This guide provides practical information on how to cut, form and fabricate Red Dog wear resistant overlay plates. Unless otherwise indicated, the procedures described apply to standard compositional grades of overlay with structural carbon steel substrates. Special instructions for overlay plate with, for example, high strength or stainless alloy substrates are provided where applicable.
Red Dog Plate Ranges
The Red Dog overlay plate range has been developed to combat abrasion, erosion and impact at either ambient or elevated temperatures. The range comprises different hardfacing chromium or tungsten carbide alloys deposited onto a carbon steel or alloy substrate.
The recommended method of cutting overlay plate is by plasma-arc, as the high chromium and carbon contents of the hardfacing overlay preclude the use of oxy-fuel and most mechanical means. The special properties of the very hard overlay alloy and a ductile substrate allows these materials to be formed and fabricated into complex shapes, including concave or convex curves.
Wear resistant liners may be installed into structures using a variety of methods including plug welding, stud welding and bolting. Fabrications can be produced by conventional welding of the carbon steel substrate.
Both Red Dog's chromium and tungsten carbide alloy hardfacing overlay act like stainless steel during cutting. This precludes the use of conventional shearing or oxy-fuel flame cutting processes.
There cutting methods can be used:
- Plasma Arc
- Carbon arc
- Abrasive saw
Plasma arc cutting
Overlay plates, including those with special substrates, can be easily cut with a hand held or machine mounted torch using either air or inert gas plasma-arc processes. Typical systems feature a minimum 150 amp power supply and the higher the amperage employed, the faster the cutting speed can be achieved.
Overlay plates may be cut from either side, but to accommodate the natural bevel created by this process it is recommended that cutting takes place from the alloy side. Cutting speed should be adjusted to minimize the build-up of slag on the underside of plate.
Carbon arc cutting (Gouging)
A compressed air supply and a conventional constant current DC welding power supply, with a minimum OCV of 60V (80V recommended) is required for carbon arc cutting and gouging. An arc voltage in the range of 35 - 56 volts is desirable.
Typical parameters for copper coated gouging rods are:
|Diameter||Amperage (DC Reverse Polarity)||Minimum Air Flow||Recommended Air Flow|
|Up to 6.3mm||1/4”||250-400A||3cfm @ 40psi||100 l/min @ 3 Bar||9 cfm @ 80psi||300 l/min @ 6 Bar|
|9.5mm & above||3/8"||350-600A||6cfm @ 90psi||200 l/min @ 6 Bar||15 cfm @ 80psi||500 l/min 6 Bar|
Cutting should be carried out from the carbon steel side of the plate by first marking out the cutting lines and then dot punching to ensure continued visibility during the process. After cutting plates from the substrate side, all slag should be removed with an abrasive grinding disc.
Limited straight line cutting can also be achieved using an abrasive saw (as used to cut concrete) fitting with silicon carbide wheel.
Most standard grade of Red Dog overlay plate can be cold formed into curved and conical sections using either rolls or press brakes. Red Dog T214X has only limited form-ability and a number of special chromium/tungsten and tungsten carbide grades can only be used as flat profiles and fabrications.
Direction of Rolling
Wherever possible, plates should be formed with the weld beads aligned in the direction of rolling. (See figure 1).
The minimum recommended diameter to which Red Dog overlay plate can be formed will depend on the thickness of the plate, the type of substrate and whether the bend is concave (alloy facing on the inside) or convex (alloy facing on the outside). See figure 2.
The table below shows typical minimum diameters for cold forming* T200X plate.
|Red Dog Grades T200X||Nominal substrate thicknesses
||Minimum Diameter Concave||Minimum Diameter Convex|
|Single layer overlays from 3.2-6.3mm )1/8” - 2/4”)||9.5mm (3/8”)||400mm (10”)||250mm (16”)|
|Double layer overlays from 8.0-12.5mm (5/16” - 3/8”)||12.5mm (1/2”)||450mm (16”)||400mm (18”)|
When using pyramid or pinch rolls, it is recommended that the top roll is protected with a sleeve to prevent damage to the hardfacing. This should be fabricated from 12 mm (1/2") thick carbon steel and sized approximately 50 mm (2") larger than the roll diameter to facilitate installation and removal and to prevent binding.
