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
  • 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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/4998—Combined manufacture including applying or shaping of fluent material
  • Y10T29/49982—Coating

Definitions

• Nickel coated steel strip having a sound dense nickel coating is produced by applying to the surface of steel strip an aqueous slurry containing nickel powder, drying the slurry, warm working the dried layer at a temperature between about 200 C. and 650 C., annealing the warm worked strip at about 600 C. to about 700 C. and cold rolling the annealed strip to achieve final densification of the coating.
• the present invention is directed to an improved and economical method for producing sound, dense coatings on steel, and more particularly, to a special method for producing nickel coatings of good quality on flat steel products using nickel powder as the source of nickel wherein a major amount of the processing is conducted at relatively low temperature.
• This process as described comprises in effect four steps, namely, sintering, cold rolling, further sintering and further cold rolling.
• a layer of aqueous slurry containing nickel powder is applied to the strip, the slurry layer is dried, the dried layer is compacted by rolling the strip at an elevated temperature but below the sintering temperature of the layer, the coated strip is annealed and then subjected to cold rolling to achieve the final densification of the coating.
• the special step of compacting the dried layer by rolling at a temperature below the sintering temperature may conveniently be called warm compaction.
• sintering of fine nickel powder occurs at temperatures of about 700 C. and above, so that the warm compaction is carried out at temperatures below this.
• the actual temperature used may be quite low, say no more than 200 C., but is preferably somewhat higher than this. Above 500 C., however, oxidation will occur in air and at this temperature or above the warm compaction must be eflected in a protective or reducing atmosphere.
• a suitable range of temperature for the warm compaction in which the operation may be conducted in air is from 200 C. to 450 C.
• the powder particles e.g., carbonyl nickel powder having a particle size of about 3 to 7 microns
• the pressure required depends on the thickness of the strip and the size of the rolls, varying substantially in accordance with the square root of both the strip thickness and the roll diameter, and can easily be determined by test.
• Coated steel strip prepared according to this invention has good corrosion resistant properties. It is, however, found that these properties may be improved still further if the strip bearing the dried slurry layer is heated to a temperature in the range 500 C. to 650 C., that is to say, as high as possible but below the sintering temperature of the dried layer before the warm compaction step.
• the cold rollin of the coated strip may be carried out if desired in two or more stages, the coated strip being annealed between each cold rolling.
• the coating In a first stage, for example, the coating may be compacted to to 85% of the theoretical maximum density, and in a second stage to the maximum density, that is, all porosity is eliminated.
• the step of cold rolling inevitably introduces stresses into the surface coating of the strip, and it is well known that a stressed material is more prone to corrosion attack than an unstressed one. It is therefore preferred to sub ject the coated steel strip to a final annealing step to relieve any stresses in the coating and thereby further enhance the corrosion resistance of the coated strip.
• the aqueous slurry may contain about 45% to about by weight, of fine nickel powder having a particle size of about 2 to about 10 microns and up to about 10% by volume of inert particles such as alumina or thoria having a particle size of about 0.01 micron to about 50 microns.
• the slurry may contain about 0.1% to about 5%, by weight, of a heat-volatilizable organic binder such as methyl cellulose and a wetting agent.
• the slurry must first be dried at low temperature and it is important not to boil it during the drying.
• the slurry will contain a binder, not only to bind the nickel powder in the layer of slurry formed on the strip but also to aid in suspending the powder in the slurry, and this binder may suitably be a methyl cellulose. If methyl cellulose is present in the slurry, then the dried layer of slurry on the strip must be heated to drive it off. This may be done in the course of warming the strip prior to the warm compaction step, a temperature of from 250 C. to 450 C.
• Annealing of the coated strip is preferably carried out in the range 600 C. to 700 C., that is to say, below the temperature at which significant sintering will occur. Annealing may be carried out at higher temperatures, for example, up to 800 C., but then sintering will also occur, and the economic advantages of working at the lower temperatures will be lost.
• Example I, II and III illustrate the invention in its widest terms
• Example IV illustrates the preferred embodiment of the invention in which the strip bearing the dried slurry layer is subjected to a temperature in the range 500 C. to 650 C. before warm compaction.
• Alkoxylated polyethylene glycol surfactant Alkoxylated polyethylene glycol surfactant.
• the bulk density of the nickel powder was 1.8 grams per cubic centimeter and the particle size from 3 to 4 microns.
• the slurry was applied to a degreased cold rolled annealed mild steel strip 3 inches wide and 0.062 inch thick to form a layer approximately 0.009 inch thick.
• the coated strip was dried at about 60 C. in air, heated for five minutes to a temperature of 380 C. in a reducing atmosphere of cracked ammonia and then warm compacted by rollingin air between rolls adjacent to the furnace. It is found that there is a temperature drop from C. to C. during the transfer from the furnace to the rolls, so the actual rolling temperature was between 360 C. and 370 C.
