EP0031034B1 - Procédé de carburation réglable ou chauffage sous gaz protecteur de pièces à usiner en acier - Google Patents

Procédé de carburation réglable ou chauffage sous gaz protecteur de pièces à usiner en acier Download PDF

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Publication number
EP0031034B1
EP0031034B1 EP80107178A EP80107178A EP0031034B1 EP 0031034 B1 EP0031034 B1 EP 0031034B1 EP 80107178 A EP80107178 A EP 80107178A EP 80107178 A EP80107178 A EP 80107178A EP 0031034 B1 EP0031034 B1 EP 0031034B1
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EP
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Prior art keywords
carburizing
gas
nitrogen
furnace
level
Prior art date
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Expired
Application number
EP80107178A
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German (de)
English (en)
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EP0031034A1 (fr
Inventor
Urs Dipl. Chem. Wyss
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Maag Zahnrader und Maschinen AG
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Maag Zahnrader und Maschinen AG
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    • 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
    • C23C8/22—Carburising of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/76—Adjusting the composition of the atmosphere

Definitions

  • the invention relates to a method for controllable gas carburizing of steel workpieces at a predetermined C level in an oven atmosphere of carrier gas obtained from methanol and nitrogen and a carburizing agent consisting of oxygen derivatives of hydrocarbons.
  • the method is also suitable for heating workpieces made of steel, whereby it is ensured that the carbon content of the material neither increases nor decreases, but is kept constant with the aid of the set C level.
  • a carrier gas is formed in a generator from natural gas, propane or other hydrocarbons and air in an endothermic reaction and this gas is then introduced into the carburizing furnace or heat treatment furnace.
  • a carburizing agent for setting the desired C level propane, natural gas or other hydrocarbons are introduced directly into the furnace atmosphere.
  • Such a method offers the possibility of automatically regulating the supply of carburizing agent according to the current need to maintain the predetermined C level via a gas component of the furnace atmosphere which is critical for this; steam (dew point), CO 2 or O 2 is suitable for this.
  • Disadvantages of this method are the necessity of a generator for producing the carrier gas outside the heat treatment or carburizing furnace and the thermal energy required for the operation of the generator.
  • a generatorless gas carburizing process is also known, in which methanol and nitrogen are introduced directly into the furnace in a corresponding ratio and the carrier gas is thus formed within the furnace.
  • a carrier gas of a composition similar to that obtained from natural gas and air in the generator by the above method is obtained (“HeatTreatmentof Metals”, 1979, pages 53 to 58).
  • the equilibrium-low levels of carbon dioxide, water vapor and methane in the carrier gas are neglected in these equations for the sake of clarity.
  • the generator process requires 5 volumes of air for 2 volumes of natural gas.
  • the methanol process requires 0.14 m 3 s of nitrogen per 100 g of methanol.
  • the content of water vapor in the furnace atmosphere can be determined continuously or from time to time, in particular by determining the dew point or the CO 2 content, and the feed of the substance (s) can be regulated via this gas component.
  • suitable carburizing agents are ethyl acetate, acetone, isopropanol or a mixture of isopropanol with water. If acetone is used as the carburizing agent, a mixture of methanol and isopropanol is suitable as the carrier gas supplying substance.
  • a disadvantage of this method is that with a low hardening temperature and / or a low C level, the dew point is relatively high, even in the region of room temperature, so that water can condense in the measuring lines, which in turn falsifies the Control size and thus incorrect feeding of carburizing agents can result.
  • the object of the invention is now a method for controllable gas carburizing or heating the surface of workpieces made of steel at a predetermined C level, which allows simple and reliable control and which is characterized by a substantial reduction in the amount of carrier gas required.
  • the process according to the invention is now based on gas carburizing in a furnace atmosphere of carrier gas obtained from methanol and nitrogen and a carburizing agent and is characterized in that, in addition to the carburizing agent, so much nitrogen is fed in that the gases after the carburizing reaction are essentially the same and essentially have constant gas composition and the supply of the carburizing agent and / or the additional nitrogen is controlled in a manner known per se via the continuously determined content of a gas component of the furnace atmosphere which is critical for the C level.
  • Ethyl acetate, acetone, ethanol or isopropanol is preferably used as the carburizing agent.
  • the control is expediently carried out either via the oxygen potential or via the water vapor content of the furnace atmosphere, ie by determining the dew point.
  • the gases after the coaling reaction contain 10 to 25% CO, 20 to 50% H 2 and 70 to 20% N 2 .
  • Essential to the invention is the matching of the additionally fed nitrogen to the amount of carburizing agent supplied, so that in the furnace atmosphere the gas composition corresponding to the carrier gas (2 CO + 4 H 2 + 4 N 2 ) does not change or changes only insignificantly, whereby the controllability is critical Gas component of the furnace atmosphere ensured and the required volume of carrier gas or in other words methanol can be significantly reduced compared to the known method.
  • the process according to the invention has the great advantage that the carrier gas generated endothermally in the generator and “consumed” during the carburizing is not only replaced by methanol and nitrogen in the appropriate ratio, but that the required amount of gas can be kept considerably smaller, since the supply of Carburizing agent with an appropriate amount of nitrogen together a shift in the gas composition is avoided.
