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Technical Paper
Soft bending anchor forming
Flat bar has a profile which is quite thin so any oxidation/chemical reaction has a large effect on strength of an anchor made from flat bar.
Round rods, when looked at under a microscope have quite a rough surface where acid in the furnace atmosphere or acid that has condensed can attack a larger surface area, also the control of size is not as good as the cold drawn wire therefore;
Anchors made from cold drawn wire are best. We then need to look at how the anchor is formed, there are two methods. • By pressing to shape • By bending using a soft bend usually by machine from CAD drawings
Pressing uses greater force which can create marks/faults including changes in cross sectional area which can cause weakness or areas where faults will develop.
Soft bending gives the best and most accurate anchors.
We then need to consider which type of alloy will be best for our application, we need to consider:
Press anchor forming
• The temperature at which the anchors will be used • The conditions that will be present in the application • The loads that the anchor will be subject to
• The selection of which alloy we should use is not easy and in many cases it is a compromise
Press anchor forming
In general the higher the temperature the higher the nickel content of the alloy to give good oxidation resistance at high temperature, BUT in areas where there are high sulphur contents present we find that nickel forms what is known as sigma phase, this makes the anchor very brittle and will cause the anchors to fail! This is applicable in incineration and cement where alternative fuels are used.
Soft bending anchor forming
Soft bending anchor forming
Upper anchor manufactured by press, lower anchor made by soft bending March 2018 Issue
Microscope view of the surface of wires ENGINEER THE REFRACTORIES 15
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