Metal fusion bonding – Process – With shaping
Reexamination Certificate
2002-05-10
2004-10-19
Stoner, Kiley (Department: 1725)
Metal fusion bonding
Process
With shaping
C228S199000, C228S234300, C428S615000
Reexamination Certificate
active
06805276
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a method for welding a base material and a deposit metal, and particularly relates to a welding method for reducing the residual stress after welding a deposit metal to a base material, and increasing the fatigue strength of a base material and welded joint portion.
2. Conventional Art
Herebelow, a summary of the conventional art shall be described with the welding of a bond cable for a railroad rail.
FIG. 1
schematically illustrates a joint portion of a railroad rail. While the rail
100
which is anchored to a tie
120
by means of a spike
110
is such that a predetermined gap
130
with an adjacent rail is left in order to allow for thermal expansion, they are connected to each other electrically by means of bond cables
140
. This is because the rails
100
are also used as channels for passing the drive current and control signals of railway cars.
FIG. 2
is a perspective view showing an enlargement of the area of attachment of the bond cables
140
. In the example shown, the end portion
150
of the bond cable is welded to a web on the rail
100
by means of a deposit metal
160
. The procedure for welding the deposit metal
160
to the web on the rail
100
is performed on-site after the rail
100
has been lain. Examples of methods for performing the weld include many types such as low-temperature wax welding, arc welding and others, with many procedures having been proposed, but of these, copper thermit welding has the highest joint strength at the welding portion yet does not require high levels of skill, and has consequently come into popular use in recent years.
Thermit welding is a method wherein a mixed powder of aluminum and copper oxide (or iron oxide) is ignited near the surface of the base material, to melt and weld the copper (or iron) and a portion of the base material with the heat of the chemical reaction.
PROBLEMS TO BE SOLVED BY THE INVENTION
Although thermit welding is a welding method which is convenient and can achieve high strength as described above, it leaves residual stress in the area of the weld, thus decreasing the fatigue strength. For example, as described in Miki et al., <<Methods of Increasing Fatigue Strength by Improvements to Weld Toe Portion>>,
Journal of Japan Welding Society
, vol. 17, no. 1, reduction of the stress concentration at the weld toe portion and reduction of tensile residual stress caused by welding are known to be effective for improving the fatigue strength of weld joints. Additionally, this paper also describes that hammer peening, in addition to TIG treatments and grinder treatments, have some effect as methods for relieving this stress.
Hammer peening is a method in which the weld portion is struck by a hammer to plastically deform the base material, and the tensile residual strength of the weld is relieved by the residual strength on the pressed side caused by this deformation, so as to consequently lessen the decrease in the fatigue strength caused by the weld. As described in the paper, in the hammer peening process, the blows are struck at the peripheral portions of the weld where the residual tensile strength is believed to be highest. While this hammer peening process can raise the fatigue strength to some extent, there are reports that fatigue cracks can develop from scratches formed in the base material during the hammer peening process.
REFERENCES:
patent: 4348131 (1982-09-01), Shimanuki et al.
patent: 5134267 (1992-07-01), Atsumi et al.
patent: 5742020 (1998-04-01), Adachi et al.
patent: 5759299 (1998-06-01), Yokoyama et al.
patent: 5964964 (1999-10-01), Kurebayashi et al.
patent: 6126208 (2000-10-01), Asada et al.
patent: 6223974 (2001-05-01), Unde
patent: 355084273 (1980-06-01), None
patent: 357001573 (1982-01-01), None
patent: 410146688 (1998-06-01), None
patent: 410296461 (1998-11-01), None
patent: 995991 (1983-02-01), None
Translation of JP-410296461A.
ECI
Harrington & Smith ,LLP
Stoner Kiley
LandOfFree
Deposit metal welding method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Deposit metal welding method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Deposit metal welding method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3320150