Providing Hardfacing Solutions in Townsville

CORODUR HARDFACING

HARDFACING/SPECIAL ELECTRODES

HARDFACING APPLICATIONS

Is a tubular electrode filled with fused tungsten carbide and a special nickel alloy for manual welding. This alloy is specially designed for application where extreme abrasion in combination with corrosion is encountered. Corodur-NISE can be overlayed on steel castings, nickel based and stainless steel alloys. The alloy combination of CORODUR-NISE is specially designed for items that are exposed to corrosive media and excessive wear conditions. The matrix is highly resistant to acids, lye’s and other corrosive media.

Is an open arc tubular wire filled with fused tungsten carbide (FTC) for semi-automatic application, where extreme abrasive wear is encountered. For hardfacing of low alloyed steels that have a maximum of 0,45% carbon (a higher carbon content could lead to cracking). Also for hardfacing and repairing tools and machine parts exposed to wear. The area to be hardfaced should be free of rust, scale, grease or other dirt. Depending on the base metal’s alloy and the size of the area to be hardfaced the advisable preheating temperature should be between 350-500 deg C (662-932 deg F). If the voltage and the welding current are kept on the lowest setting possible the tungsten carbide granular will be prevented from melting. During welding, position the arc that the weld metal is deposited in coarse droplets.

Setting Wire Feed Tension

The Symptoms

The most common problem with mig welding is with the wire not feeding correctly. To keep things simple, lets ignore the feed rollers, wire type and polarity settings for the minute and focus on the actual arc of weld. The weld process itself is not that much different to the old “stick” welding that most are familiar with. In stick welding, the arc is ignited by coming close to the work to strike an arc and slowly feeding the electrode down into the weld as it is consumed. With MIG, the electrode is wire and instead of having to push it down into the weld, the feed motor pushes the wire out at the same rate as it is burned up.

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As the weld is consuming the wire at a steady rate, any irregularity in the feeding of the wire can severely affect the arc. For instance, if the wire grabs for some reason and stops feeding for a split second, the arc will “climb” up the wire and burn it off at the contact tip. This is the most common complaint and usually the first step in where it all goes wrong for a lot of users. Usually, the first reaction is to increase wire tension a few turns to make sure that it doesn’t stick again, then try and continue welding. Increasing wire tension can actually give the same or worse results than not enough tension.

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If we go back to basics, we have the issue of the wire burning onto the tip. Assuming that the wire speed adjustment is correct, this has most likely happened from the wire not feeding smoothly as discussed before. Before we do anything, we need to determine the reason for the wire slipping in the first place. Generally, the first item to look at would be if the drive roll is correct for the wire type and size. V-type rolls are for solid steel wire, U shape for aluminium and Knurled (serrated) for flux core and gasless wires. Next would be the liner inside the gun assembly and possibly the contact tip. The liner should be periodically cleaned and replaced. To clean the liner, remove the wire and blow compressed air in from the tip end back toward the welding machine. It is recommended to remove the gun assembly from the welder before this to prevent debris ending up inside wire feed unit. The liners can build up with dust/rust and other contaminants making it difficult for the wire to run smoothly. Liners are consumable items and do require replacing over time. Increasing wire tension will not correct this.

Tension Too High

The most common problem we see is the wire tension is far too high and “birds nest” of wire inside the feed motor assembly. This is from not correcting the feed issue as it occurs and just “cranking up” the tensioner thinking this is why it is not feeding. Having the tension too high deforms the cross-sectional shape of the wire as well as encouraging the wire to want to coil up. Trying to feed wire that wants to bend itself into a coil down a straight MIG gun is never going to end well, no matter how hard the machine tries.

Tension Too Low

It is rare to see a machine with too low of tension. The end result is that the wire slips and does not feed when pushed against the work. Tension should be increased in half turn increments until wire feeds correctly.

Setting Your Machine

Tension is not a one size fits all, nor is there any “charts” as every machine, wire and roller will be different. If you are running gasless wire for instance, you will have a knurled drive roll that has lots of grip on the wire. With this in mind you only need light wire tension where as a U roller for aluminium, you will need slightly more tension as it will tend to slip. This must be remembered when changing wire types in your machine. The best way to set wire tension is to cut the wire before it enters the wire feeder and pull out the remaining wire from the gun. Don’t pull wire back onto the spool as this wire may be deformed in shape having already been through the feed rollers. Remove the contact tip and wind wire tension off until it feels loose. Straighten the first 3 inches of wire out and feed through the rollers into the MIG gun. By straightening the wire, you are less likely to damage your liner.

REMOVE YOUR EARTH LEAD FROM THE MACHINE

This will prevent arcing in the next few steps. Pull the trigger or wire inch button to start feeding wire through the liner. If the rollers are slipping at this stage, increase tension ½ turns at a time until feed is resumed. Once wire is around 2” out of the gun end, replace contact tip and trim wire to about 1” from the contact tip. Firmly hold the end of the wire between the fingers WITH A GLOVED HAND and pull the trigger to feed wire. You should only just be able to make it slip. If it is slipping to easy, increase the wire tension in ½ turns as before. If you can’t make it slip, reduce tension by 1 turn and try again. Once you have found the correct tension, make a note of the setting for that type of roller/wire combination. If you have to increase this after a period of time you may need to look at cleaning or replacing the liner.

Remember, if it cant feed properly, it wont weld properly.