Conventional (Dry) Welding Procedure for Rollers and Idlers {0679, 4150, 4159, 4180, 7950} Caterpillar

Caterpillar Products

Machines with Grease Lubricated Track with Swage

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Track Drills

MD5150C (S/N: SEY1-UP)

Introduction

© 2019 Caterpillar All Rights Reserved. This guideline is for the use of Caterpillar 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 Undercarriage Reconditioning Bulletin contains the necessary information 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 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 Undercarriage Reconditioning Bulletin must be used with the latest technical information that is available from Caterpillar.

For technical questions when using this document, work with your Dealer technical Communicator (TC).

To report suspected errors, inaccuracies, or suggestions regarding the document, submit a form for feedback in the Service Information System (SIS Web) interface.

Summary

Idler and roller rebuilding is a profitable operation that provides the dealer and the customer a viable rebuild option at a reasonable expense. This rebuild procedure allows for the idler or roller to be resurfaced to the original dimensions. Provide for equivalent wear rates as a new idler or roller. The instructions given in this guideline provide the necessary information to evaluate and rebuild an idler or roller. Considerations have been taken to improve rebuild efficiency and increase wear life. Necessary tooling is listed throughout the procedure.

References

Safety

Illustration 1	g02139237

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 to perform these functions properly.

This bulletin may contain hazardous steps. A safety alert symbol like the one below is used to indicate a hazard.

Warning messages identify a specific, imminent, latent, hazard that has a reasonable probability of resulting in personal injury or death if the warning is ignored.

Show/hide table

Personal injury or death can result from fumes, gases and ultraviolet rays from the weld arc. Welding can cause fumes, burn skin and produce ultraviolet rays. Keep your head out of the fumes. Use ventilation, exhaust at the arc, or both, to keep fumes and gases from your breathing area. Wear eye, ear and body protection before working. Protect yourself and others; read and understand this warning. Fumes and gases can be dangerous to your health. Ultraviolet rays from the weld arc can injure eyes and burn skin. Electric shock can cause death. Read and understand the manufacturer's instructions and your employer's safety practices. Do not touch live electrical parts. See "American National Standard Z49.1, Safety in Welding and Cutting" published by the American Welding Society. American Welding Society 2501 N.W. 7th Street Miami, Florida 33125 See "OSHA Safety and Health Standards, 29 CFR 1910", available from U.S. Department of Labor. U.S. Department of Labor Washington, D.C. 20210

Canceled Part Numbers and Replaced Part Numbers

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

Note: The true center line must be kept on all idler rebuild procedures. All idler width dimensions are based off center line of the idler. Measure from machined retainer surface on hub to establish the true center line of hub.

Preparation

Illustration 2	g02352954
Trimming roller using a torch

Clean the surface and flanges of rollers and idlers to remove rust, oil, water, and dirt to avoid porosity, hydrogen embrittlement, and unsound welds.

Determine if the edge of the single flange roller is rolled over at the inside on the tread area. Trim away any rollover with a torch or grind before starting the weld. Refer to Illustration 2. Trimming the roller will prevent spalling from cracks in the fatigued metal. The rollers and idlers should be inspected for abnormal wear. Flat places or thin spots should be built up before completely building up to the desired diameter. Some idlers which have been subjected to extreme conditions may develop cracks at or near the base of the flange. These cracks should be welded before rebuilding. A more ductile wire should be used to insure a quality weld. Be sure to follow correct preheating procedures before manually welding the idler.

After the roller or idler has been cleaned, remove the plug and drain the oil. Disassemble the roller or idler clean the internal components and the roller assembly or idler assembly.

Set Up

Illustration 3	g02353376
Weld head in correct position above roller. (A) Approx. 25.4 mm (1.00 inch) for 203 mm to 228 mm (8 inch to 9 inch) (1) Flux holder (2) Flux tube (3) Welding head (4) Roller

After disassembly, mount the roller or idler in the automatic welder and preheat if necessary. Establish the center line of the roller or idler . Position the wire 19.1 mm to 25.4 mm (0.75 inch to 1.00 inch) off center of the roller, in the direction opposite to rotation as shown in Illustration 3.

Illustration 4	g02353416
Weld head in correct position above idler. (B) Approx. 31.7 mm to 38.1 mm (1 1/4 inch to 1 1/2 inch) (1) Flux holder (2) Flux tube (3) Welding head (5) Idler

For idlers, position the wire 31.7 mm to 38.1 mm (1.25 inch to 1.50 inch) off center of the idler, in the direction opposite to rotation as shown in Illustration 3.

Illustration 5	g02353417
Lead affects weld bead shape (6) Proper bead (7) Too far off center (8) Too close to center

If the wire is too close to center, the molten metal will peak and may even spill, resulting in an unsatisfactory surface. Refer to Illustration 4.

If the wire is too far off center, a concave bead will be formed, sometimes with center line cracking.

Flux control plays an important part in shaping the weld bead. To produce a good quality weld deposit, properly support the granular flux with a non-burning flux holder between the flux tube and the roller or idler surface. The depth of the flux can best be established by slowly decreasing the flux control lever until the welding action is submerged. The gases will puff up around the welding wire and sometimes burn. The flux must not be disturbed in or about the welding zone.

Preheat

Welding procedures should be followed which will slightly preheat the roller before the highly stressed edges are welded. Usually this procedure provides satisfactory results but when all the original hardness is not worn away, preheating to 260 °C (500 °F) is essential.

If the welding is done in cold ambient air, remove the “chill” from the roller. The temperature of the roller should be at least 21 °C (70 °F) before welding on any roller. An open torch or a small oven may be used to preheat the rollers.