When using a brake press from small diameter pipe, cones and square to round transitions, it is recommended that a hydraulic press is employed for the best results. Forming can be carried out with a male and female die, using a radiused top tool (min. 38cm/ 11/2") over a 'V' block.
For thicknesses above 20mm (3/4") forming can be assisted by the application of heat either locally, using a broad flame oxy-gas torch, or generally for larger sections, in a furnace.
To ensure that there are no significant changes in the properties of the plate, hot forming temperatures should not normally exceed 650°C (1,200°F), with furnace soaking times of no more than 1 hour. Higher temperatures may be used in special circumstances.
Further information on forming individual plate grades and thicknesses and specific forming techniques can be obtained from Kubes Alloys directly.
Hot forming is recommended where 90 degree corners are needed when fabricating square to round transitions.
Special Substrates: Where high strength alloy steel substrates are used, whether in cold or hot forming, more power will be required to form the plate to the same diameters as conventional carbon steel substrates.
Flat profiles and formed sections can be fabricated into larger items or finished structures using conventional welding procedures. Liners may be fixed to existing structures by bolting or by various welding techniques.
All structural welds must be applied to to the substrate.
Methods of attachment - Fillet Welding
The easiest method for attaching Red Dog overlay plate to an existing structure is by a fillet weld. Care should be taken to ensure that the weld is applied to the substrate only and does not overlay the hardfacing or it's penetration, as this can lead to carbon contamination and embrittlement of the weld. This is best achieved by stopping the fillet approximately 3mm (1/8") below the alloy/base plate interface which should be clearly visible on a ground edge.
Any common welding process may be used including:
- Shielded metal arc welding (US - SMAW) / Manual metal arc welding (UK - MMA)
- Gas metal arc welding (GMAW) using solid wire.
- Flux cored arc welding (FCAW) using gas shielded or open arc wires.
Selection of welding rods/wires
Where the overlaid plate has a standard carbon steel substrate and the structure onto which the plate is to be attacked also comprises carbon steel or a steel which does not require preheat, the following types of consumables may be used:
- Coated rods: AWS A5.1 - E7016 EN499 E424 B12HS or E7018 EN499 E463 B32HS
- Solid Wire for CO2 welding: AWS A5.18 - ER70S-3 EN440 G/W 2Si or ER70S-6 EN440 G3 Si1
- Flux cored wires: AWS A5.20 - E70T-1 EN758 T460 RC3H10 or E71T-1 EN758 T463 PM1HS
If the structural member requires preheat, either because of it's chemical composition, yield strength or thickness, a grade of welding rod or wire should be selected compatible with normal practice for that base material:
For example: AWS A5.5 - E8018B2 (EN 1599 ECr.Mo1 B32HS)
If the Red Dog overlay has a stainless or alloy steel substrate and the structure to which it is to be welding is a high alloy manganese steel, through-hardened steel or a type AISI-410 or 304 stainless alloy, then a suitable dissimilar metal alloy suck as a AWS A5.4 - E309 (EN1600 E23.12 LR21) stainless type rod (electrode) or wire should be used.
Red Dog overlay plate can be attached to another plate or structure by plug welding through a series of holes. Each hole should have a minimum 25mm (1 inch diameter, typically set at between 300mm - 600mm (12-24") spacing.
Fixing holes should be cut by either carbon-arc gouging or plasma-arc cutting from the substrate side where possible to prevent chromium and carbon contaminating the carbon steel. When gouging plates thicker than 9.5mm (3/8") it is recommended that a hole is first drilled into the substrate to stop just short of the alloy interface before gouging is started.
All slag should be removed from the fixing holes by grinding or chipping/hammering.
The plate is then attached to the structure by welding the outside diameter of the hole through 360 degrees and then filing the remaining space using the pattern shown in figure 4.
The thickness of the weld should be determined using the same criteria as for fillet welding and should stop 3mm (1/8") short of the overlay alloy layer. When the weld has been filled to the desired level, it can be protected from abrasion by 'capping' with a suitable wear resistant alloy using Red Dog Armolloy tubular hardfacing rods (electrodes).
A standard carbon steel stud can be easily welded to the back of the Red Dog overlay plate using most types of stud welding equipment. The minimum recommended stud size is 19mm (3/4") and the number and spacing of the studs will depend on the size and shape of the plate being attached.
Studs with a diameter greater than 12.5mm (1/2") may be hand welded with the SMAW (manual metal arc process) using an E7018 rod. Since only a fillet weld is employed rather than a full penetration weld, a greater number or studs will be needed to secure the plate. See figure 5.
