UNS S44800

HuaNickel UNS S44800 is a 2% Ni Cr29Mo4 super ferritic stainless steel with the addition of nickel that gives this steel higher toughness and lower brittle transition temperature than non-high-purity Cr29Mo4 steel. The high chromium and molybdenum content make this steel have better overall corrosion resistance, pitting corrosion resistance, and crevice corrosion resistance.

UNS S44800Chemical composition：

	Cr	Ni	Mo	C	N	C+N	Mn	P	S	Si	Cu
Min	28	2	3.5	≤
Max	30	2.5	4.2	0.01	0.02	0.025	0.3	0.025	0.02	0.2	0.15

UNS S44800Physical properties：

Density /g ·cm	Linear expansion coefficient(21～100℃)a /10-6·K-1	Specific heat capacityc/J(kg·K)-1	Thermal conductivityλ/W·(m·K)-1 (21～100℃】	Resistivityg /μΩ ·m
7.7	9.4	448	17	0.72

UNS S44800Mechanical properties：

Steel vari	Heat treatment status	σp0.2/MPa	σb/MPa	δ/%	Hardness(HRB)
Pipe	Annealed state	550	690	25	B95
Plate	Annealed state	515	655	25	B95
ASTMmin	Annealed state	415	550	20

UNS S44800Alloy properties：

This steel annealed state has a single ferrite structure. However, at medium temperature (e.g. welding) heating, for example, there will be intermetallic phase σ(x) precipitation near 750~950°C (see Fig. 1-1-47), and at the same time, carbide Crz₃C₆ and nitride Cr₂N will precipitate above 950°C. Because this steel has a higher molybdenum content than the aforementioned 00Cr28Ni4Mo2 steel, it is more sensitive to the precipitation of σ phases.

UNS S44800Uses of alloys：

This steel can be used in heat exchange equipment with seawater and Cl- water as cooling medium, and can also be used in acidic media such as sulfuric acid, formic acid, acetic acid, oxalic acid, etc.

UNS S44800Process performance：

Welding performance: In order to make HuaNickel UNS S44800 steel have good post-weld performance during the welding process, it is necessary to maintain the high cleanliness of this steel, for this reason, it is necessary to make careful preparations for shielding gas, filler metal, base metal, etc. before welding, and clean up the pollution of the welded joint in time after welding.

Heat treatment: The suitable heat treatment process for this steel is 950~1050 °C heating and heat preservation and quenching. If it is lower than 950°C, the toughness and corrosion resistance of the steel will be reduced due to the precipitation of σ(x) phase; Above 1050°C, the performance of steel will be reduced due to the precipitation of carbon and nitride.

Relevant standards：