Rail Welding Machine RQ 4006 SE


Automatic Rail Welding Machine RQ 4006 SE


The Automatic Rail Welding Machine RQ 4006 is a multi-purpose, light machine for repair welding, build-up, etc. in frogs, diamonds and switch area of normal tracks and LRT embedded tracks. It can be used for submerged arc and open arc welding. Solid wire, flux covered wire or welding tapes can be used as filler material. Additional welding equipment is required for welding tapes.

The actual Automatic Welding Machine is mounted on a special carriage usable on embedded or standard track (track gauge adjustable). Due to its compact size and low weight, it can be set on or off the rails (especially LRT track) in seconds. This ensures economical operation even while the trains are running! A single operator controls the machine.

Track Maintenance

Why do tracks in cities and populated areas have to be serviced and maintenend?

Reduction of noise emissions: Rail wear, damaged crossings, potholes, corrugation of the rail head surface etc. result in a substantial increase in noise emissions to the environment. Residents have become sensitized and want quieter rail vehicles.

Economy: Tracks in cities are installed principally in streets. The costs for replacing track complexes when they have become worn exceed the costs for replacing railway tracks of Vignole rails that have their own separate roadbed many times over. Repairing the wear and damages of such complexes by welding is therefore a more cost-effective option, and the installation life of the track complex is lengthened.

autoweld02What are the most frequent occurrences of wear or damages, and how can they be repaired?

Inside running edge wear in curves: The most frequent work on tracks is the buildup welding of the worn inside running edge of curve rails. As a result of the high lateral acceleration, which is due to the fact that tram rails usually have no camber, strong wear will occur. The wear can occur not only to the inside running edge, but on the guide rail as well. An inside running edge wear of 0.07" to 0.59" is normally admissible. Once the wear exceeds this value, the rail has to be rebuilt by welding. In the case of long track sections the use of an automatic welding machine is the most effective way to perform the welding work.

autoweld03Reduction of vertical wear by means of rail head surfacing

With this 2-groove welding technology 2 grooves are ground into the rail head, filled out with a hard electrode (450 HB, approx. 1,600 N/mm2) and surface-ground. The same weld can also be made with a somewhat wider groove at the center of the rail head.

The purpose of both welds is:

To reduce the higher wear on the rail head in particular over acceleration and deceleration sections, at stops or before signals. To significantly retard corrugation. These welding procedures are carried out with a welding machine using the open-arc method.

Tape welding

Narrow track bends that have a tendency to screech can be clad-welded with a chrome band electrode. The chrome band itself serves as the electrode and is welded to the rail with the submerged-arc method. As demonstrated by the experience in the city of Zurich the curve screeching can be reduced by 80%.


General remarks relating to the weldability of rails:

Normally, the welding work has to be performed while the line is in service or at night during the vacation periods. Pre-heating is scarcely possible because the rails are embedded in the pavement. Rails with a tensile strength of 700 N/mm2 (approx. 210 HB) can be welded unproblematically. It is also possible to weld them numerous times and without preheating. The welding of rails with a strength of 900 N/mm2 (approx. 250 HB) is problematic due to the high carbon content. The rail has to be preheated, and there is a great risk of stress cracking.

Removal of short-pitch corrugations and small waves on the rail head by grinding:

Today, the formation of corrugations is experienced by all rail vehicle operators. Since there are various theories on the occurrence mechanism, no further deliberations on this subject will be made here. In any case, corrugations cause strongly audible vehicle traveling noises and strongly perceivable vibrations which cause damage to the roadbed and to the vehicles. The only sensible way to remove corrugations is by grinding the rail surface. It is even extremely effective to prevent the corrugations from exceeding a size of max. 0.2 - 0.3 mm by periodic grinding. The RQ 1002 corrugation grinding machine and the RQ VM 7000 2-way rail grinding machine are excellently suited for such grinding work.

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