speeds for porosity in fillet welding. It clearly shows that MX-200 is far more resistant to shop primer than conventional rutile-type flux-cored wire and solid wire at a wide range of welding speed.
MX-200 can release you from the headache of porosity in the fillet welding of shop-primer-paint coated steel plates in horizontal and flat positions
Basic characteristics
MX-200 is a metal type flux cored wire suited for fillet welding of mild steel and 490 Mpa high ten sile strength steel painted with shop primer. The M of the trade designation stands for Metal, while X reflects the expectation excellence. MX-200 was developed as an exclusive-use flux-cored wire for fillet welding in the horizontal and flat positions with CO2 gas shielding.
How shop primer causes porosity
Shop primer is a coat of paint applied to the sur face of steel plates in order to protect them from rusting during a long fabrication period. Shop primer is often used in shipbuilding and bridge construction. Shop primer can be a predominant cause of porosity in fillet welds. Porosity is believed to occur because the arc heat decomposes shop primer into several gases and metallic vapors, which form pores in the weld metal. The degree of porosity depends on the type and coating thickness of the shop primer, the type of welding wire and welding parameters.
Advantages characteristics
A typical flux-cored wire can overcome the poros ity problem caused by shop primer if the welding speed is reduced or if the shop primer is partly removed from where the fillet welds will be laid on .
However, if you need to do fillet welding much more effectively, using higher welding speeds and without removing shop primer, you will encounter the porosity problem.
Figure 1 shows the results of testing different types of welding wires and a wide range of welding
Besides better resistance to shop primer, MX-200 provides the following advantages:
(1) Glossy, smooth bead appearance due to thin, regular slag covering.
(2) Regular bead profile at a wide range of welding speeds due to excellent fusion at the toe of the fillet weld.
(3) Less spatters due to smooth droplet transfer.
(4) Smaller leg length (approx. 4mm) can be made more easily due to a stable arc at lower amper age.
Figure 2 shows an example of bead appearance and a cross sectional profile of a fillet weld using MX-200. It shows smooth, regular bead appear ance and regular leg length with proper penetration at the root of the fillet weld.
Figure 2: Bead appearance and cross-sectional macrograph of a fillet weld (MX-2OO, 1.2mm0, 28OAmp., 28-32volt, 5Ocm/min.)
In addition to excellent resistance against shop primer and unsurpassed usability, MX-200 is well suited for high speed welding. Figure 3 shows the relationship between welding speed and leg length of fillet welds. You can determine the required welding speed for different leg lengths using this figure.
MX-200 can be used in automatic welding as well as semi-automatic welding. Figure 4 shows an example of an automatic welding process in which a portable fillet-welding carriage and MX-200 are used in fillet welding of longitudinal components in shipbuilding.
Kobe Steel is sure MX-200 will provide you with efficient fillet welding at higher welding speeds and with increased mechanization in your work shops
Suitable for automatic welding
MX-200 persistently earns a good reputation among users in shipbuilding, bridge construction, machinery fabrication, railway-car fabrication, steel structure fabrication due to the outstanding features:
(1) Excellent resistant to shop primer
(2) Excellent usability
(3) Excellent high speed weldability
