US3857740A - Precipitation hardening high strength cold rolled steel sheet and method for producing same - Google Patents

Precipitation hardening high strength cold rolled steel sheet and method for producing same Download PDF

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US3857740A
US3857740A US00377308A US37730873A US3857740A US 3857740 A US3857740 A US 3857740A US 00377308 A US00377308 A US 00377308A US 37730873 A US37730873 A US 37730873A US 3857740 A US3857740 A US 3857740A
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temperature
annealing
sheet
cold rolled
rolled steel
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US00377308A
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H Gondo
H Takechi
H Masui
K Ozaki
T Kawano
K Namba
K Sakurai
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Nippon Steel Corp
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Nippon Steel Corp
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Priority claimed from JP6867072A external-priority patent/JPS535610B2/ja
Priority claimed from JP6961573A external-priority patent/JPS5427822B2/ja
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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
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
    • C21D8/0426—Hot rolling
    • 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
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
    • C21D8/0436—Cold 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
    • C21D8/0473—Final recrystallisation annealing

Definitions

  • the production technics for precipitation hardening high strength cold rolled steel sheets established by the present invention is novel and unique.
  • a precipitation hardening high strength cold rolled steel sheet comprising 0.03 to 0.25% C, not more than 1.5% Si, 0.6 to 2.5% Mn, 0.01 to 0.15% Al, 0.01 to 0.40% effective Ti (total Ti% 3.4[N%] 1.5[%]- 1.5 [S%]) and satisfying 4 [C%] 0.6% effective Ti% 4 [C%], with the balance being Fe and unavoidable imparities.
  • the steel slab having the composition as defined in the above (1) is heated at a temperature not lower than 1,200C, hot rolled, subjected to finishing rolling at a finishing temperature not lower than 870C, coiled at a temperature between 560 and 680C, acid pickled, cold rolled with a reduction rate not less than 30%, and subjected to recrystallization annealing at a temperature between 600 and 900C.
  • the recrystallization annealing temperature in the above (2) is higher than coiling temperature of the hot rolling.
  • the effective Ti content used in the present invention means Ti content obtained by reducing Ti amount which is combined with N, O, and S from the total Ti content.
  • finishing temperature of the hot rolling a higher temperature is desirable for the steel composition of the present invention.
  • the hot rolled steel sheet is the final product, rather a lower finishing temperature is applied in most cases to precipitate slightly coarse precipitates to improve toughness.
  • the cold rolled steel sheet is the final product, it should be avoided to precipitate coarse precipitates during the hot rolling prior to the completion of the finishing rolling, and thus a higher finishing temperature is more desirable.
  • the problem of toughness can be solved by appropriate coarsening of the fine TiC during the recrystallization annealing.
  • the coiling temperature of the hot rolling if the temperature is too high, almost all of TiC is precipitated or coarsened, so that the strength of the cold rolled steel sheets is not enough. On the other hand, if the coiling temperature is too low, the appropriate amount of fine TiC favourable for the strength and the drawability is not precipitated during the hot coiling, and a considerable amount of fine TiC precipitates during the recrystallization annealing to make the strength unstable, and particularly it is impossible to produce the cold rolled steel sheets having good drawability.
  • the reduction rate of the cold rolling is a veryimportant factor in the present invention.
  • the optimum reduction rate of the cold rolling in the present invention is determined not merely for the aim to obtain a recrystallization texture favorable for the drawability as in the convention cold rolled steel sheets, but also in view of the fact that the amount of internal defects (dislocation) which varies depending on the reduction rate affects the amount and size of the TiC precipitates and the recrystallization temperature itself so that the optimum reduction rate of the cold rolling is determined thereby.
  • the recrystallization annealing temperature it must be higher that the coiling temperature of the hot rolling. Otherwise it is impossible to produce the desired high strength cold rolled steel sheets of the present invention.
