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Choosing Stainless Steel

We’ve been asked recently why surgical instruments generally aren’t manufactured from 440 stainless steel, which is a good question. 440 would generally be used for cutlery, swords, it can also be hardened up to 58 Rockwell, making it much harder than the higher of the 420 range stainless steels that are normally used for surgical instruments.

I think the main reason would come down to the slight pliability on the 420 stainless. 420 offers a bit of ‘give’ when hardened which is perfect for artery forceps, needle holders, dissecting forceps and means they are not too brittle. 440 also has a lot more carbon in it, which is the reason it can be made a lot harder; this may have an impact when washing and sterilising, as if not dried or processed correctly, there could be an increased risk of corrosion, however, 440 also has a lot of chrome, so bright polished finish should counteract this.

This is worth a read for some further education  http://en.wikipedia.org/wiki/SAE_steel_grades

ISO 7153 does highlight that 440 can be used for items that are required to be very rigid and hard, such as scalpels and shears, so perhaps it could be considered as an alterative for dissecting scissors, where a tungsten carbide edge is normally required. with a higher chrome content, it could be argued that it will wash better.

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Daniel Coole has been involved in the surgical instruments and the medical device industry for the past 17 years and is the Managing Director of innovative surgical instrument manufacturer, Surgical Holdings. Daniel is also the Vice Chairman of the Association for British Healthcare Industries Surgical Instrument Group.

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