US3645801A - Method of producing rolled steel having high-strength and low-impact transition temperature - Google Patents

Method of producing rolled steel having high-strength and low-impact transition temperature Download PDF

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US3645801A
US3645801A US786844A US3645801DA US3645801A US 3645801 A US3645801 A US 3645801A US 786844 A US786844 A US 786844A US 3645801D A US3645801D A US 3645801DA US 3645801 A US3645801 A US 3645801A
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temperature
rolling
workpiece
cooling
percent
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US786844A
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English (en)
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George F Melloy
Joseph D Dennison
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Bethlehem Steel Corp
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Bethlehem Steel Corp
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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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0231—Warm rolling
    • 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
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling

Definitions

  • This invention is directed to rolled steel and a method of producing the same. For convenience, the method is sometimes hereinafter called continuum rolling.”
  • Normal practice used to produce hot-rolled steel consists of heating the steel to a temperatureat which it is fully austenitic and then reducing the steel to final dimensions as rapidly as possible with a minimum of heat loss, generally finishing above the Ar temperature. Such practice takes advance of ease of working at high temperature, but does not develop the combination of desirable properties possible of development in as-rolled steel.
  • the cross-sectional area of the workpiece is reduced to final size and'shape in a sequence of rolling passes.
  • Such passes may include two general types, those intended mainly to reduce the cross-sectional area of the workpiece and those intended mainly for gage or shape and which may be accompanied by relatively little reduction.
  • a rolling sequence should comprise a few passes as possible or practical. Each pass intended primarily for reduction should therefore effect as great a reduction in cross-sectional area as possible or practical.
  • development of the aforementioned higher strength by low-finishing-temperature rolling requires reduction of cross-sectional area of approximately percent or more at the lower-than-normal temperature.
  • the steels of this invention are characterized in their asrolled condition (a) by having greater strengths and lower impact transition temperatures than steels of the same composition produced by hot rolling and (b) by having lower impact transition temperatures than steels of the same composition produced to the same strength by low-finishing-temperature rolling.
  • the method of this invention comprises:
  • step 3 4. continuing the rolling of said workpiece as it is cooling in the temperature range between the Ar, temperature and 600 F., and 4. preventing complete recrystallization at any time after completion of step 2.
  • the benefits of the invention are primarily applicable to steels containing not more than 0.35 percent carbon and not more than a total of 3 percent of other elements other than iron.
  • FIG. 1 is a schematic diagram showing the relationship between typical cooling curves of steel plates and curves representing various percentages of recrystallization.
  • FIG. 2 shows a possible continuum rolling sequence superimposed on a recrystallization diagram similar to FIG. 1.
  • FIG. 3 is a graph comparing impact transition temperatures and yield points or yield strengths of steel of a particular composition produced by continuum rolling with those of steel of the same composition produced by (1) hot rolling and (2) low-finishing-temperature rolling.
  • the method of this invention differs from prior art methods in that (a) the steel must be rolled in two temperature ranges, namely, between the Ar and the Ar temperatures and between the Ar temperature and 600"v F. and preferably in three temperature ranges, namely, the two first-mentioned temperature ranges and the hot-rolling temperature range and (b) complete recrystallization at any time after completion of the rollingin the Ar -Ar temperature range must be avoided.
  • the workpiece for rolling in the Ar -Ar, temperature range is a steel workpiece at a temperature at which it is essentially completely austenitic.
  • Various methods of obtaining said workpiece will be recognized by those skilled in the art but preferably said workpiece is obtained by hot rolling.
  • the amount of reduction in such hot rolling is not critical, but from a practical viewpoint it is helpful to take as much reduction as possible because of ease of working.
  • Such rolling in the Ar -Ar temperature range must be carried out as the workpiece is cooling in that range and must comprise one or more rolling passes including at least one reduction pass.
  • the meaning of theterm reduction pass encompasses both'a single pass in which the reduction of the cross-sectional area of the workpiece is at least 15 percent and two or more passeseffecting an amount of reduction and taken inrapid enough succession to prevent any recrystallization between passes.
  • rolling Following the rolling in the Ar -Ar,. temperature range, rolling must be continued as the workpiece is cooling in the Ar,-600 F. temperature range and must comprise one or more rollingpasses in that range including at least one reduction pass.
  • temperature range must be such that complete recrystallization of the deformed grains produced by the last reduction pass in said temperature range does not take place at any time after such last reduction pass and preferably such that percentage recrystallization does not exceed 60 percentat any time after such last reduction pass.
  • percentage recrystallization means the cross-sectional area of recrystallized grains expressed as apercentage of total cross-sectional area on a plane transverse to the direction of maximum elongation of the workpiece during rolling.
  • FIG. 1 illustrates diagrammatically the principles upon which reduction in the Ar -Ar, range and in the Ar,-600 F. range depend.
  • the abscissa represents time on a logarithmic scale with zero time representing the time at completion of a reduction pass.
  • the ordinate represents temperature, with the Ar;, and Ar, temperatures indicated.
  • Lines 1, 2, and 3 represent, respectively, times and temperatures for commencement of, 60 percent and percent recrystallization.
