US3301120A - Tempered threaded members and method of making - Google Patents

Tempered threaded members and method of making Download PDF

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Publication number
US3301120A
US3301120A US414208A US41420864A US3301120A US 3301120 A US3301120 A US 3301120A US 414208 A US414208 A US 414208A US 41420864 A US41420864 A US 41420864A US 3301120 A US3301120 A US 3301120A
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United States
Prior art keywords
tempered
threaded
hardness
case
threads
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Expired - Lifetime
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US414208A
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English (en)
Inventor
Calvin D Loyd
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.)
Caterpillar Inc
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Caterpillar Tractor Co
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Filing date
Publication date
Application filed by Caterpillar Tractor Co filed Critical Caterpillar Tractor Co
Priority to US414208A priority Critical patent/US3301120A/en
Priority to GB46736/65A priority patent/GB1067184A/en
Priority to FR39993A priority patent/FR1454933A/fr
Application granted granted Critical
Publication of US3301120A publication Critical patent/US3301120A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
    • F16B35/00—Screw-bolts; Stay-bolts; Screw-threaded studs; Screws; Set screws
    • 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

Definitions

  • Threaded members are especially prone to stress failure because of the very nature of their configuration. Specifically, the thread configuration with its attendant notches and acute angles creates lines of concentrated stress from which cracks are initiated and high internal stresses are set up.
  • FIG. 1 is a schematic longitudinal sectional view through a stud made in accordance with the present invention
  • FIG. 2 is a schematic cross section through a threaded member made in accordance with the invention and further illustrating the hardness at various radii from the center line of such threaded member;
  • FIG. 3 is a schematic illustration of a through-hardened notched test specimen and an accompanying graph illustrating the hardness and tensile strength gradients in a cross section through said test specimen;
  • FIG. 4 is a schematic illustration of a notched test specimen made according to the present invention and an accompanying graph illustrating the cross-sectional hardness and tensile strength thereof;
  • FIG. 5 is a schematic longitudinal sectional view through a bolt made in accordance with the invention.
  • threaded members are provided which have increased ultimate strength as well as high resistance to crack origination and propagation.
  • Such threaded members of the present invention are provided with a hardness gradient extending from the peripheral surface of the stud or bolt through the area of the threads and into the central core portion of the member. More specifically the case portion of the threaded member is tempered, i.e., reduced in hardness, while the central core portion of the member remains hard. The presence of a hardness gradient in the threaded portion of the member reduces stress concentration in the thread roots and thereby in turn reduces the brittle behavior of the metal normally caused by notches.
  • FIG. 1 of the drawings such a case tempered threaded member is illustrated in FIG. 1 of the drawings wherein a stud 11 has a hardened central portion 12 comprising the main body of the member.
  • the stud 11 is further provided with an outer case portion 13 that has been tempered to a hardness somewhat less than that of core portion 12.
  • FIG. 1 illustrates a sharp discontinuity in hardness between outer tempered case 13 and hardened core portion 12, in actuality the tempered case merges into hardened core portion 12 as illustrated in FIG. 2 of the drawings.
  • FIG. 2 is an illustration of the cross-sectional hardness of a typical threaded member of the invention.
  • the large dots thereon with the indicating numerals illustrate actual points at which the hardness of such cross section has been tested, and the indicating numerals indicate the Rockwell C hardness at those particular points in the cross section.
  • core portion 12 has a Rockwell C hardness varying from about 44 at center portion thereof to about 46 at the case interface.
  • case 13 has a Rockwell C hardness varying from about 35 at the outermost portion thereof to about 41 as the case approaches the interface with the hardened core 12.
  • tempered case 13 extends inwardly further into stud 11 than the depth of roots 16 of threads 14.
  • the relatively soft outer case 13 provides a more ductile material in the root area of the threads to reduce notch sensitivity and stress concentration in stud member 11. As stud member 11 is loaded in tension and/or bending, the material in the thread roots 16 yields slightly to eliminate stress concentration. This yielding permits .the stronger, relatively harder, unnotched core portion 12 to support the load.
  • the threaded members of the present invention may be fabricated from any conventional stud or bolt steel, it being necessary only that the steel be susceptible to conven* tional hardening and tempering processes.
  • Hardened core 12 and tempered case 13 of the threaded member are produced by well known conventional heat treatment methods, it being necessary only that the previously hardened stock be case tempered to a depth greater than the ultimate depth of the threads to be provided thereon.