  • hydrocarbons as carbonizing agents for example in a carrier gas generator or when methanol or nitrogen is introduced, results in an even greater amount of hydrogen in the furnace due to the carbonization reaction (for example CH 4 -jC + 2 H 2 ), the larger the surface to be carburized.
  • the composition of the furnace atmosphere can shift very quickly with large surfaces.
  • the endothermic carrier gas had to be supplied in large excess, so that not only a sufficient overpressure is guaranteed, but above all a constant gas composition.
  • the CO content must be constant for proper control of the C level via the CO 2 content or via the oxygen potential of the furnace gas.
  • Acetone as a carbonizing agent or for regulating the C level If 100 g of methanol and nitrogen (0.14 m 3 s ) are used to generate the carrier gas, acetone alone as a carbonating agent would lead to a slight increase in the CO content , so that if the amount of carrier gas was greatly reduced or the acetone was fed at a high rate when the C level was controlled via a constant CO 2 content or constant O 2 potential, the C level would be too high.
  • a change in the gas composition which disrupts the exact control process can be avoided in the manner of the additional nitrogen supply which is adapted to the coaling agent requirement and is described in A, B and C. According to the invention, there is therefore the possibility of reducing the amount of carrier gas to be supplied in the unit of time very greatly, in extreme cases to the amount necessary to maintain a slight excess pressure.
  • the method according to the invention can be used both for carburizing and for heating to hardening temperature at a set C level. In both cases the principle of regulation is the same.
  • a carburizing furnace 1 is connected to a C-level control device 2 via a control gas line 1a.
  • the carburizing furnace 1 can be a pot furnace, shaft furnace, chamber furnace or continuous furnace.
  • the C level control device 2 can be a device which works as a controlled variable via the CO 2 content determined by IR spectrometry, via the dew point or the oxygen potential.
  • the carburizing furnace 1 is connected to a methanol feed line 6 with a first sight glass 6a and a first pump 5 with adjustable output with a methanol container 3 and with a storage vessel 4 for carburizing agent via a line 8 with a second sight glass 8a and a second pump 7 with adjustable power.
  • the second pump is operated by the control device 2.
  • the nitrogen feed line 13 to the carburizing furnace 1 is connected via a first flow meter 12 to a first control valve 11 and a second flow meter 15 to a second control valve 14 via a common pressure regulator 10 to a nitrogen tank 9.
  • a solenoid valve 16 is provided, which can be actuated by the control device 2 and ensures that the nitrogen supply only takes place when the second pump 7 also feeds coaling agent into the furnace.
  • the proportion of the nitrogen proportional to the methanol and the amount of nitrogen to be supplied together with the carburizing agent is set.
  • the furnace can be, for example, such as is shown in DE-PS 1 192 486. It has a lining 17 with heating elements 18. In the lining there is a retort 19 with an insulated cover 20, which is sealed gas-tight at point 21.
  • a charging frame 22 which carries the workpieces 23 to be treated, is located within the retort. These are flushed on all sides by the furnace gas circulated by a fan 24.
  • the arrangement of the fan 24, an upper guide plate 25 and a lateral guide plate 26 results in a gas flow, as indicated by the arrows.
  • Furnace gas can be vented at 27.
  • a batch of 20 sprockets made of 17CrNiMo6 should be carburized to a depth of 1 mm in a pot oven.
  • the pinions were inserted into the oven preheated to approx. 750 ° C in a conventional rack, the oven was closed and the oven chamber was immediately flushed with nitrogen in order to displace the air.
  • the furnace temperature was set to the carburizing temperature (on the temperature controller).
  • the amount of nitrogen was set to 0.63 m 3 s / h with the aid of the manually operated valve 11 and the amount of methanol via the pump 5 to 450 g / h, so that when the carburizing temperature of 920 ° C. was reached had set the desired basic composition of the furnace atmosphere of 18-20% CO, 38-40% H 2 and approx. 40% N.
  • the additional amount of nitrogen was set to 0.574 m 3 s / h and the acetone pump to a delivery rate of 700 g / h via valve 14.
  • the control unit now controlled the supply of acetone and additional nitrogen necessary to maintain the desired C level.
  • the methanol pump 5 could now be set to a lower delivery rate of 300 g / h and the nitrogen supply via the manually operable valve 14 and the flow meter 15 to 0.420 m 3 s / h.
  • the dew point, the CO 2 content and the oxygen potential decreased; these were now kept at a constant value with controller 2, ie 1% C.
  • the carburization was complete after 6.25 h.
  • the basic procedure in a double-chamber furnace was the same as for carburizing.
  • the pinions were fed through the pre-chamber in the loading basket into the oven chamber, which was preheated to approx. 750 ° C.
  • the furnace chamber and pre-chamber were immediately flushed with nitrogen in order to displace the air, the oven temperature was set to 800 ° C and, during heating, the amount of nitrogen to 0.630 m 3 s fh and the amount of methanol to 450 g / h set so that the desired base gas composition of 18-20% CO, 38-40% H 2 and approx. 49% N 2 was reached when the hardening temperature of 800 ° C was reached.
  • the additional amount of nitrogen was set to 0.155 m 3 s / h and the acetone pump to a delivery rate of 400 g / h via the manual valve 14.
  • the control unit 2 now took over the supply of acetone and nitrogen necessary to maintain the C level of 0.80%.
  • the methanol pump 5 was set to a delivery rate of 300 g / h and the nitrogen supply to 0.420 m 3 s fh.
  • the methanol pump 5 and the acetone pump 7 were switched off, while the nitrogen supply for flushing out the furnace chamber and prechamber was set to a much higher value.
  • the pinions in the prechamber were then quenched.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

