Hi guys, I daily machine S80, S130, S143 corrosion resistant steel. Can anyone provide information on these steels i.e. which group they fall into (300 or
400 series), hardness values & whether they are austenitic or marstenitic. I can't seem to nail down any info apart from the following:
S143 is a precipitation hardenable stainless steel. The grade is known as FV520B and contains about 0.05% Carbon, 14% Cr, 1.5% Mo, 5% Ni and 1.5% Cu. This is the same basic steel as S144 and S145 aswell the only differnce being the heat treatment given and thus the properties achived. S144 is stronger then S143 but has lower toughness. S145 takes this a step further but there is a significant loss of toughness. This is primarily a British grade (FV - Firth Vickers, ex Sheffield) used in the European aerospace industry and as such is not part of the AISI series. S143/4/5 is not AMS
5659. AMS 5659 is 15/5PH grade which has less Ni and Mo but a bout 3.5% Cu. This too has several heat treatment conditions.
Just to add about specs. The British Standard 'S' series aerospace specs are widely recognised in the British and European aerospace industries but most of the grades have AMS equivelents and are thus named differently by the Americans.
Just a few examples: S155 = AMS 6417/6419/6527 - used to make aircraft undercarrages (and drive shafts in Formula 1) S132 = the main alloy used to make central shafts in commerial jet engines (and Formula 1 crankshafts) S82/156 = used in many commercial/military helicopters for gears in the main gearbox (and some Formula 1 cars / Bugatti Veryon)
On the drawings, AMS 5659 is offered as an alternative but is heat treated if used. Does S143 fall into the austenitic or marstenitic category? As the material is supplied in certain diameter lengths I take it the material would be cold drawn, but would they at any point be quenched and tempered or annealed?
Most precipitation hardening grades are supplied in 1 of 3 conditions:
Softened (annealed): typically 650 deg C for up to 12hrs - for forging.
Solutuion treated: 1050 deg C for 1/2 to 1hr, cooled in air or oil - for rough machining:
Precipitation hardened: depends on grade but notmally between 450 and
650 deg C for 1 to 6 hrs - final heat treatment usually with some finish machining or ginding before final use.
Unlike alloy steels, PH stainless steels are softer after solution treatment than after precipitation hardening which is why most maching is done after solution treatment. Normally these types of steels are not cold drawn but turned/peeled to produce a fine finish. The company I work for makes 15,000+ tonnes of these types of steels per year and the majority of this type of steel is supplied in the solution treated condition and bright finished.
As for 15-5PH (AMS 5659) as an alternative to S143, you need to be careHul what finish heat treatment condition is required. 15-5Ph has 5 or 6 different precipitation hardening treatments depending on the required combination of tensile strength and toughness. The conditions are H900, H925, H975, H1025, H1075 & H1150, the number refering to the final heat treatment temperature in deg Fahrenheit. The higher the temperature the more toughness is sachived but at the expense of tensile strength. Typicall
15-5PH is used in the H1025 condition which gives the best combination of both properties.
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