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US3926689A - Method of producing hot rolled steel rods or bars - Google Patents

Method of producing hot rolled steel rods or bars Download PDF

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Publication number
US3926689A
US3926689A US411227A US41122773A US3926689A US 3926689 A US3926689 A US 3926689A US 411227 A US411227 A US 411227A US 41122773 A US41122773 A US 41122773A US 3926689 A US3926689 A US 3926689A
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United States
Prior art keywords
bar
rod
core
surface layer
quenching
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Expired - Lifetime
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US411227A
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Yves Jean Respen
Paul Andre Cosse
Mario Economopoulos
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Centre de Recherches Metallurgiques CRM ASBL
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Centre de Recherches Metallurgiques CRM ASBL
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Priority to US05/617,156 priority Critical patent/US4016015A/en
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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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
    • 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
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite
    • 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
    • C21D2221/00—Treating localised areas of an article
    • C21D2221/10—Differential treatment of inner with respect to outer regions, e.g. core and periphery, respectively

Definitions

  • the present invention relates to a treatment for improving the quality of a rolled steel rod or bar and especially a concrete-reinforcing rod or bar.
  • the process can be applied to both killed and semikilled steels and rimming steels.
  • the main qualities looked for in a steel rod or bar are, inter alia, as high as possible a yield point for the grade of steel, used as well as weldability, fatigue resistance, and sufficient ductility for the intended use.
  • the steel can be subjected to a suitable cooling treatment, preferably applied directly at the exit of the rolling mill, which enables the yield point of the rod or bar to be raised to some extent.
  • the present invention provides a process for the production of a steel rod or bar in a hot rolling mill, including superficially quenching the rod or bar at the exit of the finishing stand, with the core of the rod or bar having a temperature of approximately 850C at the end of the quenching step.
  • the invention provides a process for the production of a, steel rod or bar in a hot rolling mill, including: superficially quenching the rod or bar at the exit of the finishing stand, to give the surface layer of the rod or bar a bainitic or martensitic structure, with the core of the rod or bar remaining austenitic and subsequently cooling the rod or bar at such a rate that the austenitic core transforms to ferrite and carbides.
  • the rod or bar is subjected to superficial quenching by means of a suitable cooling liquid, and the conditions of quenching are selected so that at the outlet of the liquid-cooling zone, the core of the rod or bar has a temperature of about 850C (e.g. 800860C).
  • the rod or bar stays on the cooler (air cooling), so that it is possible for the quenched surface layer to become tempered and for the austenitic core of the rod or bar to transform to ferrite and carbides (e.g. to transform to pearlite).
  • the quenched surface layer is either of martensite or bainite.
  • the desired quenching of the bar is obtained by selecting the cooling devices and suitably adjusting the length and arrangement of these devices, for example cooling sprays.
  • the steel may have an yield point of 45 kg/mm when the installation has a low heat transfer coefficient, and may have an yield point of 65 kg/mm if this coefficient is raised, if, for example, a short cooling spray is used but where very intense cooling of the rod or bar has taken place (e.g., if the water contains a mineral salt or a surface-active agent in suspension or solution).
  • the example just given allows the improvement in the quality of the rod or bar obtained by implementing the process of the invention to be appreciated.
  • the rolled test-pieces examined were concrete-reinforcing bars 12 mm in diameter and of steel having the following composition:
  • the process according to the invention enables rod and bar of a particular type to be obtained, namely having a bainitic or martensitic surface layer and a core composed of ferrite and carbides.
  • FIG. 1 shows the variation of the hardness of the steel along a radius of a cross-section of a concrete-reinforcing bar as treated according to the invention.
  • the hardness (DI-IP) is shown along the ordinate while the abscissa indicates the distance (d) from the surface of the bar.
  • FIG. 2a illustratesa cross-section of a concrete-reinforcing bar treated according to the invention in which the surface layer and core can be distinctly seen.
  • FIG. 2b shows the martensitic surface layer, and
  • FIG. shows the ferrite and carbides which constitute the core of the bar (magnification: 500 x).
  • a process for the production of a steel rod or bar in a hot rolling mill comprising: superficially quenching the rod or bar at the exit of a finishing stand to form bainite or martensite in the surface layer of the rod or 2.
  • a process for the production of a steel rod or bar in a hot rolling mill including: superficially quenching the rod or bar at the exit of a finishing stand, to give the surface layer of the rod or bar a bainitic or martensitic structure, with the core of the rod or bar remaining austenitic; and subsequently cooling the rod or bar at such a rate that the austenitic core transforms to ferrite and carbides.
  • a process for the production of a steel rod or bar in ahot rolling mill comprising: superficially quenching the rod or bar at the exit of a finishing stand, to transform austenite in the surface layer of the rod or bar to bainite or martensite, with the core of the rod or bar remaining austenite; and subsequently cooling the rod or bar at such a rate that the core of austenite transforms to ferrite and carbides while the surface layer is tempered by the heat transferred from the core.