  • the desired strength of the final cold steel sheet product is not easy particularly in case of a precipitation hardening steel grade as mentioned above, and that in the present invention it is most desirable to precipitate beforehand a part of the fine TiC during the coiling of the hot rolling and to make it coarse appropriately and to precipitate the remainder of the fine TiC during the recrystallization annealing.
  • the steel sheet after the recrystallization annealing is again cold rolled with a reduction rate not less than 30% and then subjected to continuous annealing between 600 and 900C, and the steel composition contains one or more elements from the group A consisting of Nb, V, Mo, and W in an amount of 0.01 to 0.1%, one or more from the group B consisting of Cr, Ni and Cu in an amount of 0.03 to 1.0%, and/or one or more from the group C consisting of Zr, Ca Mg and rare earth elements in an amount of 0.01 to 0.1% (amount to be added).
  • One of the features of the present invention is to obtain high strength properties and drawability due to the fine carbides such as TiC, and for this purpose it is necessary to control the precipitation of TiC etc. through the control of the hot and cold rolling conditions.
  • the conditions of the hot rolling and the cold rolling are precisely combined, whereas in the present invention as the cold rolling and annealing is done two times, it is necessary to set the lower limits both for the slab heating temperature and the finishing temperature of the hot rolling so as to dissolve fully Ti, C etc. and to set the upper limit for the coiling temperature so as to substantially restrict the precipitation of TiC etc. during the stage of the hot rolled steel sheet.
  • the optimum range of the coiling temperature for controlling the amount and size of the precipitates after the hot coiling would be narrow, if the one-time cold rolling and annealing method is applied as in the conventional art, but it is not necessary to set the lower limit severely in the present invention.
  • the desired strength and the recrystallization texture desirable for the drawability can be obtained.
  • the fine TiC favourable for the strength and drawability is effectively precipitated, and the fine TiC is precipitated more uniformly as compared with the conventional art in which the final product is obtianed by only one cold rolling and annealing after the hot coiling so that much higher strength and better drawability can be obtained finally by the second rolling and annealing.
  • the final annealing may be done either by a box annealing or by a continuous annealing, but it is desirable to employ continuous annealing in order to assure uniform annealing temperature.
  • the conditions of the first cold rolling and annealing are limited naturally in view of the above objects. Thus it is necessary to set the lower limit of the cold reduction rate in order to precipitate the fine TiC uniformly during the first annealing. Also the temperature of the first annealing is important, and it is undesirable to apply a temperature below the hot coiling temperature.
  • the lower limit of the cold reduction rate is important.
  • the optimum cold reduction rate is determined not for the purpose of obtaining a recrystallization texture favourable for drawability as in case of conventional cold rolled steel sheets, but it is determined by the fact that the amount of internal defects which varies depending on the reduction rate affects the amount and size of the TiC precipitates'and also affects the recrystallization annealing temperature itself. Therefore, the lower limit of the reduction rate is essential also in the second cold rolling.
  • the annealing temperature is important, and the lower limit of the annealing temperature is essential for precipitation of the fine TiC which has not been precipitated in the first cold rolling and annealing.
  • the upper limit of the annealing temperature is essential for maintaining the fine TiC required for the strength.
  • Ti and C are essential elements for precipitation hardening of the steel. What is important in the present invention is that no satisfactory strength of the cold rolled steel sheet is obtained and the tensile strength is at most 50 Kg/mrn unless the condition of the effective Ti% 4 [C%]. And what is more important is that good spot weldability is required by the natures of the applications to which the present cold rolled steel sheet is intended. Even when the strength of the steel is high enough, safety of structures made of the steel sheet is not assured if the weld portion peels off. The present inventors have found that if the carbon content not fixed by Ti exceeds 0.15% the spot weldability lowers. Thus the condition of C% [effective Ti%] 0.15% must be satisfied.
  • Si and Mn are also important for maintaining the strength.
  • S is not specifically limited in the present invention.
  • S combines with Ti and sulfides in elongated form is hardly formed so that the amount of S is not required to be severely restricted as in ordinary steel compositions.
  • the sheet thickness is thin and no severe restriction of the S content is needed for the bendability of the sheet.
