Technical Presentations at the January 2005 Meeting
Dr Baxter showed how the cost of different alloying elements influenced
the price of stainless steel and influenced the cost of both corrosion and
mechanical performance. The cost indices are significantly reduced by
using the lean duplex stainless steel, LDX 2101®.
The corrosion performance of the grade was discussed with particular
emphasis on its resistance to both general and localized corrosion. In
general terms, LDX 2101®
considerably outperforms, for example, 1.4307 /type 304 stainless steel.
The mechanical performance of the alloy was discussed. The proof strength
is nominally twice that of 304-type stainless steel. The main implication
of this is that material utilization is potentially improved, by as much
as 30-40%. This can have attendant benefits associated with material cost
and unit weight.
Baxter described how LDX 2101®
should be considered as a "tolerant" duplex stainless steel when
presentation finished by describing actual and potential applications for
this grade of stainless steel. The common theme for applications is that
is a high strength corrosion resistant alloy. As such, it is frequently
considered a substitute for C-Mn steel, galvanized steel or painted
systems. It is even considered an alternative in some 304 or ferritic type
stainless steel applications, particularly where strength is an issue.
Magnesium is used successfully on aircraft; including both military and
civilian fixed wing and rotorcraft applications. The main benefit of
using magnesium is its low density, being only 2/3 that of aluminium.
Lightweight is of significant benefit to not only the aerospace industry,
seeking to improve performance and pay load capacity, but also other areas
of transport. Most noticeable
growth over the last 15 years has been in the automotive industry who have
embraced the use of Magnesium. The
growth has been driven by at least 3 themes:
Need to improve fuel
economy and emissions
Applications range from thin wall covers to gearboxes and most recently
engine block applications.
It is anticipated that magnesium usage will increase in aircraft, for
similar reasons of environment (already seen in the automotive market) and
payload performance. The
benefits of weight reduction being far more beneficial and valuable in the
air transport market.
So what are the barriers to change? Two
themes often arise when discussing Magnesium for new applications: Fire
and Corrosion. Fire is not an
issue unless the melting point of the component is exceeded.
General corrosion resistance of Magnesium alloys has improved
significantly as this attribute has been designed into the alloys.
Galvanic corrosion requires design input if the component is likely
to be exposed to potential galvanic situations.
The advent of new high temperature alloys (WE43, Elektron 21) have raised the melting point (further reducing potential for fire) and offer vastly improved general corrosion performance. It is important that specifications and advisory notes recognise the improvements made in the last 20 years of alloy development and application.
Seawater duties cover Cooling water, Firewater,
Washdown, Injection water and Ballast water.
Equipment comes in the form of Seawater
Lift Pumps, Seawater Filters, Heat Exchangers, Pipe and Fittings,
Firewater Pumps, Deluge sets and Nozzles.
Typical conditions are:
Each of the
following materials was discussed with respect to suitability:
In summary, none of the above materials is perfect for all applications, rather it is the case that different materials will prove more suitable for different applications.