considered to be constant regardless of the thickness of the velocity boundary layer, the diffusion time is proportional to the thickness of the velocity boundary layer.
  • the velocity boundary layer thickness is halved and the same diffusion time is given, the hydrogen concentration at the packed bed surface will be doubled and the water vapor concentration at the packed bed surface will be halved, It is estimated that even if the thickness of the packed bed is doubled, the concentration of hydrogen and water vapor in the lowermost layer of the packed bed can be made the same. Therefore, assuming that the concentration is constant, the packed layer thickness and the velocity boundary layer thickness are inversely proportional, that is, it is estimated that the packed layer thickness and ⁇ v are in a proportional relationship.
  • d / ⁇ v ⁇ 2.8 (mm 1/2 ⁇ s 1/2 ) is more preferable.
  • the lower limit of d / ⁇ v is not particularly limited. The lower the better, the lower the better. However, if d is excessively decreased, the production efficiency decreases, and if v is excessively increased, the cost increases. It is preferable to set it as the above, and it is more preferable to set it as 0.3 or more.
  • the average gas flow velocity v (mm / s) is obtained by changing the volume flow rate f of hydrogen-containing gas supplied to the moving bed furnace (volume of hydrogen-containing gas supplied per second). It is defined as dividing by the cross-sectional area S of the floor furnace.
  • the cross-sectional area refers to the area of the space inside the annealing furnace that is perpendicular to the conveying direction of the atomized iron-based powder (in the belt furnace, the belt traveling method).
  • the cross-sectional area S is the cross-sectional area at the highest temperature in the annealing furnace.
  • the deoxidation zone is usually at the highest temperature. May be used.
  • the volume flow rate f is a volume flow rate at the measurement position of the cross-sectional area S. That is, considering the volume expansion of gas at a high temperature, the above flow rate is multiplied by the volume expansion coefficient obtained from the temperature at the position.
  • the definition of the cross-sectional area S will be further described.
  • the cross-sectional area of the internal space of the moving bed furnace is used as it is as the cross-sectional area S without subtracting the area of objects existing in the furnaces.
  • a radiant tube type heat treatment furnace as shown in FIG. 1, a radiant tube, a belt, a roll (not shown) for feeding the belt, and iron-based powder laminated on the belt are contained in the furnace.
  • existing in the cross section of the space part in the furnace the gas flow rate is slower in the part where there is no radiant tube or roll, but it is particularly important to control the flow rate in this slow part. It was because it was found from.
  • the cross-sectional area of the belt or iron powder packed-layer thickness portion is negligible with respect to the entire cross-sectional area of the furnace, so there is no need to consider it.
  • the dew point of the hydrogen-containing gas introduced into the furnace is preferably 0 ° C or less.
  • the dew point of the atmospheric gas lower than the equilibrium dew point determined from the equilibrium reaction represented by the above equations (2) to (4). There is. Therefore, it is preferable to lower the dew point of the introduced hydrogen-containing gas, and specifically, it is preferable to set it to 0 ° C. or less.
  • the hydrogen-containing gas flowing upstream in the iron-based powder conveyance direction contains water vapor generated by the reaction.
  • the dew point is higher than the hydrogen-containing gas at the time of supply. Considering this, the dew point of the introduced hydrogen-containing gas is kept low at 0 ° C. or less. Thereby, even if a dew point rises with progress of reaction, deoxidation reaction can fully be advanced.
  • the equilibrium dew point increases, so it seems that the dew point of the hydrogen-containing gas may be increased at first glance.
  • the reaction rate of the deoxidation reaction reaction
  • the generation rate of H 2 O also increases.
  • the dew point of the in-furnace gas also tends to increase. Therefore, it is preferable to control the dew point of the hydrogen-containing gas introduced into the moving bed furnace as described above.
  • the dew point is set to 40 ° C. or less in the iron-based powder that does not contain an easily oxidizable element such as Cr and Mn as in the prior art.
  • the temperature is preferably 0 ° C. or lower.
  • the lower the dew point of the hydrogen-containing gas the better the deoxidation reaction proceeds.
  • a gas with a low dew point is expensive, and the use of a gas with an excessively low dew point causes an increase in production cost. Therefore, it is usually preferable to set the dew point to ⁇ 40 ° C. or higher.
  • the moving bed furnace includes a sealing unit for preventing gas leakage and intrusion.
  • a sealing unit for example, a water-sealed tank (15 in FIG. 1) as described in Patent Document 4 can be used, but it is more preferable to use a system that does not use water such as a seal roll.
  • the sealing means is preferably provided at both ends on the upstream side and the downstream side in the transport direction.
  • the atmospheric temperature is set to 1000 ° C. or higher in order to make the equilibrium dew point higher than the dew point raised by H 2 O generated by the deoxidation reaction. It is preferable.
  • the upper limit of the ambient temperature is not particularly limited, but is preferably about 1200 ° C. in consideration of the heat resistance performance of the apparatus, the manufacturing cost, and the like.
  • the “atmosphere temperature” is a temperature measured by a thermocouple at a position 20 mm immediately above the surface of the iron-based powder (packed bed) in the moving bed furnace.
  • the holding time t is 10 4 -0.0037 ⁇ T hours or more according to the ambient temperature T (° C.) because O can be further reduced. .
