aplicación arm

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Pautas de reutilizacin y recuperacinApplication of Abrasion-Resistant Material

Application of Abrasion-Resistant Material

SMCS - 0679; 0751

SEBF8782August 2002

SMCS Codes: 0679, 0751

GUIDELINE FOR

PRODUCT UPDATE

Application of Abrasion-Resistant

Material

Al l Machines That Are Equipped with Ground Engaging Tools (GET)

Table of ContentsIntroduction 2

Cerrar SIS

Pantalla anterior

Producto: NO SE HA ESCOGIDO NINGUN EQUIPOModelo: NO SE HA ESCOGIDO NINGUN EQUIPO

Configuracin: NO SE HA ESCOGIDO NINGUN EQUIPO

Nmero de medio -SEBF8782-00 Fecha de publicacin -03/09/2002 Fecha de actualizacin -04/09/2002

SEBF87820001

Page 1 of 25Bsqueda del medio - SEBF8782 - Application of Abrasion-Resistant Material

01/12/2010https://sis.cat.com/sisweb/sisweb/techdoc/techdoc_print_page.jsp?returnurl=/sisweb/s...


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Necessary Equipment 3Safety Equipment 6Equipment Sources 6Basic ARM Welding Process 8Spray vs. Globular Transfer 9

Transition Current 9Basic Weld Parameters for ARM 9Getting Ready 10Welding Parameters Sheet 11Getting Started 12Evaluating Quality of ARM Beads 13Specifics for Caterpillar Parts 14Miscellaneous Information 16Production Costs 16Cost Calculation Tables 17-18

Introduction

Caterpillar has developed a weld operation to apply carbide particles to the wear surface ofCaterpillar Ground Engaging Tools (GET), and to other parts where the process would bebeneficial. Although the weld bead is made with general filler wire, the carbide particles areheld 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 infine, loose material, the operation typically increases the life of GET components by a factorof five or more times. High impact loads, such as large rocks or chunks of concrete, maycause the beads to break off the surface of the piece.

This guideline provides a list of required equipment, and outlines the procedurerecommended by Caterpillar. Also included are miscellaneous process tips gathered fromexperience. If the Caterpillar procedure is learned and followed, dealer stores can receive aletter of certification from Dealer Support that ensures company warranty coverage of tipsto which ARM is applied. Dealer Support personnel are available to providetraining/certification instruction on-site if desired. The choice of equipment will affect theinvestment required to set up the operation.

Illustration 1

A.R.M. Equipment




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Personal injury or death can result fromelectric shock, from the fumes, gases,and ultraviolet rays of the weld arc, and

from other work necessary in the ARMprocess. Protect yourself and others;read and understand this warning.

Welding fumes and gasses can bedangerous to your health. Useventilation, exhaust at the arc, or both,to keep fumes and gasses from yourbreathing zone and the general area.

Ultraviolet rays from the weld arc can

cause blindness and burn skin , andprolonged exposure can lead to skincancer. Due to the high current, theseeffects are more severe with an ARMprocess than with other weldingoperations. Wear correct eye, head, andbody protection during welding.

The wearing of safety glasses,preferably with side shields, must bemandatory for all people at all times in

your shop area.

Electric shock can kill. Do not touch liveelectrical components.

Make sure safety caps are always inplace on all gas cylinders unless theyhave been secured in a fixture for use.

Read and understand the weldingequipment manufacturers instructions,

and your employers safety practices.See American National Standard Z49.1,"Safety in Welding and Cutting"published by the American WeldingSociety.

American Weld ing Society

2501 N.W. 7th Street

Miami, Florida 33125

See "OSHA Safety and Health

Standards, 29 CFR 1910", available fromU.S. Dept. of Labor.




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Necessary Equipment

One option in setting up an ARM operation is to use existing equipment. A second option isa machine developed by Caterpillar and supplier Rodger Spriggs. The following bulletedpoints provide guidelines as to what is necessary, and include some explanations. Sourcesof equipment are listed under the "Equipment Sources" heading.