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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)
  • Manufacturing & Machinery (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Articles (AREA)
  • Heat Treatment Of Strip Materials And Filament Materials (AREA)

Abstract

Steel rod or bar at the exit of the finishing stand of a hot rolling mill is superficially quenched, so that the surface layer of the rod or bar is given a bainitic or martensitic structure. Immediately after quenching, the core of the rod or bar is at about 850*C and, therefore, still austenitic. Subsequent air cooling allows the austenite to transform to ferrite and carbides, while the surface layer is tempered by the heat transferred to it from the core.

Description

United States Paten Respen et a1. y
[ Dec. 16, 1975 METHOD OF PRODUCING HOT ROLLED STEEL RODS OR BARS Inventors: Yves Jean Respen, l-lerstal; Paul Andre Cosse, Bellaire; Mario Economopoulos, Liege, all of Belgium Centre de Recherches Metallurgiques Centrum voor Research in de Metallurgie, Brussels, Belgium Filed: Oct. 31, 1973 Appl. No.: 411,227
Foreign Application Priority Data Assignee:
Oct. 31, 1972 Belgium 790867 US. Cl. 148/l2.4; 148/143; 148/156; 148/157 Int. Cl. BZIB 3/00 Field of Search 148/13, 14, 18, 39, 143, 148/144,145,152,153, 156,157, 12 B,
[56] References Cited UNITED STATES PATENTS 3,111,436 11/1963 McGavin 148/143 3,756,870 9/1973 Kasper et a1 148/153 X Primary ExaminerL. Dewayne Rutledge Assistant ExaminerArthur J. Steiner Attorney, Agent, or Firm Holrnan & Stern [57] ABSTRACT 5 Claims, 5 Drawing Figures U.S. Patent Dec. 16, 1975 Sheet 2 of2 3,926,689
(5OOX) (5OOX) METHOD OF PRODUCING HOT ROLLED STEEL RODS OR BARS BACKGROUND OF THE INVENTION The present invention relates to a treatment for improving the quality of a rolled steel rod or bar and especially a concrete-reinforcing rod or bar.
The process can be applied to both killed and semikilled steels and rimming steels.
The main qualities looked for in a steel rod or bar are, inter alia, as high as possible a yield point for the grade of steel, used as well as weldability, fatigue resistance, and sufficient ductility for the intended use.
To improve the weldability and ductility of steel, it is necessary to reduce its carbon and manganese contents, which, however, causes a reduction in its tensile strength. In order to remedy this disadvantage, the steel can be subjected to a suitable cooling treatment, preferably applied directly at the exit of the rolling mill, which enables the yield point of the rod or bar to be raised to some extent.
When a rod or bar (such as concrete-reinforcing rod or bar) is cooled by convection or radiation, the law of cooling almost only depends on its diameter, which has the result that, for a bar of a specific diameter, it is nec essary in order to modify its elastic limit, to use other means in order to complement the pure and simple act of cooling.
Of these means, it is particularly worth mentioning the addition of dispersoidal elements (e.g. Nb and V) which cause grain refinement and precipitation hardening of the ferrite. This is indeed efficacious but has the disadvantage that the cost increases as the yield point is raised.
Thus what is desired is a process which avoids the aforesaid disadvantage without the carbon and manganese contents in the steel having to be increased in a way which is unacceptable from the point of view of weldability.
SUMMARY OF THE INVENTION In one aspect, the present invention provides a process for the production of a steel rod or bar in a hot rolling mill, including superficially quenching the rod or bar at the exit of the finishing stand, with the core of the rod or bar having a temperature of approximately 850C at the end of the quenching step.
In another aspect, the invention provides a process for the production of a, steel rod or bar in a hot rolling mill, including: superficially quenching the rod or bar at the exit of the finishing stand, to give the surface layer of the rod or bar a bainitic or martensitic structure, with the core of the rod or bar remaining austenitic and subsequently cooling the rod or bar at such a rate that the austenitic core transforms to ferrite and carbides.