  • the relationship between the said t and T was determined from the result of having conducted the experiment which manufactures alloy steel powder with various T and t. Specifically, the O content of the obtained alloy steel powder was plotted on a Tt diagram, and a curve (contour line) connecting the same oxygen content was determined as an approximate expression.
  • the upper limit of the retention time is not particularly limited, but the retention time is preferably 4 hours or less because the production cost only increases even if the retention time is longer than the time required for completion of the deoxidation reaction.
  • Patent Document 4 it is supposed that one or more kinds of processes of decarburization, deoxidation, or denitrification are continuously performed by using a continuous moving bed furnace to heat-treat the iron-based powder. Further, in the description of Patent Document 4, each of the decarburization, deoxidation, and denitrification treatment steps is made independent using the divided space of the moving bed furnace, and the decarburization step is performed at 600 to 1100 ° C. In the denitrification process, the iron-base powder is heat-treated by controlling the temperature independently at 450 to 750 ° C.
  • Patent Document 4 as the atmosphere gas, a reducing gas such as H 2 or AX gas at decarburization zone or an inert gas such as N 2 or Ar, reduction such as H 2 or AX gas in deoxidation zone It is said that gas mainly composed of H 2 is used in the denitrification zone.
  • FIG. 1 A heat treatment apparatus 100 shown in FIG. 1 is provided on a furnace body 30 divided into a plurality of zones by a partition wall 1, that is, a decarburization zone 2, a deoxidation zone 3, and a denitrification zone 4, and an entrance side of the furnace body 30.
  • the hopper 8 is provided, a wheel 10 provided on the entrance / exit side of the furnace body 30, a belt 9 that continuously rotates by the wheel 10 and circulates in each zone in the furnace body 30, and a radiant tube 11.
  • the product powder 13 is stored in the product tank 14.
  • the reaction in each zone is considered as follows.
  • the ambient temperature is controlled to 600 to 1100 ° C. by the radiant tube 11, and the water vapor (H 2 O gas) introduced from the water vapor inlet 12 provided on the downstream side of the decarburization zone 2
  • the atmospheric gas in the deoxidation zone 3 which is the next zone, to a dew point of 30 to 60 ° C.
  • an atmospheric gas discharge port 6 is provided to discharge the atmospheric gas to the outside of the apparatus.
  • the decarburization reaction formula is represented by the following formula (I).
  • C (in Fe) + H 2 O (g) CO (g) + H 2 (g) (I)
  • the ambient temperature is controlled to 700 to 1100 ° C. by the radiant tube 11, and deoxidation is performed from the crude iron-based powder using the atmospheric gas from the denitrification zone 4 (dew point: hydrogen gas of 40 ° C. or less). Is going to do.
  • the ambient temperature is controlled to 450 to 750 ° C. by the radiant tube 11, and hydrogen gas (dew point: 40 ° C.) as a reaction gas is supplied from the atmosphere gas inlet 5 provided on the downstream side of the denitrification zone 4.
  • hydrogen gas dew point: 40 ° C.
  • the following is introduced to denitrify the crude iron-based powder.
  • the water sealing tank 15 functions to block the mixing of the outside gas into the furnace gas and the leakage of the inside gas to the outside of the furnace.
  • FIG. 1 a typical example of a heat treatment temperature pattern by a belt furnace type heat treatment apparatus described in Patent Document 4 is shown in FIG.
  • the iron-based powder to be treated is first heated in the decarburization zone, then soaked in the deoxidation zone, and finally in the denitrification zone.
  • the hydrogen gas introduced in the direction opposite to the flow of the iron-based powder first enters the denitrification zone, denitrifies the iron-based powder while being heated, and then enters the deoxidation zone and is kept at a constant temperature.
  • the iron-base powder is deoxidized while finally entering the decarburization zone together with a predetermined amount of water vapor, and the iron-base powder is decarburized while being cooled.
  • the C content in the atomized iron-based powder is set to 0.8% or less so that the decarburization can be completed only with water vapor generated by the deoxidation reaction. Therefore, decarburization can be completed without additionally introducing water vapor.
  • An atomized iron-based powder having the component composition shown in Table 1 was produced by the water atomization method. These atomized iron-based powders were heat-treated using a moving bed furnace and crushed to obtain alloy steel powder for powder metallurgy. Table 2 shows the atomized iron-based powder used and the heat treatment conditions. Further, in the heat treatment, the atomized iron powder is supplied into the moving bed furnace so as to have a packed bed thickness d shown in Table 2, and a hydrogen-containing gas so as to have an average gas flow velocity v shown in Table 2. The heat treatment was carried out continuously while supplying. The component composition of the obtained alloy steel powder for powder metallurgy was as shown in Table 3. In addition,% display in the composition of the hydrogen-containing gas shown in Table 2 means vol%.
  • the obtained alloy steel powder has a C content of 0.1% or less and an O content of 0. .28% or less.
  • the O content exceeded 0.28%.
  • the obtained alloy steel was 0.1% or less, the O content was 0.2% or less, and the O content was further reduced.
  • powder symbols B1 to B3 an O content of 0.28% or less was obtained, but a lower O content was obtained as the H 2 concentration of the hydrogen-containing gas used was increased.
  • D1 to D4 it can be seen that in D2 to D4 where the dew point is 0 ° C. or less, the O content is 0.15% or less, and a much better result is obtained.
  • E1 to E3 and F1 to F3 those having an ambient temperature of 1000 ° C. or higher and satisfying the condition of t ⁇ 10 4 ⁇ 0.0037 ⁇ T (powder symbols: E3, F3) have an O content. A much better result was obtained at 0.15% or less.