  • one inch bars of S.A.E. 8630 steel were hardened and case tempered in the following manner: The bars were 4 were then threaded by conventional techniques to produce threaded test studs. The strength of these case tempered studs was then compared to studs of the same alloy wherein one stud was a production stud, another stud had heated to a temperature of approximately 1560 F. and 5 been nitrided for hours, and a third case hardened thereafter water quenched to through-harden the bars. stud. All of the studs were then tested for strength both The hardened bars were then tempered at 400 F.
  • Notched test specimens as illustrated by numeral 21 in FIG. 4 of the drawings were produced by the process as illustrated supra. These case tempered notched test specimens were compared with a conventional throughhardened production stud test specimen as illustrated at numeral 22 in FIG. 3 of the drawings. Immediately below the test specimens 21 and 22 in FIGS. 4 and 3 respectively, of the drawings is reproduced a graph of a stress diagram and the cross-sectional hardness gradient of the specimen immediately thereabove. The solid line indicates the stress diagram for its respective test specimen, while the broken line indicates the specimen hardness. It should be noted that the hardness gradient line 23 for conventional production specimen 22 indicates that the hardness remains constant over the entire cross section of the specimen. This illustrates the conventional through-hardness condition of the stud.
  • Hardness gradient line 24 of specimen 21 produced by the method of the present invention indicates that there is a tempered case portion wherein the hardness decreases from that shown by the core portion to a somewhat softer condition in the peripheral areas thereof.
  • the horizontal portion 26 of the stress diagram for case tempered test section 21 and the horizontal portion 27 of the stress diagram for conventional test specimen 22 indicate the ultimate tensile strength of the respective specimen.
  • the test specimen produced according to the present invention and having a case tempered portion had an ultimate tensile strength of approximately 260,000 pounds per square inch, where- ;as the test specimen produced by conventional throughhardening methods had an ultimate tensile strength of only 160,000 pounds per square inch.
  • case tempered bars As illustrated in Table I, the case tempered studs produced according to the present invention have significantly higher ultimate strength both in tension and wedge tension than studs produced by other methods. In addition it was noted that despite the high strength of the studs of the invention, appreciable elongation occurred in the threads.
  • case tempered bolts demonstrate improved physical properties when provided with a tempered case both at the threaded portion thereof as well as at the head portion.
  • FIG. 5 of the drawings there is illustrated a bolt 28 having a head portion 29 and a threaded shank portion 30.
  • the outer periphery of shank portion 30 has been tempered to form a softer casing 31 in which threads 32 are rolled.
  • Casing 31 extends throughout the length of shank portion 30 and also extends around shoulder 33 where head 29 meets shank 30.
  • Case tempering of the head end of the bolt where it meets the shank portion greatly reduces the stress concentration in that area whereby a bolt of improved properties is provided.
  • some bolts produced according to the present invention and having a case hardened portion at the head end as well as the threaded section when tested according to S.A.E. specifications, exhibited yield strengths of as high as 188,300 pounds per square inch and ultimate strengths of as high as 224,600 pounds per square inch.
  • Such bolts also exhibited a breaking stress of as high as 224,100 pounds per square inch in a wedge tension test.
  • threads may be machined or rolled into untreated bar stock
  • the threaded stock is heated and quenched to through-harden the piece.
  • the threaded through-hardened stock is then induction tempered and quenched to provide a tempered case portion. It is only necessary to temper the threaded member to a depth greater than the root depth to the threads. However, this can be accomplished readily by those skilled in the art.
  • a threaded steel member having a circular crosssection and high resistance to cracks and crack propogation comprising:
  • a tempered casing constituting the outer peripheral portion of said member, said casing extending radially inward from the periphery of said member and merging into said core portion, the hardness of said tempered casing decreasing from that exhibited by said core portion to a substantially softer condition through said peripheral portion;
  • said threaded member being characterized by a significantly higher ultimate strength in tension and wedge tension than that exhibited by a threaded member composed of the same steel but having a case hardness which is the same or greater than its core hardness.
  • a high strength threaded steel member having a circular cross-section comprising:
  • said threaded member being characterized by a significantly higher ultimate strength in tension and wedge tension than that exhibited by a threaded member composed of the same steel but having a case hardness which is the same or greater that its core hardness.
  • a process for producing high strength solid, threaded members comprising the steps of:
  • a process for producing high strength solid, threaded members comprising the steps of:
  • a process for producing high strength solid, threaded members comprising the steps of:

