Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
  • C22C33/0207—Using a mixture of prealloyed powders or a master alloy
  • C22C33/0228—Using a mixture of prealloyed powders or a master alloy comprising other non-metallic compounds or more than 5% of graphite
• • 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
  • B22F1/12—Metallic powder containing non-metallic particles
• • 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
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/02—Compacting only
  • B22F3/03—Press-moulding apparatus therefor
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
• • 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
  • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Definitions

• Powder metallurgical composition comprising carbon black as flow enhancing agent.
• the invention relates to iron-based powder metallurgical compositions . More particularly, the present invention relates to compositions containing flow agents to improve flowability, but also to improve apparent density.
• Powder metallurgical compositions are well known for the production of powder metallurgical parts.
• Production of powder metallurgical parts involves filling of the powder in a compaction tool, compaction of the powder and subseguent sintering of the compacted body.
• a prerequisite for filling of the powder is that the powder is free-flowing and has a sufficient flow.
• a high flow rate of the powder is essential to obtain a high production rate giving lower production costs and a better economy for each part produced.
• Apparent density is essential for the tool design. Powder with low apparent density needs higher filling height which results in unnecessarily high pressing tools, and this in turn will result in longer compaction strokes and lower pressing performances.
• compositions contain an iron or iron-based powder and a lubricant.
• the compositions may also include a binding agent, graphite and other alloying elements.
• Hard phase material, liquid phase forming material and machinability enhancing agents may also be included.
• the iron-based powder may be of any type of iron-based powder such as water-atomised iron powder, reduced iron powder, pre-alloyed iron-based powder or diffusion alloyed iron-based powder.
• Such powders are e.g. the iron powder ASClOO.29, the diffusion alloyed iron-based powder Distaloy AB containing Cu, Ni and Mo, the iron-based powder Astaloy CrM and Astaloy CrL pre-alloyed with Cr and Mo, all available from H ⁇ ganas AB, Sweden.
• the amount of carbon black in the iron-based powder composition according to the invention is between 0.001 and 0.2% by weight, preferably between 0.01 and 0.1%.
• the primary particle size of the carbon black is preferably below 200 nm, more preferably below 100 nm and most preferably below 50 nm.
• the specific surface area is in a preferred embodiment between 150 and 1000 m 2 /g measured by the BET-method. However, other types of carbon black having other surface areas and primary particle sizes are possible to use.
• Carbon black is normally used as filler in rubber material and as colour pigments. It is also used for its electrical conductivity, in products for reducing static electricity. Carbon black in combination with iron or iron-based powders is disclosed in US patent 6 602 315. This patent discloses a composition wherein an alloying powder is bound to an iron-based powder by binder, to which carbon black may be added. US 6 602 315 does not disclose any content, particle size or effect of carbon black and is only relevant to the binding material. Also in patent application JP 7-157838 a powder composition containing carbon black is disclosed. Here the purpose of carbon black is to deoxidize a base-material.
• compositions according to the present invention may also include alloying elements chosen from the group consisting of graphite, Cu, Ni, Cr, Mn, Si, V, Mo, P, W, S and Nb
• a lubricant or a combination of different lubricants may be added to the powder metallurgical composition.
• the lubricant may be present as a particulate powder or bonded to the surface of the iron-based powder.
• the binder may also be added in its natural liquid state with a capacity of forming a film around the iron-based powder.
• Another alternative is to use the lubricants as binding agents by heating the composition above the melting point of the lubricant or above the melting point of at least one of the lubricant components followed by cooling the composition to a temperature below the melting point.
• the lubricants may be selected from the group consisting of fatty acids, amide waxes such as ethylene bisstearamide (EBS), or other derivates of fatty acids such as metal stearates, polyalkylenes such as polyethylene, polyglycols, amide polymers, or amide oligomers .
• EBS ethylene bisstearamide
• polyalkylenes such as polyethylene, polyglycols, amide polymers, or amide oligomers
