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
  • C21D1/62—Quenching devices
• • 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
• • 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
  • C21D2241/00—Treatments in a special environment
  • C21D2241/01—Treatments in a special environment under pressure
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/32—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for gear wheels, worm wheels, or the like

Definitions

• the present invention relates to a gas quenching cell for steel parts and more particularly to a method of gas quenching of steel parts used in such a quenching cell.
• Methods of gas quenching of steel parts have many advantages over liquid quenching processes, including the fact that treated parts come out dry and clean.
• the gaseous quenching of steel parts which have previously undergone a heat treatment (heating before quenching, annealing, tempering, etc.) or thermochemical treatment (carburizing, carbonitriding, etc.) is generally carried out with a gas under pressure, generally between 4 and 20 bars.
• the quenching gas is, for example, nitrogen, argon, helium, carbon dioxide or a mixture of these gases.
• a tempering process is to cool rapidly the steel parts which are generally at temperatures comprised between 75O 0 C and 1000 0 C. At such temperatures, the steel is essentially in the form of austenite which is only stable at elevated temperatures.
• An operation of Quenching allows for rapid cooling to obtain a transformation from austenite to martensite which has high hardness properties. The quenching operation must be relatively fast so that all the austenite is transformed into martensite without formation of other phases of pearlite or bainite type steel which have hardness properties lower than martensite.
• a quenching cell generally comprises at least one motor, generally of the electric type, rotating a stirring element, for example a helix, adapted to circulate the quenching gas in the quenching cell.
• a stirring element for example a helix
• a quenching operation is carried out vector ⁇ by imposing a static pressure of quench gas in the quenching cell and controlling the motor at a maximum speed to achieve maximum velocity of the quenching gas in materials steel to cool.
• the present invention aims to obtain a quenching process of steel parts and a quenching cell for the implementation of such a method for obtaining quenched parts with improved fatigue strength and / or reduced deformations.
• Another object of the present invention is to obtain a quenching cell for carrying out the quenching process according to the invention and whose structure is little modified compared to a conventional quenching cell.
• the present invention provides a method for quenching a steel load by flowing a gas at the load through a means of leads ⁇ gas.
• the drive means is controlled to discharge the gas at the load at a speed which varies according to a velocity profile of which at least a portion comprises, successively, a bearing at a first speed and a bearing at one second. speed higher than the first speed.
• the gas after being discharged at the level of the charge, is cooled by an exchanger in which circulates a cooling fluid ⁇ sement.
• the drive means is controlled to bleed the gas at the bearing load at the first bearing speed at the second speed when the temperature of the coolant reaches a given threshold temperature.
• the static pressure of the gas at the load is decreased during the bearing at the first speed relative to the bearing at the second speed.
• the gas after s 'be disposed at the load, is cooled by a heat exchanger in which circulates a cooled fluid ⁇ ment, the drive means being controlled to s' to discharge the gas at the level of the load according to a velocity profile comprising successively a first bearing at the second speed, a bearing at the first speed and a second bearing at the second speed, the transition between the first bearing at the second speed and the bearing at the first speed being carried out during a phase of rising of the fluid temperature cooling .
• the drive means is controlled to bleed the gas at the first bearing load at the second bearing speed at the first speed when the temperature of the coolant exceeds a given threshold temperature.
• the drive means is controlled to bleed the gas at the bearing load at the first speed at the second bearing at the second speed as the temperature of the coolant decreases. below a given additional threshold temperature.
• the drive means is controlled to bleed the gas at the level of the first stage load at the second stage speed at the first speed after a determined period of time.
• the gas after s 'be disposed at the load, is cooled by a heat exchanger in which circulates a cooled fluid ⁇ ment, the drive means being controlled to s' exhausting the gas at the load according to a velocity profile comprising, from the beginning of a quenching operation successively a bearing at the first speed and a bearing at the second speed, the transition between the bearing at the first speed and the bearing at the second speed being carried out during a phase of raising the temperature of the cooling fluid.
• the drive means is controlled to bleed the gas at the bearing load at the first bearing speed at the second speed after a determined period of time.
• the present invention also provides a gas quenching cell of a load comprising a motor driven stirring member for causing gas flow between the load and a heat exchanger.
• the cell comprises means adapted to vary the driving speed of the stirring element to cause the gas to flow at the level of the load at a speed which varies according to a speed profile comprising at least one step successively a step. first gear and a bearing at a second speed greater than the first gear.
• FIGS. are two views of an exemplary embodiment of a gas quenching cell according to the invention
• FIG. 2 represents the evolution of the quenching gas velocity at the level of a charge contained in a quenching cell according to FIGS. 1A and 1B and the evolution of the temperature of the cooling fluid of an exchanger of the cell. in the case of a conventional quenching process
