WO2006111829A1 - Method for obtaining enhanced fatigue strength in welded metal joints and hammer head for use at cold working - Google Patents
Method for obtaining enhanced fatigue strength in welded metal joints and hammer head for use at cold working Download PDFInfo
- Publication number
- WO2006111829A1 WO2006111829A1 PCT/IB2006/000928 IB2006000928W WO2006111829A1 WO 2006111829 A1 WO2006111829 A1 WO 2006111829A1 IB 2006000928 W IB2006000928 W IB 2006000928W WO 2006111829 A1 WO2006111829 A1 WO 2006111829A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- hammer head
- weld toe
- cold working
- radius
- contact surface
- Prior art date
Links
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
- C21D7/00—Modifying the physical properties of iron or steel by deformation
- C21D7/02—Modifying the physical properties of iron or steel by deformation by cold working
- C21D7/04—Modifying the physical properties of iron or steel by deformation by cold working of the surface
Definitions
- the present invention relates to a method for obtaining enhanced fatigue strength in welded metal joints comprising a weld toe, where the weld toe is subjected to cold working such that a visible and/or measurable indentation at the weld toe is produced.
- the present invention also relates to a hammer head for use at cold working of a weld toe for obtaining enhanced fatigue strength in welded metal joints and -components.
- the fatigue life of welded constructions is often reduced as a consequence of untreated welds in critical areas .
- the large amount of heat required during welding results in a substantial shortening of the fatigue life after welding. This is mainly due to residual stresses in the transverse direction of the weld toe.
- the geometry of the weld toe makes the fatigue life even shorter.
- the fatigue life of metal constructions can be improved by cold forging (hammering) of the weld toe such that the residual stresses are locally eliminated and advantageous compressive stresses are established in the metal surface (hammer peening) .
- hammering cold forging
- An object of the present invention is to provide a method for obtaining enhanced fatigue strength in welded metal joints and - components .
- the cold working is carried out in a pregrinded steering groove or a pregrined track rounding the weld toe profile to a geometry fitting the geometry of the hammer head.
- the weld toe is subjected to the cold working sufficiently to produce a smooth-forged hammered track without individual indentations deviating more than 10 % of the average indentation obtained by the cold working.
- An object of the present invention is also to provide a hammer head for use at cold working.
- the initially defined hammer head characterized in that the hammer head has a slightly convex, elongated contact surface in the length direction for contact with the weld toe.
- the elongated contact surface of the hammer head has a radius in the transverse direction that is smaller than the radius in the length direction.
- the elongated contact surface of the hammer head has a smoothly rounded form in each end.
- the contact surface of the hammer head is polished with a surface smoothness better than Ra 1.2.
- the radius of the hammer head in its length direction is larger than two times the radius of the hammer head in its transverse direction and smaller than 20 times of the radius in the transverse direction.
- the present invention combines geometrical improvement of the weld toe profile with elimination of residual stresses and establishment of beneficial compressive stresses, in that the hammer peening is carried out in a novel way by means of a hammer head, where the geometry of the hammer head is strongly changed in relation to prior art, with significantly improved geometry as a result .
- the present invention is preferably used for hammer peening.
- Fig. 1 shows a hammer head according to an embodiment of the invention, mounted in a pneumatic hammer
- Fig . 2 shows a side view of the hammer head in Fig. 1 ;
- Fig . 3 shows a frontal view of the hammer head in Fig. 2,
- Fig . 4 shows a weld ready for grinding of a steering groove at the weld toe
- Fig . 5 shows a pregrinded steering groove
- Fig . 6 shows position of the hammer head in the steering groove
- Fig . 7 shows a finished cold worked weld toe
- Fig . 8 shows fatigue strength of a specific untreated weld
- Fig . 9 shows fatigue strength of the same type of weld as in Fig. 8 after it has been cold worked according to an embodiment of the invention
- Fig. 10 shows a preloading load sequence applied to the welds tested, and for which the results are presented in Figs. 8 and 9.
