Application of Abrasion Resistant Material{0374, 0679, 0751, 0759, 6800} Caterpillar

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Introduction

© 2013 Caterpillar All Rights Reserved. This guideline is for the use of Cat dealers only. Unauthorized use of this document or the proprietary processes therein without permission may be violation of intellectual property law. Information contained in this document is considered Caterpillar: Confidential Yellow.

This Reuse and Salvage Guideline contains the necessary information in order to allow a dealer to establish a parts reusability program. Reuse and salvage information enables Caterpillar dealers and customers to benefit from cost reductions. Every effort has been made in order to provide the most current information that is known to Caterpillar. Continuing improvement and advancement of product design might have caused changes to your product which are not included in this publication. This Reuse and Salvage Guideline must be used with the latest technical information that is available from Caterpillar.

For questions or additional information concerning this guideline, submit a form for feedback in the Service Information System. In order to address an urgent issue, use the following resources in order to communicate your request to Caterpillar Repair Process Engineering:

• Caterpillar Dealer Technical Communicator

• Dealer Solution Network

• Caterpillar Technical Representative

• Knowledge Network

Canceled Part Numbers and Replaced Part Numbers

This document may not include canceled part numbers and replaced part numbers. Use NPR on SIS for information about canceled part numbers and replaced part numbers. NPR will provide the current part numbers for replaced parts.

Summary

Caterpillar has developed a weld operation to apply carbide particles to the wear surface of Caterpillar Ground Engaging Tools (GET). This process is also applied to other parts where the process would be beneficial. Although the weld bead is made with general filler wire, the carbide particles are held in place to resist tool wear. The application, known as Abrasion Resistant Material (ARM), is intended for high abrasion and low to medium impact loads. When working in fine, loose material, the operation increases the life of GET components by a factor of five or more times. High impact loads, such as large rocks or chunks of concrete, may cause the beads to break off the surface of the piece.

This guideline provides a list of required equipment and outlines the procedure recommended by Caterpillar. Also included are miscellaneous process tips gathered from experience. The choice of equipment will affect the investment required to set up the operation.

Important Safety Information

Illustration 1	g02139237

Work safely. Most accidents that involve product operation, maintenance, and repair are caused by failure to observe basic safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs. A person must be alert to potential hazards. This person should also have the necessary training, skills, and tools in order to perform these functions properly. Safety precautions and warnings are provided in this instruction and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons. Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. Therefore, the warnings in this publication and the warnings that are on the product are not all inclusive. If a tool, a procedure, a work method, or operating technique that is not recommended by Caterpillar is used, ensure that the procedure is safe for you and for other people to use. Ensure that the product will not be damaged or be made unsafe by the operation, lubrication, maintenance, or the repair procedures that are used.

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Improper operation, lubrication, maintenance or repair of this product can be dangerous and could result in injury or death. Do not operate or perform any lubrication, maintenance or repair on this product, until you have read and understood the operation, lubrication, maintenance and repair information.

Safety precautions and warnings are provided in this manual and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons.

The hazards are identified by the safety alert symbol which is followed by a signal word such as danger, warning, or caution. The "WARNING" safety alert symbol is shown below.

Illustration 2	g03070577

This safety alert symbol means:

Pay attention!

Become alert!

Your safety is involved.

The message that appears under the safety alert symbol explains the hazard.

Operations that may cause product damage are identified by "NOTICE" labels on the product and in this publication.

Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. The safety information in this document and the safety information on the machine are not all inclusive. Determine that the tools, procedures, work methods, and operating techniques are safe. Determine that the operation, lubrication, maintenance, and repair procedures will not damage the machine. Also, Determine that the operation, lubrication, maintenance, or the repair procedures will not make the machine unsafe.

The information, specifications, and illustrations in this guideline are based on information which was available at the time of publication. The specifications, torques, pressures, measurements, adjustments, illustrations, and other items can change at any time. These changes can affect the service that is given to the product. Obtain the complete, most current information before you start any job. Caterpillar dealers can supply the most current information.

