EP0092629B1 - Process for the manufacture of rods and tubes from steels with great mechanical properties - Google Patents

Process for the manufacture of rods and tubes from steels with great mechanical properties Download PDF

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Publication number
EP0092629B1
EP0092629B1 EP82420154A EP82420154A EP0092629B1 EP 0092629 B1 EP0092629 B1 EP 0092629B1 EP 82420154 A EP82420154 A EP 82420154A EP 82420154 A EP82420154 A EP 82420154A EP 0092629 B1 EP0092629 B1 EP 0092629B1
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Prior art keywords
bars
tubes
weight
steel
hot
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German (de)
French (fr)
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EP0092629A1 (en
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Bernard Heritier
Philippe Maitrepierre
Jaime Rofes-Vernis
Alain Wyckaert
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Ugine Aciers
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Ugine Aciers
Ugine Savoie SA
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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
    • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese

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

Abstract

The invention relates to a method of making steel bars and tubes with good mechanical characteristics. The process consists of manufacturing a low alloy steel containing 0.06 to 0.12% carbon as well as additions with well-determined contents of Si, Mn, Nb, Al, B and optionally V. The steel is used in a raw state of hot rolling, optionally followed by tempering. The bars and tubes obtained in this manner are used for applications in which it is necessary to have a high elastic limit associated with high resistance.

Description

Le procédé qui fait l'objet de l'invention concerne une nouvelle méthode de fabrication de barres et de tubes en acier faiblement allié, présentant à l'état brut de transformation à chaud de hautes caractéristiques mécaniques, la limite d'élasticité, la charge de rupture et la résilience étant particulièrement élevées. Le procédé concerne également une méthode qui permet d'abaisser de façon très importante les frais de transformation de l'acier sous forme de barres ou de tubes à hautes caractéristiques mécaniques.The process which is the subject of the invention relates to a new method of manufacturing bars and tubes of low alloy steel, having in the raw state of hot transformation high mechanical characteristics, the elastic limit, the load. and the resilience being particularly high. The method also relates to a method which makes it possible to significantly reduce the costs of transforming steel in the form of bars or tubes with high mechanical characteristics.

L'invention concerne aussi des barres et des tubes présentant de hautes caractéristiques mécaniques à l'état brut de laminage à chaud grâce à la combinaison d'une composition définie à l'intérieur de fourchettes précises et d'une structure à prédominance bainitique.The invention also relates to bars and tubes having high mechanical characteristics in the raw state of hot rolling by virtue of the combination of a composition defined within precise ranges and a predominantly bainitic structure.

De façon plus précise, l'invention concerne des barres ou tubes présentant des caractéristiques mécaniques au moins égales aux caractéristiques minimales du grade N80 de l'American Petroleum Institute, obtenues par une méthode d'élaboration et de transformation beaucoup plus économique que les méthodes habituellement utilisées.More specifically, the invention relates to bars or tubes having mechanical characteristics at least equal to the minimum characteristics of grade N80 of the American Petroleum Institute, obtained by a production and transformation method much more economical than the usual methods. used.

Les méthodes habituelles de fabrication de barres ou tubes présentant des caractéristiques mécaniques correspondant au grade N80 de l'American Petroleum Institute, consistent à élaborer un acier faiblement allié tel que l'acier suivant norme AFNOR 40MD7. Cet acier contient en % en masse ; C 0,25 à 0,50 ; Mn 1,20 à 1,70 ; Mo 0,20 et les impuretés habituelles. Après coulée en lingots ou en barres de coulée continue, cet acier est transformé par laminage à chaud en barres de la section voulue, par exemple des barres rondes de 100 à 200 mm de diamètre. A l'état brut de laminage à chaud, ces barres ont généralement une limite élastique d'environ 750 MPa mais une résilience faible inférieure à 30 Joules/cm2, mesurée sur éprouvettes KCU.The usual methods of manufacturing bars or tubes having mechanical characteristics corresponding to grade N80 of the American Petroleum Institute, consist in developing a low alloy steel such as steel according to standard AFNOR 40MD7. This steel contains in% by mass; C 0.25 to 0.50; Mn 1.20 to 1.70; Mo 0.20 and the usual impurities. After casting in ingots or in continuous casting bars, this steel is transformed by hot rolling into bars of the desired section, for example round bars of 100 to 200 mm in diameter. In the raw hot rolling state, these bars generally have an elastic limit of around 750 MPa but a low resilience of less than 30 Joules / cm 2 , measured on KCU test pieces.

