EP0538575B1 - Verfahren zum Abkühlen einer Werkstückcharge innerhalb eines Wärmebehandlungsprozesses - Google Patents

Verfahren zum Abkühlen einer Werkstückcharge innerhalb eines Wärmebehandlungsprozesses Download PDF

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Publication number
EP0538575B1
EP0538575B1 EP92113958A EP92113958A EP0538575B1 EP 0538575 B1 EP0538575 B1 EP 0538575B1 EP 92113958 A EP92113958 A EP 92113958A EP 92113958 A EP92113958 A EP 92113958A EP 0538575 B1 EP0538575 B1 EP 0538575B1
Authority
EP
European Patent Office
Prior art keywords
cooling
measuring probe
workpiece
measuring
heat treatment
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP92113958A
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German (de)
English (en)
French (fr)
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EP0538575A1 (de
Inventor
Bernd Dr. Edenhofer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ipsen International GmbH
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Ipsen International GmbH
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Filing date
Publication date
Application filed by Ipsen International GmbH filed Critical Ipsen International GmbH
Publication of EP0538575A1 publication Critical patent/EP0538575A1/de
Application granted granted Critical
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Anticipated expiration legal-status Critical
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Classifications

    • 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
    • C21D1/767—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material with forced gas circulation; Reheating thereof
    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • C21D11/005—Process control or regulation for heat treatments for cooling
    • 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
    • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
    • C21D1/613—Gases; Liquefied or solidified normally gaseous material