References

Necessary Equipment

Illustration 3	g03336365
ARM Equipment

One option in setting up an ARM operation is to use existing equipment. A second option is a machine developed by a supplier. The following points provide guidelines as to what is necessary, and include some explanations. Sources of equipment are listed under "Equipment Sources" section.

• Although the function may seem similar, equipment for submerged arc operations will not work for ARM. Instead of a flux delivery hopper, a carbide particle feed system is necessary to deliver the particles to the weld bead at a controlled rate. One example is a vibratory feeder unit, shown in Illustration 4. The major components consist of a vibratory feeder assembly, control box, particle hopper, metering pipe, and adjustable feed tube assembly.

Illustration 4	g03336423
Vibratory Particle Feeder

• ARM requires a mechanism for precision control of weld torch travel. The travel of the carriage that carries the torch must be smooth and consistent. The speed must be adjustable. Surplus track rebuilding machines can be adapted for this purpose. Dealer Support has received inquiries about the feasibility of using robots for ARM torch control. A motion/function control "do loop" would need developed and recorded for each part number to be run. Also, a precision table-mounted fixture system is necessary to hold each individual part in the same spot. The ARM beads would then be applied to each part consistently. Because of this procedure, robots are better suited for production welding, as opposed to individual piece part work.

• Caterpillar recommends the use for a weld head oscillator with the carriage. The adjustable side-to-side speed and width movement, along with adjustable torch delay at each side, allow precise process control when applying wide ARM beads. Also, less time is required to apply wide beads to parts and less heat is transferred to the base metal. Beads of 25.4-35.1 mm (1-1.38 inch), 38.1 mm (1.5 inch), can be easily run.

• A control unit, power supply, and connection cables capable of 600 DC Amperes are required. Correct ARM application requires high current levels. Power supply examples are a DC-600 by Lincoln, and Deltaweld 652 by Miller.

• A water-cooled torch system must be used. The high ARM current and heat will destroy a torch without this feature. Examples of water-cooled torches are the Binzel RB 610 D, Lincoln Magnum 450WC, and Tweco TAM500-332.

Illustration 5	g03336472
Water Cooled Torch and Particle Feed Tube

• A CO² / Argon regulator, gas hose, and solenoid-controlled valve are necessary to provide shielding gas. The hose must be long enough to accommodate the full range of carriage movement from wherever the gas cylinder is secured.

• 98% Argon / 2% Oxygen shielding gas is recommended. Most welding operations use a 75% Argon / 10% CO² mixture. To produce good penetration and large weld pool, a higher Argon concentration is required. 90% Argon/ 10% CO² can be used. However, the oxygen in the preferred mixture helps to blend the edge of a bead with the base metal. Shielding gas usage will be approximately 100-1100 l/hr (35-40 ft³/hr).

• AWS class ER70S3 weld wire such as Lincoln SuperArc L-50 should be used in the operation. Lincoln SuperArc L-50 is a solid, general application wire, and works best for creating the large weld pool. Wire sizes from 0.76 mm (0.03 inch) to 2.4 mm (0.09 inch) have been used, but 1.5 mm (0.059 inch) is a good choice for general ARM work.

• A wire reel assembly and drive rolls capable of handling the above wire is also necessary. Any existing wire straighteners and swivel mounting plates can probably be reused.

• A welding table with a surface made of 19 mm to 25 mm (0.75 inch or 1 inch) steel plate is required to provide a surface for welding, clamping and preheating operations. The table should be about 3-4.5 m (10-15 ft) long and 1 m (3.28 ft) wide, and adequately reinforced. Add holes for studs or bolts to the table surface to clamp and pre-bend long parts. The table can be separate or part of the torch carriage system.

Illustration 6	g03336640
Table for Welding Equipment

• An abrasive chop saw of sufficient capacity is needed to section samples for inspection. Examples are DeWalt DW871 or Milwaukee 6176-20.

• Carbide particles of ASTM (American Society For Testing And Materials) size 12 to 35 are recommended by and available from Caterpillar.

