This short practical guide course is suitable for the metal repair needs of any farm.
Most farmers may not realize that adjusting the voltage, current, and wire speed on the welding machine can produce a transmission pattern that is fine-tuned for thick metals. Karl Hoes of Lincoln Electric said that the limiting factor for the spherical or spray pattern is that they can only be used for "metal thicknesses of ⅛ inches and thicker, and can only be used for flat and horizontal fillet welds."
Spherical transfer (short arc): Voltage, amperage and feed speed are all higher than standard short circuit mode. This will cause a large amount of welding wire to be discharged from the end of the welding wire and into the weld puddle. This mode provides deep penetration welds on thick materials, but produces a lot of spatter.
Spray arc transfer: Volts, amperes and wire speed are higher than spherical mode. It produces a stream of tiny droplets, which are sprayed from the wire to the metal. For true spray transfer, you need to use a gas rich in argon. Arc spraying allows the use of large diameter wires, so a large amount of metal is deposited and you will get beautiful weld beads. It can only be used for flat or horizontal fillet welds; its puddles are very fluid. Be sure to replace the spray gun nozzle with a device approximately 3 inches long or longer.
"Farmers often cannot adequately prepare the metal before welding," said John Lesner of Miller Electric. "This includes removing paint, rust, dirt, and other surface contaminants, but it also means sanding cracks." Leisner can easily understand that metal preparation is the last thing you need to do when welding repairs are required during peak seasons or feeding livestock. Things to care about.
"I'm not saying that the repair area must be absolutely original," he said, adding that aluminum welds are an exception (see Tip 6 on welding aluminum). "At the very least, tap the repair area with an electric wire brush to remove rust and dirt."
Cleaning removes impurities absorbed into the metal during welding; if they stay, they will damage maintenance. If cleaning is not possible, avoid using MIG welders for repairs. "Use a rod welder and a 6011 electrode. Also, reduce your travel speed. This allows air bubbles to boil out of the molten weld before these impurities are trapped in the weld," he said.
Hydrogen is the most serious impurity surrounding the welding seam. Because it is everywhere (in water, dirt, rust, paint, feces, grease), hydrogen is a huge challenge for welders. What can be done to eliminate hydrogen? Clean, clean, clean some more. "Hydrogen, along with high residual stress and crack-sensitive steel, can cause cracking hours or days after welding," said Hoes of Lincoln Electric. "High-strength steel (usually used for farming tools), thick metal sections and constrained parts are more prone to hydrogen cracking."
One of the surprising aspects of welding is that even novice welders can experience some success. However, Hose and Leisner warned that there are some hard and fast rules that can produce durable weld repairs.
Push or pull: The rules here are simple. "If it produces slag, you drag it," Leisner said. In other words, when using a rod welder or flux-cored wire machine for welding, you can drag the electrode or wire. Otherwise, you can use metal inert gas (MIG) welding to push the wire.
Working angle: For wire welding, place the welding gun at an angle of 10° to 15° with the direction in which you push the weld. For bar welding, maintain a lead angle of 20° to 30° in the dragging direction. Use fillet welding (T-shaped) welding to keep the rod or wire (regardless of the welding process) at a 45° angle between the two pieces of metal.
Arc distance: Adjust the travel speed to keep the welding arc within the first third of the welding pool. For wire (flux core or MIG) welding, maintain a working distance of ⅜ to ½ inch. When using rod welding, pay attention to keeping the distance between the tip of the rod and the workpiece at ⅛ inches. "The arc length should not exceed the diameter of the electrode core," Leisner said.
Speed: Observe welding pits and ridges (where molten metal solidifies). Hoes said that when welding wire (MIG or flux core), the ridge should be about ⅜ inches behind the wire. A travel speed that is too slow will produce a wide and convex weld bead with shallow penetration and excessive metal deposition. On the other hand, a travel speed that is too high will produce shallow welds, resulting in narrow and highly raised weld beads. Most travel speeds of various joints are well below 40 inches per minute.
For MIG welding, the preferred proven shielding gas is 100% carbon dioxide (co²). It is economical and can provide you with deep penetration welds.
However, it is sometimes necessary to invest in more expensive protective gases, including:
The array of wires and rods sold makes the selection of electrodes confusing. Leisner and Hoes gave this shopping list of agricultural electrodes, which covers most maintenance tasks.
MIG welding wire: A good overall MIG welding wire has a diameter of 0.035 (most common) or 0.045 inches. However, when welding thin materials of ⅛ inches or smaller, please consider using 0.025 inches. The reason is that the smaller diameter welding wire is more stable at lower current, thereby providing a smaller arc force and a smaller tendency to burn through the metal.
Flux-cored welding wire: One of the most popular flux-cored welding wire is E71T-1 because "it is suitable for ex-situ (vertical, overhead) welding, provides fast freezing slag, and provides high deposition rate," Leisner said. Hoes said , If you are welding misaligned (overhead welding), you can use E71T-8 welding wire. If you want to weld coated or galvanized metal (such as textured legs), use E71T-14 welding wire because its core material will explode in the arc. This effect will volatilize the steel coating, thereby minimizing weld cracks and porosity. All these welding wires provide a higher deposition rate than rod electrodes, and their slag is easier to remove.