Methods of attachment - Countersunk Bolts
Suitable holes for countersunk bolts may be produced by direct plasma arc cutting using an orbital tool post, by piercing or gouging a straight hole and welding a pre-machined insert in place, or by a combination of direct drilling or gouging.
The minimum recommended bolt size is 9.5mm (3/8") diameter and the number and spacing required will depend upon the size and shape of the plate.
The finished counter sunk hole should allow the flat headed bolt to sit approximately 4mm below the surface of the plate. It can be protected from abrasion by 'capping' with a suitable Red Dog Armalloy tubular hardfacing electrode.
Direct plasma arc piercing
produces an acceptable countersunk hole. Working from the hardfaced side, the straight clearance hole should be cut first and then the plasma torch tilted to cut the countersunk section at an angle to match the fixing bolt.
Accurate pre-machined inserts may be used to fix overlay plates by cutting a straight hole in the plate and welding the insert in place from the carbon steel side.
Plasma arc cutting from the hardfaced side of the plate is recommended because is creates a naturally tapered hole which provides additional support for the insert.
The insert should be machined with a taper of around 3 degrees to match the hole and a chamfered weld preparation cut into the base. It is then welded into place from the carbon steel side using a low hydrogen electrode (AWS 5.1 - E7018 or 7016 type).
This process is generally used on-site when plasma-arc cutting is not available. If a large number of holes is required, welded inserts are recommended and gouging should be used purely to cut the clearance hole.
An alternative method for one or two holes involves gouging a straight hole from the carbon steel side (see also cutting). The countersunk section is then created be gouging a taper from the hardfaced side. The holes may be cleaned with abrasive cone/plug shaped grinding stones.
Red Dog overlay plate can be fabricated by welding the mild steel substrate using standard mild steel or low hydrogen electrodes. The following details are a general guide to welding Red Dog overlay plate.
Care must be taken to ensure that all structural welds stop short of the hardfacing alloy layer. The only welding carried out on the hardfaced side of the plate will involve the capping of joints, for wear protection, with a compatible Red Dog Armalloy tubular hardfacing electrode.
Grind the edge of the plate to remove any slag and scale left from cutting. Care should be taken to ensure that the weld is applied to the substrate only and does not overlap the hardfacing or it's penetration zone, as this can lead to carbon contamination and embrittlement of the weld and the adjacent area. This is best achieved by stopping the fillet approximately 3mm (1/8") below the overlay/base plate interface which should be clearly visible on a ground edge. (See figure 3).
Partial penetration butt welds involve cutting a bevel into the carbon steel base by gouging or flame cutting (see figure 6). A 2 mm to 3mm (1/16-1/8") 'land' should be left to prevent burn-through to the hardfaced layer when welding (see figure 7). Fit and tack sections, then weld using the same technique as conventional joining.
Full penetration butt welds require the hardfacing (including alloy penetration zone see figure 8) to be completely removed from the joint area by grinding/gouging back to at least 6mm (1/4") past the weld joint area. Fit and tack the bevelled sections, then using the same technique as conventional joining.
Welding Technique and Consumable Selection
The root pass must not melt through the 'land' into the hardfacing as this will lead to carbon contamination and embrittlement of the weld.
Welding consumables commonly used for structural welding of C-Mn steels should be employed and conventional welding procedures/techniques should be used.
|AWS 5.1||E7018 (SMAW)|
|AWS A5.18||E703-6 (GMAW) with75% Argon 25% CO²|
|AWS A5.20||E70T-1 (FCAW)|
Note: Where the fabrication proves difficult to align with sufficient accuracy to ensure that no contamination by the hardfacing is likely during welding, it is recommended that a 309 type stainless steel welding rod (electrode) be used.
TRITEN™ ENGINEERING GUIDE
SUMMARY OF PROCEDURES
- Always use a radiused top tool when forming a press brake.
- Ensure that no hardfacing can contaminate the welds. If in doubt, use a AWS A5.4 - E309 Stainless steel consumable during fabrication.
- Use conventional welding consumables and procedures for fabrication to match the substrate requirements.
- Cap joints on the facing side with a matching hardfacing electrode from the Red Dog Armolloy range.
Examples of Practical Application
For further information, please contact Kubes Alloys directly.