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)
US414208A 1964-11-27 1964-11-27 Tempered threaded members and method of making Expired - Lifetime US3301120A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US414208A US3301120A (en) 1964-11-27 1964-11-27 Tempered threaded members and method of making
GB46736/65A GB1067184A (en) 1964-11-27 1965-11-04 Method of producing case tempered threaded members
FR39993A FR1454933A (fr) 1964-11-27 1965-11-26 Procédé de production d'organes filetés ayant subi un revenu superficiel

Applications Claiming Priority (1)

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US414208A US3301120A (en) 1964-11-27 1964-11-27 Tempered threaded members and method of making

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US3301120A true US3301120A (en) 1967-01-31

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US (1) US3301120A (fr)
FR (1) FR1454933A (fr)
GB (1) GB1067184A (fr)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3657957A (en) * 1969-11-24 1972-04-25 Olympic Screw & Rivet Corp Rivet
US4824314A (en) * 1985-02-19 1989-04-25 Northrop Corporation Composite fastener system and manufacturing method thereof
US5700120A (en) * 1996-08-01 1997-12-23 General Electric Co. Threaded fastener and method of improving the fatigue life thereof
US6086305A (en) * 1999-01-13 2000-07-11 Illinois Tool Works Inc. Nails having selected heat treatment and hardening
US6109851A (en) * 1999-01-13 2000-08-29 Illinois Tool Works Inc. Screws having selected heat treatment and hardening
US6436474B2 (en) 1999-01-13 2002-08-20 Illinois Tool Works Inc. Method of chemically coating fasteners having improved penetration and withdrawal resistance
FR2856754A1 (fr) * 2003-06-24 2004-12-31 Hilti Ag Element de fixation
US7891925B2 (en) * 2005-12-06 2011-02-22 Blount, Inc. Shear resistant rivet and saw chain
US20160377107A1 (en) * 2015-06-23 2016-12-29 Richard Bergner Verbindungstechnik Gmbh & Co. Kg Process for producing a connecting element as well as connecting element
EP3276189A1 (fr) * 2016-07-29 2018-01-31 KAMAX Holding GmbH & Co. KG Vis tres resistante comprenant une couche souple
US20210239146A1 (en) * 2020-02-05 2021-08-05 Böllhoff Verbindungstechnik GmbH Joining element, connection structure with the joining element, manufacturing method of the joining element and corresponding connection method

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB8912482D0 (en) * 1989-05-31 1989-07-19 Unifix Ltd Anchors

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US86220A (en) * 1869-01-26 Improvement in malleable cast-iron bolts
US782467A (en) * 1904-12-01 1905-02-14 Jacob Leonard Replogle Method of manufacturing bolts or similar articles.
US2340349A (en) * 1940-04-26 1944-02-01 Budd Induction Heating Inc Internally hardened structure
US2340706A (en) * 1941-12-20 1944-02-01 Budd Induction Heating Inc Threaded pipe end
US2511706A (en) * 1945-06-16 1950-06-13 Gen Motors Corp Method of producing bearing rings
US2730472A (en) * 1952-05-07 1956-01-10 Ohio Crankshaft Co Method of manufacturing hollow tubular articles

