US2857299A - Method of heat treating steel - Google Patents

Method of heat treating steel Download PDF

Info

Publication number
US2857299A
US2857299A US443428A US44342854A US2857299A US 2857299 A US2857299 A US 2857299A US 443428 A US443428 A US 443428A US 44342854 A US44342854 A US 44342854A US 2857299 A US2857299 A US 2857299A
Authority
US
United States
Prior art keywords
steel
plate
temperature
killed
manganese
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
US443428A
Inventor
Epstcin Samuel
Jr Joseph D Dennison
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.)
Bethlehem Steel Corp
Original Assignee
Bethlehem Steel Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Bethlehem Steel Corp filed Critical Bethlehem Steel Corp
Priority to US443428A priority Critical patent/US2857299A/en
Application granted granted Critical
Publication of US2857299A publication Critical patent/US2857299A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

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
    • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation

Definitions

  • This invention relates broadly to a novel treatment of open-hearth steel plates and the improved product resulting from such treatment.
  • the invention relates to quenching semi-killed open hearth ship plates of A" thickness or greater from rolling temperatures to obtain a microstructure comprising pseudo-martensite intermingled with ferrite to lower the transition temperature in notched-bar impact tests of said plates.
  • the object of this invention is to obviate brittle fracturing in welded ships. Characteristics of such brittle fracturing are that the fracture starts at imperfections in the weld, generally aggravated also by other notch conditions, and that the fracture occurs in cold weather. While the design of the ship and the workmanship are of the greatest importance in obviating such brittle fracturing, recent work has indicated that the quality of the steel also plays an important part.
  • Such water quenched open-hearth semi-killed ship plate steel has appreciably higher yield and tensile strength and lower transition temperature than such steel air cooled from the rolling temperature.
  • the lower transition temperature is evident not only in notched-bar impact tests of the unwelded steel but also in notched tests of the aswelded plate.
  • ship plate steel of the semi-killed type containing, for example, .18% carbon and .70% manganese, and thus having a lower carbon content and a somewhat higher manganese content than ordinary ship plate steel, has a lower transition'temperature.
  • Fully aluminum killed steel of the same lower carbon and higher manganese contents has an even lower transition temperature. Since thicker ship plate is more susceptible to brittle fracturing than thinner plate it has become the practice to use ordinary ship plate steel in thicknesses up to /2", semi-killed lower carbon higher manganese ship plate steel in thicknesses from /2" to 1", and fully aluminum killed lower carbon higher manganese ship plate steel in thicknesses over 1.
  • ordinary ship plate steel is meant a steel having a tensile strength of 58,000 to 71,000 lbs. p. s. i. Such steel may contain, for example, .18% carbon and .70% manganese, and thus having a lower carbon content and a somewhat higher manganese content than ordinary ship plate steel, has
  • the increased yield strength and tensile strength after Water quenching are of marked advantage.
  • the decreased transition temperature produced by the water quenching indicates the water quenching to be of definite help in obviating brittle fracturing.
  • At present two new special classes of ship plate steel are required by the American Bureau of Shipping, Class .B, maximum carbon content 0.23%, manganese content 0.60 to 0.90%, semi-killed steel for plates /2 to 1" thick, and Class C of approximately the same composition but of fully aluminum-killed steel for plates over 1" thick. Both of these classes of steel require higher than ordinary manganese content. While manganese is generally not very costly it may yet become scarce during a period of great activity in steelmaking and/or shipbuilding.
  • Class C steel furthermore being fully aluminum-killed steel made in hot-topped big- 5 end-up molds may also require additional hot-topping and stripping facilities during such a period but our waterquenched plate of low carbon semi-killed steel in which the manganese content has not been increased shows transition temperatures in notched-bar tests as low as the new special classes of B and C steel with their increased manganese contents. This is true of the unwelded steel and also of the as-welded steel.