• FIG. 3 represents the evolution of the quenching gas velocity at the level of a charge contained in a quenching cell according to FIGS. 1A and 1B and the evolution of the temperature of the cooling fluid of a exchanger of the cell.
• FIG. 4 represents the evolution of the temperature at the level of a charge contained in a quenching cell according to FIGS. 1A and 1B treated according to a conventional quenching method and the first example of quenching process according to the invention
• Figure 5 shows the evolution of the velocity of the quenching gas at a load contained in a quenching cell according IA figures and IB and the evolution of tempera ⁇ coolant ture of an exchanger the cell in the case of a second example of a quenching process according to the invention
• FIG. 6 represents the evolution of the quenching gas velocity at the level of a charge contained in a quenching cell according to FIGS. 1A and 1B and the evolution of the cooling fluid temperature of a heat exchanger. cell in the case of a third example of a quenching process according to the invention.
• FIGS 1A and 1B schematically show a side sectional view and a front sectional view of a gas quenching cell that can be used according to the invention.
• the cell comprises an enclosure 10 of generally cylindrical or parallelepipedal shape with a horizontal axis.
• the cell is closed at one end while the other end comprises a guillotine door system 12 giving access to the cell for introducing or extracting a load to be treated 14.
• the door 12 makes it possible to close the quenching cell tightly.
• the load 14 is maintained substantially in the center of the cell on a plate 16.
• the upper part of the cell is provided with two external motors with a vertical axis 18, arranged one beside the other in the longitudinal direction of the cell. . These motors drive respective stirring elements within the cell.
• the motors 18 are electric motors.
• the cell is provided with an exchanger 22 disposed on either side of the load
• the exchanger 22 comprises a circulation duct for a cooling fluid and is adapted to cool the quenching gas passing therethrough.
• guide plates 24 which join the stirring devices 20 so as to direct the flow of gas produced by the latter between the load 14 and the exchanger 22.
• the quenching gas s flows, for example down through the charge 14 and up through the exchanger 22.
• the stirring elements 20 are turbines or fans.
• the quenching gas is, for example, nitrogen or a mixture of carbon dioxide and helium.
• the present invention consists in modifying in a controlled manner the flow rate of the quenching gas at the level of the charge 14 during a quenching operation.
• the quenching cell 18 is equipped with a speed variation system.
• the speed variation can be obtained by means of a frequency converter for electric motors.
• the motors 18 are hydraulic motors, it is possible to provide a system for varying the flow rate of the oil supplying the engines 18.
• the development of a quenching gas velocity profile at the level of the charge 14 to be quenched is obtained from a characteristic parameter representative of the average temperature at the level of the charge 14.
• the characteristic parameter corresponds to the temperature of the cooling fluid at the outlet of the exchanger
• the curve representative of the evolution of the temperature of the cooling fluid leaving the exchanger 22 is characteristic of the energy removed at the load 14.
• FIG. 2 illustrates the principle underlying the choice of the temperature of the cooling fluid at the outlet of exchanger 22 as a characteristic parameter for varying the flow rate of the quenching gas.
• FIG. 2 represents a classic example of curve 26 of evolution of the the quenching gas velocity at the level of the charge 14, in which the quenching gas flow rate is constant and corresponds to the maximum capacity of the engines 18.
• FIG. 2 also shows a curve of the evolution of the temperature of the quenching gas.
• cooling fluid at the outlet of the exchanger 22 obtained for such a velocity profile.
• Curve 30 includes an upward portion 32 flexing at a peak 34 and followed by a downward portion 36.
• the Applicant has demonstrated that the austenite-martensite transformation of the steel constituting the filler 14 occurs substantially at the level of the crown 34 of the curve 30.
• the Applicant has shown that an improvement in the fatigue strength can be obtained by limiting temperature variations of the load 14 when the austenite martensite transformation so as to allow the austenite-martensite transition is carried out at temperatures of load 14 relative ⁇ homogeneous.
• FIG. 3 represents a curve 40 representative of the evolution of the flow rate of quenching gas at the level of charge 14 for a first example of a quenching process according to the invention and a curve 42 representative of the evolution of quenching gas.
• the temperature of the cooling fluid of the exchanger 22 corresponding to such a profile of quenching gas velocities.
• the curve 30 of evolution of the temperature of the cooling fluid for a quenching gas circulating at maximum speed during the entire quenching operation was reproduced in dotted lines.
• the first quenching method consists in controlling the motors 18 so that the flow rate of the quenching gas at the level of the charge 14 corresponds successively to a first maximum speed level 42 for a duration T1, at a speed of intermediate speed bearing 44 for a duration T2 and at a second level of maximum speed 46 until the end of the quenching operation.
• the engines 18 are controlled so that the flow rate of the quenching gas drops by 30 to 60% with respect to the maximum speed.
• the curve 42 of evolution of the temperature of the cooling fluid comprises an ascending portion 48 which substantially follows that of the curve 30.
• the temperature of the cooling fluid ⁇ sement tends to stabilize so that the curve 40 comprises a portion of small variations 50.
• the curve 42 follows a downward portion 52.