• Screen mesh sieves of ASTM 12, 20, and 35 are the best way to clean excess carbide particles before reuse. Refer to Illustration 7.

Illustration 7	g03336652
Screen Mesh Sieves

• A central control panel is needed to control: power supply, wire voltage (current) and speed, carriage speed, particle feed rate, torch cooling, oscillation functions and delays and shielding gas flow.

Illustration 8	g03336657
Control Panel for ARM Equipment

The control panel should incorporate automatic start for the shield gas, adjustable delay times for carriage travel and feeder when the weld arc is started and delay for feeder stop when the bead is stopped. Another recommended feature is an electrical interlock that prevents the wire from being energized if the torch cooling water is not flowing.

All adjustable parameters should be controlled by pointed knobs on 270° potentiometers. These knobs should be mounted with graduated face plates. There is no need for face plate graduations to correspond to actual values of functions such as carriage speed or delay times. The purpose is so that a perfected set of adjustments can be recorded, and exactly duplicated, the next time the same parts are run.

In addition to equipment listed above, there are other essential or highly recommended items. An angle grinder is an indispensable tool for an ARM set-up. Use the angle grinder to remove rust, dirt, grease, and paint from parts to ensure good conductivity and prevent bead contamination. Insulation blankets are a convenient method of providing slow cooling for completed parts such as DH-3 tips to prevent cracking due to residual stress. For the same reason, a natural gas or acetylene torch and an infrared thermometer are used to preheat certain parts such as long scraper blades. An assortment of spare parts such as torch tips should be kept on hand to prevent downtime.

The machine shown in Illustrations 3 and 6 meets all Caterpillar specifications and can be specified for local power systems anywhere in the world. The machine is nearly a turnkey ARM set-up, since everything listed under "Necessary Equipment" is included except for the welding table, gas regulator, consumables and inspection equipment. Refer to "Equipment Sources" section for Supplier contact information.

Safety Equipment

Along with process equipment, there are also important pieces of equipment that are required or recommended for safety purposes.

• Because of the high current levels and Argon shielding gas used in ARM operations, a welding helmet lens of shade 13 or 14 should be used. Shades 9 to 11 are used for general arc welding operations. Some helmet manufacturers offer thin shade inserts which increase lower shaded helmets to 13 or 14.

• Safety glasses, preferably with side shields, are mandatory for all personnel at all times in the ARM area. A face mask provides added eye protection when using hand-held grinding equipment.

• The high ultraviolet radiation also requires all skin to be covered by fire-resistant protective clothing.

• Heavy insulating gloves, such as those made of leather, should be worn by operators. Because of the increased danger from electric shock, ensure not to get gloves wet if samples are being water cooled for inspection. Moisture from heavy perspiration also increases shock danger.

• Another item is a weld fume extraction system. Affix a flexible hose to the carriage and connect to a wall-mounted system to remove hazardous fumes and smoke. Use floor fans to help with ventilation. Be sure that the shielding gas function is not affected.

• During initial setup of the equipment, install a fixture to secure the shielding gas cylinder. Mount the shielding gas cylinder firmly on a wall or building support beam. Ensure that there is sufficient space for changing out cylinders safely.

Equipment Sources

Dealer Service Tool group offers various welding-related equipment including helmets, hand grinders, personal protective jackets, and hand tools. Caterpillar recommended carbide particles are offered in a 22.7 kg (50 lb) bucket, part number 9W-3679.

In addition to a complete ARM machine, individual components such as vibratory particle feeders are available from the following suppliers.

Along with basic welding equipment, Lincoln Electric can supply nearly all the miscellaneous items necessary for and ARM system. These items include torch cooling systems, weld fume extraction systems, particle feeders, and weld head oscillators. Lincoln Electric has sales and support outlets all over the world.