  • Lines 4, 5, 6, 7, and 8 represent the cooling of steel workpieces. It will be understood that the values shown in the FIGURE are illustrative only; actual values depend on the actual workpieces being considered and can be determined by known methods.
  • Point A on Line 8 indicates a temperature to which a steel workpiece has cooled and which is within the Ar -Ar, range. Line represents the cooling of said workpiece after it has been given a reduction pass at the temperature represented by Point A.
  • Line 7 represents the cooling of a steel workpiece after a reduction pass at a temperature below the Ar, temperature. It is seen that recrystallization is avoided as such reduced workpiece cools.
  • the cooling of said reduced workpiece must be accelerated by water sprays, air blasts of the like so as to prevent complete recrystallization and preferably so as to prevent exceeding 60 percent recrystallization.
  • FIG. 2 illustrates diagrammatically a possible rolling sequence for producing a /-inch plateby continuum rolling.
  • the abscissa represents time on a logarithmic scale, with zero time representing the time at completion of a reduction pass.
  • the ordinate represents temperature on an arithmetic scale, with Ar, and Ar, temperatures indicated.
  • Lines l3 represent times and temperatures for commencement of, 60 percent, and 100 percent recrystallization.
  • the horizontal dashed lines represent instantaneous return to zero time.
  • a 2%-inch slab has been rolled from A 4- inch slab at temperatures well above the Ar,, temperature and, as shown in the FIGURE, has air cooled in about 2 minutes to about,l,720 F.
  • This 2%-inch slab is given two passes at temperatures above the Ar temperature, first to 2% inches (A) and then 1% inches (B). After each of these passes the plate cools in air for about 2 minutes, cooling during the latter period to about 1,385 E, somewhat below the Ar temperature.
  • the steel In the temperature range between the Ar temperature and 600 F. the steel is given three passes, first to 3 1 inch (E), then to is inch (F), and finally to V2 inch (G). After each of the first two of these passes to the plate cools in air for about 2 minutes; after the final pass, the plate cools in air to room temperature. There is no recrystallization following any of these passes.
  • the Ar;, and Ar, temperatures of this steel were 1,500 F. and 1,320 F. respectively at a cooling rate of approximately 1,000 F ./hr.
  • Table 1 shows the temperature ranges in which the above reduction schedule was carried out. Plates A-I-I are illustrative of plates produced by prior art rolling methods, while Plates J-N are illustrative of plates produced by continuum rolling. The recrystallization characteristics of the steel and the cooling rates and intervals between passes were such that in the rolling of Plates JN the percentage recrystallization did not exceed 60 percent at any time after completion of the reduction in the Ar -Ar temperature range.
  • Table 2 shows the finishing temperature, yield point or yield strength, tensile strength, elongation, and V- l 5 Charpy impact transition temperature of each of the thirteen plates A-N.
  • FIG. 3 shows for the said 13 plates the manner in which impact transition temperature varies with strength as dependent on the method of rolling.
  • points A, B, and C represent plates produced by hot rolling
  • points I) and E represent plates finished at temperatures between the Ar and the Ar
  • points F, G, and H represents plates finished at temperatures below the Ar
  • points J, K, L, M, and N represent plates produced by continuum rolling.
  • Table 2 shows clearly that finishing thev rolling at temperatures below the Ar temperature either by low-finishing-temperature rolling or by continuum rolling increased the strength of the steel over that obtained by finishing the rolling at temperatures above the Ar, temperature.
  • the important distinction shown by both the TABLE and the FIGURE is that when such further strengthening is by low-finishing-temperature rolling impact transition temperature is raised as strength is increased, whereas when such further strengthening is by continuum rolling impact transition temperature is lowered as strength is increased. The difference is substantial.
  • Table 3 gives the percentage compositions of seven other 1 5 gg g gg steels from which specific examples of plates were produced N b mt inol ies' d f l by continuum rolling and by prior art methods.
  • Plate @52 :28 From To Re $133; these steels the balance of the composition was substantially Hot mmng iron. Varieties included are semikilled, killed, carbon, low al- A loy, bainitic, and precipitation hardening steels.
  • Every plate produced 1,130 67 100 76,100 28 +40 by continuum rolling has an unexpectedly good combination 910 '77, 500 83,600 25 90 of strength and impact transition temperature, but for the Continuum mmng reason cited above it is not poss ble to broadly characterize J n 1, 205 Gallon 71 200 18 the product of continuum rolhng in terms of specific values of K ,030 500 3, 0 2 1: 1% those properties.
  • the products of continuum a- 338- 32% f 400 rolling are characterized in their as-rolled condition (a) by N 625 113,700 15 having greater strengths and lower impact tia nsition tempe a- 65 Yield strength (0.2% oflset).
  • V-lfi Ch 7 Yield Tensile transi t i n Number Temperature Thickness, Reduction, point, strength, temperature, Reduction practice of passes range, F. inches percent K s.i. K s.i. F, Hot rolling 11 2, 200-1, 610 4-%" 87. 5 49. 3 01. 9 Do 10 2, 200-1, 605 4"-+%" 87. 5 65. 0 02. 1
  • Method of rolling a steel workpiece containing not more than 0.35 percent carbon and not more than a'total of 3 percent of other elements other than iron comprising:
  • step (b) maintaining conditions such that complete recrystallization does not take place at any time after the last reduction pass in step (b).
  • Method of rolling a steel workpiece containing not more than 0.35 percent carbon and not more than a total of 3 percent of other elements other than iron comprising:
  • step (b) maintaining conditions such that the percentage recrystallization does not exceed 60 percent at any time after the last reduction pass in step (b).
  • Method of rolling a steel workpiece containing not more than 0.35 percent carbon and not more than a total of 3 percent of other elements other than iron comprising:
  • Method of rolling a steel workpiece containing not more than 0.35 percent carbon and not more than a total of 3 percent of other elements other than iron comprising:
  • step (b) maintaining conditions such that the percentage recrystallization does not exceed 60 percent at any time after the last reduction pass in step (b).

