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
  • C21D1/18—Hardening; Quenching with or without subsequent tempering
  • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
  • C21D1/22—Martempering
• • 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
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B5/00—Muffle furnaces; Retort furnaces; Other furnaces in which the charge is held completely isolated
  • F27B5/06—Details, accessories or equipment specially adapted for furnaces of these types
  • F27B5/16—Arrangements of air or gas supply devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B5/00—Muffle furnaces; Retort furnaces; Other furnaces in which the charge is held completely isolated
  • F27B5/06—Details, accessories or equipment specially adapted for furnaces of these types
  • F27B5/16—Arrangements of air or gas supply devices
  • F27B2005/161—Gas inflow or outflow

Definitions

• the invention relates to a process for the heat treatment of batches of iron and steel parts, which are heated in a vacuum and cooled under pressure in an inert gas by inflowing and circulating gas, after a rapid cooling of the batch from annealing temperature to the martensite formation temperature by comparing the temperatures inside the batch and on the batch surface by throttling the gas circulation speed and / or the gas pressure, a temperature equalization of the total batch in the range of the martensite formation temperature is made possible before further cooling to the removal temperature from the furnace takes place.
• the inert gas is usually circulated with a blower and directed onto the batch in the furnace by means of nozzles or baffles.
• the batch of steel parts can be removed from the furnace when it has cooled to the point where there is no longer any oxidation in the air.
• the steel heated to the hardening temperature is cooled in a quenching agent so rapidly to about room temperature that the formation of ferrite, pearlite and carbide is suppressed and the hardening structure "martensite" is formed.
• the conversion to martensite begins during the rapid cooling at the so-called martensite formation temperature, which is dependent on the carbon content and the other alloy components of the steel. It is usually between 550 ° C and 150 ° C, for common tool steels around 200 ° C.
• This object is achieved in that the temperature profile inside the batch is simulated using a computer program.
• the temperature compensation takes place in such a way that when the martensite formation temperature dependent on the steel composition is reached on the batch surface, the gas circulation is reduced or completely throttled, after a temperature increase on the batch surface due to heat conduction from the interior of the batch to temperatures of 10 to 80 ° C above the martensite formation temperature Gas circulation increased again, and this alternating reduction in gas circulation is continued until a final temperature equalization between the inside of the batch and the surface of the batch has taken place in the martensite formation temperature interval.
• the temperatures on the batch surface are advantageously measured by means of electrical temperature sensors, e.g. with thermocouples, and the gas circulation and / or the gas pressure are regulated from the measured data via a computer control.
• a computer program is used in the computer control, into which the previously determined batch-specific parameters and the martensite formation temperature are entered. This computer program simulates the temperature profile inside the batch so that there is no need to install a temperature sensor there. As soon as the temperature sensor on the batch surface shows the previously entered martensite formation temperature, the gas circulation is automatically throttled. As a result, the temperature on the surface of the batch rises again, since there is an outflow of heat from the inside of the batch.
• the gas circulation is increased again by the computer control until the temperature sensor on the batch surface again shows the martensite formation temperature.
• the gas circulation is then throttled again until, after repeated throttling and increasing the gas circulation, the temperature between the surface of the batch and the interior of the batch has been equalized. It is then cooled to the removal temperature from the oven in the usual way.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Thermal Sciences (AREA)
• Physics & Mathematics (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• General Engineering & Computer Science (AREA)
• Control Of Heat Treatment Processes (AREA)
• Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
• Furnace Charging Or Discharging (AREA)
• Heat Treatment Of Articles (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=6304765

Family Applications (1)

Country Status (3)

Cited By (4)

Families Citing this family (1)

Family Cites Families (1)

• 1986
  • 1986-07-09 DE DE19863623105 patent/DE3623105C1/de not_active Expired
• 1987
  • 1987-06-26 EP EP87109238A patent/EP0253176A3/fr not_active Withdrawn
  • 1987-07-07 JP JP16797787A patent/JPS6326308A/ja active Pending

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