A carbide particle feeder is available from:

Another supplier with an extensive line of welding equipment is:

Abicor Binzel can supply water-cooled torch systems and cooler interlock switches:

Personal protective clothing, protective screens, and insulating blankets are available from:

Air quality maintenance equipment suitable for grinding dust as well as welding fumes, is available from:

Sources of welding helmets are:

ASTM screen mesh sieves are available from these two sources:

Welding-related shop equipment including abrasive wheels is available from Forney Industries:

Weld head oscillators are also available from:

The sources listed in "Equipment Sources" are not intended as the only choices. Useful information on welding operations, as well as numerous equipment manufacturers, can be found in Special Instruction, SEBD0512, "Caterpillar Service Welding Guide" and welding industry publications. Your local welding equipment supplier can assist in equipment selection.

Basic ARM Welding Process

The ARM process is done by precision control of a Gas Metal Arc Welding (GMAW) weld torch, with a carbide particle feed system. The torch creates a pool of molten base metal and weld wire, called the Drop Zone Area (DZA). The particles are fed into the DZA by a feed tube that is mounted behind the torch. The particles become suspended in the pool as the torch continues moving and the pool hardens. Table 3 lists a number of variables and the effect on the size of the DZA.

Spray vs. Globular Transfer

The ARM arc operation is done with current levels high enough to produce a "spray" wire metal transfer instead of the "globular" transfer. Refer to Illustration 9. At low welding currents, liquid metal is transferred from the wire to the workpiece in large globular drops. Globular transfer produces an uneven sound, similar to frying eggs. When viewing a globular arc, the end of the wire is rounded and there is a considerable amount of weld spatter.

Above a critical current level, the liquid steel transfer becomes a smooth, cone shaped spray of small droplets. The spray arc is stable, and the end of the wire tapers down to a point. This arc is characterized by an even sound, similar to a soft buzz, and there is little or no spatter. Because the spray transfer current levels are high, there is much more ultraviolet radiation.

Illustration 9	g03336938
Sketches of spray and globular transfer

Transition Current

The current level at which the arc takes the spray form is known as the transition current. Transition current is not a fixed level because the transition current is dependent on a number of parameters. The most important parameter is the voltage adjustment. Size and speed of the wire and the type of shielding gas also effects transition current. Table 4 gives examples of wire diameters and speeds. Table 4 also gives the start of transition current levels using 98% Argon / 2% Oxygen shielding gas. Although current levels during actual ARM operation will be higher than the levels listed in Table 4, the object is to ensure adequate penetration and create an acceptable DZA to capture particles, not to maximize current. Too much current causes extreme heat buildup in the part which should be avoided.

Basic Weld Parameters for ARM

There are a number of important parameters for good ARM application:

• Sufficient voltage (current)

• Wire size and speed rate

• Carriage travel speed

• Oscillation speed, width, and delays

• Distance "A" (distance of particle feed tube to torch tip)

• Visible stickout (distance of torch to workpiece)

• Particle feed rate

There is no single "correct setting" for each adjustment. The parameters interact with each other. Acceptable beads can be run with different but offsetting adjustments.

Getting Ready

When connecting the power supply, make sure that the system is set up for reverse polarity (weld wire is positive (+)) to ensure good penetration. The table should be grounded to the power supply from two opposite corners. Grounding the table also prevents the tendency of the arc to aim in the direction of a single ground connection. Check all mechanical functions, especially the wire feeder, carriage travel, particle feeder and oscillator to be certain that everything is operating consistently.

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Serious injury or death can result if the valve breaks off a falling gas cylinder. Never connect or remove the safety cap from the shielding gas cylinder or any other type of cylinder unless the cylinder has been secured in a holding fixture. The cylinder safety cap must be securely in place on all unused cylinders.

All test samples or parts to receive ARM should be dry and free of oil or grease. Use an angle grinder to remove dirt, paint, and loose or excess scale and rust from the weld surface. This procedure can also be done by sand blasting. The surface does not have to be perfect, but cleaning ensures good electrical contact and helps prevent contamination and porosity in the ARM bead. A light surface-grind to clean the table contact points of the part ensures adequate current flow from the part to the table.

