1974 Volume 43 Issue 9 Pages 931-943
Characteristics of “Insert-type” electron beam welding technique have been investigated to select proper uranami welding conditions for 6mm-thick and 12 mm-thick dissimilar joint, 2 1/4Cr-1Mo Steel (ASTMF22) to austenitic stainless steel (AISI316), and carbon steel (SM41A) joint.
Obtained conclusions can be summarized as follows:
1) Spiking, one of characteristics intensively observed at max. penetration part, is less than 1.5 mm in length almost 80% of all bead-on-plate welds and decreases drastically in frequency with increase of spike length. In other words, spike length tends to become larger than 1.5 mm in case “Penetroparameter”, Pp value (=hp/dB, hp: penetration depth, dB: bead width) exceeds 6 approximately. Weld bead profile becomes extremely wedge-type bead at max. penetration part.
At arbitrary part except for max. penetration part, critical Pp value, that is, Pp, s value where spiking exceeding 1.5 mm in length comes to appear is larger than 6 under ab(=D0/DF, D0: object distance, DF: focal length)>0.9, nearly equal to 6 under ab≈0.9 and less than 6 under ab<0.9 respectively. In other words, as ab value decreases, critical Pp value does either. On the same welding conditions, penetration depth becomes equal at two different ab values, where weld profile quite differs from each other. That is to say, weld profile at one ab value under 0.9 comes near to wedge-type bead and that at the other ab value beyond 0.9 becomes well-type one.
2) It is desirable in uranami welding by “Insert-type” electron beam welding technique to select proper welding conditions producing well-type bead with larger width than insert metal width itself and resulting in less spiking. In other words, ab value around 1.20 should be selected. It is also desirable to select proper joint configuration with both insert metal and root space from viewpoint of easy formation of satisfactory uranami bead. In addition, insert metal height should be decided equally to joint thickness from consideration of weld bead profile and reinforcement.
3) Range of proper uranami welding conditions widens by adoption of root-spaced joint configuration and that also becomes more effective in uranami welding with increase of joint thickness as compared with joint configuration without root space. By introduction of root-spaced joint configuration, formation mechanism of uranami bead tends to become convection-type and spattering decreases drastically which induces serious problems in application to tube welding. Therefore, this joint configuration can be highly evaluated from consideration of uranami welding of tube and pipe.
4) When insert metal isn't introduced in welding of carbon steel joint which is not fully deoxidized, weld defects, that is, porosity, undercut and underfill occur intensively. These defects, however, successfully decreases with increase of insert-cap height (or insert metal height) and cross-sectional area of insert-cap by introduction of Al-killed carbon steel insert metal.