  • the lowered transition temperature after water quenching is obtained over a wide range of finishing temperatures in rolling.
  • low transition temperatures are obtained after water quenching from a high finishing temperature in rolling of l850 to 1900 F. as from a rather low finishing temperature in rolling of 1600 to 1650 F.
  • Such quenching should, however, be from above the critical temperature of the steel being rolled.
  • the water-quenched semi-killed steel of Table I shows better yield strength, tensile strength, and transition tem- 4o perature in the unwelded condition and after welding than the new special Class C lower carbon higher manganese fully aluminum-killed steel.
  • the transition temperature in the notched-bar impact test was obtained in the usual way with standard Charpy specimens with keyhole notches, and with the transition temperature read when the impact resistance vs. temperature curve crossed ft. lbs. as the testing temperature was lowered.
  • the specimens for the notched weld-bead tensile tests were made as follows. A longitudinal specimen, the full thickness of the /1" plate, 12" long and 2.6" wide, was welded by laying a narrow weld bead longitudinally along the center of one of the flat surfaces, using a 7 in. diameter E-60l0 electrode, 175 amperes, 28 volts, and 12 in. travel per minute. The weld bead was then notched by machining the notch perpendicular to the head down to the plate surface. The notch was made quite sharp, the radius at the base of the notch being 0.0015 in.
  • the specimens were then loaded in tension to fracture at a series of lowered temperatures and a transition temperature obtained by measuring the reduction in thickness beneath the notch of the fractured specimens.
  • the transition temperature was read when the reduction in thickness vs. temperature curve crossed 5% reduction of thickness as the testing temperature was lowered.
  • the steel In water-quenching the plate steel from the rolling temperature the steel is led, for example, into a large tank of cold water, the water being preferably of a temperature of from to 120 F., after passing through the finishing rolls.
  • the plate being quenched is held in the 70 water tank for the time necessary to produce the structure of pseudo-martensite intermingled with ferrite, preferably from 5 to 60 seconds. As has been shown, 15 seconds immersion of /1" thick plate in the water at 60 F. is sufiicient for this. After such quenching the plate 75 1.
  • a method of lowering the transition temperature in the notched bar impact test of semi-killed open-hearth steel plate containing .05% to .20% carbon, .25% to .60% manganese, and the balance consisting essentially of iron, comprising hot rolling said plate and water quenching the said steel plate immediately from the hot rolling operation, the temperature at which said plate is quenched being above the upper critical temperature of the said steel plate.
  • a method of lowering the transition temperature in the notched bar impact test of semi-killed open-hearth steel plate containing 05% to .20% carbon, .25% to .60% manganese, and the balance consisting essentially of iron, comprising hot rolling said plate and directly water quenching said plate from the hot rolling operation at temperatures of from 1600" to 1900 F.
  • a method of lowering the transition temperature in the notched bar impact test of semi-killed open-hearth steel plate containing .05% to .20% carbon, .25% to .60% manganese, and the balance consisting essentially of iron, comprising hot rolling said plate and directly quenching said steel plate from the rolling operation at temperatures of from 1600 to 1900 F. in water, said water being at temperatures of from 40 to F.
  • a method of lowering the transition temperature in the notched bar impact test of semi-killed open-hearth steel plate containing .05% to .20% carbon, .25% to .60% manganese, and the balance consisting essentially of iron, comprising hot rolling said plate and directly quenching said steel plate from the rolling operation at temperatures of from 1600 to 1900 F. for from 5 to 60 seconds in water, said water being at temperatures of from 40 to 120 F.
  • a method of lowering the transition temperature in the notched bar impact test of semi-killed open-hearth steel plate containing .05% to .20% carbon, .25% to .60% manganese, and the balance consisting essentially of iron, comprising hot rolling said plate and directly water 5 quenching the said steel plate from the hot rolling operation.