In the preferred process, at the exit of the finishing stand of the hot rolling mill, the rod or bar is subjected to superficial quenching by means of a suitable cooling liquid, and the conditions of quenching are selected so that at the outlet of the liquid-cooling zone, the core of the rod or bar has a temperature of about 850C (e.g. 800860C). The rod or bar stays on the cooler (air cooling), so that it is possible for the quenched surface layer to become tempered and for the austenitic core of the rod or bar to transform to ferrite and carbides (e.g. to transform to pearlite).
According to the conditions used, the quenched surface layer is either of martensite or bainite.
From the practical point of view, the desired quenching of the bar is obtained by selecting the cooling devices and suitably adjusting the length and arrangement of these devices, for example cooling sprays.
Although, whatever conditions of quenching are applied to the rod or bar. the mechanical properties of the rod or bar are improved compared with bars which have not been subjected to this treatment, it has nevertheless been found that the improvement increases as the heat transfer coefficient of the quenching installation increases. Thus, for a treatment lasting 0.55 seconds, the steel may have an yield point of 45 kg/mm when the installation has a low heat transfer coefficient, and may have an yield point of 65 kg/mm if this coefficient is raised, if, for example, a short cooling spray is used but where very intense cooling of the rod or bar has taken place (e.g., if the water contains a mineral salt or a surface-active agent in suspension or solution).
The example just given allows the improvement in the quality of the rod or bar obtained by implementing the process of the invention to be appreciated. The rolled test-pieces examined were concrete-reinforcing bars 12 mm in diameter and of steel having the following composition:
carbon 0.24% manganese 1.3 8% silicon 0.0 8% aluminium 0.002% sulphur 0.0 20% In the as-rolled state, the bars in question had the following properties:
Yield Point (Re) 35 t l kg/mm Tensile strength (Rr) 58 i 2 kg/mm Elongation (A 33 i 2 7r Treated according to the process of the invention, by passing through a water spray with a high heat transfer coefficient, the bars had the following properties:
Re A Re/Rr Time in water spray kgfrnm 045 seconds 50 27 0.75 0.65 seconds I9 0.85
The process according to the invention enables rod and bar of a particular type to be obtained, namely having a bainitic or martensitic surface layer and a core composed of ferrite and carbides.
BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE DRAWINGS FIG. 1 shows the variation of the hardness of the steel along a radius of a cross-section of a concrete-reinforcing bar as treated according to the invention. The hardness (DI-IP) is shown along the ordinate while the abscissa indicates the distance (d) from the surface of the bar.
FIG. 2a illustratesa cross-section of a concrete-reinforcing bar treated according to the invention in which the surface layer and core can be distinctly seen. FIG. 2b shows the martensitic surface layer, and FIG. shows the ferrite and carbides which constitute the core of the bar (magnification: 500 x).
We claim:
1. A process for the production of a steel rod or bar in a hot rolling mill, comprising: superficially quenching the rod or bar at the exit of a finishing stand to form bainite or martensite in the surface layer of the rod or 2. A process for the production of a steel rod or bar in a hot rolling mill, including: superficially quenching the rod or bar at the exit of a finishing stand, to give the surface layer of the rod or bar a bainitic or martensitic structure, with the core of the rod or bar remaining austenitic; and subsequently cooling the rod or bar at such a rate that the austenitic core transforms to ferrite and carbides.
3. A process for the production of a steel rod or bar in ahot rolling mill, comprising: superficially quenching the rod or bar at the exit of a finishing stand, to transform austenite in the surface layer of the rod or bar to bainite or martensite, with the core of the rod or bar remaining austenite; and subsequently cooling the rod or bar at such a rate that the core of austenite transforms to ferrite and carbides while the surface layer is tempered by the heat transferred from the core.
4. The process as claimed in claim 3, in which the water contains a mineral salt or a surface-active agent, in suspension or solution.
5. The process as claimed in claim 1, in which the rate of removal of heat from the rod or bar during superficial quenching is higher than that obtained in a water quench.

