Please choose your delivery country and your customer group
Among duplex stainless steels, the lean duplex family is a quite new family, still in expansion. It allows a good corrosion resistance, most of the time over that of a standard 4301 austenitic grade, to high mechanical properties, far higher than that of a 4301, and to a low amount of expensive alloying elements such as nickel compared to that of a 4301. But when these grades are produced in high diameter bars, they often present a bad toughness and a poor machinability, these properties being critical when trying to use such high diameter bars in various applications. For example, the well-known 4062 and 4162 grades present an impact strength below 100 J at 20 °C and below 50 J at - 46 °C on diameter 73mm bars. Moreover, their machinability in terms of tool wear and chip breakability is below that of 4301 grades, especially when these last ones are of an improved machinability version, such as UGIMA. The poor machinability of these lean duplex grades is mainly due to their high mechanical properties which induce high cutting forces on the tools during a machining operation, thus, rapid tool wear, and is also due to their very low sulphur content (less than 10ppm) which does not help the chip breaking contrarily to what happens on a 4301 grade with 0.025%S. It is the reason why UGITECH developed these last few years the 1.4669, a new lean duplex grade with a lower nitrogen content and a higher copper content in order to improve the toughness of this kind of grades and to lower the tool wear rates when machining them via a decrease of the cutting forces on the tools. Moreover, a control of the inclusions in the grade was performed in order to improve the chip breakability of the grade when machined. Of course, this new grade keeps a corrosion resistance over that of a standard 4301.