Seven years strong with Forta


Sun Hydraulics wanted a high-strength stainless steel to replace 316 in the exterior of its hydraulic cartridge valves. The comparatively low tensile yield strength of 316 was causing failures.


Sun Hydraulics pioneered the use of a new product, Forta duplex stainless steel. The choice was based on its high tensile yield strength coupled with good corrosion resistance, machinability and competitive price.


Steel grade: Outokumpu Forta LDX 2101
Product form: Bar
Florida-based Sun Hydraulics are leading designers and manufacturers of high-performance screw-in hydraulic cartridge valves. Though small in size – the smallest only 2 inches (50.8 mm) in length – these critical components are used to control force, speed and motion in massive machinery ranging from earth-moving equipment to bucket lift applications used by power companies to access power lines.

Sun Hydraulics prides itself on being a quality-conscious trailblazer, particularly with regard to its choice of materials. In its stainless line, the company formerly used standard 316 austenitic stainless steel to manufacture its external valve components, but began looking into alternative options after discovering that 316 was not holding up as well as required.


Bold pacesetter

This was back in 2009, when Outokumpu LDX was a little-known novelty. “We heard about it through our sister facility in Coventry, UK and began testing Forta LDX 2101,” says Surry McFaul, Metallurgical Engineer at Sun Hydraulics.

In a bold move from this industry pioneer, Sun Hydraulics began using the high-strength lean duplex grade in valve manufacturing. “The main reason we switched to Forta LDX 2101 was its tensile yield strength, which ranges from 65 to 124 ksi (kilopounds per square inch). The range for standard 316 is 25–50 ksi. We needed the lean duplex as strong as or even stronger than Sun’s standard valve body made of mild steel,” says McFaul. “LDX 2101 matches 316 also in its corrosion resistance. This is important, since the upper half of our valves is exposed to the elements. The competitive price was another asset in its favour,” she adds.


Catching on in food industry

Good machinability was a further priority.

“Both our suppliers and our in-house Lathe machines these valve bodies, and the process is tricky. The exterior includes a hex at one end of the body and threads at the other end. We make it by putting 12-foot bars in a lathe through a bar feeder and drilling and boring the inside and turning, threading, and grooving the outside,” explains McFaul. The steel is supplied in bar form by Outokumpu’s Stainless Bar manufacturing facility in Richburg, South Carolina. “We have been pleased with their cooperation. Outokumpu helped us find the optimum pickling solution to remove embedded iron from Avesta Finishing Chemicals.” McFaul sees growing potential for the use of stainless steel in the valve industry. “It is definitely catching on. There are customers in sectors such as the food industry that cannot use mild or plated steel. Many of them are discovering that we have these stainless cartridge valves.”

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