Claims (5)

1. A PROCESS FOR THE PRODUCTION OF A STEEL ROD OR BAR IN A HOT ROLLING MILL, COMPRISING: SUPERFICIALLY QUENCHING THE ROD OR BAR AT THE EXIT OF A FINISHING STAND TO FORM BAINITE OR MARTENSITE IN THE SURFACE LAYER OF THE ROD OR BAR, WITH THE CORE OF THE ROD OR BAR HAVING A TEMPERATURE OF APPROXIMATELY 850*C AT THE END OF THE QUENCHING STEP; AND SUBSEQUENTLY COOLING THE ROD OR BAR AT SUCH A RATE THAT THE CORE TRANSPRMS TO FERRITE AND CARBIDES WHILE THE SURFACE LAYER OF THE ROD OR BAR IS TEMPERED BY THE HEAT TRANSFERRED FORM THE CORE TO THE SURFACE LAYER.
2. A process for the production of a steel rod or bar in a hot rolling mill, including: superficially quenching the rod or bar at the exit of a finishing stand, to give the surface layer of the rod or bar a bainitic or martensitic structure, with the core of the rod or bar remaining austenitic; and subsequently cooling the rod or bar at such a rate that the austenitic core transforms to ferrite and carbides.
3. A process for the production of a steel rod or bar in a hot rolling mill, comprising: superficially quenching the rod or bar at the exit of a finishing stand, to transform austenite in the surface layer of the rod or bar to bainite or martensite, with the core of the rod or bar remaining austenite; and subsequently cooling the rod or bar at such a rate that the core of austenite transforms to ferrite and carbides while the surface layer is tempered by the heat transferred from the core.
4. The process as claimed in claim 3, in which the water contains a mineral salt or a surface-active agent, in suspension or solution.
5. The process as claimed in claim 1, in which the rate of removal of heat from the rod or bar during superficial quenching is higher than that obtained in a water quench.
US411227A 1972-10-31 1973-10-31 Method of producing hot rolled steel rods or bars Expired - Lifetime US3926689A (en)

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US05/617,156 US4016015A (en) 1972-10-31 1975-09-26 Rolled steel rod or bar

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BE790867 1972-10-31

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JP (1) JPS49134513A (en)
BE (1) BE790867A (en)
FR (1) FR2204693B1 (en)
GB (1) GB1392269A (en)
IT (1) IT1004614B (en)
LU (1) LU68624A1 (en)
MY (1) MY8800139A (en)
NL (1) NL168001C (en)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2844331A1 (en) * 1977-10-14 1979-04-19 Centre Rech Metallurgique METHOD FOR TREATMENT OF TUBULAR STEEL PROFILES
US4175985A (en) * 1977-05-13 1979-11-27 Centre De Recherches Metallurgiques-Centrum Voor Research In De Metallurgie Method of producing steel sections of improved quality
US4242153A (en) * 1978-10-16 1980-12-30 Morgan Construction Company Methods for hot rolling and treating rod
US4298406A (en) * 1977-11-03 1981-11-03 British Steel Corporation Manufacture of steel products
EP0140592A2 (en) * 1983-10-31 1985-05-08 MORGAN CONSTRUCTION COMPANY (a Massachusetts corporation) Method and apparatus for cooling steel rod
US6330903B1 (en) * 1997-02-05 2001-12-18 Steve Weinreich Mechanism for constant balance with method for manufacture of variable pitch screw
US20090320263A1 (en) * 2008-06-26 2009-12-31 Richard Gerard Potje Methods and systems for manufacturing an axle