Although the function may seem somewhat similar, equipment for submerged arcoperations will not work for ARM. Instead of a flux delivery hopper, a carbide particlefeed system is necessary to deliver the particles to the weld bead at a controlled rate.One example is the vibratory feeder unit available from Rodger Spriggs (seeIllustration 2). The major components consist of a vibratory feeder assembly, controlbox, particle hopper, metering pipe, and adjustable feed tube assembly.

Illustration 2

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, and the speed must beadjustable. Surplus track rebuilding machines can be adapted for this purpose. DealerSupport has received inquiries about the feasibility of using robots for ARM torchcontrol. Although it is possible to do so, a motion/function control "do loop" wouldhave to be developed and recorded for each part number to be run. Also, a precisiontable-mounted fixture system would be necessary to hold each individual part inexactly the same spot, so the ARM beads would be applied to each part consistently.Because of this, robots are better suited for production welding, as opposed to

individual piecepart work. Although individual stringer (straight) beads can be applied and overlapped without it,a weld head oscillator is strongly recommended for use with the carriage. Theadjustable side-to-side speed and width movement, along with adjustable torch delay

U.S. Dept. of LaborWashington, D.C. 20210




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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 thebase metal. Beads of 1 to 1.38 in. (1.5 in. maximum) can be easily run.

A control unit, power supply, and connection cables capable of 600 DC Amperes arerequired. Correct ARM application requires extremely high current levels. Powersupply 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 BinzelRB 610 D, Lincoln Magnum 450WC, and Tweco TAM500-332.

Illustration 3

Water Cooled Torch and Particle Feed Tube

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

98% Argon/2% Oxygen shielding gas is recommended. Most welding operations usea 75% Argon/25% CO2 mixture, but to produce good penetration and large weld pool,

a higher Argon concentration is required. 90% Argon/10% CO2 can be used, but the

oxygen in the preferred mixture helps to blend the edge of a bead with the basemetal. Shielding gas usage will be approximately 1000-1100 l/hr (35-40 ft/hr).

AWS class ER70S3 weld wire such as Lincoln SuperArc L-50 should be used in the

operation. It is a solid, general application wire, and works best for creating the largeweld pool. Wire sizes from 0.76 mm (.030 in.) to 2.4 mm (.094 in.) have been used,but 1.5 mm (.062 in.) is a good choice for general ARM work.

A wire reel assembly and drive rolls capable of handling the above wire is alsonecessary. Any existing wire straighteners and swivel mounting plates can probablybe reused.

A welding table with a surface made of 19 to 25 mm (0.75 or 1 inch) steel plate isrequired to provide a surface for welding, clamping, and preheating operations. Itshould be about 3 to 4.5 m (10 to 15 ft.) long and 1 m (about 3 ft.) wide, and

adequately reinforced. Holes for studs or bolts should be added to the table surface toclamp and pre-bend long parts, where weld distortion can be a problem. The tablecan be separate, or part of the torch carriage system.




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Illustration 4

Table for Welding Equipment

An abrasive chop saw of sufficient capacity is needed to section samples forinspection. 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 they are reused (see Illustration 5).

Illustration 5

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 Shielding gas flow




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Illustration 6

Control Panel for A.R.M. Equipment

The control panel should incorporate automatic start for the shield gas, adjustable delaytimes for carriage travel and feeder when the weld arc is started, and delay for feeder stopwhen the bead is stopped. Another recommended feature is an electrical interlock thatprevents 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 should be mounted with graduated (for example 0-10.0) face plates. There is noneed for face plate graduations to correspond to actual values of functions such as carriagespeed or delay times. The purpose is so that a perfected set of adjustments can berecorded, and exactly duplicated, the next time the same parts are run.

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

The Rodger Spriggs machine is shown in Illustrations 1 and 4. This machine meets all

Caterpillar specifications and can be specified for local power systems anywhere in theworld. It is nearly a turnkey ARM set up, since everything listed under "NecessaryEquipment" is included except for the welding table, gas regulator, consumables, andinspection equipment. See the "Equipment Sources" heading for Spriggs contactinformation.