  • the maximum value of the Tvalue which indicates the drawability appears when S is present in the range of().0l2 to 0.02% in the present inventive steel sheet.
  • the optimum content of S must be determined from the view point that the drawability is most important for the press-formability in case of cold rolled steel sheets as in the present invention.
  • Nb, V, Mo and W other than Ti are effective, and addition of these elements in an appropriate amount further improves the high strength property and refines the carbides to improve the press-formability.
  • Cr, Ni and Cu are effective for strengthening the steel, and promotes the high strength property, increases work hardenability to improve the balance between the strength and the ductility and improves the press-formability.
  • Zr, Ca, Mg and rare earth elements combine with S to spheroidize the sulfide inclusions and improves the impact properties and the press-formability.
  • At least 0.03% ofcarbon is necessary for maintaining the high strength property based on the fine TiC, but carbon contents more than 0.25% no substantial desirable effect on the strength is obtained, and on the contrary the toughness and weldability etc. are deteriorated. In the point of ductility not more than 0.15% C is desirable.
  • Si is effective to strengthen the steel and its content may be determined as case may require, but Si contents more than 1.5%, the nature of hot rolling scale is deteriorated and the temper colour is promoted during the annealing. And in order to obtain a good surface condition as in ordinary mild steel sheets, it is desirable to maintain the silicon content not more than 0.8%.
  • Mn is effective to strengthen the steel and for this purpose at least 0.6% Mn is necessary. On the other hand Mn contents more than 2.5%, the hardenability is promoted, and not only causes unstableness in the strength but also gives adverse effect on the weldability. From the point of strength, not less than 0.8% Mn is desired but from the point of drawability, not more than 1.8% Mn is desirable.
  • Al is effective for deoxidation of the steel and at least 0.01% Al is necessary. But when Al is contained in an amount more than 0.15%, the deoxidation effect saturates and problems of hot embrittlement due to AlN arise. From the point of ductility, not more than 0.1% A] is desirable.
  • Ti is essential for giving the high strength properties, and at least 0.01% effective Ti is required. But in case of a steel as in the present invention where the fine TiC and the precipitation hardening are the main object, even when the effective Ti is increased more than 0.40%, the strength does not substantially increase but on the contrary the embrittlement is promoted. Further from the point ofductility not more than 0.3% effective Ti is desirable.
  • the other determining factor is the spot weldability. As mentioned hereinbefore, when the amount of carbon which is not fixed by Ti is large, the spot weldability is poor, and thus the condition of C% Ar[effective Ti%] 0.15% must be satisfied.
  • Nb, V, Mo, and W they play as precipitation hardening elements and effective to enhance the high strength properties and improve the pressformability by refining the carbides, and they must be present in an amount of at least 0.01%.
  • Cr, Ni and Cu are effective to increase the high strength properties and improve the press-formability through improvement of balance between the strength and the ductility.
  • Zr, Ca, Mg, rare earth elements combine with S to spheroidize inclusions and improve the impact properties and the press-formability, and for this effect, at least 0.01% (amount to be added)is necessary.
  • 0.01% amount to be added
  • finishing temperature it is necessary to maintain the temperature not lower than 870C to avoid precipitation of TiC during the hot rolling prior to the finishing rolling in order to assure the high temperature strength properties of the final cold rolled steel sheets.
  • a finishing temperature not lower than 890C is desirable.
  • a finishing temperature not higher than 960C is desirable.
  • the lower limit of the coiling temperature is set at 560C, but in view of the finishing temperature, a hot coiling temperature higher than 570C is desirable.
  • the cold reduction rate with a reduction rate less than 30%, the amount of internal defects such as dislocation is irregular, and it is impossible to produce a uniform precipitation site of TiC in the grains, and the strain energy stored by the cold rolling is too small for recrystallization so that the temperature zone for the partial recrystallization and the optimum temperature zone for the precipitation hardening overlap, thus causing difficulties in production.
  • a reduction rate not less than 40% is desirable.
  • the recrystallization temperature a satisfactory recrystallization temperature below 600C a full recrystallization can not be attained.