- Figure 1 shows a part of a pneumatic hammer 1 with a hammer head 2 according to an embodiment of the invention.
- the hammer head 2 is shown in more detail in Figs . 2 and 3.
- the hammer head 2 is characterized in that it has a slightly convex, elongated contact area or surface 3 , here with a radius 4 in the transverse direction that is smaller than a radius 5 in the length direction.
- the contact surface of the hammer head to be used against the weld toe (9 in Fig. 4) has a smoothly rounded form in each end 6,7.
- the radius 5 of the hammer head in the length direction is larger than two times the radius 4 of the hammer head in the transverse direction, and smaller than 20 times the radius 4 in the transverse direction.
- the figures as here given define preferred ranges.
- FIG. 4 shows a cross section through a weld 8 where one of the weld toes 9 is to be grinded with a suitable tool 10.
- Fig. 5 the pregrinded steering groove is shown.
- Fig. 6 shows a position of the hammer head 2 against the steering groove 11.
- Fig. 7 a finished cold worked weld toe 9 is shown.
- the groove bottom 11 is smooth, and folded material 12 and 13 along the groove edges is also shown.
- the other weld toe is cold worked in a corresponding way, although not shown. It should be realized that the steering groove as shown in Figs. 5, 6 and 7 is grossly exaggerated for the purpose to more clearly illustrate the exemplified embodiment.
- the pregrinding of the groove 11 is carried out by smooth movements with an even and firm, but not an intensive, pressure on the tool 10.
- the tool 10 is preferably held about 30 to 50 degrees relative the normal of the work piece and is evenly moved along the weld toe. The tool is to be moved all the time.
- the steering groove should be investigated for cracks with NDT (non destructive testing) , visual inspections will however normally be sufficient.
- the cold working is carried out by an even pressure against the continuously moving hammer tool. Usually three movements or passes by the hammer in the steering groove are recommended.
- the bottom of the groove should be smooth and without substantial singular indentations due to "jumps" of the hammer head 2.
- the surface roughness in the bottom of the groove 11 is measured to be below Ra 0.5.
- the groove edges can be slightly folded, this is however of no importance for the fatigue resistance .
- the present invention results in a more significant improvement of fatigue life than up to now known methods, also for high stresses.
- the fundamental principle and idea behind the invention have been fully confirmed by laboratory tests. These tests were performed in such a way so as to obtain a direct relationship between fatigue life of steel connections and such connections where the weld toe has been smoothly hammered, more exactly hammered by means of a pneumatic hammer with attached hammer head.
- Figure 8 shows the fatigue strength according to performed tests for untreated welds 14.
- Figure 9 shows the fatigue strength according to performed tests for cold worked welds for the same type.
- Figure 10 shows a preloading sequence that was applied to the welds tested, prior to the fatigue testing, where the probes were exposed to an even amplitude 17 of tensile stresses, after each testing probe has been loaded with five load cycles 16 to yield in form of compressive stresses such as 0.85 YS.