Safety Equipment

Along with process equipment, there are a number of extremely important pieces ofequipment that are required or strongly 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 usually




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used for general arc welding operations. Some helmet manufacturers offer thin shadeinserts which increase lower shaded helmets to 13 or 14.

The wearing of safety glasses, preferably with side shields, must be absolutely

mandatory for all personnel at all times in the ARM area, as well as anywhere in yourshop. A face mask provides added eye protection when using hand-held grindingequipment.

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

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

Another item is a weld fume extraction system. A flexible hose can be affixed to thecarriage and connected to a wall-mounted system, to remove hazardous fumes andsmoke. Floor fans can be used to help with ventilation, but be sure the shielding gasfunction is not affected.

During initial setup of the equipment, it is necessary to install a fixture to secure theshielding gas cylinder. It should be firmly mounted on a wall or building support beam,with sufficient space for changing out cylinders safely.

Equipment Sources

The Caterpillar Service Technology Group (CSTG) offers a variety of welding-relatedequipment including helmets, hand grinders, personal protective jackets, and hand tools.Caterpillar recommended carbide particles are offered in a 22.7 kg (50 lb.) bucket, partnumber 9W-3679. Consult the Tool and Shop Products Guide (NENG2500, includes CD) orcall (800) 542-8665 in the US, or +41 (22) 849 40 36 in Geneva for tool information and partnumbers.

In addition to a complete ARM machine, individual components such as vibratory particlefeeders are available from Rodger Spriggs. The address is:

Rodger W. Spriggs

2005 West Raymer Ave.

Unit "O"

Fullerton CA 92633

(714) 879-5875

Fax: (714) 879-3159

Email: [email protected]

Along with basic welding equipment, Lincoln Electric can supply nearly all the

miscellaneous items necessary for an ARM system, including torch cooling systems, weldfume extraction systems, particle feeders, and weld head oscillators (Lincoln Spreadarc).

They also have sales and support outlets all over the world.




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The Lincoln Electric Company

22801 St. Clair Ave.

Cleveland, OH 44117

(216) 481.8100

Fax: (216) 486.1751

Website: http://www.lincolnelectric.com

A carbide particle feeder, model FT-0C, is available from:

FMC Syntron

57 Cooper Ave.

Homer City PA 15748-9234

(800) 362-8999

Fax: (724) 479-4552

Website: http://www.fmcsyntron.com

Another supplier with an extensive line of welding equipment is:

Miller Electric Manufacturing Co.

1635 W. Spencer St.

P.O. Box 1079

Appleton, WI 54912-1079

(920) 734-9821

Fax: (800) 637-

http://www.MillerWelds.com

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

Alexander Binzel Corporation650 Research Drive, Suite 110Frederick MD 21703-8619

(800) 542 4867

Website:http://www.binzel-abicor.com




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

Steiner Industries

5801 North Tripp Ave.

Chicago IL 60646-6013

(800) 621-4515

Fax: (773) 588-3450

Website: http://www.steinerindustries.com

email: [email protected]

A source of multi-layer silica type insulating blankets is:

Superheat Services, Inc.

8450 W. 191st Street #14

Mokena IL 60448

(815) 464-2675

Fax: (815) 464-2681

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

Air Quality Engineering

7140 Northland Drive North

Brooklyn Park MN 55428-1520

(800) 328-0787

Fax: (763) 531-9900

Website:http://www.air-quality-eng.com

Sources of welding helmets are:

Hornell, Inc.

2374 Edison Blvd.




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Twinsburg OH 44087

(800) 628-9218

Fax: (330) 425-4576

Website: http://www.hornell.com

Sellstrom Manufacturing Co.