The particle feed tube should be a 13 mm (0.5 inch) diameter tube. Modify and install the tube to aim toward the torch, as shown in Illustration 10. Copper tubing can be used to make the tube, but stainless steel tubing lasts longer. Use a vise or hammer to form the oval shape in the end of the tube. This procedure helps to distribute the particles across wide beads. The top of this tube has a funnel to catch the particles from the stationary feeder as the tube oscillates with the torch. Refer to the bottom of Illustration 4. Do not allow the torch-mounted funnel/tube to touch the feeder distribution tube.

Distance "A" (between the tube and the torch) must be adjustable. Because of the adjustment feature, the tube can be easily bumped out of alignment when placing parts on the table. Be sure to check the tube often during operation to make sure that the tube is centered with the line of torch travel. Distance "A" measurements can be taken from the outer housing of the torch to the center or edge of the feed tube. The measurement can also be taken along the adjustment mechanism that holds the tube. The actual measurement method is not important, as long as the measurements are accurate and consistent.

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Serious injury or death can result from contact with an energized weld wire. Do not use a metal ruler to check visible stickout. Use marked wooden gage blocks to check stickout dimensions.

The vertical length between the torch tip and the workpiece is known as visible stickout. Refer to Illustration 10. Stickout is set around 16 mm (0.63 inch) to 22 mm (0.87 inch). When working on tips that have an uneven surface height, support the part with steel shim blocks or make a fixture to fit the part, so that the line of the average weld surface is as level as possible. Set the stickout dimension to the average weld surface of the part.

Illustration 10	g03337093
(1) Detail for the end of the feed tube (2) Length of stickout (3) Base metal

Welding Parameters

Illustration 11	g03337101
(2) Length of stickout (3) Base metal (4) Weld pool (5) Feed tube

Getting Started

SAE 1018, or any soft steel bar stock of 25.4 x 50.8 x 152.4 mm (1 x 2 x 6 inch) or similar dimensions is ideal for running sample beads. Begin torch oscillation immediately when starting the arc. However, carriage travel and particle feeding need a slight delay. This delay is necessary to establish an adequate weld pool to receive the particles. The oscillation rate is slightly more than one shift per second. Oscillation widths of 16-19 mm (0.63-.75 inch) are used. Continue feeder operation for a brief time after the arc is stopped to be sure that the end of the bead is filled with particles.

The key to the operation is practice. The effect of changing parameters can be learned by inspecting beads. When making various adjustments, be sure to adjust only one parameter at a time prior to each test. This procedure will help get a feel for the result of changing individual variables. Use a paint stick to mark samples with progressive numbers. Record the sample number and all parameter settings on copies of the Welding Parameters sheet (Illustration 11 and Table 5). Samples and the respective settings can then be easily compared.

To begin, run beads with different adjustments including oscillation parameter without adding particles. When the plain beads are acceptable, record and save the settings on a copy of the Welding Parameter sheet. The settings can be duplicated when necessary to run butter beads. The function of butter beads is discussed in the "Applying ARM to Caterpillar Parts" section.

After practice with the plain beads, begin experimentation with particle feeding. Adding room-temperature particles cools the DZA pool. To compensate, torch speed needs decreased by about 25%. Adjustments to voltage (current), and high wire speed will also likely be required. Use a stopwatch to obtain the potentiometer setting numbers for adjustments such as carriage, wire, and oscillation speeds. Calculate wire feed rate by running a de-energized wire for exactly 15 seconds or 30 seconds and measuring the length. Compare the values to examples provided in Table 6. These values will also be used in calculating the cost of ARM for parts.

Table 6 lists sample parameters of ARM beads. These samples are intended as examples and most likely would not be duplicated exactly.

Refer to Illustration 12 for a diagram of oscillating torch travel and ARM bead cross-section. The alternating lengthwise penetration is the result of torch dwell at each side. Dwell of the torch at the sides of the ARM bead is important to establish and maintain beads of the desired width. When welding along the center of symmetric parts or parts with extensive cross-section area, dwell should be even on both sides. To run beads lengthwise along the edge of a part, a shorter dwell along the edge is desirable. An example would be a scraper blade.

