EP0306609B1 - Procédé pour la fabrication d'un produit semi-fini ou produit fini à partir d'un acier martensitique au chrome, fortement allié et en phase unique par déformation à froid et/ou à chaud - Google Patents

Procédé pour la fabrication d'un produit semi-fini ou produit fini à partir d'un acier martensitique au chrome, fortement allié et en phase unique par déformation à froid et/ou à chaud Download PDF

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Publication number
EP0306609B1
EP0306609B1 EP88106438A EP88106438A EP0306609B1 EP 0306609 B1 EP0306609 B1 EP 0306609B1 EP 88106438 A EP88106438 A EP 88106438A EP 88106438 A EP88106438 A EP 88106438A EP 0306609 B1 EP0306609 B1 EP 0306609B1
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EP
European Patent Office
Prior art keywords
annealing
cold
finished
steel
forming
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
EP88106438A
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German (de)
English (en)
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EP0306609A2 (fr
EP0306609A3 (fr
Inventor
Christo Wassilew
Bernhard Dafferner
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.)
Forschungszentrum Karlsruhe GmbH
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Kernforschungszentrum Karlsruhe GmbH
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    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys

Definitions

  • the invention relates to a method for producing a semi-finished product or end product from single-phase, high-alloy, martensitic chromium steel by hot and / or cold working in accordance with the preamble of the first claim.
  • high-alloy martensitic chrome steel is used for certain, highly stressed parts of the system.
  • Such semi-finished products or end products are usually produced by cold and / or hot working, with intermediate heat treatment being carried out in a vacuum, inert gas or slightly reducing atmosphere after cold working of more than about 20%.
  • soft annealing is carried out at temperatures of approximately 600 to 800 ° C and a typical annealing time of 1 to 2 hours, the temperatures and the annealing time depending on the type of steel.
  • the annealing temperature of the intermediate heat treatment is 700 - 780 ° C.
  • the intermediate heat treatment breaks down the material hardening that occurs during rolling, drawing, vocational or round hammering.
  • the final heat treatment of semi-finished products or end products made of martensitic steels is the heat treatment.
  • This consists of austenitization annealing (hardness annealing), followed by an annealing anneal that improves toughness leads, excludes.
  • the austenitization annealing is carried out at temperatures above the A C1 temperature and a typical annealing time of 0.1 - 1 h.
  • the temperature of the austenitizing annealing is 1075 ° C and the annealing time is 0.5 - 1 h.
  • the subsequent annealing is carried out at temperatures below the A C1 temperature with a typical annealing time of 1 - 2 h.
  • the tempering temperature is selected depending on the desired strength and toughness of the semi-finished or end product at temperatures between approximately 580 and 780 ° C.
  • the duration of the tempering heat treatment is 1-2 hours.
  • the duration of the heat treatment should be increased by 1-2 minutes for each additional mm for plates with a wall thickness of more than 10 mm or for bars with a diameter of more than 15 mm.
  • Cooling takes place in air with a minimum cooling rate of 30 K / min for austenitizing annealing and a maximum of 15 K / min for tempering and soft annealing.
  • this ⁇ -ferrite phase is particularly favored by the result of cold working / intermediate annealing.
  • the tendency to ⁇ -ferrite formation increases with the increase in the number of cycles or the degree of cold deformation.
  • the austenitization temperature from which the ⁇ -ferrite formation begins is reduced.
  • EP-A 0 011 152 discloses a process for the production of pipes made of a nickel / chromium alloy, in which the pipes are cold drawn to a length of 6 to 7.5 m and then subjected to a two-stage heat treatment. In the first stage, the pipes are heated to a temperature of 650 to 720 ° C; in the second stage the temperature is raised to 815 to 870 ° C. The pipes are then cold drawn to the final length of approx. 26 m and subjected to a final heat treatment. The final heat treatment takes place at approx. 925 ° C and takes place in a hydrogen atmosphere. The problem of ⁇ -ferrite formation is not mentioned.