Abstract

L'invention concerne un procédé qui est destiné à produire une poudre d'alliage d'acier pour la métallurgie des poudres. Le procédé utilise un four à lit mobile et, sans avoir besoin d'analyser le gaz, ce qui rend compliquée la maintenance nécessaire, permet de traiter thermiquement une poudre à base de fer qui contient Cr et Mn et de réduire de manière stable la teneur en C et la teneur en O. L'invention concerne un procédé de production d'une poudre d'alliage d'acier pour la métallurgie des poudres. Dans ledit procédé, une poudre à base de fer atomisé qui a une composition à composant spécifique est préparée, la poudre à base de fer atomisé est fournie à l'intérieur d'un four à lit mobile de sorte qu'une couche de remplissage qui a une épaisseur de d (mm) soit formée, un gaz contenant de l'hydrogène est fourni à l'intérieur du four à lit mobile de telle sorte que le gaz contenant de l'hydrogène ait une vitesse d'écoulement moyenne du gaz de v (mm/s), et la poudre à base de fer atomisé est réduite par traitement thermique à l'intérieur du four à lit mobile et une poudre d'alliage d'acier pour la métallurgie des poudres est produite, et d et v satisfont à l'expression d/√v ≤ 3,2 (mm1/2∙s1/2).
PCT/JP2016/004119 2015-09-11 2016-09-09 Procédé de production de poudre d'alliage d'acier pour la métallurgie des poudres WO2017043090A1 (fr)

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JP2016575265A JP6112277B1 (ja) 2015-09-11 2016-09-09 粉末冶金用合金鋼粉の製造方法
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09170002A (ja) * 1995-10-19 1997-06-30 Kawasaki Steel Corp 鉄粉の仕上げ熱処理方法および仕上げ熱処理装置
JP2006016688A (ja) * 2004-05-31 2006-01-19 Jfe Steel Kk 鉄粉の仕上げ熱処理方法および装置

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09170002A (ja) * 1995-10-19 1997-06-30 Kawasaki Steel Corp 鉄粉の仕上げ熱処理方法および仕上げ熱処理装置
JP2006016688A (ja) * 2004-05-31 2006-01-19 Jfe Steel Kk 鉄粉の仕上げ熱処理方法および装置

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