Description

United States Patent METHOD OF HEAT TREATING STEEL Samuel Epstein and Joseph D. Dennison, Jr., Bethlehem,
Pa., assignors to Bethlehem Steel Company, a corporation of Pennsylvania No Drawing. Application July 14, 1954 Serial No. 443,428
Claims. (Cl. 14812.4)
This invention relates broadly to a novel treatment of open-hearth steel plates and the improved product resulting from such treatment.
More particularly, the invention relates to quenching semi-killed open hearth ship plates of A" thickness or greater from rolling temperatures to obtain a microstructure comprising pseudo-martensite intermingled with ferrite to lower the transition temperature in notched-bar impact tests of said plates.
The object of this invention is to obviate brittle fracturing in welded ships. Characteristics of such brittle fracturing are that the fracture starts at imperfections in the weld, generally aggravated also by other notch conditions, and that the fracture occurs in cold weather. While the design of the ship and the workmanship are of the greatest importance in obviating such brittle fracturing, recent work has indicated that the quality of the steel also plays an important part.
It has recently been shown that ship plate steel which becomes brittle in notched-bar impact tests at relatively warm temperatures is more likely to be the origin of brittle fracturing in a welded ship than ship plate steel which only becomes brittle in notched-bar impact tests at relatively cold temperatures. The temperature at which such brittleness ensues in a series of notched-bar impact tests "ice example, .25% carbon and .45% to manganese.
We have discovered, however, that severe accelerated cooling, by water quenching from the rolling temperature, of semi-killed open hearth ship plate steel, containing .05 to .20% carbon and ordinary manganese content, i. e., .25 to .60% manganese can give as low transition temperatures as are obtained upon ordinary rolling and air cooling of the recently developed semi-killed and fully aluminum-killed lower carbon higher manganese ship plate steels, producing transition temperatures ranging from 0 to 70 F. in the unwelded condition and from 20 to 50 F. in the welded condition.
The explanation of this appears to be that the severe accelerated cooling by water quenching of the coarse grained steel present after the ordinary finishing temperature in commercial rolling produces a pseudo-martensitic structure With which ferrite is intermingled. This structure of pseudo-martensite and ferrite produced by water quenching has a quite low transition temperature in notched-bar impact tests, considerably lower than the structure of ferrite and pearlite produced by ordinary cooling from the rolling temperature.
Such water quenched open-hearth semi-killed ship plate steel has appreciably higher yield and tensile strength and lower transition temperature than such steel air cooled from the rolling temperature. The lower transition temperature is evident not only in notched-bar impact tests of the unwelded steel but also in notched tests of the aswelded plate.
This is shown in the following data in Table I on semikilled open hearth ship plate steel thick of the following composition:
O Mn P S Si Table 1 Tensile Properties Transition Temperature NotWelded Keyhole Charpy Impact Test, F.
Welded N etched Weld-Bead Tensile Test, F.
Yield Strength,
p. s. i.
Tensile Strength, p. s. 1.
E1. in 2", Percent Red. of I Area, Percent As Air Cooled from the Finishing Temperature in Rolling, of 1,650 F As Water-Quenched for 15 Seconds from the Same Finishing Temperature at continually lowered testing temperatures hasbeen called transition temperature.
It has also recently been shown that ship plate steel of the semi-killed type containing, for example, .18% carbon and .70% manganese, and thus having a lower carbon content and a somewhat higher manganese content than ordinary ship plate steel, has a lower transition'temperature. Fully aluminum killed steel of the same lower carbon and higher manganese contents has an even lower transition temperature. Since thicker ship plate is more susceptible to brittle fracturing than thinner plate it has become the practice to use ordinary ship plate steel in thicknesses up to /2", semi-killed lower carbon higher manganese ship plate steel in thicknesses from /2" to 1", and fully aluminum killed lower carbon higher manganese ship plate steel in thicknesses over 1. By ordinary ship plate steel is meant a steel having a tensile strength of 58,000 to 71,000 lbs. p. s. i. Such steel may contain, for
The data in Table I indicate that by proper choice of the carbon and manganese content of the steel it is possible to stay Within the yield, tensile, and elongation requirements in the tensile test for ordinary ship plate steel (yield strength 32,000 p. s. i. minimum, tensile strength 58,000 to 71,000 p. s. i., elongation in 2" 22% minimum) after water quenching.
The increased yield strength and tensile strength after Water quenching are of marked advantage. The decreased transition temperature produced by the water quenching indicates the water quenching to be of definite help in obviating brittle fracturing. At present two new special classes of ship plate steel are required by the American Bureau of Shipping, Class .B, maximum carbon content 0.23%, manganese content 0.60 to 0.90%, semi-killed steel for plates /2 to 1" thick, and Class C of approximately the same composition but of fully aluminum-killed steel for plates over 1" thick. Both of these classes of steel require higher than ordinary manganese content. While manganese is generally not very costly it may yet become scarce during a period of great activity in steelmaking and/or shipbuilding. Class C steel furthermore being fully aluminum-killed steel made in hot-topped big- 5 end-up molds may also require additional hot-topping and stripping facilities during such a period but our waterquenched plate of low carbon semi-killed steel in which the manganese content has not been increased shows transition temperatures in notched-bar tests as low as the new special classes of B and C steel with their increased manganese contents. This is true of the unwelded steel and also of the as-welded steel.
