Metal fusion bonding – Process – With protecting of work or filler or applying flux
Patent
1985-05-31
1987-06-02
Godici, Nicholas P.
Metal fusion bonding
Process
With protecting of work or filler or applying flux
228 42, B25K 3102
Patent
active
046696504
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for joining tubular parts of metal by forge/diffusion welding, comprising the following steps:
establishing a joint between opposed bounding surfaces on the respective parts to be joined, which joint having the form of a cavity with varying height,
heating the parts to a predetermined temperature at least in those areas bordering on the joint, the cavity of the joint during the heating being supplied with an inert or reducing flushing gas,
joining the parts by pressing them together, and cooling the parts.
Such a method is described in the Applicant's International Publication No. NO. 83/03565, published on 27th October 1983. In this method the joint is initially given the form of a cavity having increasing height from the periphery towards the middle, i.e. in case of tubular parts the joint would be approximately closed along the periphery both on the inside and the outside of the parts. The joint is provided with at least one connecting conduit for the supply of inert or reducing flushing gas.
The object of the present invention is to simplify and improve the above method, e.g. as regards the flushing and the initial form of the cavity.
This is obtained according to the invention by a method of the above type, which is characterized in that the joint during the heating and flushing is held sufficiently open to permit flushing transversally through the joint, the gas being supplied from the outside of the joint.
This simplifies the supply of flushing gas and also ensures quick and efficient flushing of the joint.
According to a further feature of the invention, the joint is initially given increasing height from one side of the tubular parts to the other. This will simplify the preceding machining of the ends of the tubular parts, for instance by giving them the form of truncated cones having different apex angles. Such shaping of the ends of the tubular parts permits the use of the method with less restrictive requirements to the roundness of the tubular parts.
In accordance with an advantageous embodiment of the invention, the cavity of the joint may be closed on one side by means of a sealing device comprising means for supply of the flushing gas.
The method according to the invention can also be adapted for welding under water. In this case it will be advantageous to cover the joint area on the opposite side of the sealing device by means of a collar or the like, which is filled with flushing gas through the joint in order to prevent direct contact with the surrounding medium. Before commencing the heating, the space between the sealing device and the joint area may be emptied for surrounding medium by displacing it by means of flushing gas.
According to a further advatageous feature of the invention, during the pressing together of the parts the joint is brought to close successively in the direction towards the supply direction of the flushing gas. Thereby the flushing gas will be forced out of the joint during the joining, so that it will not be necessary to evacuate the joint in advance.
It has surprisingly been found that the joining of the parts can take place very quickly, 1-2 sec. without post-heating, if one as reducing gas is using hydrogen with less than about 100 ppm of H.sub.2 O/O.sub.2 for usual structural steels, e.g. steels containing about 0,2 percent C, 0,7 percent Mn and 0,3 percent Si. For high strength steels alloyed with e.g. 0,2 percent C, 1,6 percent Mn, 0,55 percent Si and residues of Ti or Al, the joining can also take place very quickly if the hydrogen has less than about 15 ppm of H.sub.2 O/O.sub.2. In order to ensure complete oxide removal from the joint for alloyed steels, it is suggested according to the invention that the flushing with hydrogen is maintained until the contents of H.sub.2 O/O.sub.2 in the flushing gas leaving the joint is less than about 15 ppm.
For the better understanding of the invention it will be described more closely with reference to the examplifying embodiments shown in the appended drawings, in which:
F
REFERENCES:
patent: 2805315 (1957-09-01), Chapman
patent: 3194466 (1965-07-01), Davis
patent: 4143802 (1979-03-01), Winterbottom
patent: 4375008 (1983-02-01), Dathe
patent: 4566625 (1986-01-01), Moe
Godici Nicholas P.
Skillman Karen
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