Welding is an important task in agriculture during all times of the year.

A working knowledge of key welding processes is vital when equipment breaks down, especially during planting and harvesting times.

Welding joins metal pieces together and the weld itself becomes integral to its strength. A related process known as hardfacing deposits wear-resistant surfaces on existing metal components thus extending their service life. Hardfacing is commonly performed on metal edges that scrape or crush other tough materials, such as a plow blade cutting through the soil.

Welding and hardfacing applications

Farmers regularly need to repair and even modify machinery and equipment, such as gates, chutes, animal pens and hitches. Repairing a broken plow or combine in the field by welding can literally save an entire crop during harvest time. The needs of beef cattle can usually be taken care of with mild steel. Such steel contains roughly 0.05–0.25% carbon, making it malleable and ductile, but also leaving it with a relatively low tensile strength. Dairy cattle, and virtually the entire milk-handling system, require stainless steel. The bovines may look similar, but their welding needs are very different.

Figure 1: A welder joins part of a metal fence. Fabricating or repairing fences and other enclosures is important in agricultural welding. Source: U.S. Navy

Many items in agriculture benefit from hardfacing that effectively addresses three categories of wear: abrasion, impact and metal-to-metal. Abrasion is one of the most common types of wear. It is most often found in relation to so-called earth-engaging tools such as tractor buckets, blades, teeth, grain handling products and feed mixers. The impact wear group includes equipment used to pound and smash, such as crusher hammers. And metal-to-metal wear includes steel parts that roll or slide against each other and include crane wheels, pulleys, idlers on track-drives, gear teeth and shafts.

Know your metal

Prior to welding or hardfacing, it is important to identify the working metal. On the farm, almost all implements are high-strength steels (either high- or low-alloy); many are higher carbon steels. These simple tests can help identify the type of steel.

The first is a magnetic test. If a magnet sticks to the implement then it is likely iron-based. A magnet that does not stick is likely a manganese or stainless product.

The second is a spark test. Take a grinder to the item and observe the sparks that are produced. If you see a roughly 30″ long, moderately large volume of yellow sparks with just a few sprigs and/or forks then this indicates mild steel. If you see a 25″ long, slight to moderate volume of yellow orange sparks, a few forks with intermittent breaks and few if any sprigs then this indicates alloy steels. Finally, if you see a 15″ long large volume of red sparks with numerous and repeating sprigs, then this indicates high carbon metal.

A third test, known as a chisel test, also may be used. In this test, if the metal fractures in large chunks when you take a chisel to it, this means you have cast iron, which can be difficult to weld unless using special high-nickel electrodes and heat-treating. However, if the chisel produces corkscrew-like shavings, then you are most likely looking at a weldable steel.

Once the base material has been identified, decide on your final goal for the project. If the item is a hitch bar on a tractor, for example, then the goal likely is strength and ductility to ensure against breakage. That means welding is in order. If the item is an earth-engaging tool where long-term surface durability is important, then hardfacing may be the more appropriate choice.

Be sure to read the conclusion of this two-part series on welding in agriculture.