• the transition from the first maximum speed stage 42 to the intermediate speed stage 44 is carried out when the temperature of the cooling fluid reaches a first given threshold temperature, which corresponds to a temperature slightly lower than the temperature at the summit 34 of the curve 30. It is therefore substantially the temperature of the cooling fluid for which austenite-martensite transformation of the load 14 begins.
• the transition from the intermediate speed bearing 44 to the second maximum speed stage 46 is performed when the temperature of the coolant ⁇ sement, towards the end of the small variation portion 50, decreases below a second threshold temperature given, for example, equal to the first given threshold temperature, and which is representative of the fact that the austenite-martensite transformation of the charge 14 is complete.
• the austenite-martensite transformation of the charge 14 is then performed in its entirety for a flow rate of the quenching gas that is less than the maximum speed.
• the intermediate speed is adjusted to a value such that the thermal power recovered by the exchanger 22 corresponds to the thermal power released by the load 14 during the austenite-martensite conversion which is an exothermic reaction.
• the temperature of the filler 14 is then maintained at a substantially constant and homogeneous temperature during the entire austenite-martensite transformation. 14.
• the intermediate speed ⁇ is adapted to obtain the temperature of the coolant as constant as possible during the portion 50.
• the static pressure of the gas of Quenching can be maintained at a constant value throughout the quenching operation between 4 and 20 bar.
• the static pressure of quench gas in the quenching cell is decreased during the application of the speed stage interme ⁇ diary in a range of 30% to 80% of the static pressure quenching gas during the first and second maximum speed stages. This makes it possible to control, in combination with the intermediate speed of the quenching gas, the thermal power taken from the charge 14 during the austenite-martensite transformation.
• Figure 4 shows two curves 54, 56 of evolution of the measured temperature at the load 14 during a tempering operation of load 14 respectively for a conventional tempering process in which the rate of flow ⁇ gas quenching remains constant and maximum and the first example of quenching process according to the invention. More precisely, the curve 56 was obtained in the case where the duration T1 of application of the first maximum speed stage 42 is 50 seconds and the duration T2 of the intermediate speed stage 44 is 310 seconds. The intermediate speed corresponds in this example to 30% of the maximum speed.
• the static pressure of the quench gas which in this example is nitrogen, is 16 bar during the first and second maximum speed stages 42, 46 and 2 bar during the intermediate speed stage 44. note that after 50 seconds, the curve 56 decreases significantly less than the curve 54.
• the variation of the temperature of the load 14 is limited during the austenite-martensite transformation.
• the Applicant has demonstrated an improvement in the fatigue strength of the parts constituting the quenched load 14 according to the first example of quenching process of the invention.
• One explanation would be that since the austenite-martensite transformation takes place at temperatures whose variations are limited, fewer internal mechanical stresses appear in the load 14, which results in an improvement in the fatigue strength.
• the Applicant has shown an increase in the fatigue strength of the order of 20% by in comparison with cold oil quenching (oil at 60 ° C.) or quenching with nitrogen at constant pressure (16 bar) and with a maximum flow rate of the quenching gas.
• the first and second threshold temperatures depend on many parameters, including the type of steel constituting the charge 14 and the area of the exchange surface between the charge 14 and the quenching gas.
• the determination of the first and second threshold temperatures can be performed by quenching the charge 14 with a maximum gas flow rate so as to determine the curve shown in FIG. 2 associated with the charge 14.
• the first and second Threshold temperatures then correspond to a given percentage of the maximum temperature of the curve 30. It is then possible for the same type of charge to implement the first example of the method of the present invention by providing a temperature sensor at the level of the output of the heat exchanger 22 connected to a microcontroller adapted to control the engine 18.
• the passages of the first maximum speed bearing 42 to the intermediate 44 and the speed step speed step ⁇ interme diary 44 to the second maximum speed stage 46 are respecti vely ⁇ performed when the cooled fluid temperature ⁇ ment exceeds the first threshold temperature and dimi naked below the second threshold temperature.
• the transition from the intermediate speed bearing 44 to the second maximum speed stage 46 can then be automatically performed after the duration T2, determined, for example, empirically.
• the intermediate speed bearing 44 is maintained even after the temperature of the cooling fluid decreases below the second given threshold temperature, as defined above, towards the end of the weak portion. Variations 50.
• the transition from the intermediate speed bearing 44 to the second maximum speed stage 46 is then performed only after the lapse of a duration greater than the duration T2 as defined above.
• the curve 42 comprises, after the portion of small variations 50, a downward portion whose slope is, in absolute value, lower than the slope of the downward portion 52 shown in FIG. which is extended by an additional portion of small variations.
• the passage of the intermediate speed bearing 44 to the second maximum speed stage 46 can then be performed when the temperature of the cooling fluid decreases below a threshold temperature. data that is representative of the passage between the descending portion and the additional portion of small variations.