Claims (3)

1. Procédé de carburation gazeuse, ou de réchauffage, réglable, de pièces d'acier sous atmosphère protectrice à un niveau de C prédéterminé, mis en oeuvre dans une atmosphère de four comprenant un gaz porteur obtenu à partir de méthanol et d'azote et un agent de carburation composé de dérivés oxygénés d'hydrocarbures, caractérisé en ce qu'en complément de cet agent de carburation, on introduit suffisamment d'azote pour qu'après la réaction de carburation, les gaz présentent une composition pratiquement constante et qui reste pratiquement constante, et en ce qu'on règle l'introduction de l'agent de carburation et/ou celle de l'azote additionnel, d'une façon connue en soi, d'après la teneur, mesurée en continu, d'un constituant gazeux de l'atmosphère du four qui est critique pour le niveau de C.
2. Procédé suivant la revendication 1, caractérisé en ce qu'on utilise comme agent de carburation de l'acétate d'éthyle, de l'acétone, de l'étha- nol ou de l'isopropanol.
3. Procédé suivant l'une des revendications 1 et 2, caractérisé en ce qu'on effectue le réglage d'après le potentiel en oxygène, la teneur en CO2 ou la teneur de l'atmosphère du four en vapeur d'eau, notamment par détermination du point de rosée.
EP80107178A 1979-12-20 1980-11-19 Procédé de carburation réglable ou chauffage sous gaz protecteur de pièces à usiner en acier Expired EP0031034B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH1130379A CH643597A5 (de) 1979-12-20 1979-12-20 Verfahren zum regelbaren aufkohlen oder erwaermen in schutzgas von werkstuecken aus stahl.
CH11303/79 1979-12-20

Publications (2)

Publication Number Publication Date
EP0031034A1 EP0031034A1 (fr) 1981-07-01
EP0031034B1 true EP0031034B1 (fr) 1985-09-25

Family

ID=4372157

Family Applications (1)

Application Number Title Priority Date Filing Date
EP80107178A Expired EP0031034B1 (fr) 1979-12-20 1980-11-19 Procédé de carburation réglable ou chauffage sous gaz protecteur de pièces à usiner en acier

Country Status (9)