This is indicated by the following data in Table II for Class B and Class C steel, which may be compared with the data in Table I for our semi-killed open hearth steel is still quite warm, amply so to aid in subsequent straightening. However, it longer quenching times than this are used no great harm is done as the transition temperature is just as low after complete quenching to the water temperature. The steel can then be tempered if desired to as high as 1000 F. without raising the transition temperature; such tempering lowers the yield and tensile strength somewhat by approximately 5000 p. s. i.
The lowered transition temperature after water quenching is obtained over a wide range of finishing temperatures in rolling. As low transition temperatures are obtained after water quenching from a high finishing temperature in rolling of l850 to 1900 F. as from a rather low finishing temperature in rolling of 1600 to 1650 F. Such quenching should, however, be from above the critical temperature of the steel being rolled.
Table II Tensile Properties Transition Temperature Not Welded Welded Yield Tensile El. in 2" Red.of Strength, Strength, percent Area,
p. s. i. p. s. 1. Percent Keyhole Notched Charpy Weld-Bead Impact Tensile Test, F. Test, F.
Class B Steel, Air Cooled from the Finishing Temperature in Rolling (C 0.19%, Mn 0.71%, Si 0.05%) Semi-Killed 35, 000 62, 000 32. 0 62. 0 7 23 Class 0 Steel, Also Air Cooled as Above (C 0.17%, Mn0.73%, Si0.21%) Fully Aluminum-Killed 37, 000 62, 000 32.0 61.0 33 12 We claim:
which has been water-quenched from the rolling temperature.
The water-quenched semi-killed steel of Table I shows better yield strength, tensile strength, and transition tem- 4o perature in the unwelded condition and after welding than the new special Class C lower carbon higher manganese fully aluminum-killed steel.
Regarding the preceding data, the transition temperature in the notched-bar impact test was obtained in the usual way with standard Charpy specimens with keyhole notches, and with the transition temperature read when the impact resistance vs. temperature curve crossed ft. lbs. as the testing temperature was lowered.
The specimens for the notched weld-bead tensile tests were made as follows. A longitudinal specimen, the full thickness of the /1" plate, 12" long and 2.6" wide, was welded by laying a narrow weld bead longitudinally along the center of one of the flat surfaces, using a 7 in. diameter E-60l0 electrode, 175 amperes, 28 volts, and 12 in. travel per minute. The weld bead was then notched by machining the notch perpendicular to the head down to the plate surface. The notch was made quite sharp, the radius at the base of the notch being 0.0015 in. The specimens were then loaded in tension to fracture at a series of lowered temperatures and a transition temperature obtained by measuring the reduction in thickness beneath the notch of the fractured specimens. The transition temperature was read when the reduction in thickness vs. temperature curve crossed 5% reduction of thickness as the testing temperature was lowered.
In water-quenching the plate steel from the rolling temperature the steel is led, for example, into a large tank of cold water, the water being preferably of a temperature of from to 120 F., after passing through the finishing rolls. The plate being quenched is held in the 70 water tank for the time necessary to produce the structure of pseudo-martensite intermingled with ferrite, preferably from 5 to 60 seconds. As has been shown, 15 seconds immersion of /1" thick plate in the water at 60 F. is sufiicient for this. After such quenching the plate 75 1. A method of lowering the transition temperature in the notched bar impact test of semi-killed open-hearth steel plate containing .05% to .20% carbon, .25% to .60% manganese, and the balance consisting essentially of iron, comprising hot rolling said plate and water quenching the said steel plate immediately from the hot rolling operation, the temperature at which said plate is quenched being above the upper critical temperature of the said steel plate.
2. A method of lowering the transition temperature in the notched bar impact test of semi-killed open-hearth steel plate containing 05% to .20% carbon, .25% to .60% manganese, and the balance consisting essentially of iron, comprising hot rolling said plate and directly water quenching said plate from the hot rolling operation at temperatures of from 1600" to 1900 F.
3. A method of lowering the transition temperature in the notched bar impact test of semi-killed open-hearth steel plate containing .05% to .20% carbon, .25% to .60% manganese, and the balance consisting essentially of iron, comprising hot rolling said plate and directly quenching said steel plate from the rolling operation at temperatures of from 1600 to 1900 F. in water, said water being at temperatures of from 40 to F.
4. A method of lowering the transition temperature in the notched bar impact test of semi-killed open-hearth steel plate containing .05% to .20% carbon, .25% to .60% manganese, and the balance consisting essentially of iron, comprising hot rolling said plate and directly quenching said steel plate from the rolling operation at temperatures of from 1600 to 1900 F. for from 5 to 60 seconds in water, said water being at temperatures of from 40 to 120 F.
5. A method of lowering the transition temperature in the notched bar impact test of semi-killed open-hearth steel plate containing .05% to .20% carbon, .25% to .60% manganese, and the balance consisting essentially of iron, comprising hot rolling said plate and directly water 5 quenching the said steel plate from the hot rolling operation.
References Cited in the file of this patent UNITED STATES PATENTS Pierce Aug. 7, 1906 Kenney Nov. 28, 1916 6 OTHER REFERENCES Reed: Photomicrographs of Iron and Steel, 1929, page 63