When rebuilding fabricated type idlers, the surface to be rebuilt should be preheated only when necessary to bring the temperature up to approximately 21 °C (70 °F).

Illustration 6	g02353418
Drill or cut hole in the side of fabricated type idlers before welding

Fabricated idlers should be preheated to 149 °C (300 °F). All cast type idlers except for D11 must be preheated to a temperature of at least 204 °C (400 °F) before rebuilding. D11 idler preheat temperature will be no less than 316 °C (600 °F). Start the preheating at the hub. As the heat builds up, gradually work the heat from the hub to the rim. When the idler has been preheated, the welding cycle should begin immediately and continue without interruption. If the welding cycle takes a long time, the hub should be reheated occasionally to minimize stress.

General Procedures Build-Up and Hard-Surfacing

Illustration 7	g02353419
Build up low area with partial pass (9) Third Hard Surface Pass (10) Second Hard Surface Pass (11) First Hard Surface Pass (12) Double flange roller (13) Partial pass buildup material

On rollers or idlers that are worn concave, the low area should be filled with a partial pass of the build-up material using a uniform stepover (partial overlapping of successive weld beads). Another method would be to vary the stepover and/or travel speed. A small stepover for areas which are concave. Larger stepover where the contour of the roller does not require a large amount of metal. A reduction in travel speed will also deposit more metal per linear inch. After the low surfaces have been restored evenly, complete hard surfacing passes should be applied to build the component up to the desired diameter. Refer to Illustration 7.

To minimize bore shrinkage, the roller is kept away from excessive heating by minimizing the heat input. Table provides typically used weld speed, amperage, and voltage values for a given component. Allow the rollers to cool between passes. General sequence when surfacing a set of rollers with the thin wall bushings pressed into the roller, the temperature at the bushing must not exceed 315 °C (599 °F). Start welding at outer flange and finish welding at the inner flange. Rollers should not cool below 205 °C (401 °F) between passes.

A template and large calipers used as a gauge aid in restoring rollers and idlers to original dimensions.

Note: The true center line must be kept on all idler rebuild procedures. All idler width dimensions are based off center line of the idler. Measure from machined retainer surface on hub to establish the true center line of hub.

A stepover of 1/3 to 1/2 the bead width every revolution finishes with a smooth surface.

When the roller flanges are hard surfaced, the roller axis may be positioned 5 degrees to 45 degrees from the horizontal.

Illustration 8	g02353420
Roller flange build-up (3) Welding head (4) Roller

Move the head 4.233 mm (1/16 inch) to 3.175 mm (1/8 inch) further off center from the position used for building up the tread area as shown in Illustration 8.

Illustration 9	g02353421
Idler edge beads (14) Improper bead (15) Proper edge bead

Illustration 10	g02353422
Idler edge bead build-up (16) Idler flange (17) Build up on edge first

Rebuilding the edge of the idler to size by laying successive beads one on top the other before stepping over is an advantage. It is difficult to hold the molten metal and flux on the edge if the idler is too hot from welding the tread area. Refer to Illustration 8 and Illustration 9.

Welding should be started at the edge of the idler and continue into the base of the flange.

When the idler flanges are hard-surfaced, the idler can be placed either in a horizontal position or tilted 20 degrees from the vertical. The surface of the idler acts as a flux support when placed in these positions.

Note: The true center line must be kept on all idler rebuild procedures. All idler width dimensions are based off center line of the idler. Measure from machined retainer surface on hub to establish the true center line of hub.

Travel Speed

Travel speed affects the penetration and bead width. If the travel speed is doubled, the penetration and bead width is reduced to about half. Penetration is reduced because the same amount of wire is spread over a greater length of work.

Lead

Illustration 11	g02353423
Correct lead will give the proper bead (A) Approx. 25.4 mm (1.00 inch) for 203 mm to 228 mm (8 inch to 9 inch) (2) Flux feed tube (6) Proper bead

Note: First bead on roller will be oval or convex at proper distance setting.

Lead plays an important part in submerged arc welding on cylindrical work and compares closely with rod position in manual welding. On cylindrical work, the arc is about 1 inch ahead of top center to give the molten flux an opportunity to form the desired bead. The one basic requirement is that the molten metal must at least partially solidify before the molten metal passes top center. Refer to Illustration 11.

Lead is an adjustment that must be understood by an operator. Voltage, current, or travel speed adjustments should not be used to overcome a faulty lead adjustment. Bead shape will demonstrate to the operator whether the lead is correct or not.

Illustration 12	g02353424
Too far off center (18) Bead high oval (19) Bead irregular along edge (20) Bead flat-may hair crack down center or concave

Illustration 13	g02353636
Too close to center (21) Bead with knots (22) Bead with narrow raised places

Too much lead causes a wide, flat bead that may even be depressed in the center. If the lead is huge, the ripples will reverse and indicate a metal overrun. If the lead is too short, the ripples are long, the bead is high and rough with extra weld overrun. Correct lead gives a smooth, slightly crowned bead with about 30 degree lines or ripples. For examples of improper weld beads due to wrong lead, refer to Illustration12 and Illustration 13.

Cooling

Upon completion of the welding cycle, the rollers or idler should be removed from the machine and allowed to cool slowly.

It is important to “Slow Cool Down” the roller or idler after the roller or idler has been surfaced. Proper cooling method can be accomplished by placing the roller or idler in a “Slow Cool Down” box. The roller or idler should remain in the insulated box until safe to handle by hand. The roller or idler should not be placed near drafts and should never be placed on the floor in the vertical position. Potential rim cracking could occur.

After the fabricated idler has cooled, plug weld the hole on the side.