Dans le but de leur conférer les caractéristiques mécaniques désirées, on leur fait subir un traitement thermique comportant 'un recuit d'austénitisation à une température d:environ 875 °C, suivi d'un refroidissement à l'air jusqu'au voisinage de la température ambiante et enfin, un revenu à une température d'environ 600 à 650 °C.In order to give them the desired mechanical characteristics, they are subjected to a heat treatment comprising an austenitization annealing at a temperature of about 875 ° C., followed by air cooling to the vicinity of the room temperature and finally, an income at a temperature of about 600 to 650 ° C.

Les barres ainsi obtenues présentent des caractéristiques mécaniques conformes au grade N80, à savoir :

Figure imgb0001
The bars thus obtained have mechanical characteristics in accordance with grade N80, namely:
Figure imgb0001

Ces opérations de traitement thermique après laminage sont coûteuses en temps de fabrication, en frais de manutention et de contrôle ainsi qu'en énergie thermique et nécessitent, de plus, de disposer d'importantes installations spécialisées pour l'exécution de tels traitements.These post-lamination heat treatment operations are costly in terms of manufacturing time, handling and control costs as well as thermal energy and also require the use of large specialized facilities for carrying out such treatments.

On a cherché la possibilité de mettre au point un procédé d'élaboration et de transformation appliqué à une composition particulière d'acier permettant d'obtenir à l'état brut de laminage à chaud, des barres présentant directement les caractéristiques mécaniques exigées par les utilisateurs. On a recherché aussi la possibilité de réaliser, à partir de ces barres, par perçage à chaud, puis laminage à chaud sur mandrin, des tubes présentant à l'état brut de laminage à chaud des caractéristiques mécaniques comparables à celles de ces barres.We looked for the possibility of developing an elaboration and transformation process applied to a particular steel composition making it possible to obtain, in the raw state of hot rolling, bars having directly the mechanical characteristics required by the users. . The possibility has also been sought of producing, from these bars, by hot drilling, then hot rolling on a mandrel, tubes having in the raw hot rolling state mechanical characteristics comparable to those of these bars.

On a recherché en particulier la.possibilité d'obtenir à l'état brut de laminage à chaud des barres ou tubes présentant une limite d'élasticité E supérieure à 550 MPa associée à une résilience KCU supérieure à 80 J/cm2..We sought in particular the possibility of obtaining in the raw state of hot rolling bars or tubes having an elastic limit E greater than 550 MPa associated with a resilience KCU greater than 80 J / cm2. .

On a eu l'idée, suivant l'invention, d'élaborer un acier présentant la composition suivante en % en masse : C 0,060 à 0,120 et de préférence 0,080 à 0,110 ; Si 0,30 à 0,70 ; Mn 1,30 à 2,00 et de préférence 1,50 à 1,80 ; Nb 0,050 à 0,120 ; B 0,0025 à 0,0060 ; AI 0,040 à 0,080 ; N .¡;; 0,010 ; V _ 0,120 ; éventuellement S 0,040 à 0,070 ; reste Fe et impuretés habituelles. Cet acier étant le plus souvent élaboré à partir de ferrailles peut contenir d'assez nombreuses impuretés métalliques telles que Ni, Cr, Cu et Mo, le total des impuretés métalliques ne dépassant pas environ 1 %. Une addition éventuelle de V jusqu'à 0,12 %, de préférence entre 0,060 et 0,12 %, peut également être effectuée. Il peut comporter aussi une addition de S jusqu'à une teneur d'environ 0,040 à 0,070 % pour améliorer l'usinabilité. On peut combiner avec cette addition de très petites additions de métaux alcalino-terreux tels que Ca et/ou Mg, et/ou de métaux des terres rares pour améliorer l'isotropie des caractéristiques mécaniques.We had the idea, according to the invention, of developing a steel having the following composition in% by mass: C 0.060 to 0.120 and preferably 0.080 to 0.110; If 0.30 to 0.70; Mn 1.30 to 2.00 and preferably 1.50 to 1.80; Nb 0.050 to 0.120; B 0.0025 to 0.0060; AI 0.040 to 0.080; NOT .;; 0.010; V _ 0.120; optionally S 0.040 to 0.070; remains Fe and usual impurities. This steel being most often produced from scrap metal can contain quite a number of metallic impurities such as Ni, Cr, Cu and Mo, the total of metallic impurities not exceeding about 1%. A possible addition of V up to 0.12%, preferably between 0.060 and 0.12%, can also be carried out. It can also include an addition of S up to a content of approximately 0.040 to 0.070% to improve the machinability. It is possible to combine with this addition of very small additions of alkaline earth metals such as Ca and / or Mg, and / or of rare earth metals to improve the isotropy of the mechanical characteristics.