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL170159C (en) * 1973-06-04 1982-10-01 Estel Hoogovens Bv METHOD FOR MANUFACTURING WELDABLE LOW CARBON STEEL MATERIAL BY CONTROLLED COOLING
DD106661A1 (en) * 1973-09-24 1974-06-20
BE839080A (en) * 1976-03-01 1976-07-01 PROCESS FOR MANUFACTURING REINFORCING BARS
DE2620377A1 (en) * 1976-05-08 1977-11-17 Aeg Elotherm Gmbh METHOD FOR HEAT TREATMENT OF THICK-WALLED STEEL PIPES
DE2900271C2 (en) * 1979-01-05 1984-01-26 Stahlwerke Peine-Salzgitter Ag, 3150 Peine Weldable reinforcing steel and process for its manufacture
DE3431008C2 (en) * 1984-08-23 1986-10-16 Dyckerhoff & Widmann AG, 8000 München Heat treatment of hot rolled bars or wires
US4786338A (en) * 1985-10-31 1988-11-22 Norio Anzawa Method for cooling rolled steels
US4824492A (en) * 1987-12-23 1989-04-25 Chaparral Steel Company Method for producing a precipitation hardenable martensitic low alloy steel forging
DD268258A1 (en) * 1988-01-08 1989-05-24 Florin Stahl Walzwerk HOEHERFESTER STAHL, ESPECIALLY CONCRETE STEEL BZW. DRAWERIVORMATERIAL, WITH IMPROVED MATERIAL PROPERTIES AND BETTER PROCESSABILITY
BE1005964A6 (en) * 1992-06-29 1994-04-05 Centre Rech Metallurgique Protection method of hot rolled steel product.

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3111436A (en) * 1961-01-17 1963-11-19 Mills James Ltd Method of hardening plain carbon and low alloy steels
US3756870A (en) * 1971-05-10 1973-09-04 Park Ohio Industries Inc Induction heating method of case hardening carbon steel rod

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE762838A (en) * 1971-02-11 1971-08-11 Centre Rech Metallurgique PROCESS AND DEVICE FOR THE MANUFACTURING OF CONCRETE RODS,

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3111436A (en) * 1961-01-17 1963-11-19 Mills James Ltd Method of hardening plain carbon and low alloy steels
US3756870A (en) * 1971-05-10 1973-09-04 Park Ohio Industries Inc Induction heating method of case hardening carbon steel rod

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4175985A (en) * 1977-05-13 1979-11-27 Centre De Recherches Metallurgiques-Centrum Voor Research In De Metallurgie Method of producing steel sections of improved quality
DE2844331A1 (en) * 1977-10-14 1979-04-19 Centre Rech Metallurgique METHOD FOR TREATMENT OF TUBULAR STEEL PROFILES
US4204892A (en) * 1977-10-14 1980-05-27 Centre De Recherches Metallurgiques Centrum Voor Research In De Metallurgie Heat-treating tubular steel sections
US4298406A (en) * 1977-11-03 1981-11-03 British Steel Corporation Manufacture of steel products
US4242153A (en) * 1978-10-16 1980-12-30 Morgan Construction Company Methods for hot rolling and treating rod
EP0140592A2 (en) * 1983-10-31 1985-05-08 MORGAN CONSTRUCTION COMPANY (a Massachusetts corporation) Method and apparatus for cooling steel rod
EP0140592A3 (en) * 1983-10-31 1985-09-25 Morgan Construction Company Method and apparatus for cooling steel rod
US6330903B1 (en) * 1997-02-05 2001-12-18 Steve Weinreich Mechanism for constant balance with method for manufacture of variable pitch screw
US20090320263A1 (en) * 2008-06-26 2009-12-31 Richard Gerard Potje Methods and systems for manufacturing an axle
US8122580B2 (en) 2008-06-26 2012-02-28 American Railcar Industries, Inc. Methods for manufacturing an axle

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Publication number Publication date
JPS49134513A (en) 1974-12-25
NL7314593A (en) 1974-05-02
IT1004614B (en) 1976-07-20
GB1392269A (en) 1975-04-30
MY8800139A (en) 1988-12-31
BE790867A (en) 1973-02-15
LU68624A1 (en) 1973-12-27
NL168001B (en) 1981-09-16
FR2204693B1 (en) 1976-06-18
NL168001C (en) 1982-02-16
FR2204693A1 (en) 1974-05-24

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