  • a recrystallization temperature higher than 900C the structure partially transform into austenite, thus causing large unstability in the strength.
  • the temperature of the first recrystallization annealing is higher than the hot coiling temperature.
  • the second annealing not lower than 600C is necessary in order that part of the fine TiC which precipitated during the first annealing is allowed to grow appropriately, and part of the TiC which did not precipitate during the first annealing is allowed to precipitate finely.
  • an annealing temperature not lower than 650C is desirable in order to promote the recrystallization.
  • the steel was prepared in a converter and made into slabs by an ordinary ingot-making method and partly by a continuous casting (B,, B C and C and subjected to hot rolling, cold rolling and annealing as specified in Table l to obtain cold rolled steel sheets of final thickness of 1.0mm and 1.6mm. The sheets were all subjected to 1.0% skin pass rolling.
  • the chemical compositions of the steels as well as their mechanical properties and weldability are shown in Table l.
  • the box annealing in this example was conducted by heating'the steel at a heating rate 20 to 40C/hour, holding the steels at different temperatures for 6 hours and cooling the steels in the furnace.
  • the continuous annealing was done by rapidly heating the steels, holding them at their respective temperature for 2 to 4 minutes and subjecting them at a temperature between 400 and 450C except the grades C and C
  • the testing method for the weldability is as under. The samples were spot welded under the following conditions and subjected to the under two tests.
  • a structure prepared by spot welding as shown in FIG. 1 was cooled to 30C, and a steel lamp of 80 kg load was dropped on the structure to see if there is peeling off at the spot weld, and a sample showing peeling off at even one point was estimated as bad (X mark), and s sample showing completely no peeling off was estimated as good (0 mark).
  • the cold rolled steel sheets of the chemical composition produced according to the present invention show both excellent drawability and weldability, with a tensile strength of 50 to Kg/mm
  • the steel composition limited by the condition of 4[C%]- 0.6% effective Ti% 4[C%] is necessary, and this limitation is very important for the present high strength cold rolled steel sheets to be used in applications where safety of structures is most con cerned.
  • EXAMPLE 2 The steels of compositions shown in Table 2 were prepared in a converter, and subjected to an ordinary ingot-making method and partly to continuous casting (F, F to obtain slabs, which were subjected to hot rolling, cold rolling and annealing as specified in Table 1 to obtain cold rolled steel sheets of final thickness of 1.0mm and 1.6mm. The sheets were all subjected to 1.0% skin pass rolling. The mechanical properties Tvalues and weldability of the obtained cold rolled steel sheets are shown in Table 2.
  • the box annealing in this example was conducted by heating the steels at a heating rate 20 to 40C/hour, holding them at different temperatures for 6 hours and subjecting them to an ameter, and the bore was expanded using a conical punch.
  • Stamping Spot weldability bore expansion Low temtest Hardness perature 1 Value (percent) in weld peeling test First cold rolling annealing Cold reduction e(percent) Annealing type 55 Box annealing- 70 Box annealing 70 Continuous anneal Yield Elongapoint tion (kg/mm!) (percent) Coiling temperatemperae( C.) ture( C.) rat Tensile strength (kg/mm!) Heating Finishing temperature( O.) tur Grade OOOOXOOOOOXOOOOOOOOOOO mmnw z uwwmmwwwwmwwwmmwwwmm LLLLLLLLLLLLLLLLLLLL 64864246363626.4464 ZRWnmQMOMQQWRWQLQmQWDWiZZZ- 445545445552333446 .mwLLQQmOMQLLQLTAXmAmO 55 766556674444557 Inventive steel.
  • a method for producing a precipitation hardening high strength cold rolled steel sheet comprising heating a steel slab containing 0.03 to 0.25% C, not more than 1.5% Si, 0.6 to 2.5% Mn, 0.01 to 0.15% Al, 0.01 to 0.40% effective Ti (total [Ti%]- 3.4[N%]- 1.5[O%]- 1.5[S%]) and satisfying the condition of 4[C%]- 0.6% effective Ti% 4[C%], with the balance being Fe and unavoidable impurities at a temperature not lower than 1,200C, hot rolling the slab, subjecting the hot rolled sheet to a finishing rolling at a temperature not lower than 870C, coiling the sheet at a temperature between 560 and 680C, acid pickling the sheet, cold rolling the sheet with a reduction rate not less than and subjecting the sheet to recrystallization annealing at a temperature between 600 and 900C.
  • said steel slab further comprises at least one element selected from at least one of Groups A, B and C in a total amount of 0.01 to 0.1% for Group A elements, 0.03 to 1.0% for Group B elements and 0.01 to 0.1% of actually added amount for Group C elements, said Group A consisting of Nb, V, Mo and W, said Group B consisting of Cr, Ni and Cu, and said Group C consisting of Zr, Ca, Mg and rare earth elements.