Rod electrode: Leisner said that the universal electrode is 6011 electrode because it can provide good penetration welds. "For thicker materials that require deeper penetration of the weld, please use 6010 welding rod," he said.
"If you want to solder thinner solder and need less penetration, please use 6013 welding rod instead." The most common rod size is ⅛ inches. "Use larger diameter rods for thicker metals and smaller diameter rods for thinner metals," Hose suggests.
The presence of more and more aluminum in agricultural equipment forces the problem of metal repairs. The good news is that any wire welder can handle aluminum, and the process is relatively easy to learn. But there are some rules you must follow, Hoes said. These rules include:
Purchase a U-groove drive roller to support the wire, but do not crush it. Keep the drive roller adjusted on the loose side.
Replace the cable gasket with Teflon, nylon or similar gasket products.
Use only argon or argon helium.
Choose aluminum filler wire with a diameter of 3/16 or 1/6 inch. These larger wires are easier to connect to the spray gun cable.
Use a contact tip that is about 0.0115 inches larger than the wire diameter.
Use organic solvents (such as acetone), weak alkaline solutions (such as strong soap) or citrus degreasers to remove grease, oil, feces or dirt. Avoid using strong alkaline or acid cleaners.
Use a new stainless steel wire brush (only for aluminum welding operations) to brush repairs to remove the aluminum oxide that occurs naturally on the metal surface. Alumina melts at 3,700°F, while base metals melt at 1,200°F. The oxide on the repaired surface will inhibit the penetration of the filler metal.
Preheat the restoration to 230°F. To minimize cracking. Tack welds are placed at the beginning and end of the repair to help preheat and prevent deformation.
Use short guns and straight cables. If you want to do a lot of aluminum welding, consider buying a spool welding gun.
Push in the weld to reduce pollution and increase shielding gas coverage.
Use higher current intensity and voltage settings and welding travel speed for hot welding and fast welding to prevent burn-through.
Fill the weld at the end of the weld. Hoes warned that craters are the main cause of cracking in aluminum welds. To fill the crater, continue to feed the wire at the end of the welding, and move your direction of travel about 1 inch in the opposite direction.
Hoes says that manufacturers are increasingly turning to metals that are difficult to weld, such as high-strength steel, especially in farming tools to reduce weight. When repairing high-strength steel, it is essential to remove all rust, paint, grease and moisture first to get bare metal. Next, preheat the repaired part before welding.
"The higher the carbon content of the steel (common in high-strength steels), the more preheating is required," Hoes said. "Preheating is required to prevent cracking after welding." Leisner added that when repairing high-strength steel, use small-diameter, low-hydrogen electrodes, such as 7018 rods. Finally, keep the welding speed slow; this keeps the molten pool melted by giving the hydrogen bubbles time to boil. The result is a better finished weld.
Hoes said that weld cracks are due to one or more of the following reasons:
Leisner says that rigid parts are more prone to cracking. If possible, weld towards the unconstrained end of these parts and leave a 1/32 inch gap between the plates to allow free shrinkage as the weld cools. Shot blast while each bead is still hot to relieve pressure.
Hoes says that gravity is your enemy when working out of position, so by using less voltage and lower wire feed speed to create smaller puddles, you can counteract its effects (especially when welding wires). Leisner says that reversing the polarity to concentrate the heat on the electrode tip will cause the welding temperature to decrease, allowing the weld pool to cool faster to prevent dripping. Here are more tips from two experts about welding misalignment:
Horizontal weld: Reduce the working angle to 0° or 15°, and then weld at a steady speed to keep the molten pool in place.
Vertical welding: Weld downwards on 3/16 inch and thinner steel. However, this movement can be a challenge. The molten pool can lead the arc to become an insulator and reduce the penetration depth. On 1/16 inch and thicker steel, use left and right techniques to weld in an upward motion, moving the arc from the right to the center, and then to the left to create a triangle.
Overhead welding: reduce the current intensity and move quickly to keep the molten pool narrow. Use circular motion and whiplash to prevent the weld pool from overflowing the weld.
Leisner said, “If the crack is in a location where the surface cannot be prepared for welding, it will definitely need to be strengthened for welding repair.” "Always strengthen high stress points, such as hinges on folding tools."
Hoes added that if a part is damaged more than once at or near the same location where it was last repaired, it also needs to be reinforced.
When reinforcing, be sure to chamfer the edge at a 30° angle where the new metal meets the old metal. Doing so can provide better weld penetration.
For heavier material parts, please leave a small piece of land (space) at the bottom of the joint. To do this, first chamfer the edges, and then grind along the bottom of the chamfer until the thickness of nickel is reached.
This is the final reinforcement reminder. "Materials over 1/4 inch thick should usually be welded in multiple passes," Leisner said.
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