One Sellstrom Drive

Palatine IL 60067

(800) 323-7402

Fax: (847) 358-8564

Website: http://www.sellstrom.com

J ackson Products

5801 Safety Drive N.E.

Belmont MI 49306

(800) 253-7281

Fax: (616) 784-7870

Website: http://www.jacksonproducts.com

ASTM screen mesh sieves are available from these two sources:

Fisher Scientific UK Ltd

Bishop Meadow Road,

Loughborough,

Leicestershire LE11 5RG

01509 231166

Fax: 01509 231893

email: [email protected]

Website: http://www.fisher.co.uk

W.S. Tyler

8570 Tyler Boulevard




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Mentor, Ohio, USA

800-321-6188

Fax: 440-974-0921

Email: [email protected]

Website: http://www.wstyler.com

Welding related shop equipment including abrasive wheels is available from ForneyIndustries:

Forney Industries, Inc.

Central Office

P.O. Box 563

1830 LaPorte Ave.

Ft. Collins, CO 80521

(800) 521-6038

Fax: (970) 498-9505

Website: http://www.forneyind.com/

Weld head oscillators are also available from:

Gullco International Inc.

21568 Alexander Road

Cleveland, Ohio, 44146

(440) 439-8333

Fax: (440) 439-3634

Website: http://www.gulco.com

The sources listed in "Equipment Sources" are not intended as the only choices. Usefulinformation on welding operations, as well as numerous equipment manufacturers, can befound in welding industry publications such as Welding Design and Fabrication. Your localwelding equipment supplier can assist in equipment selection, and will have manycomponents available to get your operation restarted in case of equipment failure. You canalso contact Dealer Support at (309) 675-8263 if you have questions about any equipment.

Basic ARM Welding Process




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Simply stated, 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 moltenbase metal and weld wire, called the Drop Zone Area (DZA). The particles are fed into theDZA by a feed tube that is mounted behind the torch. The particles become suspended inthe pool as the torch continues moving and the pool hardens. Table 1 lists a number ofvariables and their effect on the size of the DZA.

Table 1

Spray vs. Globular Transfer

The ARM arc differs from ordinary GMAW operations in that it is done with current levelshigh enough to produce a "spray" wire metal transfer instead of the usual "globular" transfer

(see Illustration 7). At low welding currents, liquid metal is transferred from the wire to theworkpiece in large globular drops. Globular transfer produces an uneven sound, similar tofrying eggs. When viewing a globular arc, the end of the wire is rounded and there is aconsiderable amount of weld spatter.

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

Illustration 7

Effect of Weld Variables on DZA Size

Increase in: DZA:

Amperage Increases

Voltage Increases

Stickout Distance Little Change

Travel Speeds Decreases

Wire Size Increases

Particles DecreasesOscillation Width Increases




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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 it is dependent on a number of parameters.The most important of these is the voltage adjustment, but size and speed of the wire, andthe type of shielding gas also have an effect. Table 2 gives examples of wire diameters andspeeds, and the start of transition current levels, using the 98% Argon/2% Oxygen shieldinggas. Although current levels during actual ARM operation will be higher than those listed in

Table 2, the object is only to ensure adequate penetration and create an acceptable DZA tocapture particles, not to maximize current. Too much current causes extreme heat buildupin the part, which should be avoided.

Table 2

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 eachother, and acceptable beads can be run with different but offsetting adjustments.

Getting Ready

When connecting the power supply, make sure the system is set up for reverse polarity(wire is positive [+]), to ensure good penetration. Because of the high current flow, the tableshould be grounded to the power supply from two opposite corners. This also prevents thetendency of the arc to aim in the direction of a single ground connection. Check all

Sample Transition Current Adjustments

Wire Diameter

Current

(Amps) Wire Speed/min.

1.14 mm (0.045 inch) 220 6375 mm (251 inch)

1.57 mm (0.062 inch) 275 4546 mm (179 inch)

1.98 mm (0.078 inch) 310 3454 mm (136 inch)

2.39 mm (0.094 inch) 370 3124 mm (123 inch)




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mechanical functions, especially the wire feeder, carriage travel, particle feeder, andoscillator, to be certain that everything is operating consistently.

All test samples or parts to receive ARM should be free of oil or grease and completely dry.

Use an angle grinder to remove dirt, paint, and loose or excess scale and rust from theweld surface. This can also be done by sand blasting. The surface does not have to beperfect, but cleaning ensures good electrical contact and helps prevent contamination andporosity in the ARM bead. A light surface grind to clean the table contact points of the partis also recommended, to ensure adequate current flow from the part to the table.

