Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/40—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions
  • C23C8/42—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions only one element being applied
  • C23C8/44—Carburising
  • C23C8/46—Carburising of ferrous surfaces

Definitions

• the replenishing material is a mixture of activator and cyanide salt only, wherein the activator cyanide salt proportion is identical to that of the starting salt.
• This invention relates to the process of carburizing metals by means of molten cyanide baths containing activators.
• the invention relates more specifically to novel replenishing-salts and novel replenishing steps in the process as a whole.
• the present practice prior to the invention is for the workmen to add to the bath a desired quantity of cyanide salt from a stock of same, and add also a desired or specifiedquantity of the activator, also from a stock of the same.
• the salt for the latter baths contains both cyanide and activator, but also contains diluents such as alkaline chlorides or carbonates.
• the activator content of this premixed salt is not equal to the activator content to be maintained in the bath, so that with such baths it is not possible to produce and maintain over long periods, an exact predetermined surface carbon content.
• this invention airns in the direction of providing a more exact control of the bath and particularly of the replenishing step and materials, with the view of eliminating mistakes and errors as much as possible and to make the replenishing operation as exact and foolproof as possible.
• the first aspect of the improved replenishing method and material is that the replenishing salt is supplied by a single stock of material so that it was not necessary for the workmen to obtain replenishing materials from two stocks and to mix them.
• the first aspect of the novel replenishing salt is that it is a premix of the cyanide salt and the activator in predetermined proportions from which the workman merely draws as much as needed for replenishing.
• the single replenishing premix includes both the activator and the cyanide salt.
• the second aspect is based upon the knowledge that it is only the cyanide salt that is consumed by decomposition during carburizing. We are not speaking here of reduction of liquid level due to drag out losses but rather a change in the proportions of cyanide salt and activator that occurs during the use of the process.
• the replenishing salt of the invention is made up of the activator and cyanide'salt but the novel aspect is that the percentage of activator with respect to the cyanide salt is exactly the same as the percentages of these two ingredients at the start of the carburizing operation and before decomposition of the cyanide salt.
• the novel replenishing salt includes only cyanide salt and activator and these are in the proportions of the same two ingredients at the start of the operation. This novel salt then for replenishing, maintains the bath in such a state that it returns the bath into the state desired to establish the desired carbon potential.
• the bath At the end of the specific period of operation, let us say one day, the bathis found to have its cyanide content reduced to 7 percent and the carbonate content increased to 73 percent but the activator content is the same 20 percent.
• the constancy of carbon potential of a bath can be predetermined and maintained by insuring a con stant prefixed level of the activator
• the constancy of the activator can be maintained by using as a replenishing salt, a premix containing cyanide but whose activator content is exactly the same as the activator content originally desired for the bath.
• replenishing salt which is used to offset chemical deterioration.
• This replenishing salt would be without carbonate and would be 20 percent activator and 80 percent cyanide salt in the example given.
• ADVANTAGES A. Salt consumption was reduced over a long time by the use of a premix formula. There was no tendency to add excess salt either by error or inexperience or guesswork and personal variations and human errors did not affect the replenishing operation and consequently there was no tendency to use more salt than was actually required for replenishing.
• a molten cyanide salt carburizing process employing a bath of the molten cyanide salt and an activator of the group consisting of barium chloride and strontium chloride; and wherein the bath at starting of a first period of operation, has a predetermined ratio of activator to cyanide salt; and,
• the bath at the end of that first period of operation, has the same amount of activator, plus a reduced but satisfactory amount of cyanide and an amount of carbonate formed by decomposition of the cyanide;
• the bath at the end of a second period of operation has the same amount of activator, plus a further reduced and now unsatisfactory amount of cyanide and an increased amount of carbonate; and requires restoration to make up for the loss of cyanide in such second period of operation;
• the step of restoring the bath after the second period of operation by adding a restoration salt premix of the cyanide salt and the activator, wherein the activator-cyanide salt proportion is identical to that at the start of the first period of operation; and without carbonate.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Cosmetics (AREA)
• Chemically Coating (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=25230518

Family Applications (1)

Country Status (10)

Cited By (1)

Citations (3)

• 1969
  • 1969-04-29 US US820337A patent/US3635768A/en not_active Expired - Lifetime
• 1970
  • 1970-04-17 AT AT350670A patent/AT300874B/de active
  • 1970-04-18 DE DE2018711A patent/DE2018711C3/de not_active Expired
  • 1970-04-22 CH CH598670A patent/CH534219A/de not_active IP Right Cessation
  • 1970-04-28 SE SE05889/70A patent/SE358421B/xx unknown
  • 1970-04-28 ES ES379136A patent/ES379136A1/es not_active Expired
  • 1970-04-29 CA CA081411A patent/CA928621A/en not_active Expired
  • 1970-04-29 FR FR7015745A patent/FR2040405A1/fr active Pending
  • 1970-04-29 GB GB2053170A patent/GB1312982A/en not_active Expired
  • 1970-04-30 JP JP3713570A patent/JPS5440493B1/ja active Pending

Patent Citations (3)

Non-Patent Citations (2)

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