Patent GB-911991-A (GB)
Title: Method of manufacture of homogeneous metal alloys or cermets
IPC: C22C1/10
Filed: 1959-01-17
Abstract: In the manufacture of homogenous metal alloys or cermets, a solution, or colloidal suspension, containing dissolved values of the metals required in the alloy or cermet is formed in aqueous nitric acid, sulphuric acid, aqueous ammonia or water and the solution or suspension is subjected in the form of droplets to a temperature above the dissociation temperature of the dissolved metal compounds for a period not exceeding 30 seconds; thereafter the molecular mixture so formed is reduced to an alloy or cermet. Decomposition is generally affected at 150 DEG -450 DEG C. and the product, if desired, may be further heated to remove any residue of the solvent and thereafter comminated before reduction to form the alloy or cermet, with, for example, hydrogen, methane, or a solid carbonaceous material.  According to Examples (1) iron filings and nickel shot were separately dissolved in nitric acid and thereafter mixed together with chromic oxide dissolved in water and the solution concentrated to raise its boiling point to 120 DEG C.  The resulting solution was fed dropwise on to a metal surface at 300 DEG C. and nitric acid recovered from the evolved gases.  The solid product was heated subsequently at 800 DEG C., ground in a mill, and reduced at 1250 DEG C. with dry hydrogen.  A stainless steel powder of spongy structure resulted which could be melted down in a zirconia crucible to form a stainless steel alloy free from carbon and silicon.  (2) A cermet containing alumina is formed by dissolving aluminium hydroxide in nitric acid and adding it to the solution of iron and nickel nitrates and chromium oxide of Example 1 and converting the mixed solution to a homogenous p  powder by feeding it dropwise to a metal surface maintained at 300 DEG C.  The dried product was reduced with water gas at 1000 DEG C. after which the powder was mixed with lamp black to reduce the remaining oxide and finally heated in hydrogen at 1150 DEG C.  The final powder obtained may be rolled into strips and sintered in conventional manner.  (3) Tungstic and molybdic acids were dissolved in aqueous ammonia in excess and the mixed solution was dropped on to a hot surface maintained at 150 DEG C. and left there for 30 seconds.  The molybdenum/tungsten mixed oxide formed was ground and reduced with hydrogen to form an alloy containing equal amounts of tungsten and molybdenum.  (4) An alloy containing 28,6% cobalt, 3,6% copper, 51,2% iron and 16,4% nickel was prepared by dissolving cobalt, copper, iron and nickel in excess nitric acid and feeding the solution dropwise to a surface maintained at 300 DEG C. The oxides were then heated at 800 DEG C. to remove residual oxides of nitrogen, and finally reduced at 900 DEG C. in hydrogen.  The alloy produced may be mixed with a 50% aluminium 50% iron alloy and heated at 875 DEG C. with hydrogen to produce an alloy containing 8% aluminium, 14% nickel, 24% cobalt, and 51% iron.  (5) A steel containing 97,75% Fe, 2% Ni and 0,25% Mo was prepared by evaporating a nitrate solution of the metals followed by reduction in hydrogen; the alloy obtained was mixed with 0,55 parts of lamp black and heated at 750 DEG C. under hydrogen to increase the tensile strength of the steel formed. (6) Iron oxide and titanium oxide were dissolved in excess sulphuric acid and the solution fed dropwise to a hot plate maintained at 450 DEG C.  The product was calcined at 800 DEG C. ground and reduced with hydrogen to obtain a ferro-titanium containing equal amounts of iron and titanium.  (8) Basic zirconium carbonate was dissolved in nitric acid and the solution added to a nitric acid solution of nickel oxide, copper and iron.  After concentration the combined solution was fed dropwise to a surface maintained at 350 DEG C. and the product was calcined at 800 DEG C. and reduced with hydrogen.  The product contained 60% Ni, 33% Cu, 7% Fe and 90% zirconium dioxide.  Further examples relate to the production of alloys containing 20% Co and 80% W, to the production of a 90% Cu, 10% Zn brass and to a 70% Fe, 20% Al ferro aluminium. Specification 477,617 is referred to.ALSO:In the manufacture of homogenous metal alloys a solution, or colloidal suspension, containing dissolved values of the metals required in the alloy or cement is formed in aqueous nitric acid, sulphuric acid, aqueous ammonia or water and the solution or suspension is subjected in the form of droplets to a temperature above the dissociation temperature of the dissolved metal compounds for a period not exceeding 30 seconds; thereafter the molecular mixture so formed is reduced to an alloy or cermet. Decomposition is generally affected at 100-450 DEG C. and the product, if desired, may be further heated to remove any residue of the solvent and thereafter comminuted before reduction to form the alloy, with for example hydrogen, methane, or a solid carbonaceous material.  