US3547715A - Method for surface hardening polygonal steel rods and product treated according to the method - Google Patents

Method for surface hardening polygonal steel rods and product treated according to the method Download PDF

Info

Publication number
US3547715A
US3547715A US631013A US3547715DA US3547715A US 3547715 A US3547715 A US 3547715A US 631013 A US631013 A US 631013A US 3547715D A US3547715D A US 3547715DA US 3547715 A US3547715 A US 3547715A
Authority
US
United States
Prior art keywords
rod
heating
surface hardening
treated according
section
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US631013A
Inventor
Bror Rossander
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.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Application granted granted Critical
Publication of US3547715A publication Critical patent/US3547715A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/06—Surface hardening
    • C21D1/09—Surface hardening by direct application of electrical or wave energy; by particle radiation
    • C21D1/10—Surface hardening by direct application of electrical or wave energy; by particle radiation by electric induction
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Definitions

  • United 'States Patent O U.S. Cl. 148-146 3 Claims ABSTRACT OF THE DISCLOSURE A method of surface hardening a drill rod having a portion of polygonal cross-section and a thickened portion and which is made up of a low alloy steel having a carbon content not greater than about 0.6%, which includes heating only the peripheral section of the rod to a hardening temperature while simultaneously rotating the rod in a high frequency cross-field heater whose crossfield is substantially perpendicular to the longitudinal extent of the rod to thereby obtain a substantially uniform depth of heating along the longitudinal extent of the rod including the thickened portion and thereafter quenching the rod to obtain a uniformly hardened surface layer along the entire longitudinal extent of the rod.
  • This invention relates to a method of surface hardening a drill rod having a thickened portion at least partly surrounding the rod.
  • the surface hardening has as its main object to induce compressive stresses in the material surface in order to increase the fatigue strength, that is to increase the working life of the drill rod.
  • a low-alloy steel with a carbon content of about 1% is used for drill rods.
  • This steel cannot always be hardened without formation of small cracks whereby especially the fatigue strength is reduced.
  • a lowalloy steel with at maximum 0.60% C is used which is alloyed in known manner, so that it has the necessary toughness after treatment by the method according to the present invention.
  • This treatment a surface hardness higher than resulting from normal hardening is obtained without causing any formation of small cracks.
  • the resistance t upsetting and wear is increased substantially at the same time as the fatigue strength is improved considerably.
  • the method according to the invention is of particular importance in the treatment of drill rods, in view of the fact that these rods when being used for percussion drilling are subjected to alternate compression-tensile stresses of considerable size. This results in many cases in fatigue breaks in the rods, particularly in and about those parts which were heated locally and upset 0r which otherwise were given a dimension deviating from that of the rod. In these parts so-called stress-raisers are easily caused. As it is especially the size of the tensile stresses which is of decisive importance for the strength of the rods, it is desirable to decrease the effect of these stresses. Such a decrease is obtained by indicating the compressive stresses in the material surface as described above.
  • a surface hardening is obtained by induction in a longitudinal field heater.
  • the depth of penetration of the eddy currents is dependent of the distance between the coil and the rod. If the rod for instance has local changes in section in form of a collar, a shank or the like being located nearer the coil than the rod itself, these local changes become more heated than the rod-the heat penetrates deeper in the material. Thus, in such a heater the heating effect is dependent of the air gap.
  • the method comprises: heating only the peripheral section of the rod at the same time as at least a part of the peripheral section of the thickened portion to the hardening temperature by rotating the rod in a high frequency cross field heater having a cross field substantially perpendicular to the longitudinal extend of the rod, thereby obtaining a substantially uniform depth of the heating section along the rod and the thickened portion, and quenching the rod.
