Processo de fabricação de placas de desgaste

Wear Plate Manufacturing Process and fabrication

WEAR PLATE MANUFACTURING PROCESS AND FABRICATION MANUAL: This manual states practical details on how to cut, create and fabricate wear-resistant overlay wear plates. If not otherwise specified, then the processes we are going to give rundown details of applying to standard compositional grades of overlay with structural carbon steel substrates. There are important instructions for overlay wear plates with, such as high strength steel or stainless alloy substrates are made available where needed.

Details about WALDUN Wear Plates Ranges

The WALDUN overlay wear plates ranges which were established to resist abrasion, erosion and impact at either ambient or higher temperatures. The ranges consist of various tungsten carbide alloys or hardfacing chromium deposited onto an alloy substrate or carbon steel.

However, Plasma-arc has been the best method of the cutting overlay plate and is well recommended. Due to the fact that high chromium and carbon contents of the hardfacing overlay hinder the use of oxy-fuel and almost all mechanical means. These particular properties of the very hard overlay alloy and a ductile substrate enables these materials to be manufactured and fabricated into complex shapes, such as convex or concave curves.

Different types of methods such as plug welding, bolting and stud welding are normal use for installation of the wear resistance liners into structures. Fabrications can be manufactured by conventional welding of the carbon steel substrate in wear plate manufacturing process.

wear plate manufacturing process | CUTTING PROCESS

In the wear plate manufacturing process | cutting process, both WALDUN’s tungsten and chromium carbide alloy hardfacing overlay put on an act like stainless steel. Meanwhile, this prevents the use of conventional shearing or oxy-fuel flame cutting processes for it. However, any of these 3 cutting methods can be used. They are Carbon arc, plasma arc or Abrasive saw.

Here are the full details about the different cutting processes use below;

Plasma Arc Cutting Method: 

All overlay wear plates, even those with special substrate can be cut with ease making use of a handheld or machine mounted torch by the use of either air or inert gas plasma-arc method. The typical systems feature a lower limit of 150 amp power supplies and the higher the amperage used, the quicker the cutting speed can be accomplished.

Moreover, overlay wear plates can be cut from either side, but in order to fit in with the natural bevel formed by this process. It is best that cutting occurs from the alloy side. Also, the cutting speed should be modified to lower the accumulation of slag on the underneath of the plate.

Carbon Arc Cutting Method:

Carbon Arc cutting can also be known as Gouging. In this particular method, a conventional constant current DC welding power supply and compressed air supply, with a minimal OCV of 60Volts or 80Volts which is most time the best is needed for carbon arc cutting and gouging. An arc voltage within the range of 35 to 56volts is advisable.

In the table below contain the typical parameters for copper-coated gouging rods.

Diameter		Amperage (DC Reverse Polarity)	Minimal Air Flow
Up to 6.3mm	1/4”	250-400A	3cfm @ 40psi	100 l/min @ 3 Bar
9.5mm & upward	3/8″	350-600A	6cfm @ 90psi	200 l/min @ 6 Bar

However, in carbon arc, the cutting should be done from the carbon steel side of the plate by first sketching out the cutting lines. And then proceed to dot punching to make sure there’s enough visibility throughout the process. Most importantly, endeavour to get rid of all slag with an abrasive grinding disc after cutting plates from the substrate side.

Abrasive Saw Method:

With abrasive saw fitting with silicon carbide wheel, limited straight-line cutting can be accomplished.

Cold Forming

Majority standard grade of WALDUN overlay wear plates can be cold-formed into conical or curved parts employing either rolls or press brakes. Meanwhile, WALDUN has only minimal form-capability and a number of a particular chromium/tungsten and tungsten carbide grades can most effective use as fabrications and flat profiles.

Direction of Rolling

At any time achievable, plates should be formed with the weld beads structured within the direction of rolling.

Minimum Diameter

The least approved diameter to which WALDUN overlay plate can be formed will be determined by the type of substrate, thickness of the plate and whether the bend is convex (with alloy facing on the outside) or concave (with alloy facing on the inside).

Typical least diameters for cold forming plate shown in the table below:

WALDUN Grades	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”)

Moreover, when making use of pinch rolls or pyramid, it’s more advisable that the top roll is covered with a sleeve to avoid destruction to the hardfacing. Also, this need to be fabricated from 12mm (1/2″) thick carbon steel and exact size of 50mm (2″) bigger than the roll diameter to enable installation and elimination and to avoid binding.

However, when applying a brake press from minimum diameter pipe, cones and square to round transitions. It’s best that a hydraulic press is adopted for quality results. Forming can also be executed with a female and male die, employing a radiuses main tool (minimum of 38cm/ 11/2″) over a ‘V’ block.