• the lubricants are selected from the group consisting of polyalkylenes, amide waxes, amide polymers or amide oligomers .
• binders are selected from the group consisting of cellulose ester resins, high molecular weight thermoplastic phenolic resins, hydroxyalkylcellulose resins, and mixtures thereof.
• binders are selected from the group of cellulose ester resins and hydroxyalkylcellulose resins.
• machinability improving agents hard phase material and liquid phase forming agent.
• carbon black is used as flow agent in bonded mixtures, i.e. mixtures, wherein finer powder of e.g. alloying element particles are bonded by means of a binding agent to the surface of the iron or iron-based powder particles, as these mixtures often have poor flow properties.
• carbon black is preferably added after the binding operation has been effectuated.
• the binding operation may be accomplished by heating the mixture during mixing to a temperature above the melting point of the binding agent and cooling the mixture until the binder has solidified.
• the binder may also be added dissolved in a solvent.
• the binding operation is in this case accomplished by evaporating the solvent by means of heating or by vacuum.
• the composition is compacted and sintered to obtain the final powder metal part.
• the specific surface area was determined by the BET- method.
• the particle size was measured by electron microscopy and refers to the primary particle size of the carbon black.
• Iron-base powder ASClOO.29 available from Hoganas AB,
• Powder properties were measured. Flow property was measured using the standard method, Hall-flow cup according to ISO 4490 and the apparent density, AD, was measured using standard method ISO 3923.
• Carbon black type CB 1 was selected in order to determine the optimal added amount to the iron-based powder mixture.
• the mixtures were prepared according to the description of example 1. Added amounts of alloying elements, binder/lubricant, flow agent and graphite are shown in table 3.
• Test pieces according to ISO 2740 were compacted at a pressure of 600 MPa at ambient temperature and sintered at 112O 0 C in an 90/10 N 2 /H 2 atmosphere.
• table 4 the mechanical properties are presented for the powder compositions according to table 3.
• Example 3 shows that the new flow agent can be used in compositions for warm compaction.
• One test mixture, B5, and one reference mixture, R3, of 3 000 grams, respectively, were prepared as follows.
• Example 4 shows that the new flow agent can be used in combination with different iron-based powders.
• the mixtures were prepared according to the method of example 1 and the same binder/lubricant system as in example 1 was used.
• the iron-based powder used and amount of additives are shown in table 6.
• the identifications RA, RB, RC, RE and RF indicate that the mixtures are reference mixtures containing 0.06% flow agent Aerosil A- 200, available from Degussa AG.
• the identifications C, E, and F indicate that the mixtures are reference mixtures without any flow agents. Carbon black CBl was used in all mixtures.
• the iron or iron-based powder used were:
• Distaloy AB a diffusion alloyed iron-based powder containing Cu, Ni and Mo from H ⁇ ganas AB.
• Astaloy CrM a pre-alloyed iron-based powder containing
• Astaloy CrL a pre-alloyed iron-based powder containing
• the powder properties of the powder mixtures were measured. Test pieces according to ISO 2740 were compacted at a pressure of 600 MPa at ambient temperature and sintered at 1120 °C 90/10 N 2 /H 2 atmosphere. Mechanical properties such as green strength, GS, dimensional changes, DC, as well as sintered density, SD, were determined and the results are presented in table 7.
• Table 7 shows that carbon black gives improved flow, AD and green strength in mixtures having different base powders compared to mixtures containing a known flow agent.
• Example 5 shows that the new flow agent also improves flow of a plain mixture without any binding agents (not bonded mixture) .
• Three mixtures containing the iron powder ASClOO.29, 2 % of a copper powder, 0.5 % of graphite, 0.8% of ethylene bisstearamide as lubricant and different amounts of carbon black, CBl, according to table 8 were prepared. A mixture without any carbon black was used as reference mixture. The flow rate was measured on the different mixtures. Table 8

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Powder Metallurgy (AREA)
• Treatment Of Steel In Its Molten State (AREA)
• Lubricants (AREA)
• Catalysts (AREA)
• Ceramic Products (AREA)

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• 2004
  • 2004-07-02 SE SE0401778A patent/SE0401778D0/xx unknown
• 2005
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  • 2005-07-01 RU RU2007104034/02A patent/RU2348486C2/ru not_active IP Right Cessation
  • 2005-07-01 AT AT05756261T patent/ATE531467T1/de active
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