Definitions

  • the invention relates to a method for cooling a workpiece batch within a heat treatment process by means of gas cooling, in which the parameters determining the cooling process, such as cooling gas speed and cooling gas pressure, are set as a function of temperatures determined during the cooling process and the cooling process is controlled in this way.
  • the invention has for its object to control the cooling of the workpiece batch so that the desired heat treatment result is achieved at a given workpiece cross-section without taking temperature measurements at this or another point on the workpiece.
  • the temperature profile over the cross section of at least one measuring probe of defined geometry and defined material arranged in the batch space is continuously recorded and by means of a computer based on these temperature profiles to the measuring probe via the Determination of the heat flow density and the heat transfer at the probe, the temporal temperature profile in the workpiece, ie in the cross-section of the workpiece of interest, is calculated and that the computer uses a comparison device to carry out a continuous comparison between the actual temperature profile thus calculated and a predetermined target temperature profile and controls the parameters determining the cooling process depending on the result of this comparison.
  • sensors e.g. thermocouples
  • the basis of this process is the control of the cooling process on the basis of temperature profiles, which are recorded by means of a measuring probe of defined geometry and defined material.
  • a measuring probe for the case of quench hardening in a water or oil bath is described in a contribution by Liscic and Filetin in the journal "Härterei-Technische-Mitteilungen 41 (1986)", booklet 4, pages 208ff.
  • This measuring probe makes it possible at any time during the heat treatment To determine the temperature of the probe at one or more points of its cross section.
  • the temperature profile in the measuring probe and the heat flow density and the heat transfer coefficient on the surface of the measuring probe are measured at all times during cooling calculated.
  • the surface temperature and the temperature profile in the workpiece cross-section of interest in each case are then determined for the given geometry of the workpiece for each point in time.
  • the calculated actual temperature profile in the workpiece obtained in this way is compared with a predetermined target temperature profile in the workpiece, which is determined for the respective geometry of the workpiece cross section, for example from the corresponding ZTU diagram of the material in question, and which gives an optimal result of the heat treatment, in particular a optimal hardness result, can be expected.
  • the parameters determining the cooling process are then controlled, i.e. the speed of the cooling gas directed onto the workpiece batch and / or the gas pressure of the cooling gas.
  • the cooling process can also be controlled via a corresponding selection of the cooling gas introduced into the batch space, for which purpose nitrogen, helium, argon or hydrogen are preferably considered.
  • the parameters determining the cooling process are then carried out in such a way that the actual temperature profile calculated for the cross-section of the workpiece under consideration at all times largely corresponds to the target temperature profile obtained from the ZTU diagram.
  • the desired heat treatment result is achieved at the predetermined cross section of the workpiece, without temperature measurements being necessary at this or at another point on the workpiece.
  • the temperatures are preferably recorded at different points in the cross section of the measuring probe, of which at least two measuring points are located within the measuring probe.
  • a total of three measuring points are arranged within the measuring probe, these measuring points being at different distances from the surface of the measuring probe.
  • Particularly meaningful temperature values can be obtained if at least one measuring point is located close to the surface within the measuring probe.
  • the gas temperature in the batch space is also required to calculate the actual temperature profile, it is proposed with an advantageous embodiment of the method to detect the gas temperature near the surface of the measuring probe. Alternatively, a mathematical calculation of the gas temperature is also possible.
  • the shape of the measuring probe is modeled on the points of the workpiece that are decisive for the success of the heat treatment process.
  • This further development of the method can be used with particular advantage in the case of large workpiece series, in which case the actual temperature profiles calculated for the workpiece reproduce the actual temperature profile particularly precisely, so that the cooling process can be controlled particularly precisely.
  • the computer calculates the target temperature profile from the ZTU diagram of the material of the workpiece. It is therefore it is not necessary to save workpiece-specific cooling curves in the computer. Rather, the computer only needs a file of the relevant ZTU diagrams and automatically calculates the target temperature profile in the workpiece at the relevant location if the required hardness is known.
  • FIG. 1 the batch space 1 of a vacuum furnace for the heat treatment of metallic workpieces is shown in broken lines.
  • the vacuum furnace is prepared to carry out a complete heat treatment process, so in addition to a heating system, it has a blower-assisted cooling system in which a cooling gas, for example nitrogen, helium, argon or hydrogen, is introduced into batch space 1 and in this way allows the workpiece to cool down quickly or the batch of workpieces.
  • the cooling process is controlled by a control device 2, which controls both the speed v gas and the gas pressure p gas .
  • the cooling speed and thus the hardness that can be achieved on the workpiece within the heat treatment process can thus be influenced by the control device 2.
  • a measuring probe 4 next to a workpiece 3, which is provided with a total of four measuring points for temperature measurement. Measuring points arranged within the measuring probe 4 result in temperature values T 1, T 2 and T 3, while a further measuring point arranged near the surface of the measuring probe 4 detects the temperature T o in the batch space 1 near the surface of the measuring probe 4.
  • the structure of the measuring probe 4 is shown in FIG. 2.
  • the measuring probe 4 consists of a solid metal cylinder into which a total of three bores 5 running parallel to the longitudinal axis of the cylinder are incorporated to accommodate sensors.
  • the holes 5 extend to different extents to the surface 6 of the measuring probe 4.
  • a first measuring point 7a is formed by a thermocouple, which is located at the blind hole-like end of the shortest of the three holes 5. This measuring point 7a therefore detects the temperature in the core of the measuring probe 4.
  • the second measuring point 7b is located at a distance of approximately 4 mm from the surface 6 of the measuring probe 4, while the third measuring point 7c is installed just below the surface 6 of the measuring probe 4. The distance to the surface 6 is only about 1.5 mm.
  • thermocouples In order to avoid the influence of heat on the sensors designed as thermocouples through the holes 5, the holes 5 are closed after the thermocouples have been inserted.
  • Current conductors, not shown, of the thermocouples lead out of the measuring probe 4 and are connected to a measured value acquisition of a computer controlling the cooling process.
  • Fig. 1 it is shown that the temperatures T1, T2 and T3 determined at the three measuring points of the measuring probe and the temperature T o determined just above the surface of the measuring probe 4 together with the geometry and the material used of the measuring probe 4 one in the computer performed calculation step are in which the temperature profile T s , the heat flow density on the surface and the heat transfer coefficient of the heat transferred between the surface and the cooling gas are determined at any time during the cooling for the measuring probe 4. This calculation is carried out using the known equations of convective heat transfer and heat conduction.
  • This data and the data relating to the geometry and the material of the workpiece 3 are used by the computer in a further computing step in order to calculate the temperature inside and on the surface of a predetermined cross section of the workpiece 3 for the respective point in time. It is assumed that the heat transfer conditions on the measuring probe 4 and workpiece 3 are largely the same. On the basis of this assumption, it is concluded from the temporal temperature profiles determined on the measuring probe 4 that the temperature profiles in the workpiece 3 are corresponding, but additionally influenced by the geometry and the material of the workpiece 3. For this purpose, the known heat conduction equations in three-dimensional form for the respective point in time as well as the specified workpiece geometry are solved in a subroutine of the computer.
  • the actual temperature curve T w determined in this way is in good agreement with the actual temperature curve in the workpiece 3 if the cooling conditions, ie the temperature and the speed of the cooling gas, on the measuring probe 4 and the workpiece 3 are the same. In practice, this is met with sufficient accuracy if the measuring probe 4 is arranged near the workpiece 3 in the batch space 1.
  • the Desired temperature curve T w is to be calculated in a subroutine from the ZTU diagram of workpiece 3 applicable to the respective material.
  • the ZTU diagram is used to calculate the target curve that just results in the desired hardness of the material.
  • the computer In order to bring the actual temperature profile T w, as close as possible to the target temperature profile T w, target, the computer then carries out a comparison step 8, with the control device 2 depending on the result of this comparison determining the parameters v Gas , p gas in the sense of the best possible approximation to the desired temperature profile T w, should control.
  • the entire cooling process is therefore fully automated and computer-controlled. Only as much cooling gas and environmental energy is used to distribute the cooling gas as is necessary.
  • the heat treatment process makes it possible to achieve the desired hardness at any desired point on the workpiece.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Control Of Heat Treatment Processes (AREA)
  • Heat Treatment Of Articles (AREA)
  • Heat Treatments In General, Especially Conveying And Cooling (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
EP92113958A 1991-10-25 1992-08-17 Verfahren zum Abkühlen einer Werkstückcharge innerhalb eines Wärmebehandlungsprozesses Expired - Lifetime EP0538575B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4135313A DE4135313A1 (de) 1991-10-25 1991-10-25 Verfahren zum abkuehlen einer werkstueckcharge innerhalb eines waermebehandlungsprozesses
DE4135313 1991-10-25

