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
  • 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
• • 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
  • C21D7/00—Modifying the physical properties of iron or steel by deformation
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/0093—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for screws; for bolts
• • 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
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/008—Martensite
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below

Definitions

• the present invention relates to a method of making high-strength steel parts and the parts produced thereby, and more particularly it relates to a method in which a blank of high-strength steel is warm formed into a desired geometric configuration while maintaining the high-strength properties of the steel blank.
• Steel parts have heretofore been formed using cold forging or hot forging techniques which are well known in the art.
• hot forging parts from steel the material is initially heated to about
• the strength of the part is increased and the part must therefore be annealed between successive cold forming operations to relieve internal stress, which adds to the time and cost of such processes.
• warm forging may be utilized to form parts from materials at an intermediate temperature which is high enough to reduce the strength of the material and thereby facilitate forming, and yet is below the hot forging temperature at which scaling and decarburization occurs.
• One such warm forming method is disclosed in U.S. Pat. No. 3,557,587.
• Certain other patents disclose processes which include rolling and extruding steps carried out at "warm” temperatures so as to avoid the drawbacks of decarburization and scaling and/or to impart or improve desired metallurgical and mechanical properties to the steel. See U.S. Pat. Nos. 2,767,836; 2,767,837; 2,880,855; 3,076,361;
• the present invention is directed to a method of making high-strength steel parts from blanks of high-strength steel material having a tensile strength of at least about 120,000 psi and a yield strength of at least about 90,000 psi.
• the present invention provides a method of making high-strength steel parts from blanks of high-strength steel material by warm forming the blank to provide a part having a desired geometric configuration, whereby the mechanical properties of tensile strength and yield strength of the part are substantially the same as or greater than the blank.
• the present invention also provides a method of making high-strength steel parts including warm forming a blank of high-strength steel material whereby the mechanical properties of tensile strength and yield strength of the part are substantially the same as or greater than the blank and wherein the part, with the desired mechanical properties of tensile strength and yield strength, is produced without further strengthening processing steps.
• the method of the present invention is useful for producing a wide variety of high-strength steel parts including various types of bolts (U-bolts, eye-bolts, J-bolts, hex-head bolts, square-head bolts, etc.), axles, cam shafts, screws, sway bars and other parts susceptible to forming by the warm forging or forming process disclosed herein.
• bolts U-bolts, eye-bolts, J-bolts, hex-head bolts, square-head bolts, etc.
• axles cam shafts
• screws sway bars and other parts susceptible to forming by the warm forging or forming process disclosed herein.
• the method of the present invention for making a high-strength steel part includes providing a blank of high-strength steel material having a tensile strength of at least about 120,000 psi, and preferably at least about 150,000 psi, and a yield strength of at least about 90,000 psi, and preferably at least about 130,000 psi.
• the high-strength steel material utilized as the blank has been hot reduced and cold drawn to provide the blank having the mechanical properties of tensile strength and yield strength stated above.
• the high-strength steel material may be exemplified by the following composition, by weight percent: carbon about 0.30 to about 0.65% manganese about 0.30 to about 2.5% vanadium up to about 0.35% iron balance
• the high-strength steel material has the following composition, by weight percent:
• the blank having a composition and mechanical properties of tensile strength and yield strength as given above, is thereafter warm formed at a temperature of about 300 to about 1200°F to provide a part having a desired geometric configuration, whereby the mechanical properties of tensile strength and yield strength of the part are substantially the same as or greater than the blank.
• the temperature at which the part is formed is related to the chemical composition of the steel material used.
• the formed part, with the mechanical properties of tensile strength and yield strength given, is produced without any further strengthening processing steps subsequent to the warm forming thereof.
• the blank of high-strength steel material having a tensile strength of at least about 120,000 psi and a yield strength of at least about 90,000 psi, which is used as the starting piece in the method of the present invention is produced by any suitable method known in the art.
• One such method is disclosed in U.S. Pat. No. 3,904,445 to the present inventor, and the specification in its entirety is incorporated herein by reference.
• the '445 patent discloses a processing sequence to produce a high-strength steel bar stock of the type particularly useful for producing threaded fasteners, including U-bolts. In the described process, the bar stock produced has a fine grained structure between about ASTM No. 5-8.
• a steel having a chemistry falling within certain disclosed ranges, is subjected to a standard hot reducing operation to within 10%-15% of final gauge.
• the hot reduced bar stock is then cut or severed into individual lengths for rapid air cooling. Thereafter the individual lengths of hot reduced bar stock are subjected to a cold finishing to final gauge.
• the final step is a controlled stress relieving step to increase the mechanical strength properties.
• This stress relieving step comprises heating the lengths of bar stock to between about 500-850°F for about 1 hour, but may or may not be necessary.
• Such bar stock, with and without further stress relieving may be used to form the starting blank material of high-strength steel.
• the following examples illustrate the practice of the present invention to produce a U-bolt from high-strength steel bar stock produced in accordance with the method disclosed in my U.S. Pat. No. 3,904,445, described above.
• High-strength steel bar stock of Grade 8 strength steel, having a diameter of 0.825", is cut to lengths of approximately 36". This stock has a tensile strength of at least about 150,000 psi and a yield strength of at least about 130,000 psi. Both ends of the bar stock segments are threaded using known threading processes to provide 21 ⁇ 2" threaded sections at either end thereof. The bar stock segments are then heated to approximately 850 °F and a medial section of each bar stock segment is flattened using a mechanical forging press applying approximately 1,000 tons of pressure. The flattened section of the bar stock is approximately 7/16" thick and IV wide. Thereafter, the bar stock segments are bent at the location of the flattened section to form the U-bolt product.
• the flattening step provides elongation to the bar stock segment such that the total length of the finished U-bolt product is somewhat in excess of 36".
• the finished U-bolt product has the desired mechanical properties of tensile strength and yield strength originally possessed by the bar stock and therefore requires no further strengthening processing steps.
• the finished bars of Table II had desired mechanical properties greater than those originally possessed by the bars of Table I.
• the tensile strengths increased from about 140,000 psi to about 160,000 psi and the yield strengths increased from about 130-132,000 psi to about 148-150,000 psi.
• the method provides for warm forming a blank into a part whereby the mechanical properties of tensile and yield strengths may be substantially the same as or greater than the blank.

Landscapes

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

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

Family

ID=25250021

Family Applications (1)

Country Status (6)

Cited By (3)

Citations (6)

• 1993
  • 1993-01-21 WO PCT/US1993/000519 patent/WO1993015233A1/en not_active Application Discontinuation
  • 1993-01-21 BR BR9305812A patent/BR9305812A/pt not_active IP Right Cessation
  • 1993-01-21 JP JP5513314A patent/JP2878842B2/ja not_active Expired - Lifetime
  • 1993-01-21 CA CA002128019A patent/CA2128019C/en not_active Expired - Lifetime
  • 1993-01-21 EP EP93904550A patent/EP0624205A1/en not_active Ceased
  • 1993-01-21 KR KR1019940702598A patent/KR100230882B1/ko not_active IP Right Cessation

Patent Citations (6)

Non-Patent Citations (2)

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