Hot Forming

In hot forming, for thickness greater than 20mm (3/4″) forming could be aided by the implementation of heat either by local method that’s applying a broad flame oxy-gas torch or through a general method for bigger sections in a furnace. In order to be sure that there are no obvious changes in the properties of the plate, hot forming temperatures shouldn’t be over 650°C (1,200°F), with furnace soaking times of not more than one hour. Perhaps, high temperatures can be used in some rare circumstances.

In addition, more details on forming individual plate thickness, grades and specific forming techniques can be gotten straight from WALDUN. During fabricating square to round transitions, hot forming is only endorsed when 90° corners are required.

Special Substrates:

However, in a situation where high strength alloy steel substrates are applied, be it in cold or hot forming, extra power will be needed to form the plate to the exact diameters as conventional carbon steel substrates.

FABRICATION

Different Flat profiles and formed segments can be fabricated into bigger items or completed structures making use of welding processes.  Liners may be fastened to already existing structures through bolting or via different welding techniques. In addition, every structural welds need to be applicable to the substrate.

Methods of attachment for Fillet Welding

The simplest method for connecting WALDUN overlay plate to an existing structure is through the fillet weld. Enough caution must be taken to make sure that the weld is only applied to the substrate without having it overlay the hardfacing or its penetration. Because this can result in carbon pollution and embrittlement of the weld. And it’s best carried out through stopping the fillet at exact 3mm (1/8″) below the alloy/base plate interface and it should be well visible on a ground edge.

Any of these three general welding processes can be used such as:

Gas metal arc welding (GMAW) by use of solid wire.

Shielded metal arc welding (US – SMAW) / Manual metal arc welding (UK – MMA)

Flux-cored arc welding (FCAW) by use of gas shielded or open arc wires.

Selection of welding rods/wires

Selection of welding rods occurs in the place where the overlaid plate has a standard carbon steel substrate and the structure towards the plate that is to be struck. Also, it consists of carbon steel or steel that doesn’t need preheat. Hence the following categories of consumables can be applied such as:

Solid Wire for CO2 welding:  AWS A5.18 – ER70S-3 EN440 G/W 2Si or ER70S-6 EN440 G3 Si1

Coatedrods:AWSA5.1-E7016EN499E424B12HSorE7018EN499E463B32HS

Flux-cored wires:  AWS A5.20 – E70T-1 EN758 T460 RC3H10 or E71T-1 EN758 T463 PM1HS.

But, if the structural member needs preheat, maybe due to its chemical composition, yield strength or thickness. Then a grade of welding rod or wire should be selected in accordance with standard practice for that base material.

For instance:  AWS A5.5 – E8018B2 (EN 1599 ECr.Mo1 B32HS)

However, if the WALDUN overlay has an alloy or a stainless steel substrate and the structure for it to be welded is a high alloy manganese steel, by-hardened steel, a 304 stainless alloy oratypeAISI-410 stainless alloy. Therefore an appropriate different metal alloy, for example, an AWS A5.4 – E309 (EN1600 E23.12 LR21) stainless type rod (electrode) or wire should be applied.

Methods of Attachment for Plug Welding

In this method, the WALDUN overlay plate can be connected to another plate or structure through plug welding by a series of holes.  Each of the holes is expected to have at least a minimum of 25mm (1-inch diameter – perfectly set at the range of 300mm – 600mm) spacing.

Either carbon-arc gouging or plasma-arc cutting method should be used to cut the fixing holes from the substrate side. This will help to avoid chromium and carbon contaminating carbon steel. However, with gouging plates of thickness 9.5mm (3/8″) and above, it is most advisable that the hole is first drilled into the substrate to end short of the alloy interface before beginning with gouging.

Also, every slag should be eliminated from the fixing holes through grinding or hammering. The plate is then connected to the structure through welding the outside diameter of the hole by 360° and then proceeds with filing the remaining space up.

However, employing the same method as for fillet welding, it will be used to decide the thickness of the weld and should end 3mm short of the overlay alloy layer. The weld is prevented from abrasion through capping with the appropriate wear resistant alloy using WALDUN Armolloy tubular hardfacing rods (electrodes) once the weld is filled up to the right capacity.

Method of Attachment for Stud Welding

In this method, a common carbon steel stud can be welded with easy to the back of the WALDUN overlay plate make use of many types of stud welding equipment. The least requirement for stud size is 19mm (3/4″) and the number and spacing of the studs will rely on the size and shape of the plate being connected.

Studs with a diameter higher than 12.5mm (1/2″) may be hand welded with the manual metal arc procedure operating an E7018 rod. Due to this, only a fillet weld is applied rather than a full penetration weld, a higher quantity of studs will be required to fasten the plate.

Methods of attachment for Countersunk Bolts

The appropriate holes for countersunk bolts may be manufactured by direct plasma arc cutting method by an orbital tool post, through piercing or gouging a straight hole and welding a pre-machined thrust in place, or through the means of composition of direct drilling or gouging.

