Classifications

• • 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
  • B22F3/18—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces by using pressure rollers
• • 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
  • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
• • 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
  • B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
  • B22F5/006—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of flat products, e.g. sheets
• • 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
  • B22F7/00—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
  • B22F7/02—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite layers
  • B22F7/04—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite layers with one or more layers not made from powder, e.g. made from solid metal
• • 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
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
  • B22F2998/10—Processes characterised by the sequence of their steps

Definitions

• This invention relates to a process for the production of metal strip from powdered metal which is particularly, but not exclusively, applicable to the production of steel strip.
• This process basically comprises the steps of forming a slurry comprising a suspension of a metal powder in a binder composition, depositing on a support surface, such as a metal band or drum, a coating of the slurry to form, after any necessary drying, a self-supporting metal powder/binder strip, removing the strip from the support surface and rolling it to effect compaction and thereafter sintering the compacted strip in a reducing atmosphere at a temperature below the melting point of the metal.
• a support surface such as a metal band or drum
• Water-based binder compositions are preferred for a variety of reasons including economy and absence of fire hazard and film-forming cellulose derivatives have been found to generally meet the requirements of suitable film-forming materials for formulation of the binder compositions.
• the metal powder/binder strip obtained by deposition and drying of the slurry should possess sufficient strength and flexibility to withstand mechanical handling before the first compaction step in which the metal particles are cold-welded and inter-locked.
• the preferred binders are film-forming, watersoluble cellulose ethers, particularly those containing methyl groups, e.g. methyl cellulose, since metal powder/binder strip of good strength and flexibility can be formed from binder compositions based on these cellulose ethers.
• a process for the production of strip from powdered metal which comprises depositing on a support surface a coating of a slurry comprising a suspension of powdered metal in a binder composition containing a hygroscopic substance, drying the coating on the support surface, rolling the dried coating to effect compaction and sintering the compacted coating at a temperature below the melting point of the metal.
• the process is generally carried out by application of the slurry of powdered metal and binder to a moving belt or drum, for example by roller coating.
• the metal powder/binder strip is removed from the belt or drum, compacted by rolling and then subjected to a first sintering step.
• the hygroscopic substance is conveniently added to the binder composition prior to dispersing the powdered metal therein.
• the binder composition may be added to the water before or after the addition of the cellulose derivative.
• the powdered metal is then stirred into the resultant binder composition.
• the hygroscopic substance should, of course. be compatible with the binder.
• the hygroscopic substance is a water-soluble polyhydroxy compound such as glycerol, low molecular weight polyalkylene glycols, e.g. trimethylene glycol, polyhydric alcohols, e.g. sorbitol, mannitol, and sugars, e.g. invert sugar, Inorganic hygroscopic material may also be used, e.g. calcium chloride.
• the hygroscopic substance is preferably present in an amount of up to 1 percent by weight of the suspension. It is found that if substantially larger proportions of hygroscopic substance are employed, too much water tends to be retained in the cellulose derivative during the slurry drying and this causes difficulties in the subsequent processing steps.
• a self-supporting strip is produced in the manner described in our above co-pending application and the subsequent steps of the process are carried out in the manner described in that application.
• An aqueous methyl cellulose solution was formed by dissolving 0.6 parts by weight of methyl cellulose in 30 parts by weight of water.
• 0.1 parts by weight of the sodium salt of an aliphatic dicarboxylic acid and 0.1 parts by weight of a polyoxylated polyalkylene glycol sold under the Trade Mark Supronic were incorporated in the methyl cellulose solution, the former additive being a corrosion inhibitor and the latter a surface-active agent.
• a series of binder compositions were prepared by dissolving various quantities of glycerol in samples of the methyl cellulose solution.
• test strips were then made by the following steps:
• Hoganas iron powder is made by the direct reduction of high grade magnetic ore.
• the powder particles are irregular in shape and compact well to give good green" strength.
• the powder contains certain impurities especially silica, discrete particles of oxides and surface oxides and these impurities do tend to have a deleterious effect on the mechanical properties of strip made from Hoganas powder.
• Makin iron powder is made from molten high grade pig iron or scrap by water atomisation, followed by crushing and heat treatment. This gives an iron powder which is feathery and ragged in shape. The powder tends to be a little more pure than Hoganas powder.
• Sintrex powder is produced by the electrolytic deposition of iron. The powder is dendritic in shape and of high purity which gives excellent green strength and sintered properties. It is, however, rather more expensive than Hoganas or Makin powders.
• the effect of the presence of the glycerol is to produce a significant improvement in the ultimate tensile strength of the finished strip and more important this is accompanied by a substantial improvement in the percentage elongation of the final strip, this demonstrating greatly improved ductility.
• Glycerol and the other organic hygroscopic substances mentioned above are preferably used in the practice of the present invention because their use results in the development of improved mechanical properties in the final strip as demonstrated b the above tests.
• thermogelling property An important feature of solutions of certain cellulose ethers (e.g. methyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose) is their thermogelling property.
• a slurry containing a solution of methyl cellulose is heated to above approximately 50 C., thermogelling occurs which prevents settling out of the metal powders.
• thermogelling occurs which prevents settling out of the metal powders.
• slurry drying above the gel temperature results in more flexible dried metal powder/binder strip because of the homogenous distribution of the metal powder.
• a process for the continuous production of a strip from powdered metal which. comprises:
• a coating of a slurry comprising a suspension of powdered metal in a binder composition containing a film-forming cellulose derivative as the binder, and a hygroscopic substance compatible with said binder, said hygroscopic substance selected from the group consisting of low molecular weight polyalkylene glycols, polyhydric alcohols, sugars, and calcium chloride,
• non-ionic surface-active agent is a polyoxyalkylene glycol.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Composite Materials (AREA)
• Materials Engineering (AREA)
• Powder Metallurgy (AREA)

Applications Claiming Priority (1)

Publications (1)

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ID=10005460

Family Applications (1)

Country Status (9)

Cited By (10)

Families Citing this family (3)

Citations (2)

• 1968
  • 1968-03-14 GB GB1248468A patent/GB1257032A/en not_active Expired
• 1969
  • 1969-03-12 FR FR6906903A patent/FR2003864A1/fr active Pending
  • 1969-03-12 NL NL6903838A patent/NL6903838A/xx not_active Application Discontinuation
  • 1969-03-13 LU LU58200D patent/LU58200A1/xx unknown
  • 1969-03-13 ES ES364747A patent/ES364747A1/es not_active Expired
  • 1969-03-13 US US807101A patent/US3653884A/en not_active Expired - Lifetime
  • 1969-03-13 SE SE03473/69A patent/SE335904B/xx unknown
  • 1969-03-13 BE BE729811D patent/BE729811A/xx not_active IP Right Cessation
  • 1969-03-14 AT AT250069A patent/AT290864B/de not_active IP Right Cessation

Patent Citations (2)

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