The particle feed tube should be a 13 mm (.5 inch) diameter tube, modified and installedaiming toward the torch as shown in Illustration 8. Copper tubing can be used to make thetube, but stainless steel tubing will last longer. Use a vise or hammer to form the oval shapein the end of the tube. This helps to distribute the particles across wide beads. On manyinstallations, the top of this tube has a funnel to catch the particles from the stationary

feeder as the tube oscillates with the torch (see bottom of Illustration 2). Do not allow thetorch-mounted funnel/tube to touch the feeder distribution tube.

Distance "A" (between the tube and the torch) must be adjustable. Because of theadjustment feature, the tube can easily be bumped out of alignment when placing parts onthe table. Be sure to check the tube often during operation, to make sure it is centered withthe line of torch travel. Distance "A" measurements can be taken from the outer housing ofthe torch to the center or edge of the feed tube, or along the adjustment mechanism thatholds the tube. The actual measurement method is not important, as long as themeasurements are accurate and consistent, and can be recorded for duplication later.

The vertical length between the torch tip and the workpiece is known as visible stickout(see Illustration 8). Stickout is usually set around 16 mm (0.63 inch) to 22 mm (0.88 inch). Iftips with an uneven surface height are to be run, either support the part with steel shimblocks or make a fixture to fit the part, so that the line of the average weld surface is aslevel as possible. Set the stickout dimension to the average weld surface of the part.

Serious injury or death can result from contact with an energized weld wire. Do notuse a metal ruler to check visib le stickout. Make and use marked wooden gageblocks of the most-used stickout dimensions.

Serious injury or death can result if thevalve breaks off a falling gas cylinder.Never connect, or remove the safety capfrom the shielding gas cylinder or anyother type of cylinder, unless it has beensecured in its holding fixture. Shoppersonnel must be required to keepvalve safety caps in place on all unusedcylinders.




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Illustration 8

(1) Detail for the end of the feed tube

(2) Length of stickout(3) Base metal

Welding Parameters Number____________

Illustration 9

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

Table 3




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Notes:

Getting StartedSAE 1018, or any soft steel bar stock of 1 X 2 X 6 inch or similar dimensions is ideal forrunning sample beads. Torch oscillation should begin immediately when starting the arc,but carriage travel and particle feeding should be slightly delayed. This is necessary toestablish an adequate weld pool to receive the particles. The oscillation rate is usuallyslightly more than one shift per second, and oscillation widths of 16-19 mm (.63-.75 in.) areusually used. Feeder operation should continue for a brief time after the arc is stopped, tobe sure the end of the bead is filled with particles.

The key to the operation itself is practice. In this way, the effect of changing parameters canbe learned by inspecting beads. When making various adjustments, be sure to adjust onlyone parameter at a time prior to each test, to get a feel for the result of changing individualvariables. Use a paint stick to mark samples with progressive numbers. Record the samplenumber and all parameter settings on copies of the Welding Parameters sheet. Samplesand their respective settings can then be easily compared.

To begin, run beads with different adjustments including oscillation parameters, but withoutadding particles. When the plain beads are acceptable, record and save these settings on acopy of the Welding Parameter sheet. The settings can be duplicated when it is necessaryto run butter beads. The function of butter beads is discussed in the "Applying ARM to

Caterpillar Parts" heading. After practice with plain beads, experimentation with particlefeeding can begin. Adding room-temperature particles cools the DZA pool. To compensate,torch speed should be decreased by about 25%. Adjustments to voltage (current), and wirespeed will also likely be required.

Wire Diameter Traverse Speed

Type of Welding Wire Wire Feed Rate

Width of Weld Bead Voltage

Height of Weld Bead

Amperage

Weld Penetration Setting of Carbide FeedMachine

Shielding Gas Carbide Feed Rate

Flow Rate Width of Oscillation

Visible Stickout Speed of Oscillation

Dimension (A) Dwell of Oscillation(Right and Left)




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Although the potentiometer setting numbers for adjustments such as carriage, wire, andoscillation speeds will not correspond to their actual values, a stopwatch can be used toobtain these numbers. Wire feed rate can be calculated by running an un-energized wire forexactly 15 or 30 seconds and measuring the length. The values can be compared toexamples provided in Table 3, and will also be used in calculating the cost of ARM forparts.