  • the object of the invention is to provide a process for the production of semi-finished products and end products which excludes the formation of ⁇ -ferrite during steel processing or by which the ⁇ -ferrite possibly formed during steel processing is dissolved again, so that any high degree of deformation can be achieved and a single-phase ⁇ -ferrite-free material is available after completion of the shaping and tempering treatment, regardless of the number of consequences of cold deformation / heat treatment.
  • This stabilization annealing is preferably carried out at 950 ° C in a vacuum, inert gas or slightly reducing atmosphere.
  • the additional stabilization annealing according to the invention before the intermediate heat treatments or before the heat treatment is indispensable if successive cold deformation steps, in particular by pulling, rolling, vocational or rotary hammers, are aimed at, since otherwise the processability of the material deteriorates increasingly and damage occurs with further deformation occur due to crack formation, which are due to the increased tendency to brittle fracture due to the ⁇ -ferrite component formed. However, such damage can only occur on the claimed finished product.
  • the additional stabilization annealing effectively eliminates the cause of the increased tendency to brittle fracture, the formation of ⁇ -ferrite during processing. Already formed ⁇ -ferrite can be dissolved again by the stabilization annealing. In the case of semi-finished products or end products produced entirely or mainly by hot working, a stabilization annealing carried out before the tempering treatment is sufficient.
  • the additional stabilization annealing makes it possible to obtain a ⁇ -ferrite-free and thus single-phase material; any ⁇ -ferrite components that have formed during the deformation are dissolved by the stabilization annealing.
  • Fig. 1 shows a micrograph of a seamless tube made of 12% chromium steel 1.4914, which was created by several sequences of cold drawing processes and intermediate annealing (780 ° C, 1h) with a total degree of deformation of about 70%.
  • the austenitization annealing was carried out at 1075 ° C (1 / 2h), the tempering annealing at 750 ° C (2h).
  • the mixture was cooled by blowing with argon (30 ° C./min); the cooling rate after tempering is 15 ° C / min. From Fig. 1 it can be seen that the structure of this tube contains ⁇ -ferrite in a considerable amount.
  • the tube was destroyed by cracking during further processing.
  • the exact analysis of the crack formation showed that the cracks arise at the phase boundary ⁇ -ferrite / matrix.
  • Fig. 2 shows a micrograph of a seamless tube of the same steel composition, which was processed as described above, but with the difference that after 20-25% cold forming before the intermediate heat treatment, a stabilization annealing was carried out at 950 ° C with a duration of 2 hours .
  • a stabilization anneal (950 ° C, 2h) was also carried out before the final heat treatment. After the stabilization annealing, it was cooled by blowing with argon. It can be clearly seen from FIG. 2 that the structure is single-phase and ⁇ -ferrite is free.
  • FIG. 3 shows a micrograph of a 5.5 mm thick plate made of 12% chromium steel 1.4914, which was produced by rolling with a total degree of cold deformation of 75%, intermediate annealing taking place after every 25% cold deformation. After reaching a degree of cold deformation of 75%, a tempering treatment was carried out. The conditions of the heat treatments corresponded to those of Example 1. The ⁇ -ferrite fractions can be clearly seen.
  • FIG. 4 shows a micrograph of a plate of the same type of steel, which was produced in the same way, but before each intermediate annealing and before the tempering treatment, a stabilization annealing was carried out at 950 ° C. with an annealing duration of 2 h (cooling by blowing with argon). 4 clearly shows that the structure is single-phase and ⁇ -ferrite is free.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Articles (AREA)

Claims (5)