Claims (1)

1. A METHOD OF LOWERING THE TRANSITION TEMPERATURE IN THE NOTCHED BAR IMPACT TEST OF SEMI-KILLED OPEN-HEARTH STEEL PLATE CONTAINING .05% TO .20% CARBON, .25% TO .60% MANGANESE, AND THE BALANCE CONSISTING ESSENTIALLY OF IRON, COMPRISING HOT ROLLING SIAD PLATE AND WATER QUENCHING THE SAID STEEL PLATE IMMEDIATELY FROM THE HOT ROLLING OPERATION, THE TEMPERATURE AT WHICH SAID PLATE IS QUENCHED BEING ABOVE THE UPPER CRITICAL TEMPERATURE OF THE SAID STEEL PLATE.
US443428A 1954-07-14 1954-07-14 Method of heat treating steel Expired - Lifetime US2857299A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US443428A US2857299A (en) 1954-07-14 1954-07-14 Method of heat treating steel

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US443428A US2857299A (en) 1954-07-14 1954-07-14 Method of heat treating steel

Publications (1)

Publication Number Publication Date
US2857299A true US2857299A (en) 1958-10-21

Family

ID=23760776

Family Applications (1)

Application Number Title Priority Date Filing Date
US443428A Expired - Lifetime US2857299A (en) 1954-07-14 1954-07-14 Method of heat treating steel