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US00377308A 1972-07-11 1973-07-09 Precipitation hardening high strength cold rolled steel sheet and method for producing same Expired - Lifetime US3857740A (en)

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JP6867072A JPS535610B2 (de) 1972-07-11 1972-07-11
JP6961573A JPS5427822B2 (de) 1973-06-20 1973-06-20

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Cited By (14)

* Cited by examiner, † Cited by third party
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US3936324A (en) * 1975-03-14 1976-02-03 Nippon Kokan Kabushiki Kaisha Method of making high strength cold reduced steel by a full continuous annealing process
US3951696A (en) * 1973-08-11 1976-04-20 Nippon Steel Corporation Method for producing a high-strength cold rolled steel sheet having excellent press-formability
US4020312A (en) * 1974-11-27 1977-04-26 Nippon Kokan Kabushiki Kaisha Method of manufacturing thick, high-strength steel pipe for low temperature service
US4082576A (en) * 1976-10-04 1978-04-04 Youngstown Sheet And Tube Company Ultra-high strength low alloy titanium bearing flat rolled steel and process for making
US4105474A (en) * 1976-04-12 1978-08-08 Nippon Steel Corporation Process for producing a high tension steel sheet product having an excellent low-temperature toughness with a yield point of 40 kg/mm2 or higher
US4219371A (en) * 1978-04-05 1980-08-26 Nippon Steel Corporation Process for producing high-tension bainitic steel having high-toughness and excellent weldability
US4328032A (en) * 1980-03-13 1982-05-04 Sybron Corporation Titanium and niobium high strength steel alloys
US4331488A (en) * 1979-10-18 1982-05-25 Kobe Steel, Ltd. Cold-rolled ultra low carbon steel sheet with improved press-forming properties
US4376661A (en) * 1978-06-16 1983-03-15 Nippon Steel Corporation Method of producing dual phase structure cold rolled steel sheet
US4398950A (en) * 1979-07-10 1983-08-16 Inland Steel Company High strength cold rolled, weldable steel strip
US4591395A (en) * 1983-05-05 1986-05-27 Armco Inc. Method of heat treating low carbon steel strip
US6518533B1 (en) * 2001-11-01 2003-02-11 Ltv Steel Company, Inc. High strength steel tubing
US6582537B1 (en) * 1998-09-08 2003-06-24 Thyssen Krupp Stahl Ag Method for producing cold-rolled bands or sheets
US6764645B2 (en) * 2001-11-28 2004-07-20 Diado Steel Co., Ltd. Steel for machine structural use having good machinability and chip-breakability

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FR2419332A1 (fr) * 1978-03-07 1979-10-05 Kobe Steel Ltd Acier structural soudable contenant du niobium et possedant une bonne soudabilite
FR2419333A1 (fr) * 1978-03-07 1979-10-05 Kobe Steel Ltd Acier structural soudable au niobium
JPS6046166B2 (ja) * 1980-11-26 1985-10-15 川崎製鉄株式会社 焼付硬化性を有する良加工性冷延鋼板の製造方法
JPS5980752A (ja) * 1982-10-28 1984-05-10 Nippon Kokan Kk <Nkk> 硫化水素環境で溶接部の耐水素割れ性及び耐硫化物応力腐食割れ性に優れた鋼
JPH0674487B2 (ja) * 1986-11-28 1994-09-21 新日本製鐵株式会社 耐サワ−性の優れた高靱性電縫鋼管
US5221373A (en) * 1989-06-09 1993-06-22 Thyssen Edelstahlwerke Ag Internal combustion engine valve composed of precipitation hardening ferritic-pearlitic steel
JP3037767B2 (ja) * 1991-01-21 2000-05-08 川崎製鉄株式会社 低降伏比高強度溶融亜鉛めっき鋼板及びその製造方法