Après coulée sous forme de lingots ou de barres de coulée continue, on transforme lesdits lingots ou lesdites barres dans des conditions contrôlées. Le dégrossissage des lingots, au blooming, est effectué de façon classique à une température d'environ 1 200 à 1 050 °C. Les barres ainsi obtenues, ou bien les barres de coulée continue subissent un laminage contrôlé à une température comprise entre 1 000 et 700 °C en une seule chaude jusqu'à l'obtention de barres de la section voulue, circulaire ou non, avec un taux de réduction de la section initiale d'au moins 50 %.After casting in the form of ingots or bars of continuous casting, said ingots or said bars are transformed under controlled conditions. The roughing of the ingots, during blooming, is carried out in a conventional manner at a temperature of approximately 1,200 to 1,050 ° C. The bars thus obtained, or else the continuous casting bars undergo a controlled rolling at a temperature of between 1000 and 700 ° C. in a single hot operation until bars of the desired section are obtained, circular or not, with a reduction rate of the initial section of at least 50%.

Dans le cas du laminage de tubes, la barre brute de laminage à chaud est percée par perçage à chaud puis l'ébauche de tube obtenue est laminée à chaud sur mandrin jusqu'à la dimension désirée. Pour les barres comme pour les tubes, il peut être avantageux d'effectuer un revenu permettant de compléter la précipitation du Nb et dont l'intérêt principal est de relever la limite d'élasticité. Ce revenu est de préférence effectué à une température comprise entre 550 et 700 °C.In the case of tube rolling, the raw hot rolling bar is pierced by hot drilling and then the tube blank obtained is hot rolled on a mandrel to the desired dimension. For bars as for tubes, it may be advantageous to make an income to complete the precipitation of Nb and whose main interest is to raise the elastic limit. This tempering is preferably carried out at a temperature between 550 and 700 ° C.

Les hautes caractéristiques mécaniques des produits obtenus par le procédé suivant l'invention résultent essentiellement de l'action de l'opération de laminage à chaud effectuée, dans des limites de température définies et avec un taux de corroyage bien déterminé, sur un acier dont la composition est à l'intérieur des limites précisées plus haut. Grâce à sa faible teneur en carbone, associée à une température en manganèse bien définie et à une combinaison d'additions de niobium, bore et aluminium, dans des proportions critiques, il est possible de supprimer les traitements classiques qui étaient considérés comme obligatoires pour obtenir ces caractéristiques mécaniques tout à fait particulières.The high mechanical properties of the products obtained by the process according to the invention essentially result from the action of the hot rolling operation carried out, within defined temperature limits and with a well-defined wrought rate, on a steel whose composition is within the limits specified above. Thanks to its low carbon content, associated with a well-defined manganese temperature and a combination of additions of niobium, boron and aluminum, in critical proportions, it is possible to eliminate the conventional treatments which were considered compulsory in order to obtain these very specific mechanical characteristics.

L'exemple non limitatif ci-après décrit un mode de mise en oeuvre du procédé suivant l'invention.The nonlimiting example below describes an embodiment of the method according to the invention.

On élabore un acier contenant en % en masse : C 0,085 ; Si 0,452 ; Mn 1,520 ; Nb 0,060 ; AI 0,071 ; B 0,0049 ; N 0,007 ; Ni 0,136 ; Cr 0,167 ; Cu 0,228 ; S 0,028 ; P 0,017 ; reste Fe et impuretés habituelles.A steel is produced containing in% by mass: C 0.085; If 0.452; Mn 1.520; Nb 0.060; AI 0.071; B 0.0049; N 0.007; Ni 0.136; Cr 0.167; Cu 0.228; S 0.028; P 0.017; remains Fe and usual impurities.