See Illustration 10 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 thetorch at the sides of the ARM bead is important to establish and maintain beads of thedesired width. When welding along the center of symmetric parts or parts with extensivecross-section area, dwell should be even on both sides. To run beads lengthwise along theedge of a part, for example a scraper blade, a shorter dwell along the edge is desirablesince there is less area for heat sink.

Illustration 10

After running ARM samples, cool them and use an abrasive wheel chop saw of sufficientsize to make a clean, smooth cut through the bead for inspection of penetration and particledispersion. Since the particles are very hard, softer abrasive wheels are generally moresuccessful to prevent wheel loading and minimize burning. Bead inspection is covered onpages 12 and 13. Later on, as parameters for given parts are optimized, keep a binder ofparameter sheets marked with the part number of each part. With these sheets, set up timeis significantly reduced each time the same parts are to be run. Good quality test samples,or sectioned tips with the ARM surface repainted, can be put on display to encourage ARMsales.

Table 3 lists sample parameters of ARM beads. These are intended as starting points orexamples, and most likely would not be duplicated exactly.

Table 4

Sample Setup Parameters

Parameter Initial SettingsWire Size 1.14 mm (.045 inch) 1.57 mm (.062 inch) 1.98 mm (.078 inch) 2.39 mm (.094 inch)

Voltage 26 30 32 34




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(1)Hard particle feed rates will vary greatly, based on the differences in particle feed systems

NOTICE

Although water can be used to cool test samples for inspection, GET tips or other partsintended for sale and/or use should never be water cooled. Rapid cooling can cause stress

cracks in the base metal. Also, ARM should not be applied to parts immediately after theyare brought into the shop from outside storage in cold climates. Allow them to reachambient room temperature, or preheat as necessary.

Particles that fall to the side of the beads should be gathered and reused, but it is importantto prevent bead contamination by removing dirt and other foreign material. First, sweep amagnet about 13 mm (0.5 inch) above the particles as they lay on the table. This will attracthigh iron debris such as weld berries and pieces of wire. Next, stack 12, 20, and 35 meshscreens with the 12 on top, over a bucket. Gather the particles and shake them in thescreens. This holds any large debris on top and lets fines fall into the bucket, so thecleaned particles can be returned to the hopper. The 20 screen stops half of the particles

so they 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. A mixture of 90-95% methanol alcohol and 5-10% nitric acid should be prepared and applied to the sectionsurface with a cotton swab or small squeeze bottle. Rinse the part in water to removeexcess acid after etching. Be careful to avoid skin contact when using this mixture.

Visually, the area of an ideal ARM bead cross section should be comprised of a 50% wireand base metal mixture, and 50% particles (see Illustration 11). The particles should be asevenly distributed from side-to-side and top-to-bottom as possible. Perfect distribution is

Amperage 280 320 380 460

Travel Speed 146 mm/min (5.75 in/min) 152 mm/min (6 in/min) 203 mm/min (8 in/min) 305 mm/min (12 in/min)

Wire Feed Speed 889 cm/min (350 in/min) 457 cm/min (180 in/min) 292 cm/min (115 in/min) 279 cm/min (110 in/min)

Shielding Gas 98% Argon and 2% Oxygen at 1.1 CM/H (40 CF/H)

Visible Stickout 12.7 mm (.50 inch) 19.0 mm (.75 inch) 22.2 mm (.87 inch) 25.4 mm (1.00 inch)

Bulk Feed Rate (1) 0.23 kg/min (.5 lbs/min) to 1.23 kg/min (2.7 lbs/min)

Distance "A" 15.9 mm (.63 inch) 19.0 mm (.75 inch) 22.2 mm (.87 inch) 25.4 mm (1.00 inch)




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difficult to achieve because some of the particles will melt into the hotter top of the pool,and many tend to sink to the bottom. Optimizing distance "A" is a good method of gettingthe best distribution. At minimum, the bottom 75% of the weld bead should have goodparticle distribution and only the top quarter may have a reduced amount of particles. Byweight, a bead should be 40% wire and 60% particles. These numbers are checked by aseries of weight measurements. Contact Dealer Support at (309) 675-8263 for weightinspection procedure details. When running oscillating beads, the particle deposit should beone pound per 32-36 inches of bead length.

