The strength, toughness and hardness of UNS R30035 – between 180-230 ksi Yield Strength, and up to 51 HRC – depending on whether produced to meet NACE MR0175 / ISO 15156 or AMS 5844 / AMS 5845 make this a difficult alloy for our customers to tackle, unless they have prior experience. This is probably why Broder Metals Group are frequently asked for advice on how to machine UN S R30035.
So, while we are not machinists ourselves, we have gone out to seek the best advice we can, and are indebted to Thomas C. Williams, Applications Engineer – Energy of Carpenter Technology Corporation for the advice below.
While pointing out that the material’s machineability depends on the manufactured condition (e.g. to AMS 5758 – solution heat treated and centreless ground only, to AMS 5844 – solution heat treated and cold drawn, to AMS 5845 – Solution heat treated, cold drawn and aged, or Solution heat treated, cold drawn and aged to be compliant to NACE standard MR0175 / ISO 15156) the advice is that following parameters can be used:
Speed and feed rates:
- Drilling: 7.6 m / minute (25 sfm) and 0.1 mm / rev (0.005 in / rev)
- Turning: 9.1 m / minute (30 sfm) and 0.254 mm / rev (0.010 in/rev)
- High speed steels and carbide tools can be used
- Recommended cutting fluids include soluble oil, sulphured oil or chlorinated oil.
We would remind that the material contains 33-37% Nickel, 19-21% Chrome, and 9-10.5% Molybdenum, small additions of Titanium and Iron (1% max each), Carbon, Manganese, Silicon, Phosphorous and Sulphur (all less than 0.15% each). Cobalt is the balancing element (around 33%), and all sensible precautions must be taken to avoid any dust being inhaled or being in contact with bare skin.
In addition, we have been told by machinists who have produced bolts on our behalf for customers in need of full supply, that Alloy 718 can be taken as a base for machining, but that the machinist must take into account the difference in Yield Strength and Hardness between the 2 materials.
Finally, we would caution machinists and fabricators that exposure to temperatures above the recommended aging levels may result in a significant (and non-reversible) loss of strength caused by the reversion of the cold worked metallurgical structure to a much softer annealed structure. Of course, the recommended ageing levels also depend on the specification the material is aimed at and the properties aimed for – for further information on this point see article 2 and article 3 in this series.
Broder Metals Group hope that these articles are useful and would welcome enquiries for our stock range and any questions not covered.
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