UGI 4418 AIR QT1150

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Description

UGI 4418 AIR stainless steel is a low-carbon super-martensitic grade with the addition of nickel. It is specifically designed for the aerospace market. It combines high mechanical strength with excellent resilience and very good corrosion resistance, considerably higher than those of conventional high-carbon Fe-Cr-C martensitic steels. This grade exhibits excellent cryogenic properties.


In the quenched and tempered state, the UGI 4418 AIR microstructure consists predominantly of tempered martensitic (see figure on the right side of the material page). It may contain traces of ferrite (less than 5%) and residual austenite, depending on the diameter and the heat treatments used.


The microcleanliness guarantees are as follows (rating as per ASTM E45/method A):


GradesEpit (mV/ECS) ± 20 mV
1.4006 (AISI 410)185
1.4307 (AISI 304L) (with S=0.02%)400
1.4542 (17-4-PH AISI 630)380
1.4418375


UGI 4418 AIR is also available in an electro-slag-remelted (ESR) version.


UGI 4418 AIR is magnetizable.

Related Standards

Equivalent Materials

This material data has been provided by Ugitech SA.

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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Properties

General

PropertyValue

Density

7.7 g/cm³

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Mechanical

PropertyTemperatureValueComment

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

175 GPa

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400 °C

170 GPa

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Elongation

8.0 %

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min., Transverse

14 %

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min.

Hardness, Brinell

341.0 - 401.0 [-]

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HBW

Tensile strength

1150.0 - 1300.0 MPa

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1150.0 - 1300.0 MPa

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Transverse

Thermal

PropertyValueComment

Coefficient of thermal expansion

0.0000103 1/K

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20 to 100°C

0.0000108 1/K

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20 to 200°C

0.0000112 1/K

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20 to 300°C

0.0000116 1/K

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20 to 400°C

Specific heat capacity

430 J/(kg·K)

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Thermal conductivity

15 W/(m·K)

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Electrical

PropertyValue

Electrical resistivity

8e-07 Ω·m

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Chemical properties

PropertyValueComment

Carbon

0.06

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max.

Chromium

15.0 - 17.0 %

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Copper

0.5

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max.

Manganese

1.5

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max.

Molybdenum

0.8 - 1.2 %

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Nickel

4.0 - 5.0 %

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Nitrogen

0.02 %

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min.

Phosphorus

0.03

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max.

Silicon

0.6000000000000001

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max.

Sulfur

0.005

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max.

Technological properties

Property
Application areas

  • Fasteners
  • Rotary parts
  • Fittings and connectors
  • Brake pistons
  • Structural parts
  • Shaft and pins
  • Tanks

  • Cold Forming

    UGI 4418 AIR can be cold formed by conventional cold-working processes (bar drawing, wire drawing, forming, profiling, etc.). Its high mechanical properties require particular attention. After or during cold-forming operations, quenching may be necessary to soften the grade. In the event of high levels of deformation, a complete quenching and tempering process is recommended.

    Corrosion properties

    Due to its high percentage of nickel, chromium and molybdenum and its low carbon content, UGI 4418 AIR has good corrosion resistance.

    Localized corrosion

    Pitting corrosion: The pitting potentials were measured as specified in ISO 15158-2014 in a solution containing 0.02M NaCl at 23°C. UGI 4418 AIR also has far better pitting corrosion resistance than a 13% Cr martensitic (type 1.4006). The results show that the pitting corrosion resistance of UGI 4418 AIR is similar to that of 1.4542 and 1.4307 (containing 0.020% of sulphur).


    GradePitting potential
    (mV/ECS at ± 20 mV)
    1.4006 (410)185
    1.4307 (304L)400
    1.4542 (17-4PH)380
    UGI 4418 AIR375


    Intergranular corrosion: Its structure and composition make UGI 4418 AIR insensitive to intergranular corrosion.

    Heat Treatment

    Softening

    UGI 4418 AIR is difficult to soften due to its chemical composition leading to a very low transformation point (Ac1). Soft annealing is generally carried out between 600 and 650°C.


    Quenching

    UGI 4418 AIR quenching heat treatment consists of austenitizing between 1010°C and 1060°C, followed by oil quenching (or air quenching for smaller sections). To limit the risks of quenching cracks, tempering must be carried out as soon as possible after the quenching operation, after returning to the ambient temperature.


    Tempering

    The tempering temperature must be adjusted according to the mechanical properties required.

  • QT 900 level: tempering between 550°C and 620°C
  • QT 1100 and QT1150 levels: tempering between 375°C and 405°C


    The tempering period is generally between 2 h and 4 h and is followed by air or oil cooling. Double tempering can be used to soften the grade further. The temperature range between 400°C and 450°C should be avoided, as it can lead to excessive metal embrittlement (see chart on the right side of the material page).

  • Hot forming

    Forging

    Heating between 1150°C and 1200°C is recommended. Hot forming (forging) must preferably be carried out at a temperature of between 1200°C and 900°C, followed by air cooling. The behaviour of UGI 4418 AIR during forging is equivalent to that of a type 1.4301 austenitic grade. Full heat treatment, austenitizing/quenching followed by tempering, is recommended after hot forming.

    Other

    Available products:


    ProductProfileFinishToleranceDimensions (mm)
    BarsRoundHot rolled descaledK13-K1222-115
    Turnedh11-h1022-115
    Turned polishedh11-h10
    h9
    22-115
    22-55
    Groundh9-h8-h75-115
    Drawnh95-30


    Other products: contact the supplier

    Welding

    UGI 4418 AIR can be welded by electric arc (GMAW, GTAW, SMAW, etc.) and by most other processes (spot welding, seam welding, LASER, etc.). Due to its low percentage of carbon and its nickel content, UGI 4418 AIR is easier to weld than most martensitic stainless steels.

    Low-carbon martensite combined with finely dispersed residual austenite gives the heat-affected zones (HAZ) of UGI 4418 AIR excellent toughness in the as-welded condition. UGI 4418 AIR is therefore only slightly susceptible to cold cracking after welding and it is not normally necessary to preheat the parts, unless the parts to be welded are very thick or their geometry is liable to generate high stress concentrations at the welds after cooling (in this case, preheating at 100-120°C is recommended).

    If the Weld Metal (WM) does not require the mechanical properties of UGI 4418 AIR, an austenitic grade such as A316LM or A316LT can be used as filler metal. Post-weld heat treatment is then generally not necessary. Where the WM must have the same mechanical properties as those of UGI 4418 AIR, a homogeneous filler metal must be used (such as “16 5 1”). In this case, post weld heat treatment at 580-600°C is recommended.

    For GMAW with homogeneous filler metal, a slightly oxidizing shielding gas such as Ar + 1-2% CO₂ will be chosen to avoid too high a percentage of oxygen in the WM, thus ensuring good impact properties for these WMs.