According to examples: (1) iron filings and nickel shot were separately dissolved in nitric acid and thereafter mixed together with chromic oxide dissolved in water and the solution concentrated to raise its boiling point to 120 DEG  C.  The resulting solution was fed dropwise on to a metal surface at 300 DEG  C. and nitric acid recovered from the evolved gases.  The solid product was heated subsequently at 800 DEG  C. ground in a mill and reduced at 1250 DEG  C. with dry hydrogen.  A stainless steel powder of spongy structure resulted which could be melted down in a zirconia crucible to form a stainless steel alloy free from carbon and silicon.  (3) Tungstic and molybdic acids were dissolved in aqueous ammonia in excess and the mixed solution was dropped on to a hot surface maintained at 150 DEG  C. and left there for 30 seconds.  The molybdenum/tungsten mixed oxide formed was ground and reduced with hydrogen to form an alloy containing equal amounts of tungsten and molybdenum.  (4) An alloy containing 28.6% cobalt, 3.6% copper, 51.2% iron and 16.4% nickel was prepared by dissolving cobalt, copper iron and nickel in excess nitric acid and feeding the solution dropwise to a surface maintained at 300 DEG  C.  The oxides were then heated at 800 DEG  C. to remove residual oxides of nitrogen, and finally reduced at 900 DEG  C. in hydrogen. The alloy produced may be mixed with a 50% aluminium 50% iron alloy and heated at 875 DEG  C. with hydrogen to produce an alloy containing 8% aluminium, 14% nickel, 24% cobalt, and 51% iron. (5) A steel containing 97.75% Fe, 2% Ni and 0.25% Mo was prepared by evaporating a nitrate solution of the metals followed by reduction in hydrogen the alloy obtained was mixed with 0.55 parts of lamp black and heated at 750 DEG  C. under hydrogen to increase the tensile strength of the steel formed.  (6) Iron oxide and titanium oxide were dissolved in excess sulphuric acid and the solution fed dropwise to a hot plate maintained at 450 DEG  C.  The product was calcined at 800 DEG  C. ground and reduced with hydrogen to obtain a ferrotitanium containing equal amounts of iron and titanium.  Further examples relate to the production of alloys containing 20% Co and 80% W, to the production of a 90% Cu 10% Zn brass and to a 70% Fe 20% Al ferro aluminium.  Specification 477,617 is referred to.ALSO:In the manufacture of homogenous metal alloys or cermets, a solution, or colloidal suspension, containing dissolved values of the metals required in the alloy or cermet is formed in a gaseous nitric acid, sulphuric acid, aqueous ammonia or water and the solution or suspension is subjected in the form of droplets to a temperature above the dissociation temperature of the dissolved metal compounds for a period not exceeding 30 seconds; thereafter the molecular mixture so formed is reduced to an alloy or cermet. Decomposition is generally affected at 100-450 DEG C. and the product, if desired, may be further heated to remove any residue of the solvent and thereafter comminuted before reduction to form the alloy or cermet, with, for example, hydrogen, methane, or a solid carbonaceous material.  According to examples (1) iron filings and nickel shot were separately dissolved in nitric acid and thereafter mixed together with chromic oxide dissolved in water and the solution concentrated to raise its boiling point to 120 DEG C. The resulting solution was fed dropwise on to a metal surface at 300 DEG C. and nitric acid recovered from the evolved gases.  The solid product was heated subsequently at 800 DEG C. ground in a mill and reduced at 1250 DEG C. with dry hydrogen.  A stainless steel powder of spongy structure resulted which could be melted down in a zirconia crucible to form a stainless steel alloy free from carbon and silicon.  (2) A cermet containing alumina is formed by dissolving aluminium hydroxide in nitric acid and adding it to the solution of iron and nickel nitrates and chromium oxide of Example 1 and converting the mixed solution to a homogenous powder by feeding it dropwise to a metal surface maintained at 300 DEG C.  The dried product was reduced with water gas at 1000 DEG C. after which the powder was mixed with lamp black to reduce the remaining oxide and finally heated in hydrogen at 1150 DEG C.  The final powder obtained may be rolled into strips and sintered in conventional manner.  (3) Tungstic and molybdic acids were dissolved in aqueous ammonia in excess and the mixed solution was dropped on to a hot surface maintained at 150 DEG C. and left there for 30 seconds.  The molybdenum/tungsten mixed oxide formed was ground and reduced with hydrogen to form an alloy containing equal amounts of tungsten and molybdenum.  (4) An alloy containing 28,6% cobalt, 3,6% copper, 51,2% iron and 16,4% nickel was prepared by dissolving cobalt, copper iron and nickel in excess nitric acid and feeding the solution dropwise to a surface maintained at 300 DEG C. The oxides were then heated at 800 DEG C. to remove residual oxides of nitrogen