US3767387A - High tensile strength steel having excellent press shapability - Google Patents

High tensile strength steel having excellent press shapability Download PDF

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Publication number
US3767387A
US3767387A US00128334A US3767387DA US3767387A US 3767387 A US3767387 A US 3767387A US 00128334 A US00128334 A US 00128334A US 3767387D A US3767387D A US 3767387DA US 3767387 A US3767387 A US 3767387A
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steel
percent
press
shapability
tensile strength
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T Yamaguchi
H Kido
T Nakagawa
T Omori
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JFE Engineering Corp
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Nippon Kokan Ltd
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    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium

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  • ABSTRACT Hot rolled high tensile strength steel having excellent press shapability comprises a composition consisting Oct. 5," 1967 Japan 42/63780 of 003 to 25 of C 0 to 50 f Si 0 30 130% of Mn, less than 0.010% of S, 0.005% to 0.10% of A1, US. Cl. 75/124 0 005% to 005% of Nb the balance of i and impw gf id f- 7 57l 2 :1 rities, and the sum of %C 10(%S) is up to 0.25%.
  • This invention relates to hot rolled, high tensile strength steel having excellent press shapability, more particularly excellent bending shapability and workability into expansible flanges.
  • the high tensile strength steels of excellent press shapability according to this invention comprise a composition consisting essentially of from 0.03 to 0.25 percent of C, from to 0.60 percent of Si, from 0.30 to 1.80 percent of Mn, up to 0.010 percent of S, from 0.005 to 0.10 percent of Al, from 0.005 to 0.050 percent of Nb, and the balance of Fe and impurities.
  • the sum of %C l0(%S) is up to 0.25 percent.
  • FIG. 1 is a diagrammatic representation of a device utilized to test the novel steels
  • FIG. 2 is a plot of the carbon content versus press shapability
  • FIG. 3 is a plot of the sulfur content versus press shapability, and
  • FIG. 4 is a graph to show the relationship between the phosphorus content and press shapability
  • FIG. 5 is a plot of sulfur content versus numbers of charges of molten steel in the ladle
  • FIG. 6 is a diagrammatic representation of a steel specimen used to determine the notch elongation thereof
  • FIG. 7 is a plot of notch elongation versus press shapability
  • FIG. 8 is a plot of notch elongation versus carbon content
  • FIG. 9 is a plot of notch elongation versus sulfur content
  • FIG. 10 is a plot of notch elongation versus 7C l0(%S)
  • FIG. 11 is a plot of notch elongation versus yield point.
  • the shapability of steel stocks is usually determined by an authorized method of testing, such as those proerty of propagation of minute cracks already present in steel blanks. Accordingly, it is desirable to use a model testing device simulating the actual press working, as illustrated in FIG. 1 of the accompanying drawing.
  • the testing device shown in FIG. 1 comprises a punch 1 and a die 2 having a letter V shaped notch of degrees at its center, the punch head being shaped to correspond to this configuration.
  • a load is applied to punch 1 to perform bending work.
  • the characteristic value of the bending shapability is determined by the sum of the length of cracks formed at the ends of the blank 3. As a result of experiments, we have determined that this characteristicvalue well agrees with the actual shapability.
  • novel high tension steels whose press shapability have been determined by the testing method described above have the following composition:
  • novel steels of such composition can be relatively easily produced by electric furnaces, converters, or other conventional steel manufacturing furnaces so long as a suitable pretreatment of molten pig iron or a suitable steel manufacturing operation is adopted.
  • the novel steels can be hot rolled and may be subjected to final normalizing treatment.
  • a plurality of steel samples having compositions in the above described range excepting carbon content were prepared by melting and the relationship between carbon content in the steel and press shapability was plotted as shown in FIG. 2.
  • press shapability is greatly improved as the carbon content decreases whereas it decreases rapidly above 0.25 percent.
  • carbon content of less than 0.03 percent the effect of carbon upon high tensile strength steel was not realized.
  • a preferred range is from 0.06 to 0.15 percent. This is the reason why the carbon content of the novel steel is limited to the above ranges.
  • Press shapability of a steel involves two important factors; namely, (1) deformability of a steel (when cracks are easily caused) and (2) working defects (cracks prevailing in a steel), due to the existence of artificial defects in the steel (e.g. defects caused by the existence of non-metallic materials, which is unavoidable in steel making; scratches made on the surface of steel sheets while handling the same, or defects caused by flashes when steel sheet is cut).
  • press shapability is evaluated by means of elongation (GL 50mm) of tensile test pieces provided with notches and the results obtained with this method correspond to press results obtained at press works.
  • FIG. 7 shows press results. It is true, of course, that the limit of ,causing defects in press shapability depends upon the shape of pressed products, press conditions, etc. However, in general, a steel having less than percent of notch elongation is not regarded as a steel having excellent shapability.