Illustration 12	g03337188

After running ARM samples, cool the samples. Use an abrasive wheel chop saw of sufficient size to make a clean, smooth cut through the bead. This procedure is for inspection of penetration and particle dispersion. Since the particles are hard, softer abrasive wheels are more successful to prevent wheel loading and minimize burning.

As parameters for given parts are optimized, keep a binder of parameter sheets marked with the part number of each part. Using these sheets, set-up time is reduced each time the same parts are run. Good quality test samples can be put on display to encourage ARM sales.

Gather and reuse particles that fall to the side of the beads. Be sure to prevent bead contamination by removing dirt and other foreign material. Sweep a magnet about 13 mm (0.5 inch) above the particles as the particles lay on the table. This procedure will attract high iron debris such as weld berries and pieces of wire. Stack 12, 20, and 35 mesh screens with the 12 on top over a bucket. Gather the particles and shake in the top of the screens. This procedure holds any large debris on top and lets fines fall into the bucket. The clean particles can be returned to the hopper. The 20 screen stops half of the particles so the particles do not clog the 35 screen.

Evaluating Quality of ARM Beads

There are four main goals in producing good quality ARM beads:

• Proper density and optimized distribution of particles

• Proper penetration

• Smooth blend to the base metal at bead edges

• No cracks in the base metal

Penetration depth is much easier to see if the cut surface has been etched. Prepare a mixture of 90-95% methanol alcohol and 5-10% nitric acid and apply to the section surface with a cotton swab or small squeeze bottle. Rinse the part in water to remove excess acid after etching. Avoid skin contact when using this mixture.

The area of an ideal ARM bead cross section should be comprised of a 50% wire and base metal mixture, and 50% particles. Refer to Illustration 13. Distribute the particles as evenly as possible from side-to-side and top-to-bottom. Perfect distribution is difficult to achieve because some of the particles will melt into the hotter top of the pool. Some particles will also sink to the bottom. Optimizing distance "A" is a good method of getting the best distribution. At minimum, the bottom 75% of the weld bead should have good particle distribution. Only the top quarter may have reduced amounts of particles. By weight, a bead should be 40% wire and 60% particles. These numbers are checked by a series of weight measurements. When running oscillating beads, the particle deposit should be 0.45 kg (1 lb) per 812.8-914.4 mm (32-36 inch) of bead length.

Bead height will be about 4-5 mm (0.16-0.20 inch). Penetration should be approximately 1.5-2.0 mm (0.06-0.08 inch) at the center of the oscillating beads. Proper penetration is achieved by adjusting carriage and oscillation travel speeds and the current level.

Illustration 13	g03337286

Stringer (straight) beads tend toward a penetration of 5 mm (0.20 inch) at the center because heat is concentrated in a straight line. Check the edge of the stringer bead penetration towards the edge of the bead. Stringer beads can be run side-by-side to achieve the wide coverage of oscillating beads. However, this procedure takes extra time and more heat is transferred to the part.

Cracks may occur in the ARM bead due to the stress of uneven heat build-up from welding. Cracks in the ARM bead are acceptable. However, if the cracks are seen in the base metal, the part should not be used. These cracks with likely grow and result in failure of the piece.

Illustration 14	g03337376

Make sure the blend of ARM beads to the base metal is fairly smooth. Refer to Illustration 14. Beads should not be "piled up", appearing as a puddle of liquid mercury on a surface. A smooth blend helps prevent large pieces of material from catching on the edge of the bead and breaking away from the base metal. Causes of high bead edges are too much carriage speed and/or insufficient current level.

Specifics for Caterpillar Parts

Tips of DH-3 material are prone to stress cracking when applying ARM. Therefore, preheating and slow cooling are recommended for these parts and any high carbon parts. Caterpillar recommends preheat procedure to run a "butter bead" on the intended ARM surface. Butter beads are beads using the same wire, but with no carbide particles. While the butter bead is still warm, apply an ARM bead on top of the butter bead. Butter beads have the advantage of diluting the base metal with a weld wire. Butter beads also provide a crack-arresting layer between the base metal and ARM bead.

