Chocky Bars and Blocks: selecting, cutting, forming and welding

“Chocky Bars”, or White Iron XT Bloks, are a type of duplex wear plate that combine the extreme wear resistant qualities of a cast white iron, overlaid onto a shock-absorbing mild steel backing plate.

They are an extremely popular product as they are a highly resistant to wear and impact, while also being versatile and easy to fit.

Named Chocky Bars or Chocky Blocks due to their similar appearance to a bar or block of chocolate, it is their unique design and notched backing that make them easy to cut to size and form (bend into place) – offering tailored wear protection on flat and contoured surfaces.

This makes them perfect for providing wear protection on excavator or loader buckets – where they are usually welded to high impact areas and/or to teeth and adaptors.

However, they are also commonly used on drag lines, or in chutes, rock boxes, bins, hoppers, and other areas that see high impact.

While Chocky Bars or Chocky Blocks are often used in preventative maintenance as a protective wear part on key areas, they can also be used to quickly patch or repair damaged areas to avoid long periods of plant downtime.

How to cut Chocky Bars:

Cutting Chocky Bars or Blocks is best done using high pressure water jets. It is not recommended to use thermal cutting procedures such as plasma cutting, arc-air or an oxyacetylene (oxy) torch as there is a high risk of cracking and delamination due to localised heat penetration.

If the Chocky Bar has a section thickness at the notch of less than 25mm then it can be cut using an angle grinder, or using the following procedure:

1.    Secure the Chocky Bar or Block to be cut with a vice or clamp.

2.    Notch the backing plate at the pre-existing notch.

3.    Notch the white iron to a minimum of 3mm deep, opposite the notch in the backing plate – noting that that deeper the cut, the cleaner the Chocky Bar or Block will break.

4.    Wrap the Chocky Bar or Block with a rag and gently hit with a soft faced mallet. It should break cleanly where you have cut the notches.

How to form Chocky Bars:

“Forming” your Chocky Bars is the process of bending them to match the contour of the material or machinery they are being attached to.

First, ensure both the Chocky Bar and the surface it will be welded to are clean and free of dirt, scale, grease, water, and paint to ensure a good surface for welding and reduce the chances of weld cracking.

The forming process then varies slightly, depending whether you are forming the Chocky Bar to match an inside curve or an outside curve.

Outside curves:

1.    Tack weld one end of the bar in at least three places, using at least a half inch weld for each deposit.

2.    Using a soft face hammer, hit the unwelded end of the Chocky Bar to bend (form) the bar to match the radius of what it is protecting.

3.    Stitch weld the Chocky Bar into place, as per the Welding Procedure below.

Inside curves:

1.    Tack weld one end of the bar in at least three places, using at least a half inch weld for each deposit.

2.    Starting in the centre of the Chocky Bar, hit it with a soft faced hammer to bend (form) the bar to match the radius of what it is protecting

3.    Stitch weld the Chocky Bar into place, as per the Welding Procedure below.

Chocky Bars and Blocks Welding Instructions

OHS: Prior to commencing any welding work, a risk assessment should be carried out to identify any hazards, assess the risks associated with them, and implement risk control measures using the hierarchy of control. For more insight see Cutting Edge’s Wear Parts Welding Guide.

1.    Ensure both the Chocky Bar or Block and the surface it will be welded to are clean and free of dirt, scale, grease, water, and paint to ensure a good surface for welding to reduce the chances of weld cracking.

2.    Clamp the Chocky Bar or Block in place and tack weld one end in three places, using at least a half inch weld for each deposit.

3.    Follow with the forming process outline above if required.

4.    Stitch weld the Chocky Bar or Block into place. Weld in runs, with each weld at least 50mm apart and at alternating ends or sides to minimise heat build-up and heat penetration. Please note that it is normal to see some cracking in your Chocky Bar or Block during the welding process.

5.    The maximum temperature reached during the welding process should be 200℃. Regularly use a thermal crayon or laser temperature probe to check.

DO NOT:

  • Weld continuously which will cause the Chocky Bar or Block to warp, delaminate, and crack.
  • Deposit weld within 2mm from the bond zone / joint between white iron alloy and the mild steel backing plate.

 

Welding Consumable Guide

Welding Type AWS Standard AS/NZS Standard (Classification)
MMAW (Stick) AWS A5.1 – E7018 AS/NZS 4855-B (E4918 A U H5)

 

FCAW (Flux Cored Wire) AWS A5.20-79, Class E70T-1C-H16 AS/NZS ISO 17632-B (T49 3 T1-1 CA-K-U H10)

 

MIG (Solid Wire) AWS A5.18 – ER70S-4 AS/NZS 2717.1 (ES4-GM/C W503AH)

 

 

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