Publications (2)

Publication Number Publication Date
EP0538575A1 EP0538575A1 (de) 1993-04-28
EP0538575B1 true EP0538575B1 (de) 1995-11-02

Family

ID=6443453

Family Applications (1)

Application Number Title Priority Date Filing Date
EP92113958A Expired - Lifetime EP0538575B1 (de) 1991-10-25 1992-08-17 Verfahren zum Abkühlen einer Werkstückcharge innerhalb eines Wärmebehandlungsprozesses

Country Status (4)

Country Link
EP (1) EP0538575B1 (enrdf_load_stackoverflow)
AT (1) ATE129749T1 (enrdf_load_stackoverflow)
DE (2) DE4135313A1 (enrdf_load_stackoverflow)
ES (1) ES2081532T3 (enrdf_load_stackoverflow)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT405190B (de) * 1996-03-29 1999-06-25 Ald Aichelin Ges M B H Verfahren und vorrichtung zur wärmebehandlung metallischer werkstücke
DE19632195C1 (de) 1996-08-09 1998-03-05 Michael Fenne Verfahren zur Herstellung von Gußstücken
DE10030046C1 (de) * 2000-06-19 2001-09-13 Ald Vacuum Techn Ag Verfahren und Vorrichtung zum Bestimmen der Abkühlwirkung einer strömenden Gasatmosphäre auf Werkstücke
DE102004051546A1 (de) * 2004-10-22 2006-05-04 Ald Vacuum Technologies Ag Verfahren zum verzugsarmen Härten von metallischen Bauteilen
FR2880898B1 (fr) * 2005-01-17 2007-05-11 Const Mecaniques Sa Et Cellule de trempe au gaz pour pieces en acier
DE102008020470B4 (de) * 2008-04-23 2010-11-25 Vdeh-Betriebsforschungsinstitut Gmbh Messsystem für die Ermittlung des lokalen Wärmeübergangskoeffizienten in einem Ofen
DE102009053066B4 (de) * 2009-11-13 2019-07-11 Air Liquide Deutschland Gmbh Verfahren und Vorrichtung zum Kühlen von wärmebehandelten Elementen
US11306371B1 (en) * 2017-10-16 2022-04-19 DANTE Solutions, Inc. Gas quenching system and method for minimizing distortion of heat treated parts
DE102019006201A1 (de) * 2019-05-09 2020-11-12 Aerospace Transmission Technologies GmbH Verfahren und Fixturhärtevorrichtung zum Fixturhärten von Bauteilen

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3322386A1 (de) * 1983-06-22 1985-01-10 Schmetz Industrieofenbau und Vakuum-Hartlöttechnik KG, 5750 Menden Verfahren zur kuehlung einer charge nach einer waermebehandlung und ofenanlage zur durchfuehrung des verfahrens
DE3623105C1 (de) * 1986-07-09 1987-12-03 Degussa Verfahren zur Waermebehandlung von Stahlteilen
DE4004295A1 (de) * 1990-02-13 1991-08-14 Karl Heess Gmbh & Co Verfahren und vorrichtung zum haerten von werkstuecken mittels presswerkzeugen

Also Published As

Publication number Publication date
DE4135313A1 (de) 1993-04-29
DE4135313C2 (enrdf_load_stackoverflow) 1993-09-23
ATE129749T1 (de) 1995-11-15
ES2081532T3 (es) 1996-03-16
DE59204192D1 (de) 1995-12-07
EP0538575A1 (de) 1993-04-28

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