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US86220A (en) * 1869-01-26 Improvement in malleable cast-iron bolts
US782467A (en) * 1904-12-01 1905-02-14 Jacob Leonard Replogle Method of manufacturing bolts or similar articles.
US2340349A (en) * 1940-04-26 1944-02-01 Budd Induction Heating Inc Internally hardened structure
US2340706A (en) * 1941-12-20 1944-02-01 Budd Induction Heating Inc Threaded pipe end
US2511706A (en) * 1945-06-16 1950-06-13 Gen Motors Corp Method of producing bearing rings
US2730472A (en) * 1952-05-07 1956-01-10 Ohio Crankshaft Co Method of manufacturing hollow tubular articles

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3657957A (en) * 1969-11-24 1972-04-25 Olympic Screw & Rivet Corp Rivet
US4824314A (en) * 1985-02-19 1989-04-25 Northrop Corporation Composite fastener system and manufacturing method thereof
US5700120A (en) * 1996-08-01 1997-12-23 General Electric Co. Threaded fastener and method of improving the fatigue life thereof
US6086305A (en) * 1999-01-13 2000-07-11 Illinois Tool Works Inc. Nails having selected heat treatment and hardening
US6109851A (en) * 1999-01-13 2000-08-29 Illinois Tool Works Inc. Screws having selected heat treatment and hardening
US6273974B1 (en) 1999-01-13 2001-08-14 Illinois Tool Works Inc. Selected heat treatment and hardening method for nails
US6364972B1 (en) 1999-01-13 2002-04-02 Illinois Tool Works Inc. Method for selectively hardening a carbon steel screw
US6436474B2 (en) 1999-01-13 2002-08-20 Illinois Tool Works Inc. Method of chemically coating fasteners having improved penetration and withdrawal resistance
FR2856754A1 (fr) * 2003-06-24 2004-12-31 Hilti Ag Element de fixation
US7891925B2 (en) * 2005-12-06 2011-02-22 Blount, Inc. Shear resistant rivet and saw chain
US20160377107A1 (en) * 2015-06-23 2016-12-29 Richard Bergner Verbindungstechnik Gmbh & Co. Kg Process for producing a connecting element as well as connecting element
US10871181B2 (en) * 2015-06-23 2020-12-22 Richard Bergner Verbindungstechnik Gmbh & Co. Kg Process for producing a connecting element as well as connecting element
EP3276189A1 (fr) * 2016-07-29 2018-01-31 KAMAX Holding GmbH & Co. KG Vis tres resistante comprenant une couche souple
US20180031023A1 (en) * 2016-07-29 2018-02-01 Kamax Holding Gmbh & Co. Kg High-Strength Screw Including an Unhardening Layer
CN107664151A (zh) * 2016-07-29 2018-02-06 卡迈锡控股两合公司 具有去硬层的高强螺栓
JP2018040488A (ja) * 2016-07-29 2018-03-15 カマックス ホールディング ゲーエムベーハー アンド コーポレイテッド ケージーＫＡＭＡＸ Ｈｏｌｄｉｎｇ ＧｍｂＨ ＆ Ｃｏ．ＫＧ 未硬化層を含む高強度ねじ
US10598207B2 (en) * 2016-07-29 2020-03-24 Kamax Holding Gmbh & Co. Kg High-strength screw including an unhardening layer
US20210239146A1 (en) * 2020-02-05 2021-08-05 Böllhoff Verbindungstechnik GmbH Joining element, connection structure with the joining element, manufacturing method of the joining element and corresponding connection method

Also Published As

Publication number Publication date
GB1067184A (en) 1967-05-03
FR1454933A (fr) 1966-10-07

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