• the Applicant has shown that increasing the duration of the intermediate speed bearing 44, compared to the duration T2 as defined above for the first embodiment, makes it possible to obtain an improvement in the resilience of the parts constituting the quenched load 14 according to the variant of the first example of quenching process of the invention.
• the resilience improvement has, for example, been demonstrated by resilience tests using a Charpy sheep. For example, by multiplying the duration T2, as defined above for the first exemplary embodiment, by a factor greater than 4, the Applicant has observed an improvement in the resilience greater than 20%.
• the present invention also proposes a second example of a process for quenching a filler 14 making it possible to reduce the deformations of the filler 14 during the quenching operation, in particular the local deformations of the filler when this comprises parts of the filler. complex shapes. This makes it possible to limit the subsequent grinding steps to be provided for the quenched parts and / or to simplify the preliminary steps for designing the shapes of the parts before quenching.
• FIG. 5 represents a curve 58 representative of the evolution of the flow rate of the quenching gas at the level of the charge 14 for the second example of quenching process according to the invention and a curve 60 representative of the evolution of the quenching gas.
• the temperature of the cooling fluid of the exchanger 22 obtained with such a quenching gas velocity profile.
• the curve 30 of evolution of the temperature of the cooling fluid for a quenching gas circulating at maximum speed during the entire quenching operation was reproduced in dotted lines.
• the second exemplary embodiment of the quenching process of the invention consists in controlling the motors 18 so that the flow rate of the quenching gas at the level of the charge 14 successively corresponds to a first intermediate speed step 62 for a period of time. Tl 'and at a maximum speed level 64 until the end of the quenching operation.
• the motors 18 are controlled so that the flow rate of the quenching gas varies between 0% and 70% of the maximum speed.
• the curve 60 of evolution of the temperature of the cooling fluid comprises an upward portion 66 less marked than the upward portion 32 of the curve 30. The temperature of the cooling fluid therefore increases less rapidly than in the case where the quenching speed is maximum.
• the ascending portion 66 continues to a vertex 68 and is extended by a downward portion 70.
• the duration T1 'can extend from 5 to 30 seconds depending on the total duration of the operation quenching. In addition, the duration T1 'can be determined empirically.
• the cooling rate of the charge 14 is lower than that which would result from a maximum flow rate of the quenching gas. Cooling ⁇ being slower, the deformations of the load 14 are less important.
• the mechanical inertia of the load 14 has increased. Such an increase in mechanical inertia limits the subsequent deformations of the load 14 as the flow rate of the quenching gas is subsequently increased.
• the static pressure of the quenching gas can be kept constant throughout the quenching operation.
• an increase in the static pressure of the quenching gas may be provided during the transition from the intermediate speed bearing 62 to the maximum speed bearing 64.
• the static pressure can be increased from 2 to 5 times the initial pressure to reach a value, for example, between 4 and 20 bar.
• the Applicant has shown a reduction of the deformations at the level of the profile of the teeth in a plane perpendicular to the direction of the propeller, up to about 45% with respect to hot oil quenching (oil at 18O 0 C) and about 30% with respect to gas quenching at maximum flow rate of the quenching gas.
• the present invention also proposes a third example of a process for quenching a filler 14 corresponding to the combination of the two previously described embodiments.
• the third exemplary embodiment then makes it possible to obtain an improvement in the fatigue strength of the parts constituting the load and a reduction in the deformations of the parts constituting the load 14.
• FIG. 6 represents a curve 72 representative of the evolution of the flow rate of the quenching gas at the level of the charge 14 for the third example of quenching process according to the invention and a curve 74 representative of the evolution of the temperature of the cooling fluid of the exchanger 22 obtained with such a quenching gas velocity profile.
• the curve 30 of evolution of the temperature of the cooling fluid for a quenching gas circulating at maximum speed during the entire quenching operation was reproduced in dotted lines.
• the third exemplary embodiment of the quenching method of the invention consists in controlling the motors 18 so that the flow rate of the quenching gas at the level of the charge 14 successively corresponds to an intermediate speed bearing 76 for a duration Tl. ", a maximum speed bearing 78 for a duration T2", an intermediate speed bearing 80 for a duration T3 "and a maximum speed bearing 82 until the end of the quenching operation, by way of example, during the intermediate speed bearing 76, the motors 18 are controlled so that the flow velocity tempering gas varies between 0% and 70% of the maximum speed and during the intermediate speed stage 80, the quenching gas flow rate varies between 40% and 70% of the maximum speed.
• the curve 74 for changing the temperature of the cooling fluid comprises an upward portion 84 less marked than the upward portion 32 of the curve 30.
• the curve 74 comprises an ascending portion 86 at the intermediate speed bearing 80, the curve 74 comprises a bearing 88 of small variations and at the maximum speed bearing 82, the curve 74 comprises a downward portion 90.
• the quenching cell may be different from the cell described above.
• the axis of the motors 18 may be arranged in the horizontal, the flow of the quenching gas at the load 14 is substantially in the horizontal.
• the cell may comprise a conduit forming a loop outside the cell, the exchanger 22 being inserted into the conduit.

