By: Hobart Brothers

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Welding abrasion-resistant steel plates, commonly called AR plates, presents several unique challenges that welding operators should know how to address in order to maximize their effectiveness and efficiency. 

Welding abrasion-resistant steel plates, commonly called AR plates, presents several unique challenges that welding operators should know how to address in order to maximize their effectiveness and efficiency.

AR plates are specifically designed for long service life in harsh conditions, which is the reason for their incredibly high hardness. It&#;s also why they are often used in mining or quarrying, earthmoving and construction industries. Heavy equipment manufacturers, for example, use AR plates to extend the service life of critical components that are frequently involved in impact and/or sliding contact with abrasive materials. As a result, they are frequently used on backhoe buckets and teeth, bulldozer blades and dump truck beds to protect them from excessive wear.

AR plates come in a variety of sizes (both lengths and widths) and can range in thickness from 1/2 to more than 2 inches. Regardless of the size or thickness, it is important to note that this plate should only be used for wear applications and is not recommended for structural use.

The names of AR plate products typically indicate the hardness of the material. Most plate product numbers range from 200 to 500 &#; for example, AR 200, AR400 or AR500. The number in the material name (e.g. the 400 in AR400) usually refers to the material hardness based on the Brinell Hardness scale. As a rule, the harder the material, the more resistant it will be to abrasive wear.

Here are three common challenges that welding AR plates can present, along with their respective solutions.

Challenge No. 1: Welding an AR plate to itself or any structure with dissimilar and softer or lower-strength steel                                                                                                                             In this scenario, the biggest challenge is cracking, which could occur in the weld metal or heat-affected zone (HAZ) of the AR plate due to rapid cooling or highly restrained joints. It could also result from excessive hydrogen in the weld metal or the use of filler metals with limited resistance to cracking.

One way to combat rapid cooling and reduce hydrogen levels, and thereby reduce cracking, is to pre-heat the base metal before welding. The material to be pre-heated and its thickness will determine the proper pre-heat temperature. Figure 1 shows some pre-heating examples. Always consult the material manufacturer for the recommended preheat procedures.

Next, avoid locating the weld joint in a highly restrained area &#; an area defined by the inability of the base material, weld metal or overall weldment to expand and contract freely. Weld shorter, smaller fillet welds to reduce heat input and overall residual stresses on the AR plate.

Lastly, choose a filler metal with the least amount of hydrogen content that is still capable of providing good toughness and high impact values.

Figure 1. These figures are examples only. Always consult the material manufacturer for recommended pre-heat procedures.

Challenge No. 2: Choosing the right filler metal for welding AR plate to dissimilar steels      The tensile strength of the base metal the AR plate is being welded onto will determine which filler metal is the most appropriate. Some of the most common ASTM grade base metals joined to AR plate include A36, A572 GR50, A656, GR80 and A514 steels.

As a general rule, choose filler metals that match the lower strength of the base material and ones that feature lower hydrogen &#; both help minimize the potential for cracking. Different AR plate manufacturers recommend different tensile strengths for welding AR plate to a particular grade base metal. You should always check those recommendations before making your final filler metal selection. Figure 2 provides some filler metal options for welding AR plate.

Figure 2.

Challenge No. 3: Repairing or replacing AR plates on existing, dirty equipment or in the field Repairing equipment that has been in service and/or having to do the job in the field is never ideal, but it is often necessary. Unfortunately, the base material and the AR plate will likely be affected by dirt, rust or other debris from general use.

To address this issue, one option is to use a gas-shielded flux cored wire; this is a good choice for repairs in the shop. A wire with a T-5 basic slag system such as American Welding Society (AWS) E71T-5C is ideal for this application due to its toughness, high resistance to hydrogen pickup and ability to weld through light rust and mill scale. All of these features help improve the crack resistance of the final weld.

In the shop or field, use a low hydrogen stick electrode with a base slag system &#; an AWS E, for example &#; to repair or replace AR plate on existing equipment. Low hydrogen basic slag stick electrodes have good toughness properties to accommodate for the residual stress of welded AR plate and can provide excellent as-welded mechanical properties, high resistance to hydrogen pickup and they offer the ability to weld through contaminants (light mud, rust, or oil) that can accumulate on equipment.

In the field, where there is concern of losing shielding gas due to breezes and/or if the application doesn&#;t require high impact properties, use a self-shielded flux cored wire with a T-4, T-7 or T-11 classification. These types of wire generate their own shielding gas to protect the weld pool from contamination and eliminate the need to haul gas tanks into the field.

For more information, please visit Hardfacing Wire for Mining Equipment.

Armed with these tips, it will be easier to avoid cracks when welding AR plates &#; not to mention they can help prevent lost time and money. When in doubt about the filler metal to use or any other part of the process, consult a trusted filler metal manufacturer, distributor or steel provider, accordingly.