Bead height will usually be about 4-5 mm (0.16-0.20 inch). Penetration should beapproximately 1.5 to 2.0 mm (0.06 to 0.08 inch) at the center of oscillating beads. Properpenetration is achieved mainly by adjusting carriage and oscillation travel speeds, and thecurrent level.

Illustration 11

Stringer (straight) beads tend toward a penetration of about 5 mm (0.20 inch) at theircenter, because the heat is concentrated in a straight line. Stringer bead penetration shouldbe checked toward the edge of the bead. Stringer beads can be run side-by-side to achievethe wide coverage of oscillating beads, but this procedure takes extra time and much more

heat is transferred to the part.

Cracks may occur in the ARM bead due to the stress of uneven heat buildup from welding.This is especially true when applying long beads to thinner parts. Cracks in the ARM beaditself are acceptable, but if they are seen in the base metal, the part should not be used.

These cracks will likely grow and result in failure of the piece.

Illustration 12

It is also important to make sure the blend of ARM beads to the base metal is fairly smooth(see Illustration 12). Beads should not be "piled up", appearing as a puddle of liquidmercury on a surface. A smooth blend helps prevent any large pieces of material beinghandled by the machine, from catching on the edge of the bead and breaking it away from

the base metal. Likely causes of high bead edges are too much carriage speed and/orinsufficient current level (even if in spray transfer).




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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 as well as any high carbonparts. The Caterpillar-recommended preheat procedure is to run a "butter bead" on theintended ARM surface. Butter beads are simply beads using the same wire, but with nocarbide particles. While the butter bead is still warm, apply an ARM bead on top of it. Butterbeads have the added advantage of diluting the base metal with weld wire, and providing acrack-arresting layer between the base metal and ARM bead.

Although not the best procedure for DH-3 and high carbon parts, it is also possible topreheat with a gas torch. If using this method, do not allow the flame to touch the surfacearea where the ARM bead will be applied. The preferred procedure is to heat the tip fromthe opposite side. Heat the tips to 200 to 260C (400 to 500F) and use an infrared

thermometer to monitor the temperature. Regardless of which preheat method is used,cover the part(s) with an insulating blanket after applying the ARM bead to slow the coolingrate. Cooling can also be slowed by putting the tips in a container as they are finished, andcovering them with dry sand.

Torch preheating, and also applying beads to long parts in sections as opposed to onecontinuous bead, helps control warping of long parts such as scraper blades. Prebendingthe part to a slightly concave shape (in relation to the torch) can also prevent warping. Thiscan be done with blocks and clamps on the table surface. After running the bead(s), allowthe piece to partially cool before releasing the clamps. Through testing, a procedure can beperfected and recorded for your particular ARM installation.

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

Through service tests, Caterpillar Inc. has developed a series of standard ARM beadpatterns for various tips. These patterns provide the best balance of service life extensionversus cost of application, and are used to apply ARM to the tips available from Caterpillar.Contact Dealer Support if you would like to obtain dimensions of these patterns.

Some machines have high wear areas, for example areas inside scraper bowls, which canbenefit from ARM patterns. Since these large areas cannot be done on a table, it ispossible to overhead-mount a particle feeder with a long flexible feeder hose, and fastenthe delivery tube to an ordinary hand held torch. Although it is impossible to produce thequality of ARM described in this publication, it will still add a degree of abrasion resistanceto surfaces.