• the roll diameter was 8 inches and the load applied to the rolls was approximately 8.5 tons per inch width of the strip.
• the compacted strip was then annealed for one hour at 700 C. in cracked ammonia, allowed to cool and then cold rolled to 0.030 inch thick.
• a sample of the coated strip was immersed in boiling water for six hours; the coating was substantially impermeable, showing negligible porosity.
• EXAMPLE II A creamy slurry was prepared having the following composition, the methyl cellulose, nickel powder and surfactant being the same as those used in Example I.
• the slurry was sprayed onto three samples of cold rolled annealed steel strip 3 inches wide and 0.062 inch thick to give a layer 0.012 to 0.013 inch thick.
• the strips were then dried in air, heated to 381 C. to 385 C. in cracked ammonia, and warm compacted by rolling in air between rolls adjacent to the furnace as in Example I.
• the rolling loads were between 7.07 and 7.66 tons per inch width of the strip.
• the compacted strips were then annealed for 1 hour at 700 C. in cracked ammonia, allowed to cool, and cold rolled to 50% of their thickness using white spirit as lubricant.
• the strips were electroplated in conventional manner with 10 microinches of chromium, and subjected to the copper accelerated Acetic Acid Salt Spray Test (see British Standard 1224:1965, Appendix F). After 16 hours exposure, specimens of all three strips had protection ratings of 9, expressed according to the ratings given by Bigge in Plating, Volume 47, part 2, page 1263.
• the nickel powder had a bulk density of 1.8 grams per cubic centimeter and an average particle size of 3 microns to 4 microns.
• This slurry was applied by the curtain coating technique, this is to say, by allowing the slurry to run over a weir onto the strip below, to hot rolled steel strip four inches wide and 0.056 inch thick previously pickled in 10% HNO to remove any scale.
• the thickness of the layer of slurry was 0.014 to 0.015 inch.
• the strip was dried in air, heated to 419 C. in cracked ammonia, transferred to rolls adjacent to the furnace as in Example I, and warm compacted in air. The rolling load was about 9.2 tons per inch widh of the strip. Subsequently, the strip was annealed for 1 hour at 700 C. in cracked ammonia, allowed to cool, and then reduced in thickness by 50% by cold rolling using white spirit as lubricant.
• the strip was electroplated in conventional manner with 10 microinches of chromium, and subjected to the CASS Test as in Example II. After 16 hours exposure, the sample of strip tested had a protection rating of 9.
• Methyl cellulose powder solid under the trade mark Celacol M20
• Carbonyl Nickel powder grams 237.5 Supronic B 75 milliliter 0.75
• the slurry was applied to two samples of cold rolled and annealed steel strip 3 inches wide and 0.062 inch thick which had previously been degreased, pickled in 10% HNO for 30 seconds and then rinsed.
• the object of pickling the strip was to roughen its surface, and, hence, to increase the adhesion of the nickel coating to be formed on it. After drying in air at about 60 C., the thickness of the resulting layer was 0.017 to 0.019 inch.
• the samples were then heated in cracked ammonia to a temperature of 600 -5 C., over a period of 10 minutes and then allowed to cool to 410 C., transferred ,to a rolling mill with 8 inch diameter rolls and compacted in air under rolling loads of 8.8 and 10.1 tons per inch, respectively, at a rate of 10 feet per minute.
• the compacted strips were then annealed for 1 hour at 700 C. in cracked ammonia, and cold rolled with the use of white spirit as a lubricant to reduce their thickness by 50%.
• the invention may also be used for the production of coatings of nickel and copper, or nickel and tin, by altering the composition of the slurry to include copper or tin powders therein.
• Inert electrically non-conductive particles such as alumina or thoria may be included in the initial nickel-containing slurry and chromium deposited on nickel coatings thus produced is of the micro-cracked type.
• the initial steel strip may be coated with copper or tin as by an electrolytic process and adherence of the nickel coating to the steel is thereby facilitated.
• a method of forming a corrosion resistant coating on steel strip comprising applying a layer of an aqueous slurry containing fine nickel powder to the strip, drying the slurry layer, compacting the dried layer by warm rolling the strip at an elevated temperature between about 200 C. and 650 C,, annealing the coated strip and densifying the coating by cold rolling.
• inert particles are of thoria or alumina in the size range of 0.01 to microns.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Composite Materials (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Powder Metallurgy (AREA)
• Laminated Bodies (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Metal Rolling (AREA)
• Chemically Coating (AREA)

Applications Claiming Priority (2)

Publications (1)

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Citations (7)

Family Cites Families (1)

• 0
  • FR FR90246D patent/FR90246E/fr not_active Expired
• 1965
  • 1965-07-01 GB GB27925/65A patent/GB1087580A/en not_active Expired
• 1966
  • 1966-06-27 US US560893A patent/US3479258A/en not_active Expired - Lifetime
  • 1966-06-29 AT AT619966A patent/AT263476B/de active
  • 1966-06-29 LU LU51437A patent/LU51437A1/xx unknown
  • 1966-06-30 SE SE8930/66A patent/SE322670B/xx unknown
  • 1966-06-30 ES ES0328537A patent/ES328537A2/es not_active Expired
  • 1966-06-30 DE DE19661533015 patent/DE1533015B1/de not_active Withdrawn
  • 1966-07-01 NL NL6609207A patent/NL6609207A/xx unknown
  • 1966-07-01 BE BE683540D patent/BE683540A/xx unknown

Patent Citations (7)

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