Improve Productivity by Preventing 5 Common MIG Welding Problems

Downtime and rework can be costly for manufacturing operations. The last thing any production team wants to do is the same work twice. If you add to that any time spent troubleshooting issues in the weld cell &#; the lost production time can start to accumulate quickly. 

There are several steps operations can take to reduce the time lost to these common issues in MIG welding &#; and many of them start during weld setup and selection of consumables. Read on to learn more about five common causes of lost productivity in the weld cell and how to prevent them. 

Cause 1: Poor fit-up or weld prep

Before welding even starts, pay attention to proper fit-up and joint design, as well as base material preparation and cleaning. Good fit-up means avoiding large or inconsistent gaps between the parts. Choosing the right wire size and gas mixture and matching those in advance can help optimize performance and provide proper gap filling capabilities. 

There are several steps operations can take to reduce lost productivity in MIG welding &#; and many of them start during weld setup and selection of consumables

Certain welding wires, such as metal-cored wires, are usable on less-prepped base material by offering the ability to weld through mill scale or other surface impurities. They also offer good gap bridging. If operations are often getting parts that aren&#;t thoroughly cleaned, it may be worth testing a metal-cored wire. Otherwise, changes to the weld prep stage of the operation may be necessary to achieve better material condition prior to welding.   

Cause 2: Incorrect parameters or system setup

Using the wrong parameters or setting the wire feeder up incorrectly are common causes of lost productivity. Having the wrong settings can greatly affect the weld, sometimes without the operator even realizing the impact that a setting change can make. It&#;s important to have a thorough understanding of the wire feeder and all of its functions to set it up for optimal performance. 

When properly set up, there should be very few issues with the performance of the MIG welding gun. However, if the system is set up incorrectly or there is a poor weld circuit, it can lead to contact tip failure, since the contact tip is the smallest fuse in the weld circuit. This can result in money wasted on frequent contact tip changeover. 

Cause 3: Improper liner installation

With Bernard® AccuLock&#; S consumables, 60% of the contact tip is buried in the gas diffuser to protect it from heat damage.

MIG gun liners can wear out over time and must be changed periodically, like other consumables. However, replacement liners are often longer than necessary and must be precisely trimmed according to the style and length of the gun. If a liner is cut too short, it can result in issues like burnback, an erratic arc and wire chatter. When liners are cut too long, it can cause the wire to weave and curve as it feeds through the gun. 

With either too-long or too-short liners, the result is often poor wire feeding and downtime spent troubleshooting these problems. Maintenance and troubleshooting for liner issues can be costly, resulting in multiple hours per week lost for an operation. 

The more that liner movement within the gun can be minimized, the better your wire feedability will be. To avoid the guesswork and hassle, look for a solution that makes liner installation and trimming easier. The Bernard® AccuLock&#; S consumable system affixes the liner at both ends of the gun, so welders are assured the liner won&#;t pull back or push into the contact tip, allowing for smooth, uninterrupted delivery of the wire to the weld pool.

It&#;s also important to occasionally check to make sure the liner is clear and not blocked by debris or buildup. 

Cause 4: Loose connections or neglected maintenance  

When MIG welding consumables aren&#;t properly installed and maintained, it can result in wire feeding issues and weld quality problems that lead to lost time for troubleshooting.  

For example, a loose connection in the weld circuit means you&#;re not getting the power you expect from the power source. In that case, the operator may keep adjusting the parameters, causing an increase in resistance that leads to shortened consumable life. These issues tend to show up first in the contact tip. This is often the first thing the operator changes if they think they have a problem with their MIG gun. Changing the contact tip &#; even when the real source of the problem is a loose connection or improper setup in the circuit &#; drives up consumable costs and wastes time. 

Be sure to periodically check and tighten all connections and cables. Tight connections help optimize performance and reduce the chance of issues occurring in the system. 

With Bernard AccuLock S consumables, 60% of the contact tip is buried in the gas diffuser to protect it from heat damage. As the shielding gas flows through the gun, it cools the contact tip tail inside the gas diffuser. This helps reduce heat and wear. This also differs from traditional tips that screw onto the gas diffuser with little to no portion of the tip exposed directly to the shielding gas as it exits the diffuser to the arc. The tapered design of the consumables tightly locks the conductive parts together to minimize electrical resistance and further reduce heat buildup. The contact tips also feature coarse threads, making them less likely to become cross-threaded. 

Troubleshooting common welding problems 

Common problems in the weld cell &#; from poor fit-up or wire feeding issues to using the wrong consumables for the job &#; can cost the operation significant time and money. Addressing the causes of lost productivity often starts with proper weld prep and setup, as well as making sure the chosen consumables are right for the application. Optimizing setup and efficiency in the weld circuit makes troubleshooting that much faster when issues do arise. 

Contact us to discuss your requirements of Hardfacing Welding for Agricultural Machinery. Our experienced sales team can help you identify the options that best suit your needs.