What is NAG AISI Steel? NAG stands for Nitric Acid Grade. This is a very high-grade steel designed to be used in nitric acid applications.

This is a kind of steel where both silicon and carbon are controlled to produce a stable austenite microstructure. The result of this amalgamation is that the material is free of carbine or intermetallic precipitations of AISI steel.

What About AISI Steel Grades and Properties?

This steel comes in primarily two varieties – Cold finished 310 stainless steel and hot finished 310 stainless steel. This steel has a Brinell hardness of 180 to 220 and an elastic modulus of 200GPa.

If we examine the other mechanical properties of AISI steel, elongation at break is 34 to 45% with a fatigue strength of 240 to 280MPa. The Poisson’s ratio is 0.27 while the Rockwell B. Hardness parameter measures 82.

aisi steel
Properties of AISI

If we look at the Thermal as well as Electrical Properties, AISI steel is also of a much more resilient and durable nature than other steels.

Thermal Properties of these Steel

Latent heat of Fusion measures 310 Joules/gm while the maximum temperature for Corrosion is 440 degrees Centigrade. The maximum temperature (Mechanical) is 1040 degrees Centigrade while the melting temperature (Liquidus) is 1450 degrees Centigrade.

Other important thermal properties of this metal are its heat capacity, conductivity and Thermal Expansion.

These can be listed as:

Specific heat capacity: 480 J/kg-K

Thermal Conductivity: 15W/m-K and

Thermal Expansion: 15 µm/m-K

Electrical Properties of 310L NAG steel

If we look at the Electrical Properties of 310L NAG steel, for Cold finished 310 stainless steel the Electrical Conductivity: Equal Volume is 2.2 % IACS while for Hot finished 310 stainless steel it is 2.5 % IACS.

The chemical composition of NAG steel can best be summarized in the below table:

Element Content (%)
Iron, Fe 51.635-54.485
Chromium, Cr 25
Nickel, Ni 20.5
Manganese, Mn = 2
Molybdenum, Mo = 0.30
Silicon, Si = 0.30
Niobium, Nb = 0.25
Carbon, C 0.015

Amongst the various wrought stainless steels, NAG steel is known for containing a high amount of silicon (Si). This is typically added for the purpose of improving oxidation resistance.

The Constituent Compositions

If we look at its various constituent compositions, we find the following proportions:

Iron (Fe)                  58.9 to 65.3

Chromium (Cr)        17 to 18.5

Nickel (Ni)               14 to 15.5

Silicon (Si)               3.7 to 4.3

Manganese (Mn)    0 to 2.0

Copper (Cu)             0 to 0.5

Molybdenum (Mo) 0 to 0.2

Phosphorus (P)       0 to 0.020

Sulfur (S)                 0 to 0.020

Carbon (C)               0 to 0.018

Some of its mechanical properties are listed below:

Metric Tensile strength = 71100 psi
= 215 MPa Modulus of elasticity 28300 ksi
75 GPa Poisson’s ratio 0.3
= 40% Hardness, Brinell 155

 Final Thought

Because of its hardness, high tensile strength, and Poisson’s ratio mentioned above, NAG steel is found in a variety of industrial applications and is the preferred raw material in the production of many kinds of metal parts especially those exposed to high degrees of stress and strain.

This steel is used for the fabrication of those items that are in contact with highly concentrated nitric acid. These applications include vessels, heat exchangers, piping, valves, pumps, and other items associated with the production and storage of highly concentrated nitric acid in every business technology.

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