Country Status (1)

Country Link
US (1) US2857299A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3366471A (en) * 1963-11-12 1968-01-30 Republic Steel Corp High strength alloy steel compositions and process of producing high strength steel including hot-cold working
US3539404A (en) * 1967-05-15 1970-11-10 Youngstown Sheet And Tube Co Method of making a low alloy steel
US3753796A (en) * 1968-12-20 1973-08-21 Bethlehem Steel Corp Rolled steel having high strength and low impact transition temperature and method of producing same
USRE28523E (en) * 1963-11-12 1975-08-19 High strength alloy steel compositions and process of producing high strength steel including hot-cold working

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US827882A (en) * 1903-06-06 1906-08-07 Standard Horse Nail Company Manufacture of articles of iron or steel.
US1205998A (en) * 1916-03-20 1916-11-28 Edward F Kenney Treating rails.

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US827882A (en) * 1903-06-06 1906-08-07 Standard Horse Nail Company Manufacture of articles of iron or steel.
US1205998A (en) * 1916-03-20 1916-11-28 Edward F Kenney Treating rails.

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3366471A (en) * 1963-11-12 1968-01-30 Republic Steel Corp High strength alloy steel compositions and process of producing high strength steel including hot-cold working
USRE28523E (en) * 1963-11-12 1975-08-19 High strength alloy steel compositions and process of producing high strength steel including hot-cold working
US3539404A (en) * 1967-05-15 1970-11-10 Youngstown Sheet And Tube Co Method of making a low alloy steel
US3753796A (en) * 1968-12-20 1973-08-21 Bethlehem Steel Corp Rolled steel having high strength and low impact transition temperature and method of producing same

Similar Documents

Publication Publication Date Title
KR101858868B1 (en) Plated steel sheets for hot press forming having excellent impact toughness, hot press formed parts, and methods of manufacturing the same
EP3354755B1 (en) Method for manufacturing bainite high-strength seamless steel tube, and bainite high-strength seamless steel tube
BR112015005090B1 (en) COLD LAMINATED PLATE AND RECOZED
BR112020011672B1 (en) METHOD FOR MANUFACTURING COLD-ROLLED AND HEAT-TREATED STEEL SHEET AND COLD-ROLLED STEEL SHEET
US4946516A (en) Process for producing high toughness, high strength steel having excellent resistance to stress corrosion cracking
WO1999002747A1 (en) Ultra high strength, secondary hardening steels with superior toughness and weldability
US4575397A (en) Rail having high resistance to wear in its head and high resistance to rupture in its foot
US3726723A (en) Hot-rolled low alloy steels
JPH0453929B2 (en)
US2857299A (en) Method of heat treating steel
JPS626730B2 (en)
US2924544A (en) Metallurgical process for cold-finishing steel
EP0651060B1 (en) Process for producing extra high tensile steel having excellent stress corrosion cracking resistance
JP2005325454A (en) Thin steel sheet having excellent impact characteristic after quenching and its producing method
JPS589814B2 (en) Manufacturing method for high-toughness, high-tensile tempered steel sheet with reduced rolling anisotropy
JPH0756050B2 (en) Manufacturing method of high strength cold rolled steel sheet for non-aging, high bake hardening and press working by continuous annealing
US2069758A (en) Ferrous metal and process for producing same
JPH06256842A (en) Production of light-gaged high-strength steel sheet having excellent sour resistance
JPH022925B2 (en)
JPH0543779B2 (en)
JP2002309344A (en) Thin steel sheet having excellent toughness after quenching and production method therefor
RU2479637C1 (en) Rolled stock manufacturing method
JPH01195242A (en) Manufacture of high tension steel plate having superior toughness at low temperature with uniformity in thickness direction
KR950004775B1 (en) Making mehtod of 150kg high strength steel
JPS63145711A (en) Production of high tension steel plate having excellent low temperature toughness