Another preheat procedure is to use a gas torch. If using this method, do not allow the flame to touch the surface area where the ARM bead will be applied. Heat the tip from the opposite side. heat the tips to 200 - 260° C (400 - 500° F). Use an infrared thermometer to monitor the temperature. Always cover the parts with an insulating blanket after applying the ARM bead to slow the cooling rate. Cooling can also be slowed by putting the tips in a container as finished and covering with dry sand.

Torch preheating helps control warping of long parts such as scraper blades. Prebeading the part to a slightly concave shape can also prevent warping. This procedure can be done with blocks and clamps on the table surface. After running the beads, allow the piece to cool before releasing the clamps. A procedure can be perfected and recorded for particular ARM installation through testing.

When applying ARM to tips, start the bead at the end of the tip and move toward the retaining housing. Running the bead from the retaining housing to the tip causes an extreme heat buildup because there is not as much metal to act as a heat sink.

Some machines have higher wear areas such as inside scraper bowls. These machines can benefit from ARM patterns. Since these parts cannot fit on a table, overhead-mount a particle feeder with a long, flexible feeder hose and fasten the delivery tube to an ordinary hand held torch.

Caterpillar GET tips with and without ARM undergo a heat treat operation. This procedure provides an extra measure of hardness to the base metal for wear resistance. Tips with ARM are heat treated after the ARM beads are applied. When ARM is applied to tips in dealer shops, the heat draws out some of the hardness. Avoid excessive heat. The wear resistance of a good quality ARM bead will significantly increase the life of any GET part. The exception is if ARM beads are applied to the top and bottom of long parts such as ripper tips. If the upper and lower heat-affected zone depths are greater than two-fifths (40%) of the total tip cross section area, tip breakage may occur. Breakage is a result of small cracks that occur in the ARM bead and the gaps between the particles and weld pool. Cracks travel easier through areas with higher concentrations of stress raisers. Base metal cracking may result from ARM being applied to components with a high hardness (approximately 50 Rc and higher).

During ARM work on warm days, ensure air movement from open shop doors or fans does not blow shielding gas away from the arc. Also, if the shop is located in a warm, humid climate, ensure particles, wire, and GET tips are dry before starting. The hopper should be emptied at the end of the day. If not, an incandescent light can be positioned close above the particle hopper and left on to help keep the particles dry. A small mirror can also be positioned close to the light to check hopper capacity from the floor.

Miscellaneous Information

If ARM needs added to miscellaneous ground engaging tools at the request of a customer, more ARM is not always better. "Over carbide" is possible, thereby winding up with parts that are fully worn but still have considerable carbide remaining in areas of low material contact. Inspect the parts that have been used in the machine application. Used parts will show material flow patterns. These patterns indicate where ARM beads will be most effective and provide the best return for the customers investment. Piling ARM beads on top of each other is not recommended. The carbide in the lower bead will melt and produce a hard deposit.

Production Costs

An exact production rate for applying ARM is difficult to establish because of all the variables. A starting estimate is 740 cm²/hr (291 inch²/hr), running a 2.5 cm (1.0 inch) bead width. The overall rate of usage for hard particles is approximately 2.3 g/cm² (0.50 ounce/in²). Other items to take into account when determining the final cost are the degree of piece part cleaning required, any pre-bending or heating and the necessity to repaint the finished tips. Estimate the application cost for a given part by filling out Tables 7 through 10.

If further information is needed concerning setup, application, or costs of ARM, contact any of the following:

• The Product Support Representative of your marketing organization

• GET group hotline

• Caterpillar Dealer Support

Variable Cost Calculations Tables for the Welding Procedure

Note: The variable Cost Calculations tables do not consider fixed costs. For example, the costs for equipment, weld tables and development fixtures.