The least advisable bolt size is 9.5mm (3/8″) diameter and the number and spacing needed will depend also upon the size and shape of the plate. The completed countersunk hole should permit the flat-headed bolt to sit at exact 4mm below the surface of the plate. However, capping can be used to preserve it from abrasion with the right WALDUN Armalloy tubular hardfacing electrode.

Direct Plasma Arc Piercing

In direct plasma arc piercing, you manufacture a suitable countersunk hole. Meanwhile, the direct clearance hole should be cut first when working from the hardfaced side. And next is to cut the countersunk part at an angle to suit the fixing bolt using the plasma torch tilted.

Pre-machined Inserts

The specific pre-machined inserts can be used to restore overlay plates by first cutting a direct hole in the plate and welding the thrust in place from the carbon steel side. It’s well recommended to apply Plasma arc cutting from the hardfaced side of the plate. Due to the fact that it establishes a normal tapered hole which gives more aid for the insert.

The insert should be assembled with a taper of about 3 degrees to fit the hole and a chamfered weld composition cut into the base. This is also welded into place from the carbon steel side utilizing a low hydrogen electrode (AWS 5.1 – E7018 or 7016 type).

Gouging

This technique is generally used on-site if plasma-arc cutting is unavailable. Moreover, if a large quantity of holes is needed, then it’s more recommendable to use welded inserts and gouging should mainly be use to cut the clearance hole.

A substitute method is made available for one or two holes including gouging a straight hole from the carbon steel side. The countersunk part is then formed through gouging a taper from the hardfaced side. The abrasive cone/plug shaped grinding stones can be used to clear the holes.

STRUCTURAL WELDING

WALDUN overlay wear plates may be fabricated through welding the mild steel substrate using ordinary mild steel or low hydrogen electrodes. The following information is a general lead to welding WALDUN overlay wear plates.

Enough caution should be taken to make sure that all structural welds end short of the hardfacing alloy layer. The only welding achieved on the hardfaced part of the plate will include the capping of joints, for wear preservation, with a suitable WALDUN Armalloy tubular hardfacing electrode.

Fillet welds

In fillet weld, it involves grinding the edge of the plate to eliminate all slag and scale remaining from cutting. Maximum guidance is needed to make sure that the weld is used on the substrate only and it doesn’t overlap the hardfacing or its penetration zone. If not, it can cause carbon pollution and embrittlement of the weld and the adjacent area. However, it is best accomplished by terminating the fillet exactly at 3mm (1/8″) below the overlay/base plate interface. Thereby aiding with clearer visibility on the ground edge.

Butt Welds

Butt weld is a type of partial penetration which involve cutting a bevel into the carbon steel base either through flame cutting or gouging.

A 2mm to 3mm (1/16-1/8″) ‘land’ must be left to avoid it burning-through to the hardfaced layer during the welding process.  Fit and tack segments, afterwards weld by applying a similar method as conventional joining.

Full penetration butt welds need the hardfacing (involving alloy penetration zone) to be permanently eliminated from the joint area by grinding/gouging back to at a minimum 6mm (1/4″) past the weld joint part.  Fit and tack the bevelled segments, afterwards apply a similar technique as conventional joining.

Welding Technique and Consumable Selection in wear plate manufacturing process

During this wear plate manufacturing process, the land shouldn’t melt root pass into the hardfacing as this can cause carbon pollution and embrittlement of the weld. Welding consumables mostly make use of for structural welding of C-Mn steels must be implemented and conventional welding process should be used. For instance;

AWS 5.1	E7018 (SMAW)
AWS A5.18	E703-6 (GMAW) with75% Argon 25% CO²
AWS A5.20	E70T-1 (FCAW)

Be aware that where the fabrication finds it hard to align with enough accuracy to make sure that no contamination of any form by the hardfacing is likely during wear plate manufacturing process. Then it is best advisable to use a 309 type stainless steel welding rod (electrode).

SUMMARY OF WEAR PLATE MANUFACTURING PROCESS

Wear plate manufacturing prccess ensure to always use a radiused top tool when forming a press brake.

Make sure that no hardfacing can contaminate or pollute the welds. If not completely sure, then use an AWS A5.4 – E309 Stainless steel consumable when undergoing fabrication.

Make use of conventional welding consumables and processes for fabrication to meet the substrate requirements.

Also, Cap joints on the facing side with a similar hardfacing electrode from the WALDUN Armolloy range.

Examples of Practical Application

Fillet Welds:

A bar or strip which is necessary to ensure no contamination by the hardfacing when fillet welding.

Hardfacing ceased short of plate edge, or elimination by gouging, manufacturing a mild steel land

Fillet welds can be more intensify by welding a carbon steel angle over the joint or removed by the means of using only the angle support.