  • FIG. 1 is a plane view of a high frequency cross field heater illustrating the position of a drill rod being treated according to the invention
  • FIG. 2 is a section taken on the line II-II of FIG. l and showing the upper portion of the drill rod sectioned
  • FIGS. 3 and 4 are both sections taken on the line III-III of FIG. 2 and illustrating the penetration of heat at different methods according to the invention.
  • FIGS. 1 and 2 show as an example a hexagonal rock drill rod 1 having a collar 2 and placed in a high frequency cross field heater 3.
  • the heater is shown schematically and has in the embodiment shown two coils 4 and 5 located ⁇ by the two poles respectively of the iron core of the cross field heater 3 and connected in parallel.
  • the coils are energized with high frequency alternating current giving a magnetic cross field between the poles.
  • An iron object located between the poles displaces the lines of flux in such a way that the lines are concentrated to the peripheral portion of the object. Eddy currents effected by the cross field are substantially induced in those peripheral portions lying parallel to the direction of the field.
  • the outer contour of the cross field according to the example shown on the drawings is indicated by the broken line 6 and the arrows A indicate the direction of the current at a certain moment.
  • the eddy currents induced in the peripheral layer of the rod material and effected by the cross field cause a heating of the said peripheral section.
  • the line 7 indicates the depth of penetration of the heating section.
  • two opposite sides of the hexagonal rod 1 is heated at the same time.
  • the upset collar 2 brings about a displacement of the lines of flux outwardly causing a certain concentration increase which, however, is compensated by the larger mass of the collar.
  • the depth of the heating section along the rod 1 and collar 2 is in spite of the local change in section substantially uniform.
  • a surface hardening of a 7A hexagonal rock drill rod made of low-alloy steel having a carbon content of 0.4% is stated as an example.
  • the rod can be rotated either intermittently (FIG. 3) or continuously (FIG. 4).
  • the rod In intermittent rotation the rod is placed in the heater in such a way that two opposite sides are parallel to the direction of the field. After holding the rod 0.5 sec., the rod is turned rapidly (maximum time 0.1 sec.) to the next position, that is in a position having two other opposite sides parallel to the direction of the field.
  • One heating l rotation is completed when the rod has been turned 180o and consequently two heating rotations when the rod has been turned one rotation. After one rotation of the rod it has in this example been subjected to heating during 3.6 sec.
  • the rod is immediately cooled in preferably water, oil or the like.
  • the total heating time is about 2 or 3 sec.
  • the heating is preferably carried out in cross field heaters with machine frequency, that is frequencies up to 12,000-Hz., but also higher frequencies can be used, even radio frequencies.
  • the length of a dwell as well as how many rotations one uses is of course dependent on and adapted to the rod being worked on and can be varied within a rather large range. However, in the intermittent rotation the turning is very quick while the holding time is longer.
  • the number of steps of intermittent rotation per heating rotation can be equal to half the number of sides of the polygonal cross-sectional contour of the rod material as described above, or, when the heating in the cross field is carried out on one side the number of steps of the intermittent rotation can be equal to number of sides of the section of the cross-sectional contour of the rod, o1' the heating can be carried out with only one interruption per rotation of the rod.
  • the method of surface yhardening a drill rod including a portion of polygonal cross-section and a thickened portion at least partly surrounding the rod, said rod being made of low-alloy steel and having a carbon content not greater than 0.60% comprising: heating only the peripheral section of at least a portion of said rod including at least part of said thickened portion to the hardening temperature while simultaneously rotating said rod in a high frequency cross-held heater having a cross-field substan- 0 tially perpendicular to the longitudinal extent of said rod,

