UGI® 4545 AIR H1150

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UGI® 15-5PH AIR or UGI® 4545 AIR is a PH (Precipitation Hardening) martensitic stainless steel of premium quality, mainly designed for aerospace purposes. It is used for parts requiring a combination of high strength and high toughness. This grade also presents a good resistance to fatigue failure. This is an Electro-Slag Remelted material (according to AMS 5659 type 2) using the most advanced technology in this field. This elaboration allows a good homogeneity and isotropy of the structure and high mechanical properties in longi-tudinal but also transverse direction. (Ferromagnetic)

The microstructure observed in optical microscopy is composed of homogenous martensite with niobium car-bonitride precipitates (white particle visible in SEM), and retained austenite whose fraction depends on the metallurgical condition. The nanometric precipitation Cu rich phase can be observed under

TEM. UGI® 15-5PH AIR presents a delta-ferrite fraction inferior to 1% (lower than UGI® 17-4PH AIR) according to AMS 2315, and a former austenite grain size finer or equal to 6.

UGI® 15-5PH AIR is produced by consumable ESR. The remaining inclusions are very small and are evenly distributed in the section. The following micro-cleanliness, according to ASTM E45/A is guaranteed: A,B,C,D (Thin) < 1.5 - A,B,C,D (Heavy) < 1

Related Standards

Equivalent Materials

This material data has been provided by Ugitech SA.

"Typical" values were obtained via a literature search. "Predicted" values were imputed via artificial intelligence technology. While we have placed significant efforts in ensuring data accuracy, "typical" and "predicted" data should be considered indicative and verified by appropriate material testing. Please do contact us if additional information on the the predicted data method is required.
All metrics apply to room temperature unless otherwise stated. SI units used unless otherwise stated.
Equivalent standards are similar to one or more standards provided by the supplier. Some equivalent standards may be stricter whereas others may be outside the bounds of the original standard.

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7.8 g/cm³

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Elastic modulus

20 °C

200 GPa

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100 °C

195 GPa

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200 °C

185 GPa

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300 °C

170 GPa

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300 °C

175 GPa

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16 %

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Hardness, Brinell

277.0 [-]

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Hardness, Rockwell C

28.0 [-]

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Reduction of area

50.0 %

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Tensile strength

930 MPa

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Coefficient of thermal expansion

0.0000105 1/K

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20 to 100°C

0.0000111 1/K

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20 to 200°C

0.0000115 1/K

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20 to 300°C

0.0000119 1/K

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20 to 400°C

Specific heat capacity

500 J/(kg·K)

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Thermal conductivity

16 W/(m·K)

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Electrical resistivity

7.1e-07 Ω·m

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Chemical properties




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14.5 - 15.3 %

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2.5 - 4.0 %

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4.5 - 5.5 %

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max., min: 5xC



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Technological properties

Application areas

UGI®15-5 PH AIR is suitable for

  • Aerospace as premium Aircraft Quality
  • Sensor manufacturing, e.g. pressure sensors
  • Medical Ancillary
  • Shaft, Gear
  • Fitting
  • Structural parts …

  • Corrosion properties

    UGI®15-5 PH AIR offers good corrosion resistance, sometimes similar to that of type 18 Cr-8Ni austenitic steels in some cases.

    Nitric acidGood
    Phosphoric acidRestricted use
    Sulphuric acidRestricted use
    Acetic acidAverage
    Sodium carbonateAverage
    NaCl (fog test)Good
    Sea waterRestricted use
    Oil/gasRestricted use

    Pitting corrosion : UGI®15-5 PH AIR is much more resistant to pitting corrosion than the classical 12% Cr martensitic stainless steel. The level of pitting potential is comparable to the supermartensitic 1.4418 and to the austenitic 1.4301 (AISI 304).

    Intergranular corrosion: The low carbon content of this steel (part of it is tied up with Nb) make insensitive to intergranular corrosion when heat treated properly according to previous recommendations.

    Other mechanisms of corrosion: UGI®15-5 PH AIR is resistant to fatigue-corrosion as well as to stress corrosion in some environments and de-fined conditions. Furthermore, good resistance to corrosion-erosion should be noted due to the association of high level mechanical properties and corrosion resistance.

    General machinability

    Because of its low sulphur content and its very good micro-cleanliness, UGI®15-5 PH AIR has a poor chip breakability which can induce difficulties during machining, especially in drilling or finish turning operations. If possible, most of the machining operations to obtain the final parts have to be done in the A-condition (solution annealed) state in order to avoid too important tool wears during machining. Machining after a “precipitation hardening” heat treatment is not recommended because the higher the mechanical characteristics of the UGI®15-5 PH AIR bars to be machined, the higher the tool wears (and thus the lower the machining productivity). In A-condition, rough turning tests (ap = 1.5 mm; f = 0.25 mm/rev) performed on drawn bars have shown that the cutting speed to have a flank wear of 0.15 mm in 15 min of effective cutting with a STELLRAM SP4019 CCGT 09T308E-62 tool is ~ 145 m/min whereas that of a UGIMA®4542 (17-4 PH with improved machinability) is ~ 160 m/min. Depending on the machining operation, the machining productivity of UGI®15-5 PH AIR is found to be 10 to 30% lower than UGIMA® 4542.

