Casting testing and inspection

Published - 4th Dec 2014

At Haworth Castings, we manufacture high-quality sand and gravity die castings to meet an extremely broad range of customer requirements in the defence, medical, marine, automotive and energy markets.

Each and every casting must meet exacting specifications in terms of its mechanical properties, dimensional accuracy and tensile strength.

The casting process is a highly intricate one that involves finely balancing many different variables such as material composition, cooling rates and other factors. Due to the complexity of the process, defects can occur but we employ a comprehensive range of non-destructive testing and inspection techniques to provide quality assurance.

The nature of the tests and the frequency are generally driven by our customers’ requirements and, in this blog, we look at the most common techniques used.

Spectrographic atomic absorption

At the foundry, we conduct chemical analysis to verify the composition of every metal melt before it is poured to ensure that it meets BSI standards. This is vital because the chemical composition of an alloy will have a major effect on its performance.

Using this process, a sample of the metal is evaluated by spectrographic atomic absorption to provide a breakdown of the chemical constituents (e.g. the varying proportions of magnesium, copper or zinc). This allows us to keep a check on the chemical constituents and make any adjustments if required.

Non-destructive testing

In addition to testing during the manufacturing phase, non-destructive testing (NDT) is also conducted at the end of the production process. This is carried out at a third-party test facility run by Inidam to provide our customers with independent verification.

The two most commonly used NDT tests are:

Radiographic imaging

Radiographic inspection is one of the most effective methods for detecting defects, such as porosity. Traditionally, film techniques have been used but, increasingly, digital methods are employed due to the environmental benefits.

As part of the radiographic process, X-rays are projected towards the casting. Some of the X-rays are absorbed by the casting while others pass through and are captured by digital or photographic film detectors on the other side. Visual inspection of the resulting images reveals any internal defects or variations in quality.

Penetrant testing

This process can detect tiny cracks, pores or other surface discontinuities on a wide range of ferrous and non-ferrous materials.

The castings are dipped into a penetrant testing liquid, which is drawn into any cracks by capillary action. An inspection is then performed under ultraviolet light. The penetrant liquid contains materials that fluoresce under this light to indicate the presence of any defects.

This technique is more cost effective than radiographic imaging but it can only detect surface flaws rather than internal porosity or shrinkage.

At Haworth Castings, we offer UKAS-approved independent testing and inspection services to meet the most demanding specifications for sand and gravity die castings. Contact us today at: sales@haworthcastings.co.uk or call +44 (0)1794 512685 to find out more.

For further information about Inidam’s NDT work, please go to: www.inidam.com

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