Country Link
EP (1) EP0031034B1 (fr)
JP (1) JPS5696070A (fr)
BR (1) BR8008362A (fr)
CH (1) CH643597A5 (fr)
DE (2) DE3019830C2 (fr)
FR (1) FR2472034B1 (fr)
GB (1) GB2066301B (fr)
IT (1) IT1149924B (fr)
SU (1) SU1261567A3 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3810775A1 (de) * 1988-03-30 1989-10-12 Schlafhorst & Co W Spinnrotor
DE10321414B4 (de) * 2003-05-13 2008-12-18 Robert Bosch Gmbh Verfahren zur Wärmebehandlung von metallischen Werkstücken in Kammeröfen

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4415378A (en) * 1982-04-22 1983-11-15 Dana Corporation Case hardening method for steel parts
FR2527641A1 (fr) * 1982-05-28 1983-12-02 Air Liquide Procede de traitement thermique de pieces metalliques par carburation
US4512821A (en) * 1982-12-20 1985-04-23 Procedyne Corp. Method for metal treatment using a fluidized bed
JPS6372821A (ja) * 1986-09-16 1988-04-02 Osaka Oxygen Ind Ltd 金属処理方法
DE3718240C1 (de) * 1987-05-30 1988-01-14 Ewald Schwing Verfahren zur Waermebehandlung von metallischen Werkstuecken in einer gasdurchstroemten Wirbelschicht
DE3830559C1 (fr) * 1988-09-08 1989-03-09 Linde Ag, 6200 Wiesbaden, De
DE10307341B4 (de) * 2003-02-21 2006-02-02 Bayerische Motoren Werke Ag Tragplatte zur Aufnahme eines Tellerrades
CN109778106A (zh) * 2018-11-14 2019-05-21 苏州工业园区姑苏科技有限公司 一种网带炉的氮甲醇保护气氛的控制系统以及调节方法
CN113913731A (zh) * 2021-11-12 2022-01-11 陕西柴油机重工有限公司 压入式可控气氛发生装置

Family Cites Families (8)

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Publication number Priority date Publication date Assignee Title
GB816051A (en) * 1954-12-18 1959-07-08 Renault Improvements in or relating to a process for preparing a gas suitable for the case hardening of steel
DE1208148B (de) * 1959-05-11 1965-12-30 Hurth Masch Zahnrad Carl Verfahren zum Aufkohlen von Werkstuecken aus Eisen
GB952363A (en) * 1959-10-07 1964-03-18 Nissan Motor Heat treatment of steels with a mixed gas of nitrogen and hydrocarbon
IT649978A (fr) * 1960-06-17
DE2163476A1 (de) * 1971-12-21 1973-07-12 Jenaer Glaswerk Schott & Gen Verfahren zur erhoehung der mechanischen festigkeit von glas-metall-verschmelzungen durch aufkohlen von eisen und eisenlegierungen
LU71534A1 (fr) * 1973-12-21 1975-06-17
US4049473A (en) * 1976-03-11 1977-09-20 Airco, Inc. Methods for carburizing steel parts
US4175986A (en) * 1978-10-19 1979-11-27 Trw Inc. Inert carrier gas heat treating control process

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
Härterei Technische MItteilungen, Bd. 35, 1980, nr. 6, S, 284-288 *
Metal Progress, Bd. 114, Nov. 1978, S. 24-31 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3810775A1 (de) * 1988-03-30 1989-10-12 Schlafhorst & Co W Spinnrotor
DE10321414B4 (de) * 2003-05-13 2008-12-18 Robert Bosch Gmbh Verfahren zur Wärmebehandlung von metallischen Werkstücken in Kammeröfen

Also Published As

Publication number Publication date
JPS6350430B2 (fr) 1988-10-07
IT8026589A0 (it) 1980-12-12
FR2472034B1 (fr) 1986-05-16
SU1261567A3 (ru) 1986-09-30
JPS5696070A (en) 1981-08-03
FR2472034A1 (fr) 1981-06-26
GB2066301B (en) 1984-01-25
DE3019830C2 (de) 1983-03-24
EP0031034A1 (fr) 1981-07-01
IT1149924B (it) 1986-12-10
GB2066301A (en) 1981-07-08
DE3071126D1 (en) 1985-10-31
DE3019830A1 (de) 1981-07-02
CH643597A5 (de) 1984-06-15
BR8008362A (pt) 1981-07-07

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