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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)
US786844A 1968-12-20 1968-12-20 Method of producing rolled steel having high-strength and low-impact transition temperature Expired - Lifetime US3645801A (en)

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JP (1) JPS5341091B1 (enrdf_load_stackoverflow)
BE (1) BE743161A (enrdf_load_stackoverflow)
CA (1) CA934274A (enrdf_load_stackoverflow)
DE (1) DE1962334A1 (enrdf_load_stackoverflow)
FR (1) FR2026729A1 (enrdf_load_stackoverflow)
GB (1) GB1289320A (enrdf_load_stackoverflow)
NL (1) NL6919112A (enrdf_load_stackoverflow)
SE (1) SE359858B (enrdf_load_stackoverflow)
SU (1) SU370759A3 (enrdf_load_stackoverflow)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3849209A (en) * 1972-02-01 1974-11-19 Nippon Steel Corp Manufacturing method of high tension, high toughness steel
US3860456A (en) * 1973-05-31 1975-01-14 United States Steel Corp Hot-rolled high-strength low-alloy steel and process for producing same
US3889510A (en) * 1972-11-08 1975-06-17 Kobe Steel Ltd Hot forging process
US3918999A (en) * 1972-10-19 1975-11-11 Nippon Steel Corp Method for producing efficienty a high toughness and high tensile strength steel materials
US3963531A (en) * 1975-02-28 1976-06-15 Armco Steel Corporation Cold rolled, ductile, high strength steel strip and sheet and method therefor
US3976514A (en) * 1975-02-10 1976-08-24 Nippon Steel Corporation Method for producing a high toughness and high tensil steel
US4115155A (en) * 1974-05-03 1978-09-19 Bethlehem Steel Corporation Low carbon high yield and tensile strength steel and method of manufacture
US4119442A (en) * 1975-12-01 1978-10-10 Nippon Steel Corporation Process for manufacturing a steel product
USRE31221E (en) * 1975-02-28 1983-04-26 Armco Inc. Cold rolled, ductile, high strength steel strip and sheet and method therefor
US5542995A (en) * 1992-02-19 1996-08-06 Reilly; Robert Method of making steel strapping and strip and strapping and strip