  1. Procédé de fabrication d'un produit demi-fini ou produit fini à partir d'un acier martensitique au chrome, fortement allié et à une phase par une ou plusieurs étapes successives de déformation à froid et/ou à chaud:
    - avec des recuits intermédiaires par coalescence après des déformations à froid ayant un degré de formation à froid supérieur à environ 20 % et
    - un traitement de trempe et revenu final,
    caractérisé en que :
    a) avant les recuits intermédiaires de coalescence et
    b) après la fin du processus de déformation à froid et/ou à chaud avant le traitement de trempe et de revenu,
    on réalise pour l'obtention d'une structure sans ferrite δ un traitement à chaud supplémentaire, désigné comme traitement de stabilisation à une température supérieure à la température AC1, toutefois inférieure à la température de formation d'austénite pour l'acier correspondant.
  2. Procédé selon la revendication 1, caractérisé :
    - en ce que le recuit de stabilisation est conduit à 950°C sous vide, en atmosphère de gaz inerte ou légèrement réductrice.
  3. Procédé selon la revendication 1, caractérise :
    - en ce que la durée du recuit de stabilisation se détermine en fonction de la nuance d'acier et se monte à au moins 1/4 d'heure, de préférence à 2 heures.
  4. Procédé selon la revendication 3, caractérise :
    - en ce que la durée de recuit pour des plaques d'épaisseur supérieure à 10 mm ou pour des barres de diamètre supérieur à 15 mm est allongée de 1-2 minutes par mm d'augmentation d'épaisseur du matériau.
  5. Procédé selon la revendication 1, caractérise :
    - en ce que le refroidissement après le recuit de stabilisation se déroule à une vitesse de plus de 30 K/mm.
EP88106438A 1987-09-10 1988-04-22 Procédé pour la fabrication d'un produit semi-fini ou produit fini à partir d'un acier martensitique au chrome, fortement allié et en phase unique par déformation à froid et/ou à chaud Expired - Lifetime EP0306609B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19873730379 DE3730379A1 (de) 1987-09-10 1987-09-10 Verfahren zur herstellung eines halbzeugs oder endproduktes aus einphasigem, hochlegiertem martensitischem chromstahl durch warm- und/oder kaltverformung
DE3730379 1987-09-10

Publications (3)

Publication Number Publication Date
EP0306609A2 EP0306609A2 (fr) 1989-03-15
EP0306609A3 EP0306609A3 (fr) 1991-04-17
EP0306609B1 true EP0306609B1 (fr) 1994-08-24

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EP88106438A Expired - Lifetime EP0306609B1 (fr) 1987-09-10 1988-04-22 Procédé pour la fabrication d'un produit semi-fini ou produit fini à partir d'un acier martensitique au chrome, fortement allié et en phase unique par déformation à froid et/ou à chaud

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EP (1) EP0306609B1 (fr)
DE (1) DE3730379A1 (fr)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4009239C1 (fr) * 1990-03-22 1991-11-21 Kernforschungszentrum Karlsruhe Gmbh, 7500 Karlsruhe, De
CA2070431C (fr) † 1990-10-05 1995-11-14 Hirohisa Morishita Copolymere de polyoxymethylene et procede pour sa production
DE4101220C2 (de) * 1991-01-17 1994-10-06 Kernforschungsz Karlsruhe Verfahren zur Herstellung eines Halbzeugs oder Werkstücks
EP0643721B1 (fr) 1991-02-14 2001-05-16 PE Corporation (NY) Procede permettant de synthetiser des analogues d'oligonucleotides sulfures
DE19941993C1 (de) * 1999-09-02 2000-12-14 Benteler Werke Ag Verfahren zur Herstellung eines biegesteifen torsionsweichen Rohrprofils als Querträger für eine Verbundlenkerhinterachse eines Personenkraftwagens
CZ301718B6 (cs) * 2009-04-08 2010-06-02 Comtes Fht A.S. Zpusob zpracování ocelového polotovaru nad teplotou Ac1
CN104313278B (zh) * 2014-10-23 2016-08-17 北京科技大学 一种马氏体型耐热钢中δ铁素体含量控制方法

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4168994A (en) * 1978-11-13 1979-09-25 Combustion Engineering, Inc. Thermal homogenization of steam generating tubing

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
STAHL-EISEN-LISTE, 6. Auflage, Teil 2.1, Seiten 108, 109; 1977 Verlag Stahleisen, Düsseldorf, DE, Werkstoff-Nr. 1.4914 *
The Making, Shaping and Treating of Steel, United States Steel, 9. Auflage, 1971, Seiten 1170-1171 *

Also Published As

Publication number Publication date
EP0306609A2 (fr) 1989-03-15
DE3730379A1 (de) 1989-03-30
DE3730379C2 (fr) 1991-02-21
EP0306609A3 (fr) 1991-04-17

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