UGI® 4313 + QT780: Nickel‑Alloyed Martensitic Stainless Steel with Superior Strength and Corrosion Resistance

The UGI® 4313 grade is a low-carbon nickel-alloyed martensitic stainless steel which combines high mechanical properties, good impact strength and a corrosion resistance superior to that of conventional martensitic stainless steel grades with a high C content. It can be used between -60°C and +300°C.

In the heat-treated condition (quenching + tempering), the microstructure of UGI® 4313 consists of tempered martensite. It may possibly contain traces of ferrite and residual austenite. Depending on the tempering temperature chosen, UGI® 4313 may contain up to about 15% of residual austenite.

UGI® 4313 is ferromagnetic (it attracts the magnet), irrespective of its metallurgical condition. However, its magnetic properties (permeability, coercive force, remanence and polarization at saturation) depend on the conditions of heat treatment. It is a good candidate for applications where a compromise between mechanical strength, corrosion resistance and magnetism is required, for example for fuel injectors in the automotive sector. For more information, please consult with the supplier

Properties

General

Property	Value
Density	7.7 g/cm³

Mechanical

Property	Temperature	Value	Comment
Charpy impact energy, V-notch	-60 °C	50 J
	20 °C	70 J
Elastic modulus	20 °C	200 GPa
	100 °C	195 GPa
	200 °C	185 GPa
	300 °C	170 GPa
	300 °C	175 GPa
Elongation		15 %	min., diameter ≤ 160mm
Tensile strength		780.0 - 980.0 MPa	diameter ≤ 160mm

Thermal

Property	Value	Comment
Coefficient of thermal expansion	0.0000105 1/K	20 to 100°C
	0.0000109 1/K	20 to 200°C
	0.0000113 1/K	20 to 300°C
	0.0000116 1/K	20 to 400°C
Specific heat capacity	430 J/(kg·K)

Electrical

Property	Value
Electrical resistivity	6.000000000000001e-07 Ω·m

Chemical properties

Property	Value	Comment
Carbon	0.05	max.
Chromium	12.0 - 14.0 %
Manganese	1.5	max.
Molybdenum	0.30000000000000004 - 0.7000000000000001 %
Nickel	3.5 - 4.5 %
Nitrogen	0.02 %	max.
Phosphorus	0.04	max.
Silicon	0.7000000000000001	max.
Sulfur	0.015	max.

Technological properties

Property

Application areas

UGI® 4313 is intended for the following applications (non-exhaustive list):

Couplings, pumps, valves and compressors for chemical and petrochemical industries;

Aerospace, automotive and engine applications (especially injection);

Parts for power generation turbines;

Medical instrumentation;

Building, structures;

Military and defence applications.

Cold Forming

Wire drawing – Shaping: UGI® 4313 is suitable for cold working by conventional methods.

Corrosion properties

Localized pitting corrosion: The resistance to localized pitting corrosion largely depends on the composition of the grade; calculation of the PREN pitting index (=%Cr + 3.3x%Mo +16x%N) gives us an indication of the pitting corrosion resistance. With a calculated average PREN of 15, UGI® 4313 has a better corrosion resistance than that of the AISI 420 series (1.4034; average calculated PREN of 13.5); but it remains less satisfactory than that of the AISI 431 series (1.4057; average calculated PREN of 17).

The pitting corrosion resistance of UGI® 4313 is therefore satisfactory in moderately aggressive environments, i.e. containing less than 100 ppm of chloride ions. It is improved with a surface condition having low roughness, obtained for example by electropolishing.

General machinability

UGI® 4313 can be machined both in annealed condition (A) and in quenched and tempered conditions (QT). The annealed condition, due to its low mechanical properties, is more subject to chip sticking to the tools, which could accelerate tool wear and adversely affect post-machining surface conditions. The quenched and tempered conditions (QT) cause tool wear that is all the faster when they have high mechanical properties. Accordingly, the QT700 condition has the best machinability of the 4 available conditions.

The machinability of UGI® 4313 is similar to that of nickel-containing martensitic grade of the UGI® 4418 type. Our technical support department is at your disposal for any requests on the subject.

Heat Treatment

Annealing: Annealing between 600°C and 650°C with cooling in air or in furnace, to be performed after martensitic transformation.

Quenching: Quenching should be performed maintaining a temperature in a range between 900°C and 1150°C followed by cooling in air or in oil.

Tempering : The choice of the post-quenching tempering temperature depends on the required mechanical properties. The temperatures recommended by EN 10088-3 are:

+QT700: double tempering between 650°C and 700°C and between 600°C and 620°C

+QT780: single tempering between 550°C and 620°C

+QT900: single tempering between 520°C and 580°C

Hot forming

Heating to between 1150°C and 1200°C is recommended. Hot working (forging) of UGI® 4313 should preferably be performed in the temperature range between 1200°C and 900°C and be followed by air cooling. The behaviour of the UGI® 4313 grade during forging is similar to that of a 1.4301 type austenitic grade.

After hot working, a complete heat treatment, consisting of austenitizing and quenching and then tempering, is recommended.

Other

Available products:

Product	Shape	Finish	Tolerance	Dimensions (mm)
Descaled rolled bars	Round		12 to 13	22 to 115
Bars cold-worked by drawing, turning and grinding	Round		6 to 11	2 to 115
Wire rod	Round	Pickled		5 to 32

Other options: contact the supplier

Welding

UGI® 4313 can be welded by arc welding processes (GMAW, GTAW, SMAW, etc.) and by most other processes (spot, seam, laser, etc.). Thanks to its low carbon content and the nickel that it contains, UGI® 4313 is easier to weld than most martensitic stainless steels.

The martensite, poor in carbon, combined with the finely dispersed residual austenite, confers on the heat affected zones (HAZ) of UGI® 4313 good impact strength in the as-welded condition. UGI® 4313 is therefore relatively insensitive to cold cracking and preheating of the parts is normally not required, unless you have to weld very thick parts or parts having a shape that could engender high post-cooling weld stress concentrations (in such cases, preheating is recommended between 100°C and 200°C).

For welding with a filler, if the Weld Metal (WM) does not require mechanical properties on a par with those of UGI® 4313, it is possible to use as filler wire an austenitic grade such as UGIWELDTM 316LM. In that case a post-welding heat treatment is generally not necessary.

If the WM has to ensure mechanical properties identical to those of UGI® 4313, a homogeneous filler wire can be used. In that case, a post-welding tempering heat treatment at 540-580°C is recommended. In MIG welding with homogeneous filler wire, choose a relatively non-oxidizing protective gas such as Ar + 1-2% CO₂ to avoid an excessively high rate of oxygen in the WM, thus ensuring good impact strength for these WMs.

UGI® 4313 +QT700: High-Performance Martensitic Stainless Steel for Extreme Temperatures UGI® 4313 +QT900: High-Performance Low-Carbon Nickel Alloy for Extreme Temperatures

Metal