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5794140U (enrdf_load_stackoverflow) * 1980-12-01 1982-06-10
JP2893100B2 (ja) 1991-11-27 1999-05-17 富士写真フイルム株式会社 ハロゲン化銀カラー写真感光材料
JP3026243B2 (ja) 1993-06-08 2000-03-27 富士写真フイルム株式会社 ハロゲン化銀カラー写真感光材料

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3264144A (en) * 1962-09-13 1966-08-02 Youngstown Sheet And Tube Co Method of producing a rolled steel product
US3423252A (en) * 1965-04-01 1969-01-21 United States Steel Corp Thermomechanical treatment of steel
US3432368A (en) * 1965-02-25 1969-03-11 Ishikawajima Harima Heavy Ind Method for manufacturing nitride-containing low-carbon structural steels
US3459599A (en) * 1966-10-17 1969-08-05 United States Steel Corp Method of thermomechanically annealing steel

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3264144A (en) * 1962-09-13 1966-08-02 Youngstown Sheet And Tube Co Method of producing a rolled steel product
US3432368A (en) * 1965-02-25 1969-03-11 Ishikawajima Harima Heavy Ind Method for manufacturing nitride-containing low-carbon structural steels
US3423252A (en) * 1965-04-01 1969-01-21 United States Steel Corp Thermomechanical treatment of steel
US3459599A (en) * 1966-10-17 1969-08-05 United States Steel Corp Method of thermomechanically annealing steel

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3849209A (en) * 1972-02-01 1974-11-19 Nippon Steel Corp Manufacturing method of high tension, high toughness steel
US3918999A (en) * 1972-10-19 1975-11-11 Nippon Steel Corp Method for producing efficienty a high toughness and high tensile strength steel materials
US3889510A (en) * 1972-11-08 1975-06-17 Kobe Steel Ltd Hot forging process
US3860456A (en) * 1973-05-31 1975-01-14 United States Steel Corp Hot-rolled high-strength low-alloy steel and process for producing same
US4115155A (en) * 1974-05-03 1978-09-19 Bethlehem Steel Corporation Low carbon high yield and tensile strength steel and method of manufacture
US3976514A (en) * 1975-02-10 1976-08-24 Nippon Steel Corporation Method for producing a high toughness and high tensil steel
US3963531A (en) * 1975-02-28 1976-06-15 Armco Steel Corporation Cold rolled, ductile, high strength steel strip and sheet and method therefor
USRE31221E (en) * 1975-02-28 1983-04-26 Armco Inc. Cold rolled, ductile, high strength steel strip and sheet and method therefor
US4119442A (en) * 1975-12-01 1978-10-10 Nippon Steel Corporation Process for manufacturing a steel product
US5542995A (en) * 1992-02-19 1996-08-06 Reilly; Robert Method of making steel strapping and strip and strapping and strip

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NL6919112A (enrdf_load_stackoverflow) 1970-06-23
JPS5341091B1 (enrdf_load_stackoverflow) 1978-10-31
GB1289320A (enrdf_load_stackoverflow) 1972-09-13
BE743161A (enrdf_load_stackoverflow) 1970-06-15
SU370759A3 (enrdf_load_stackoverflow) 1973-02-15
SE359858B (enrdf_load_stackoverflow) 1973-09-10
DE1962334A1 (de) 1970-07-23
FR2026729A1 (enrdf_load_stackoverflow) 1970-09-18
CA934274A (en) 1973-09-25

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