Landscapes

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

Description

Dec. 15, 1970 D B C EI METHOD FORfSURFCE HARDNING POLYGONAL STEEL RODS AND PRODUCT TREATED ACCORDING'TO THE METHOD .l Filed April 14. 19s? Era/f' L. /Possana/er'v ROSSA'NDER 3,541,715`
United 'States Patent O U.S. Cl. 148-146 3 Claims ABSTRACT OF THE DISCLOSURE A method of surface hardening a drill rod having a portion of polygonal cross-section and a thickened portion and which is made up of a low alloy steel having a carbon content not greater than about 0.6%, which includes heating only the peripheral section of the rod to a hardening temperature while simultaneously rotating the rod in a high frequency cross-field heater whose crossfield is substantially perpendicular to the longitudinal extent of the rod to thereby obtain a substantially uniform depth of heating along the longitudinal extent of the rod including the thickened portion and thereafter quenching the rod to obtain a uniformly hardened surface layer along the entire longitudinal extent of the rod.
This application is a continuation-impart of my application Ser. No. 375,782, filed June 17, 1964, now abandoned.
This invention relates to a method of surface hardening a drill rod having a thickened portion at least partly surrounding the rod.
The surface hardening has as its main object to induce compressive stresses in the material surface in order to increase the fatigue strength, that is to increase the working life of the drill rod. For drill rods usually a low-alloy steel with a carbon content of about 1% is used. This steel, however, cannot always be hardened without formation of small cracks whereby especially the fatigue strength is reduced. According to the invention, however, a lowalloy steel with at maximum 0.60% C is used which is alloyed in known manner, so that it has the necessary toughness after treatment by the method according to the present invention. By this treatment a surface hardness higher than resulting from normal hardening is obtained without causing any formation of small cracks. Hereby the resistance t upsetting and wear is increased substantially at the same time as the fatigue strength is improved considerably.
The method according to the invention is of particular importance in the treatment of drill rods, in view of the fact that these rods when being used for percussion drilling are subjected to alternate compression-tensile stresses of considerable size. This results in many cases in fatigue breaks in the rods, particularly in and about those parts which were heated locally and upset 0r which otherwise were given a dimension deviating from that of the rod. In these parts so-called stress-raisers are easily caused. As it is especially the size of the tensile stresses which is of decisive importance for the strength of the rods, it is desirable to decrease the effect of these stresses. Such a decrease is obtained by indicating the compressive stresses in the material surface as described above.
It is true that it is known that a decrease in the effect of the tensile stresses can be obtained by prestressing of compression type. A great number of different treating methods were employed for this purpose, for example case-hardening, ntriding and llame-hardening. Disregarding the expensive and time wasting methods of casehardening and nitrdng, the methods used have proved unsuitable for the surface hardening of rod material with polygonal cross-sectional area with or without local change in section or for round section with local change in section. With the help of the present invention it is, however, possible to carry out a suitable treatment of drill rods.
According to another known method a surface hardening is obtained by induction in a longitudinal field heater. In such a heater the depth of penetration of the eddy currents is dependent of the distance between the coil and the rod. If the rod for instance has local changes in section in form of a collar, a shank or the like being located nearer the coil than the rod itself, these local changes become more heated than the rod-the heat penetrates deeper in the material. Thus, in such a heater the heating effect is dependent of the air gap.
By the method according to the present invention a substantially uniform depth of the surface hardening along the rod and the thickened portion is obtained, and said uniformity is independent of the air gap. According to the invention the method comprises: heating only the peripheral section of the rod at the same time as at least a part of the peripheral section of the thickened portion to the hardening temperature by rotating the rod in a high frequency cross field heater having a cross field substantially perpendicular to the longitudinal extend of the rod, thereby obtaining a substantially uniform depth of the heating section along the rod and the thickened portion, and quenching the rod.
The present invention has other advantages that will become apparent from an understanding of the following specification wherein reference is made to the accompanying drawings.
In the drawings:
FIG. 1 is a plane view of a high frequency cross field heater illustrating the position of a drill rod being treated according to the invention,