- the improvement as shown in Fig. 9 appears therefore regardless if the conventional effect of the hammering is reduced after the hammered specimen is exposed to yield stresses.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Forging (AREA)
- Heat Treatment Of Articles (AREA)
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP06744520A EP1937852A1 (en) | 2005-04-19 | 2006-04-19 | Method for obtaining enhanced fatigue strength in welded metal joints and hammer head for use at cold working |
AU2006238580A AU2006238580A1 (en) | 2005-04-19 | 2006-04-19 | Method for obtaining enhanced fatigue strength in welded metal joints and hammer head for use at cold working |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NO20051913A NO324010B1 (en) | 2005-04-19 | 2005-04-19 | Method for achieving increased fatigue strength in welded metal joints and hammer heads for use in cold working |
NO20051913 | 2005-04-19 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2006111829A1 true WO2006111829A1 (en) | 2006-10-26 |
Family
ID=35267070
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IB2006/000928 WO2006111829A1 (en) | 2005-04-19 | 2006-04-19 | Method for obtaining enhanced fatigue strength in welded metal joints and hammer head for use at cold working |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP1937852A1 (en) |
CN (1) | CN101218358A (en) |
AU (1) | AU2006238580A1 (en) |
NO (1) | NO324010B1 (en) |
WO (1) | WO2006111829A1 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR101799376B1 (en) * | 2011-04-14 | 2017-11-20 | 제이에프이 스틸 가부시키가이샤 | Impact tip, method for hammer peening, and method for manufacturing weld joint using the same |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS53123346A (en) * | 1977-04-04 | 1978-10-27 | Mitsubishi Heavy Ind Ltd | Treating method for toe of weld |
US4491001A (en) * | 1981-12-21 | 1985-01-01 | Kawasaki Jukogyo Kabushiki Kaisha | Apparatus for processing welded joint parts of pipes |
JPH0421717A (en) * | 1990-05-14 | 1992-01-24 | Kawasaki Steel Corp | Method for improving fatigue strength in welded joint |
WO1997040965A1 (en) * | 1996-04-26 | 1997-11-06 | Corimag S.R.L. | A tool for a demolition hammer or the like |
GB2313801A (en) * | 1996-06-05 | 1997-12-10 | Standall Tools Ltd | Percussion tool |
EP1559796A1 (en) * | 2002-10-30 | 2005-08-03 | Nippon Steel Corporation | Method of increasing toughness of heat-affected part of steel product welded joint |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP3160514B2 (en) * | 1995-11-27 | 2001-04-25 | 三菱重工業株式会社 | Method for improving ultrasonic flaw detection of weld metal |
EP1561827A1 (en) * | 2004-02-06 | 2005-08-10 | Alstom Technology Ltd | Method of welding a ferritic steel comprising a post weld heat treatment and cold working on the weld |
-
2005
- 2005-04-19 NO NO20051913A patent/NO324010B1/en not_active IP Right Cessation
-
2006
- 2006-04-19 WO PCT/IB2006/000928 patent/WO2006111829A1/en not_active Application Discontinuation
- 2006-04-19 CN CNA2006800121620A patent/CN101218358A/en active Pending
- 2006-04-19 EP EP06744520A patent/EP1937852A1/en not_active Withdrawn
- 2006-04-19 AU AU2006238580A patent/AU2006238580A1/en not_active Abandoned
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS53123346A (en) * | 1977-04-04 | 1978-10-27 | Mitsubishi Heavy Ind Ltd | Treating method for toe of weld |
US4491001A (en) * | 1981-12-21 | 1985-01-01 | Kawasaki Jukogyo Kabushiki Kaisha | Apparatus for processing welded joint parts of pipes |
JPH0421717A (en) * | 1990-05-14 | 1992-01-24 | Kawasaki Steel Corp | Method for improving fatigue strength in welded joint |
WO1997040965A1 (en) * | 1996-04-26 | 1997-11-06 | Corimag S.R.L. | A tool for a demolition hammer or the like |
GB2313801A (en) * | 1996-06-05 | 1997-12-10 | Standall Tools Ltd | Percussion tool |
EP1559796A1 (en) * | 2002-10-30 | 2005-08-03 | Nippon Steel Corporation | Method of increasing toughness of heat-affected part of steel product welded joint |
Non-Patent Citations (1)
Title |
---|
DATABASE WPI Week 200009, Derwent World Patents Index; AN 1992-076809 * |
Also Published As
Publication number | Publication date |
---|---|
CN101218358A (en) | 2008-07-09 |
NO20051913L (en) | 2006-10-20 |
AU2006238580A1 (en) | 2006-10-26 |
NO20051913D0 (en) | 2005-04-19 |
NO324010B1 (en) | 2007-07-30 |
EP1937852A1 (en) | 2008-07-02 |
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