  • FIG. 8 shows the influence of carbon upon the shapability of steels having the same tensile strength with the same content of sulphur, each of which is obtained under different manufacturing conditions (e.g., coiling temperature in hot rolling). Press shapability improves remarkably with less than 0.15 percent of carbon, but it is possible to obtain a steel having excellent shapability with less than 0.25 percent of carbon by controlling sulphur content. Preferred carbon content is within the range from 0.06 percent to 0.15 percent.
  • FIG. 9 shows the influence of sulphur upon the shapability of steels having constant carbon content. As is clear from the data, press shapability improves remarkably with less than 0.010 percent of sulphur. The slope of the curve is substantially greater in the range of 0.004 to 0.010% S, than for values of more than 0.010% S. Solid circles in FIG. 9 represent values obtained with steels having a P content of at least 0.01 1 percent, and other circles those with up to 0.010% P.
  • press shapability improves remarkably with less than 0.250 of (C% 10 X 8%).
  • FIG. 11 shows the relationship of yield point of steels of different compositions obtained under various manufacturing conditions, and press shapability. Shapability of a steel of the same composition deteriorates remarkably with a high strength value as indicated by yield point.
  • FIG. 4 The effect of phosphorus is shown in FIG. 4 which was plotted from the result of experiments wherein ingredients other than phosphous were selected to be in the range mentioned hereinabove in the same manner as has been described in connection with carbon and sulfur. As can be seen from FIG. 4, in the ordinary range of composition, it is not required to take into consideration the effect of phosphorus upon the press shapability. However, the maximum limit of the phosphorus content is, preferably 0.040 percent.
  • silicon of trace quantity is advantageous, since silicon is incorporated as a deoxidizing agent and since it is an element to impart high tensile strength to steel at low cost, incorporation thereof to some extent should be tolerated.
  • silicon content of more than 0.6 percent in steel results in increase in cost.
  • the upper limit of the silicon content should be 0.6 percent, it being understood that sufficient strength can be provided for steel with silicon content less than 0.6 percent.
  • manganese when it is utilized as a deoxidizing agent it is necessary to use it in a quantity of at least 0.3 percent.
  • this object of the invention can be achieved with a quantity of manganese of less than 1.8 percent. Incorporation of manganese in excess of 1.8 percent causes increase in the cost of the product so that the upper limit thereof was determined to be 1.8 percent.
  • the upper limit of aluminium was determined to be 0.10 percent.
  • the lower limit was determined to be 0.005 percent because, with aluminium less than this limit, it is not possible to obtain the desirable deoxidizing effect of the steels.
  • a preferred range is from 0.015 to 0.08 percent.
  • novel high tensile strength steels having excellent shapability are characterized by containing niobium, in addition to various ingredients mentioned above in order to further increase the tensile strength. It was found that the effect of incorporation of this element is especially significant where steel stocks are used in the rolled state.
  • the content of Nb was determined experimentally to range from 0.005 to 0.050 percent in due consideration of press shapability and strength of the product and it was found that this range is most suitable to attain the object of this invention.
  • compositions of sample steels prepared by a conventional converter are as follows:
  • samples A and B represent controls, whereas samples C, D and E are steel stocks embodying this invention.
  • the steels of this invention contain up to 0.010 percent sulfur, and preferably less than effective, method for desulfurizing a steel to such a sulfur content is desulfurization of molten pig iron.
  • molten pig iron having a sulfur content of 0.046 percent is tapped from a blast furnace.
  • the molten pig iron 45 tons, is poured into each of two iron la dles.
  • a desulfurizing agent 350 kg, comprising approximately 72% CaC is added to the pig iron in each ladle. Nitrogen is blown through four pipes (diameter, inch) into each ladle at a pressure of 2-5 kg/cm for 50 minutes, to agitate the molten pig iron.
  • each ladle approximately tons of desulfurized iron
  • the desulfurized iron is poured into a converter and is refined. The converter is tapped and ingots are then formed. Analysis of the steel product is as follows:
  • the press shapability of the novel steels is excellent so that when it is used for motor cars and the like it is possible to reduce the weight of steel utilized. Press working of a rear axle housing, for example, can be performed at high efficiencies with good yields.
  • the novel steels can equally be used in any field of industry requiring high mechanical strength and excellent press workability.
  • a high tensile strength steel having excellent pressability consisting essentially of, in percent by weight,
  • a steel of claim 1 wherein the percent by weight of carbon is from 0.06 to 0.15.
  • a steel of claim 1 containing up to 0.040 percent phosphorus.
  • niobium 0.027 and phosphorus 0.015 and the said sum is 0.0905.