Cet acier est coulé en lingots de 5,8 tonnes. Ces lingots sont préchauffés à 1 230 °C, puis dégrossis au blooming en barres de 182 x 182 mm à une température comprise entre 1 200 et 1 050 °C puis laminés de façon continue en barres rondes de diamètre 140 mm. La température d'entrée est d'environ 950 °C et la température à la sortie de la dernière cage du laminoir est d'environ 710 °C. On prélève sur ces barres, brutes de laminage à chaud, des éprouvettes de 10 mm de diamètre pour essais de traction ainsi que des éprouvettes pour mesures de résilience du type KCU sens long. Ces prélèvements sont faits à 25 mm de la surface (axe de l'éprouvette 0 10 mm situé à 25 mm au-dessous de cette surface).This steel is cast in 5.8-ton ingots. These ingots are preheated to 1,230 ° C, then roughed out in blooming in 182 x 182 mm bars at a temperature between 1,200 and 1,050 ° C and then continuously rolled into 140 mm diameter round bars. The inlet temperature is approximately 950 ° C and the temperature at the outlet of the last stand of the rolling mill is approximately 710 ° C. 10 mm diameter test pieces for tensile tests as well as test pieces for resilience measurements of the long KCU type are taken from these bars, rough hot-rolled. These samples are taken 25 mm from the surface (axis of the test piece 0 10 mm located 25 mm below this surface).

Le tableau ci-après donne les caractéristiques mécaniques obtenues.

Figure imgb0002
The table below gives the mechanical characteristics obtained.
Figure imgb0002

On voit que la limite élastique est supérieure à 550 MPa et que la résilience est supérieure à 80 J/cm2. Par ailleurs, les examens micrographiques montrent que la structure de la barre est homogène et à prédominance bainitique en tous points. Il est également possible d'appliquer le procédé suivant l'invention à la réalisation de barres de section autre que circulaire, telles que des barres carrées ou rectangulaires ou de section quelconque. Dans tous les cas, l'opération de laminage qui permet d'obtenir ces barres doit être effectuée à une température comprise entre 1 000 et 700 °C et le taux de corroyage doit de préférence atteindre au moins 50 % sans réchauffage intermédiaire.We see that the elastic limit is greater than 550 MPa and that the resilience is greater than 80 J / cm 2 . Furthermore, micrographic examinations show that the structure of the bar is homogeneous and predominantly bainitic in all points. It is also possible to apply the method according to the invention to the production of bars of section other than circular, such as square or rectangular bars or of any section. In all cases, the rolling operation which makes it possible to obtain these bars must be carried out at a temperature of between 1000 and 700 ° C. and the rate of working must preferably reach at least 50% without intermediate reheating.

Comme cela a été dit plus haut, il est possible d'accroître encore la limite élastique des barres brutes de laminage à chaud en leur faisant subir un revenu à une température de préférence comprise entre 550 et 700 °C.As mentioned above, it is possible to further increase the elastic limit of the raw hot-rolling bars by subjecting them to tempering at a temperature preferably between 550 and 700 ° C.

Claims (10)