Landscapes

• 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)
• Heat Treatment Of Articles (AREA)
• Heat Treatments In General, Especially Conveying And Cooling (AREA)
• Control Of Heat Treatment Processes (AREA)
• Furnace Details (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=34953723

Family Applications (1)

Country Status (10)

Families Citing this family (5)

Family Cites Families (13)

• 2005
  • 2005-01-17 FR FR0550134A patent/FR2880898B1/fr not_active Expired - Fee Related
  • 2005-04-19 US US11/109,429 patent/US20060157169A1/en not_active Abandoned
• 2006
  • 2006-01-16 CN CNA2006800024423A patent/CN101107368A/zh active Pending
  • 2006-01-16 JP JP2007550823A patent/JP5638737B2/ja active Active
  • 2006-01-16 CA CA002595020A patent/CA2595020A1/en not_active Abandoned
  • 2006-01-16 KR KR1020077018766A patent/KR20070099648A/ko not_active Application Discontinuation
  • 2006-01-16 EP EP06709405.2A patent/EP1844169B1/de active Active
  • 2006-01-16 WO PCT/FR2006/050017 patent/WO2006075120A1/fr active Application Filing
  • 2006-01-16 BR BRPI0606652-6A patent/BRPI0606652B1/pt active IP Right Grant
  • 2006-01-16 MX MX2007008652A patent/MX2007008652A/es active IP Right Grant

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events