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
US00128334A 1967-10-05 1971-03-26 High tensile strength steel having excellent press shapability Expired - Lifetime US3767387A (en)

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US (1) US3767387A (enrdf_load_stackoverflow)
BE (1) BE721875A (enrdf_load_stackoverflow)
DE (1) DE1801283A1 (enrdf_load_stackoverflow)
FR (1) FR1585316A (enrdf_load_stackoverflow)
GB (1) GB1221371A (enrdf_load_stackoverflow)
NL (1) NL6814131A (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4210445A (en) * 1977-10-18 1980-07-01 Kobe Steel, Ltd. Niobium-containing weldable structural steel having good weldability

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1221355B (de) * 1961-01-05 1966-07-21 Circulume Ltd Als Vorschaltgeraet fuer Gasentladungslampen bestimmte ringfoermige Drosselspule
JPS51533B1 (enrdf_load_stackoverflow) * 1970-12-17 1976-01-08
US3705302A (en) * 1971-03-12 1972-12-05 Gen Electric Luminaire
FR2419333A1 (fr) * 1978-03-07 1979-10-05 Kobe Steel Ltd Acier structural soudable au niobium
FR2419332A1 (fr) * 1978-03-07 1979-10-05 Kobe Steel Ltd Acier structural soudable contenant du niobium et possedant une bonne soudabilite
DE2819227C2 (de) * 1978-05-02 1984-06-14 Stahlwerke Peine-Salzgitter Ag, 3150 Peine Schweißbarer Manganstahl sowie Verfahren zum Schweißen dieses Manganstahles
US4673433A (en) * 1986-05-28 1987-06-16 Uddeholm Tooling Aktiebolag Low-alloy steel material, die blocks and other heavy forgings made thereof and a method to manufacture the material
DE3841870A1 (de) * 1988-12-13 1990-06-21 Westfalenstahl Kalt Und Profil Stahl zur herstellung von stahlbaendern fuer die fertigung von schattenmasken
US5074926A (en) * 1989-11-16 1991-12-24 Kawasaki Steel Corp. High tensile cold rolled steel sheet and high tensile hot dip galvanized steel sheet having improved stretch flanging property and process for producing same

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2233726A (en) * 1940-06-06 1941-03-04 Belding Harvey Ross Method of treating low carbon open hearth steel
US3155496A (en) * 1961-05-16 1964-11-03 Ishikawajima Harima Heavy Ind Manganese-molybdenum ductile steel
US3216823A (en) * 1965-01-19 1965-11-09 Lukens Steel Co Low alloy steel
US3259970A (en) * 1961-12-29 1966-07-12 Yawata Iron & Steel Co Method of submerged arc welding of iron and steel using nitride producing materials
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
US3402080A (en) * 1965-04-13 1968-09-17 Nippon Kokan Kk High tensile strength steel alloys
US3403060A (en) * 1964-06-18 1968-09-24 Yawata Iron & Steel Co Weldable high tensile strength steel capable of giving weld heat-affected zone having high toughness and joint strength
US3499757A (en) * 1968-12-20 1970-03-10 Lukens Steel Co Low alloy steel plate containing copper,chromoium,nickel,and molybdenum
US3562028A (en) * 1968-08-28 1971-02-09 Inland Steel Co Tough,high strength steel article

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2233726A (en) * 1940-06-06 1941-03-04 Belding Harvey Ross Method of treating low carbon open hearth steel
US3155496A (en) * 1961-05-16 1964-11-03 Ishikawajima Harima Heavy Ind Manganese-molybdenum ductile steel
US3259970A (en) * 1961-12-29 1966-07-12 Yawata Iron & Steel Co Method of submerged arc welding of iron and steel using nitride producing materials
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
US3403060A (en) * 1964-06-18 1968-09-24 Yawata Iron & Steel Co Weldable high tensile strength steel capable of giving weld heat-affected zone having high toughness and joint strength
US3216823A (en) * 1965-01-19 1965-11-09 Lukens Steel Co Low alloy steel
US3402080A (en) * 1965-04-13 1968-09-17 Nippon Kokan Kk High tensile strength steel alloys
US3562028A (en) * 1968-08-28 1971-02-09 Inland Steel Co Tough,high strength steel article
US3499757A (en) * 1968-12-20 1970-03-10 Lukens Steel Co Low alloy steel plate containing copper,chromoium,nickel,and molybdenum

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4210445A (en) * 1977-10-18 1980-07-01 Kobe Steel, Ltd. Niobium-containing weldable structural steel having good weldability

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BE721875A (enrdf_load_stackoverflow) 1969-03-14
DE1801283A1 (de) 1969-04-30
NL6814131A (enrdf_load_stackoverflow) 1969-04-09
FR1585316A (enrdf_load_stackoverflow) 1970-01-16
GB1221371A (en) 1971-02-03

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