1. A process for producing bars or tubes of steel with in the crude hot rolled state a predominantly bainitic fine structure, an elastic limit of higher than 550 MPa and a resilience of higher than 80 J/cm2, characterised in that it comprises the following steps :
- producing, in ingot or bar form, a steel containing the following in % by weight : C 0.060 to 0.120 ; Si 0.30 to 0.70 ; Mn 1.30 to 2.00 ; Nb 0.050 to 0.120 ; B 0.0025 to 0.0060 ; AI 0.040 to 0.080 ; N ≤ 0.010 ; V ≤ 0.120 ; optionally S. 0.040 to 0.070 ; the usual impurities among which the total of metallic impurities such as Ni, Cr, Cu and Mo does not exceed 1.0 ; and the balance Fe ;
- converting said ingot or said bar in the hot condition into bars or tubes with a final controlled rolling operation at a temperature of between 1 000 and 700 °C in a single heat, with a rate of reduction of the initial section of at least 50 %.
2. A process according to claim 1 characterised in that the steel contains in % by weight : C 0.080 to 0.110 and Mn 1.50 to 1.80.
3. A process according to claim 1 or claim 2 characterised in that the steel contains in % by weight: V 0.060 to 0.120.
4. A process according to one of claims 1 to 3 characterised in that the steel contains an addition of, in % by weight : S 0.040 to 0.070.
5. A process according to one of claims 1 to 4 characterised in that the bars produced by hot rolling are then subjected to hot piercing and then hot rolled over a mandrel in the form of tubes.
6. A process according to one of claims 1 to 5 characterised in that the hot rolled bars or tubes are subjected to tempering at a temperature of between 550 and 700 °C.
7. Bars or tubes of steel having in the crude hot rolled state a predominantly bainitic fine-grain structure, an elastic limit at 25 mm beneath the surface which is greater than 550 MPa and a resilience of greater than 80 J/cm2, characterised in that they contain the following in % by weight: C 0.060 to 0.120 ; Si 0.30 to 0.70 ; Mn 1.30 to 2.00 ; Nb 0.050 to 0.120 ; Al 0.040 to 0.080 ; B 0.0025 to 0.0060 ; N ≤ 0.010 ; V ≤ 0.120 ; optionally S 0.040 to 0.070 ; usual impurities among which the total of metallic impurities such as Ni, Cr, Cu and Mo does not exceed 1.0 ; and the balance Fe.
8. Bars or tubes according to claim 6 characterised in that they contain the following in % by weight : C 0.080 to 0.110 and Mn 1.50 to 1.80.
9. Bars or tubes according to claim 8 characterised in that they contain in % by weight : V 0.060 to 0.120.
10. Bars or tubes according to claim 6 or claim 7 characterised in that they contain an addition of, in % by weight : S 0.040 to 0.070.
EP82420154A 1982-04-22 1982-11-15 Process for the manufacture of rods and tubes from steels with great mechanical properties Expired EP0092629B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT82420154T ATE20479T1 (en) 1982-04-22 1982-11-15 PROCESSES FOR THE MANUFACTURE OF RODS AND TUBES FROM STEEL WITH HIGH MECHANICAL PROPERTIES.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8207281 1982-04-22
FR8207281A FR2525503B1 (en) 1982-04-22 1982-04-22

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EP0092629A1 EP0092629A1 (en) 1983-11-02
EP0092629B1 true EP0092629B1 (en) 1986-06-18

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US (1) US4474627A (en)
EP (1) EP0092629B1 (en)
JP (1) JPS591656A (en)
AT (1) ATE20479T1 (en)
CA (1) CA1198614A (en)
DE (1) DE3271793D1 (en)
FR (1) FR2525503B1 (en)

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DE3832014C2 (en) * 1988-09-16 1994-11-24 Mannesmann Ag Process for the production of high-strength seamless steel tubes
CA2135255C (en) * 1994-05-26 2000-05-16 William E. Heitmann Cold deformable, high strength, hot rolled bar and method for producing same
FR2727981B1 (en) * 1994-12-13 1997-01-10 Ascometal Sa METHOD FOR MANUFACTURING A PART OF MECHANICAL CONSTRUCTION STEEL AND A PART THUS MANUFACTURED
JP5229823B2 (en) * 2009-09-25 2013-07-03 株式会社日本製鋼所 High-strength, high-toughness cast steel and method for producing the same

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FR2231758A1 (en) * 1973-06-04 1974-12-27 Hoogovens Ijmuiden Bv
DE2620449A1 (en) * 1975-05-14 1976-11-25 Centre Rech Metallurgique Steel bolt mfr. - with hardened and tempered skin and unhardened core
DE2635188A1 (en) * 1976-08-05 1978-02-09 Bosch Gmbh Robert High tensile, cold headed bolts, screws etc. - made from patented rod or wire and then tempered

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JPS591656A (en) 1984-01-07
EP0092629A1 (en) 1983-11-02
FR2525503B1 (en) 1984-07-13
CA1198614A (en) 1985-12-31
US4474627A (en) 1984-10-02
FR2525503A1 (en) 1983-10-28
ATE20479T1 (en) 1986-07-15
DE3271793D1 (en) 1986-07-24

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