Caterpillar GET tips with, and without ARM, undergo a heat treat operation. This providesan extra measure of hardness to the base metal, for wear resistance. Tips with ARM areheat treated after the ARM beads are applied. When ARM is applied to Caterpillar tips in

dealer shops, the heat draws some of this hardness out of the part. This is the reason whyexcessive heat should be avoided. Although the Caterpillar heat treatment does providesome additional life, in most cases it is not required for tip service. The wear resistance of agood quality ARM bead will significantly increase the life of any GET part to which it is




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applied. The exception to this is if ARM beads are applied to the top and bottom of longparts such as ripper tips. If the upper and lower heat-affected zone depths are greater thantwo-fifths (40%) of the total tip cross-section area, tip breakage may occur. This is a resultof small cracks that occur in the ARM bead, and the gaps between the particles and weldpool. Cracks travel easier through areas with higher concentrations of stress raisers. Alsonote that base metal cracking may result from the ARM operation if ARM is applied to anycomponents that have high hardness (approximately Rockwell "C" 50 and higher).

During ARM work on warm days, make sure air movement from open shop doors orventilation fans does not blow the shielding gas away from the arc. Also, if your shop islocated in a warm, humid climate and morning water condensation occurs, make sure theparticles, as well as the wire and GET tips, are completely dry before starting. This preventspiecepart cracking due to hydrogen. The hopper should be emptied at the end of the day,or an incandescent light can be positioned close above the particle hopper and left on, tohelp keep the particles dry. A small mirror can also be positioned close to the light, toconveniently check hopper capacity from the floor.

Miscellaneous Information

If ARM is to be added to miscellaneous ground engaging tools at the request of a customer,more ARM is not always better. It is possible to "over carbide", thereby winding up withparts that are fully worn but still have considerable carbide remaining in areas of lowmaterial contact. Inspect parts that have been used in the machines application. Usedparts will show material flow patterns. These indicate where ARM beads will be mosteffective, and will provide the best return for the customers investment. Also, piling ARMbeads on top of each other is not recommended, since the carbide in the lower bead willmelt and produce too hard a deposit.

Some outside shops perform ARM using Nickel/Chrome hardfacing wires, to add wearresistance to the weld bead itself. Although this may be beneficial in some applications,Caterpillar has not done research in this procedure because of the added cost of thesetypes of wire.

Production Costs

It is difficult to establish an exact production rate for applying ARM because of the manyvariables, but a starting estimate is 740 cm/hr (115 in/hr), running a 2.5 cm (1.0 inch)bead width. The overall rate of usage for hard particles is approximately 2.3 g/cm (.50ounce/in.). There can be many other items to be taken into account in determining the finalcost, including the degree of piecepart cleaning required, any pre-bending or heating, and ifit is necessary to re-paint the finished tips. An estimate of application cost for a given partcan be made by filling out copies of Tables 5 through 8.

If further information is needed concerning the setup, application, and costs of ARM,

contact any of the following:

The Product Support Representative of your marketing organization GET group hotline




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Caterpillar Dealer Support

Caterpillar Dealer Support may be contacted at (309) 675-8263. The GET hotline is(800) 422-8438.

Variable Cost Calculations Tables for theWelding ProcedureTable 5

Table 6

Average Arc Time (Minutes) Net Cost of Dealer for Carbide

Weld Traverse Speed (inch/min.) Pounds of Carbide That Was Purchased

Weld Width (inches) Cost per 60 lb Spool of Welding Wire

Wire Feed Speed (inch/min.) Price of Shielding Gas

Weight of 6 feet of Welding Wire (lb) Cubic Feet of Shielding Gas

Flow Rate of Shielding Gas (cu.ft./hr.) Electrical Cost (dollars per kilowatt hour)

Voltage Setting Welders Hourly Labor Rate

Amperage of Welder Laborers Hourly Rate




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Note: The variable Cost Calculations Tables do not consider fixed costs. For

example, the costs for equipment, weld tables and development of fixtures.

Labor Cost Cost of Material Total Variable Cost Variable Costper Square Inch

Copyright 1993 - 2010 Caterpillar Inc.Todos los derechos reservados.Red privada para licenciados del SIS.

Wed Dec 1 13:53:20 EST 2010


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