Ferrite Inspection (Ferrite Scope)

Ferrite inspection is a fast, non destructive weld testing method used to measure the amount of delta ferrite content in Austenitic stainless, Duplex stainless steels and Austenitic weld metals as part of our weld inspection services.

Ferrite inspection is a widely used method to ensure the correct levels of ferrite are present in both parent materials and weld metal deposits. Ferrite inspection is used in a whole range of different industries, including but not limited to fabrication, mining, chemical, and power generation. Ferrite inspection is useful to verify whether the heat treatment applied to the material being tested reaches the correct performance balance, along with showing any damaging third phases in the materials and highlighting any deficiencies in the strength of the weld.

Differing Specifications

Different types of stainless steel require different amounts of ferrite content, depending on which job they are needed to perform. There are typically two types of stainless steels where ferrite testing is carried out, these are Austenitic and Duplex, which both contain complex microstructures of which ferrite is a component. There are differences in the two types that means the ferrite content will determine different things about the stainless steel. The ferrite content in duplex stainless steel will determine the mechanical properties of the steel along with its resistance to corrosion. In austenitic stainless steel, these things will also be determined, along with its weldability. As such, both of these types require different levels of Ferrite to serve their intended purpose. For example, an ideal ferrite content percentage for austenitic stainless steel would be within the region of 4%-8%, which is effective in controlling problems such as micro-cracking of welds as they cool. In Duplex stainless steel, the ideal percentage is somewhere around 50%, which will give the steel the required strength and toughness while reducing the risk of corrosion over a long period of time. Some specifications for duplex stainless steels allow between 30 – 70% ferrite.

Ensuring that materials have the correct amount of ferrite is vital. If the specified levels are incorrect, this can have a detrimental effect on the service life of a part, its corrosion resistance and overall durability. Additionally, when ferrite levels are outside the specified range in stainless steel weld deposits it can become susceptible to hot cracking. Ferrite inspection is key in determining that the amount of ferrite is within specified limits in contract specifications and certain construction standards for some products.

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Ferrite inspection is a common specification requirement in the manufacture of pressure vessels, pipework, storage tanks etc.

As one of the leading companies for weld testing in the UK, our market-leading portable Fischer FMP30 Feritscope is capable of measuring the ferritic content, expressed as either percentage (%) quantity or FN (Ferrite Number) in a vast range of components, large or small. Our Ferrite checking service can be performed at customer sites anywhere in the UK, or at the SureCheck weld testing facility in Cannock.

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