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US3544393A (en) * 1967-08-11 1970-12-01 Nat Steel Corp Method of manufacturing low carbon high tensile strength alloy steel
US3625780A (en) * 1968-04-29 1971-12-07 Youngstown Sheet And Tube Co Process for preparation of high-strength alloy of titanium and ferritic structure

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DE1483210A1 (de) * 1965-11-23 1969-03-20 Hoerder Huettenunion Ag Verwendung eines unlegierten Stahls mit guter Abkantbarkeit in Laengs- und Querrichtung
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US3328211A (en) * 1963-12-05 1967-06-27 Ishikawajima Harima Heavy Ind Method of manufacturing weldable, tough and high strength steel for structure members usable in the ashot-state and steel so made
US3544393A (en) * 1967-08-11 1970-12-01 Nat Steel Corp Method of manufacturing low carbon high tensile strength alloy steel
US3625780A (en) * 1968-04-29 1971-12-07 Youngstown Sheet And Tube Co Process for preparation of high-strength alloy of titanium and ferritic structure

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3951696A (en) * 1973-08-11 1976-04-20 Nippon Steel Corporation Method for producing a high-strength cold rolled steel sheet having excellent press-formability
US4020312A (en) * 1974-11-27 1977-04-26 Nippon Kokan Kabushiki Kaisha Method of manufacturing thick, high-strength steel pipe for low temperature service
US3936324A (en) * 1975-03-14 1976-02-03 Nippon Kokan Kabushiki Kaisha Method of making high strength cold reduced steel by a full continuous annealing process
USRE31251E (en) * 1976-04-12 1983-05-24 Nippon Steel Corporation Process for producing a high tension steel sheet product having an excellent low-temperature toughness with a yield point of 40 kg/mm2 or higher
US4105474A (en) * 1976-04-12 1978-08-08 Nippon Steel Corporation Process for producing a high tension steel sheet product having an excellent low-temperature toughness with a yield point of 40 kg/mm2 or higher
US4082576A (en) * 1976-10-04 1978-04-04 Youngstown Sheet And Tube Company Ultra-high strength low alloy titanium bearing flat rolled steel and process for making
US4219371A (en) * 1978-04-05 1980-08-26 Nippon Steel Corporation Process for producing high-tension bainitic steel having high-toughness and excellent weldability
US4376661A (en) * 1978-06-16 1983-03-15 Nippon Steel Corporation Method of producing dual phase structure cold rolled steel sheet
US4398950A (en) * 1979-07-10 1983-08-16 Inland Steel Company High strength cold rolled, weldable steel strip
US4331488A (en) * 1979-10-18 1982-05-25 Kobe Steel, Ltd. Cold-rolled ultra low carbon steel sheet with improved press-forming properties
US4328032A (en) * 1980-03-13 1982-05-04 Sybron Corporation Titanium and niobium high strength steel alloys
US4591395A (en) * 1983-05-05 1986-05-27 Armco Inc. Method of heat treating low carbon steel strip
US6582537B1 (en) * 1998-09-08 2003-06-24 Thyssen Krupp Stahl Ag Method for producing cold-rolled bands or sheets
US6518533B1 (en) * 2001-11-01 2003-02-11 Ltv Steel Company, Inc. High strength steel tubing
US6764645B2 (en) * 2001-11-28 2004-07-20 Diado Steel Co., Ltd. Steel for machine structural use having good machinability and chip-breakability

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Publication number Publication date
IT998222B (it) 1976-01-20
DE2334974A1 (de) 1974-07-04
FR2192181A1 (de) 1974-02-08
FR2192181B1 (de) 1976-04-30

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