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
  • C23C8/06—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 gases
  • C23C8/28—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 gases more than one element being applied in one step
  • C23C8/30—Carbo-nitriding
• • 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
  • C23C8/06—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 gases
  • C23C8/08—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 gases only one element being applied
  • C23C8/20—Carburising

Definitions

• the invention relates to a method and a device for the heat treatment of workpieces, the workpieces being heated with radiant heat which is produced by burning gaseous fuel, in particular natural gas, and wherein at least some of the workpieces are provided with a
• the invention is based, the
• the method is according to
• Hydrocarbon-containing gas in particular with natural gas, is mixed and that the gas mixture for generating the
• Carburizing atmosphere is heated.
• the environmental impact is reduced considerably.
• the proportion of carbon dioxide in the flue gas is approximately 11%. Most of this can be separated from this.
• the residual flue gas contains only less than 1% carbon dioxide after the treatment.
• the carbon dioxide is supplied to the carburizing process as an oxygen and carbon supplier, with the effect that that the carburizing time is reduced significantly, namely by 20 to 40%.
• the carburizing time depends on the temperature, the diffusion coefficient and the
• the invention has a particularly favorable effect in this area. It leads to an increase in
• Mass transfer coefficients about a factor of 2.5.
• a particular advantage of the invention is that the entire process can be carried out continuously, with the possibility, where appropriate, of the separated carbon dioxide
• the carburizing atmosphere is created by an endothermic reaction.
• the heat required for this is preferably taken from the radiant heat used to heat the workpieces. This can be done, for example, by introducing the mixture of carbon dioxide and hydrocarbon-containing gas directly into the furnace chamber. However, there is a risk that inadmissible soot formation will occur. It may therefore be more advantageous to use a gas mixture
• the endogas generator can be arranged outside the furnace chamber. However, this is usually a separate one
• This process uses the pressure-dependent Accumulation properties of carbon dioxide, for example on molecular sieves. It can be integrated into the continuous process without problems and is economically advantageous.
• the carburization reaction produces carbon dioxide and
• the slow-reacting methane which is preferably made available in the form of natural gas, is able to buffer the products of the carburization reaction and prevent it from oxidizing the material. At the same time, it is ensured that the carbon level in the
• the residual flue gas of the radiant heating remaining after the removal of the carbon dioxide can be used as a purge gas, for example for inerting locks.
• this residual flue gas for nitro-carburizing part of the workpieces, with the addition of ammonia. It is usually common to use nitro-carburizing in addition to ammonia, which is commercially available, and commercially available carbon dioxide. According to the invention, the latter two components are supplied by the residual flue gas. This leads to an additional increase in
• the invention also provides an apparatus for
• Heat treatment of workpieces with at least one furnace chamber, which is provided with gas-operated radiant tubes, and with a generator for generating carburizing gas for the
• Furnace chamber this device being characterized in that the radiant heating pipes are connected with their flue gas lines to a pressure change device and in that the
• Pressure change device with its carbon dioxide outlet line is connected to the generator.
• the pressure change device separates carbon dioxide from the flue gas of the radiant tubes, whereupon the carbon dioxide as oxygen and
• Carbon supplier enters the generator in order to react endothermically with a gas containing hydrocarbons, preferably natural gas.
• the generator is for heating it
• a common control system ensures that the individual processes are synchronized and synchronized
• gas-operated radiant heating pipes will generally also be used. It is then particularly advantageous to also connect their flue gas lines to the pressure change device, so that the flue gas is subjected to the same treatment as the flue gas of the radiant heating pipes operating in the carburizing chamber. Combinations of the features according to the invention that differ from the links discussed above are also considered to be disclosed as essential to the invention.
• the device has a first furnace chamber 1, which is used for carburizing workpieces 2 and
• gas-powered radiant tubes 3 is heated.
• the latter are connected via their flue gas lines 4 to a pressure change device 5.
• carbon dioxide is separated from the flue gas of the radiant heating tubes 3.
• the carbon dioxide passes through an outlet line 6 to a generator 7, which is also fed with natural gas via a line 8. Since the generator 7 is located inside the furnace chamber, it is heated by the radiant heating tubes 3. In the generator 7, the natural gas reacts with the carbon dioxide. The endogas generated thereby enters the furnace chamber 1 and there causes the carburizing reaction on the workpieces 2.
• Radiant heating tubes 3 freed of carbon dioxide. This results in a reduction in environmental pollution.
• the carbon dioxide is used to generate the endogas, with a substantial increase in the carburizing rate being achieved by increasing the mass transfer coefficient. This increases the profitability of the carburizing process.
• the device also has a second
• Furnace chamber 10 which is used for nitro-carburizing workpieces 11.
• the second furnace chamber is heated via Radiant heating tubes 12. These are also connected to the pressure change device 5 with their flue gas lines 13.
• the pressure change device 5 has an outlet line 14 which serves to introduce the residual flue gas from the radiant heating pipes 3 and 12 into the second furnace chamber.
• the remaining flue gas still contains a portion of carbon dioxide and a portion of nitrogen.
• ammonia which is supplied via a line 15, the residual flue gas forms the
• a control not shown, ensures that the carbon dioxide content of the flue gases in the pressure change device is distributed to the furnace chambers 1 and 10 in accordance with the respective requirements. Furthermore, the control causes one
• Oven chamber 10 can be dispensed with. Instead, the residual flue gas coming from the pressure change device 5 can be used
• the generator 7 can be arranged outside the furnace chamber 1, but additional heating is then required.
• the generator 7 can also be used entirely

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
• Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
• Processing Of Solid Wastes (AREA)
• Incineration Of Waste (AREA)
• Heat Treatments In General, Especially Conveying And Cooling (AREA)

Applications Claiming Priority (3)

Publications (2)

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Family Applications (1)

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• 1993
  • 1993-06-03 DE DE4318400A patent/DE4318400C1/de not_active Expired - Fee Related
• 1994
  • 1994-05-13 DE DE59405801T patent/DE59405801D1/de not_active Expired - Fee Related
  • 1994-05-13 WO PCT/EP1994/001542 patent/WO1994029491A1/fr not_active Ceased
  • 1994-05-13 EP EP94917627A patent/EP0703994B1/fr not_active Expired - Lifetime
  • 1994-05-13 AT AT94917627T patent/ATE165399T1/de not_active IP Right Cessation
  • 1994-05-13 US US08/553,710 patent/US5830284A/en not_active Expired - Fee Related
  • 1994-05-13 JP JP7501232A patent/JPH08511063A/ja active Pending

Non-Patent Citations (1)

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