FIG. 2 is a section taken on the line II-II of FIG. l and showing the upper portion of the drill rod sectioned,
FIGS. 3 and 4 are both sections taken on the line III-III of FIG. 2 and illustrating the penetration of heat at different methods according to the invention.
FIGS. 1 and 2 show as an example a hexagonal rock drill rod 1 having a collar 2 and placed in a high frequency cross field heater 3. The heater is shown schematically and has in the embodiment shown two coils 4 and 5 located `by the two poles respectively of the iron core of the cross field heater 3 and connected in parallel. The coils are energized with high frequency alternating current giving a magnetic cross field between the poles. An iron object located between the poles displaces the lines of flux in such a way that the lines are concentrated to the peripheral portion of the object. Eddy currents effected by the cross field are substantially induced in those peripheral portions lying parallel to the direction of the field.
The outer contour of the cross field according to the example shown on the drawings is indicated by the broken line 6 and the arrows A indicate the direction of the current at a certain moment. The eddy currents induced in the peripheral layer of the rod material and effected by the cross field cause a heating of the said peripheral section. The line 7 indicates the depth of penetration of the heating section. In the arrangement shown two opposite sides of the hexagonal rod 1 is heated at the same time. The upset collar 2 brings about a displacement of the lines of flux outwardly causing a certain concentration increase which, however, is compensated by the larger mass of the collar. As illustrated in FIGS. 1 and 2 the depth of the heating section along the rod 1 and collar 2 is in spite of the local change in section substantially uniform.
A surface hardening of a 7A hexagonal rock drill rod made of low-alloy steel having a carbon content of 0.4% is stated as an example. The rod can be rotated either intermittently (FIG. 3) or continuously (FIG. 4).
In intermittent rotation the rod is placed in the heater in such a way that two opposite sides are parallel to the direction of the field. After holding the rod 0.5 sec., the rod is turned rapidly (maximum time 0.1 sec.) to the next position, that is in a position having two other opposite sides parallel to the direction of the field. One heating l rotation is completed when the rod has been turned 180o and consequently two heating rotations when the rod has been turned one rotation. After one rotation of the rod it has in this example been subjected to heating during 3.6 sec. The rod is immediately cooled in preferably water, oil or the like.
Incontinuous rotation and at a speed of rotation of about 200 r.p.m. the total heating time is about 2 or 3 sec.
The heating is preferably carried out in cross field heaters with machine frequency, that is frequencies up to 12,000-Hz., but also higher frequencies can be used, even radio frequencies.
The length of a dwell as well as how many rotations one uses is of course dependent on and adapted to the rod being worked on and can be varied within a rather large range. However, in the intermittent rotation the turning is very quick while the holding time is longer.
The number of steps of intermittent rotation per heating rotation can be equal to half the number of sides of the polygonal cross-sectional contour of the rod material as described above, or, when the heating in the cross field is carried out on one side the number of steps of the intermittent rotation can be equal to number of sides of the section of the cross-sectional contour of the rod, o1' the heating can be carried out with only one interruption per rotation of the rod.
CIO
I claim:
1. The method of surface yhardening a drill rod including a portion of polygonal cross-section and a thickened portion at least partly surrounding the rod, said rod being made of low-alloy steel and having a carbon content not greater than 0.60% comprising: heating only the peripheral section of at least a portion of said rod including at least part of said thickened portion to the hardening temperature while simultaneously rotating said rod in a high frequency cross-held heater having a cross-field substan- 0 tially perpendicular to the longitudinal extent of said rod,
thereby obtaining a substantially uniform depth of heating along the longitudinal extent of said rod including at least part of said thickened portion, and quenching the rod to obtain a uniformly hardened surface layer along the entire longitudinal extent of said heated portion.
2. The method according to claim 1 in which the rod is rotated intermittently.
3. The method according to claim 1 in which the rod is rotated continuously.
References Cited UNITED STATES PATENTS 2,615,119 10/1952 Riegel 148-150X 2,676,098 4/ 1954 Payson 14S-36 3,041,434 6/1962 Alf 219-1061 FOREIGN PATENTS 558,499 3/1957 Italy 219,--10.43 1,023,535 1/1958 Germany 148-150 CHARLES N. LOVELL, Primary Examiner U.S. C1. X.R.
US631013A 1967-04-14 1967-04-14 Method for surface hardening polygonal steel rods and product treated according to the method Expired - Lifetime US3547715A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US63101367A 1967-04-14 1967-04-14

