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
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
• • 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

Definitions

• the steels are hot-rolled finished in the temperature range 1550 F. to 1650 F., cooled at a rate within the range 20 F. to 135 F. per second and collected by coiling or piling within a temperature range of 1025 F. to 1175 F.
• the steels modified by the incorporation of .0l% to .10% of a rare earth are further characterized by improved formability.
• This invention relates to high-strength low-alloy steels and their method of manufacture.
• 3,666,452 Patented May 30, 1972 ICC vention is to provide such steels characterized in a hotrolled finished condition by a yield strength in excess of 80,000 p.s.i., an ultimate tensile strength in excess of 95,000 p.s.i., ductility as measured by percent elongation (2 inches) in excess of 18% and superior toughness.
• Still another object of the present invention is to provide such steels which can be bent without cracking about an inside radius which is equal or less than the thickness of the steel.
• the steels of the present invention are fully killed and have the following preferred chemistry: carbon, .12% to .20%; manganese, 1.10% to 1.65%; vanadium, .05% to .20%; nitrogen, .005 to .025%; phosphorus, .04% maximum; sulfur, .025% maximum; silicon, .60% maximum; rare earth, 0 to .10%; iron, balance.
• the steels to possess the desired characteristics and properties of a yield strength in excess of 80,000 p.s.i., an ultimate tensile strength in excess of 95,000 p.s.i., ductility as measured by percent elongation (2 inches) in excess of 18% and superior toughness, are hot-rolled finished in the temperature range 1550 F. to 1650 F., and collected as by coiling or piling within a temperature range of 1025 F. to 1175 F.
• the steel For the typical length of a modern hot-mill run-out table and conventional rolling speeds, the steel must be cooled at a rate within the range of 20 F. to 135 F. per second to maintain the finishing and coiling temperature specified.
• a high-strength lowalloy steel in addition to having high strength should also have good formability, toughness, weldability and fatigue resistance.
• an object of the present invention is to provide low-alloy steels having high strength in combination with excellent formability, toughness, weldability and fatigue resistance.
• Another object of the present in- Material from Heat No. 797138 subjected to a high thermal practice, i.e., finished at a temperature above 1650 F. and coiled at a temperature above 1l7'5 F. exhibited a yield strength and ultimate tensile strength below that exhibited by material from the same heat finished and coiled Within the specified range. Material from Heat No.
• Heat No. 4391-1 contained vanadium below the minimum of .05% specified above and also had a yield strength and ultimate tensile strength significantly below the desired level.
• Heat No. 43233 contained vanadium in an amount near the upper limit employed by the steels of the invention and demonstrated a yield strength and ultimate tensile strength significantly above the specified minimum of 80,000 p.s.i.
• the ductility of the steel was 26.5.
• the specimens for which the data of Table III was obtained comprised one-half size Charpy V-notch samples.
• Heat No. 797 566 was coiled at a temperature below the minimum coiling temperature of the invention, -1 025 iF., while Heat No. 806558 was both finished and coiled above the maximum temperatures of the invention.
• Heat No. 804-982 was finished and coiled within the temperature ranges of the invention.
• Heat No. 804 982 had lower transition temperatures at 50% shear and ft.-lbs. than Heat No. 806558.
• Heat No. 804982 had lower transition temperatures at shear for both longitudinal and transverse specimens and at 10 ft.-lbs.
• a rare earth in the amount of a .01% to .10% is added to the steel.
• rare earths employed in the invention are cerium, lanthanum, praseodymium, neodymium, yttrium, scandium, or mischmetal which, of course, is a mixture of rare earths.
• the rare earths may be added in a pure form or in the form of a compound, such as a silicide. To insure good recovery, the rare earth is preferably added to the steel in the ingot mold or in the ladle after the steel has been killed.
• manganese content As is known, an increase in carbon is accompanied by a decrease in ductility, toughness and weldability so that where an impairment in these properties is acceptable to achieve higher strengths, higher carbon contents are employed. Similarly, while a manganese content of 1.10% to 1.65% is preferred, lower manganese contents can be used. Where corrosion resistance is of importance, copper is added to the steel to improve its atmospheric corrosion resistance.
• the steels of the invention possess excellent weldability and are highly resistant to either hot or cold crack ing. Preheating or postheating of the weld area is not required. In addition, the steels of the invention are often more resistant to fatigue damage than a quenched and tempered alloy steel of the same or even higher yield strength. This is because the steels of the invention are not subjected to heat treating and therefore are virtually free of surface decarburization.
• the steel of claim 1 containing .12% to .20% carbon, 1.10% to 1.65% manganese and .05% to .20% vanadium.
• a process for manufacturing a low-alloy highstrength steel characterized in the hot-rolled condition by a yield strength in excess of 80,000 psi, an ultimate tensile strength in excess in about 95,000 p.s.i., ductility as measured by percent elongation (2 inches) in excess of about 18% and good toughness comprising, hot-rolling a steel consisting essentially of at least .12% carbon, a maximum of about 1.65% manganese, at least about .05 vanadium, .005 to .025 nitrogen, .04% maximum phosphorus, .025 maximum sulfur, .60% maximum silicon, .0l% to .10% of a rare earth or mixture of rare earths, balance iron at a finishing temperature within the range of 1550 -F. to 1650 'F., cooling the hot-rolled product at a rate within the range 20 F. to 135 F. per second and collecting the cooled material at a temperature wtihin the range 1025 F. to
• a low-alloy high-strength steel having improved bending properties and consisting essentially of at least about 112% carbon, a maximum of about 1.65% manganese, at least about .05% vanadium, .005% to .025% nitrogen, .04% maximum phosphorus, .025% maximum sulfur, .60% maximum silicon, .01% to 10% of a rare earth or mixture of rare earths, balance iron,
• the steel of claim 5 containing .12% to .20% carbon, 1.10% to 1.65% manganese and .05% to .20% vanadium.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Heat Treatment Of Steel (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=25287110

Family Applications (1)

Country Status (5)

Cited By (16)

Families Citing this family (3)

• 1969
  • 1969-07-16 US US842345A patent/US3666452A/en not_active Expired - Lifetime
• 1970
  • 1970-07-03 DE DE2033002A patent/DE2033002B2/de not_active Withdrawn
  • 1970-07-10 GB GB1289373D patent/GB1289373A/en not_active Expired
  • 1970-07-15 CA CA088276A patent/CA924540A/en not_active Expired
  • 1970-07-15 JP JP45061438A patent/JPS518093B1/ja active Pending

Also Published As

Similar Documents