MONIT

HuaNickel MONIT (Ti,Nb) enterprise brand name is HuaNickel MONIT, referred to as 25-4-4, is a kind of high chromium, molybdenum super ferritic stainless steel containing stabilized elements. The steel was developed in 1974 by Nyby in Sweden. Nickel is added to reduce the brittle transition temperature of the steel; Due to the high C+N content (≤0.04%) in the initial stage, the steel has a high tendency to intergranular corrosion, and the presence of stabilizing elements is to prevent intergranular corrosion during use after welding or high temperature cooling. Due to the high chromium and molybdenum content of this steel, the local corrosion resistance caused by chloride is excellent, the strength of this steel is high, and it has acceptable plasticity, toughness and welding properties under thin cross-sectional size conditions (such as ≤3~5mm), and can replace high-nickel austenitic stainless steel and high-nickel corrosion-resistant alloy under some medium conditions.

MONITChemical composition：

	Cr	Ni	Mo	C	N	Si	Mn	S	P
Min	24.5	3.5	3.5	≤
Max	26	4.5	4.5	0.025	0.025	0.5	0.5	0.03	0.04

MONITPhysical properties：

Density p/g·cm-3	Linear expansion coefficienta/10-6K-1			Thermal conductivityλ/W·(m·K)-1			Elastic modulusE(20℃) /MPa	Specific heat capacityc(20℃) /J·(kg·K)-1
	20~100℃	20~200℃	20~400℃	20℃	200℃	400℃
7.8	11.0	11.0	11.5	22.0	23.0	25.0	22000	400

MONITMechanical properties：

Materials	Species	Sampling direction	σp0.2/MPa	σb/MPa	δ/%
MONITNb	Plate，6mm	Longitudinal	590	700	31
		Transverse	620	720	29
	Plate，12mm	Longitudinal	560	690
		Transverse	590	720	25
	Pipe，ψ25.4mm×3.3mm	—	700	750	31

MONITAlloy properties：

The heat-treated state of this steel solution (annealing) is ferrite structure. Depending on the carbon, nitrogen, titanium, and niobium content in the steel, there will also be traces and small amounts of carbon and nitride on the matrix. In the process of production, thermal processing and heat treatment, there is also the precipitation of carbon, nitride and intermetallic phases such as a¹, σ, x and Laves

MONITUses of alloys：

This steel not only has high strength but also good toughness and weldability, and has excellent resistance to chloride stress corrosion, pitting corrosion, crevice corrosion, etc., and is mainly used for equipment that is resistant to seawater and other chloride-containing media, such as manufacturing scrubbers, condensers and heat exchangers.

MONITProcess performance：

Welding process: This steel has good weldability. There is no need for preheating before welding, no heat treatment is required after welding, and there is no intergranular corrosion tendency of welded joints. This steel can be welded using the same method used to weld stainless steel.

Heat treatment: As a super ferritic stainless steel with high chromium content and molybdenum, this steel is heated and retained at medium temperature (600~950 °C), and it is easy to precipitate intermetallic compounds such as σ, x and Laves, which seriously deteriorates the performance of this steel.

Relevant standards：

ASTM A240/A240M-2020