Publications (1)

Publication Number Publication Date
US3547715A true US3547715A (en) 1970-12-15

Family

ID=24529436

Family Applications (1)

Application Number Title Priority Date Filing Date
US631013A Expired - Lifetime US3547715A (en) 1967-04-14 1967-04-14 Method for surface hardening polygonal steel rods and product treated according to the method

Country Status (1)

Country Link
US (1) US3547715A (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4082936A (en) * 1975-06-24 1978-04-04 Fuji Electric Co., Ltd. Device and method for heating die
US4486249A (en) * 1982-07-09 1984-12-04 Woodings Robert T Method of making class D sucker rods
WO2003097885A1 (en) * 2002-05-17 2003-11-27 Sandvik Ab Rock drill product and method

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2615119A (en) * 1947-08-21 1952-10-21 Caterpillar Tractor Co Steel nut and method of making
US2676098A (en) * 1951-04-06 1954-04-20 Crucible Steel Co America Drill rod steel and articles thereof
DE1023535B (en) * 1956-03-06 1958-01-30 Licentia Gmbh Device for inductive hardening of elongated round parts, such as drills or the like.
US3041434A (en) * 1958-09-19 1962-06-26 Deutsche Edelstahlwerke Ag Method of and apparatus for inductively heating metal

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2615119A (en) * 1947-08-21 1952-10-21 Caterpillar Tractor Co Steel nut and method of making
US2676098A (en) * 1951-04-06 1954-04-20 Crucible Steel Co America Drill rod steel and articles thereof
DE1023535B (en) * 1956-03-06 1958-01-30 Licentia Gmbh Device for inductive hardening of elongated round parts, such as drills or the like.
US3041434A (en) * 1958-09-19 1962-06-26 Deutsche Edelstahlwerke Ag Method of and apparatus for inductively heating metal

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4082936A (en) * 1975-06-24 1978-04-04 Fuji Electric Co., Ltd. Device and method for heating die
US4486249A (en) * 1982-07-09 1984-12-04 Woodings Robert T Method of making class D sucker rods
WO2003097885A1 (en) * 2002-05-17 2003-11-27 Sandvik Ab Rock drill product and method
US20030230433A1 (en) * 2002-05-17 2003-12-18 Sandvik Ab Rock drill product and method
US6978852B2 (en) 2002-05-17 2005-12-27 Sandvik Ab Rock drill product and method

Similar Documents

Publication Publication Date Title
JP2013532233A (en) Machine component and surface hardening method
US3477884A (en) Method of increasing the fatigue life of rolling contact elements and the resulting articles
JP2004308011A (en) Screw having partially hardened functional tip part, and method for manufacturing the same
US3377214A (en) Method for hardening crankshaft
US3547715A (en) Method for surface hardening polygonal steel rods and product treated according to the method
US6402862B1 (en) Method of hardening a bushing of a track chain
JP6780932B2 (en) Chain manufacturing equipment and chain manufacturing method
US2479934A (en) Heat treating
KR101017873B1 (en) Drill rod and method in order to manufacture the same
KR910700357A (en) Improvement of injection-induced hardening
KR910009869B1 (en) Higher strength steel,especially,reinforcing steel or drawing shop feed stock with improved material properties and improved processability
US2615119A (en) Steel nut and method of making
JP2013535570A (en) Machine component and surface hardening method
US2730472A (en) Method of manufacturing hollow tubular articles
US3510928A (en) Method for improving the torsional fatigue strength of crankshafts
CN111334656B (en) Method for heat treatment using a gradual temperature profile
US2850044A (en) Percussion drill rod
EP0808909B1 (en) A process for production of a steel component
US3652345A (en) Method of removing residual stress for improving fatigue strength of boundary of heated zone
US3623128A (en) Apparatus for improving the torsional fatigue strength of crankshafts
Strobl et al. Investigation of the diffusion couple ductile cast iron/iron
JPS6076232A (en) Manufacture of high strength hollow stabilizer
RU2170769C1 (en) Method for manufacture of bar for perforation boring of blast holes
US1927051A (en) Apparatus for treating drill bits
JPH05112809A (en) Production of ultrahigh strength steel