    Heat Treatment

    Heat treatments carried out on UGI®15-5PH AIR are composed of two steps:

  • Austenitisation, whose purpose is to get alloying elements especially Cu into supersaturated marten-site
  • Aging, whose purpose is to precipitate Cu (precipitation hardening) and, in some case to form revert-ed austenite to increase toughness. The mechanical properties, trade-off between strength and toughness, are adjusted by the aging temperature.

    Austenitisation: Solution annealing is performed around 1030-1050°C, and is interrupted by oil quenching or alternatively by air cooling for small section parts. In this condition (called condition A) hardness is intermediate because Cu precipitation hardening is not effective. Hence, the A-condition is often chosen to carry out machining or cold forming operations. In that case, we recommend performing a stress relief treatment at 300°C for 1 hour after austenitisation, in order to stabilize the material and avoid quench-cracking issues.

    Aging: Aging treatments are performed after solution treatment to make Cu rich phases precipitate and adjust me-chanical properties. After aging, the material is in the solution and aged condition, also called H-condition. Aging treatments can be performed between 480°C (condition H900) and 620°C (condition H1150). The condition H900 corresponds to the peak of hardening, for which the Cu precipitates induce a maximum of hardness. For higher temperature the hardness/strength decreases when increasing aging temperature, due to the growth of the precipitates. Beyond 580°C some reverted austenite is formed during the aging which results in an increase of the toughness but a drop of the strength. The condition H1025 is often chosen by customers because it leads to an optimal trade-off between strength and toughness.

    Softening: The lowest strength or hardness is obtained after the thermal cycle H1150M, consisting into of a solution an-nealing followed by a tempering at 760°C for 2 hours and an aging at 620°C for 4 hours. After this heat treatment cycle the mechanical properties are UTS = 780 MPa, YS = 710 MPa, HRC < 32 HRC, which is sig-nificantly lower than the condition A.

    Cond A1030/1050°C annealing
    H9001030/1050°C annealing Air or oil cooling
    + hardening
    1 h at 480°C/Air cooling
    H9251030/1050°C annealing Air or oil cooling
    + hardening
    4 h at 495°C/Air cooling
    H1025Annealing 1030/1050°C/ Air or oil cooling
    + Tempering 4 h at 550°C, Air cooling
    H1075Annealing 1030/1050°C/ Air or oil cooling
    + Tempering 4 h at 580°C, Air cooling
    H1100Annealing 1030/1050°C/ Air or oil cooling
    + Tempering 4 h at 590°C, Air cooling
    H1150Annealing 1030/1050°C/ Air or oil cooling
    + Tempering 4 h at 620°C, Air cooling

  • Hot forming

    UGI®15-5 PH AIR is suitable for forging. Reheating must be carried out at a temperature between 1150 and 1200°C, forging between 1200°C and 950°C. Cooling after forging must be performed in air or oil. The parts obtained in this way have to be heat treated (solution annealing and eventual aging, see previous section)


    Magnetic particle inspection and macro-graph

    UGI®15-5 PH AIR complies with AMS 2300: Frequency/Severity rating 0/0

    Macrostructure of UGI®15-5PH AIR is conforming to AMS 5659: class 1 to 4 are generally quoted severity A according to ASTM A604.

    Available products:

    ProductProfileSurface FinishingToleranceSize (mm)
    BarRoundSmooth Turnedk12 - k1322 - 115
    Peeled and polishedh11 - h10 - h922 - 115
    Centerless Groundh9 - h8 - h75 - 115
    Cold Drawnh95 - 21

    Other products: contact the supplier

    Surface Treatment

    Pickling procedure: UGI®15-5 PH AIR is pickled in the same way as 630 grade steel.

    If necessary, the following decontamination treatment process is recommended, to move iron particles for example:
  • 1/4 volume of 52% nitric acid (36° Baumé),
  • 3/4 volume water
  • Ambient temperature
  • Duration must be adapted
  • Wash carefully when the process is completed

    N.B.: the corrosion resistance of a stainless steel depends on many factors related to the composition of the corrosive atmosphere (chloride concentration, presence or absence of oxidizing agents, temperature, pH, ag-itation or no agitation, and so on), as well as to the preparation of the material (surfaces free from metal par-ticles, surface finish, such as hardening, polishing, and so on). Precautionary measures should be taken for certain tests such as the sodium chloride fog test (standard ISO 9227): for example marking labels (that might cause corrosion run-outs and reduce the test resistance time) should not be used on the sample.

  • Welding

    UGI®15-5 PH AIR can be welded without preheating, using most welding techniques: GMAW or GTAW (with or without filler wire), LASER, resistance or electron beam welding, etc. If the mechanical characteristics of the weld area have to be at the same level as that of the base metal, no filler metal or homogeneous filler metal (such as AWS E/ER 630) have to be used and a post weld heat treatment of precipitation hardening (see the different PH heat treatment on page 4) has to be performed on the weld. If the mechanical characteristics of the weld area does not have to be at the same level as that of the base metal, a filler metal such as ER308LSi (19 9 L Si) can be used.

    If no precipitation hardening heat treatment is done after welding, a stress relief heat treatment at 250/300°C could be useful to increase the toughness of the HAZ and avoid any risk of cold cracking due to their as-welded martensitic microstructures. Furthermore, it should be restated that the welding design should make allowance for the care required with all high steels with high proof stress: avoiding cut outs and sudden changes in cross section. For GMAW, we recommend the use of a protective gas made up of Ar+1%CO₂ or 1-2%O₂; for GMAW as well as for GTAW, gasses containing H₂ and N₂ must be avoided.