1.Introduction

ASTM A312 is a Ni-Cr based superalloy that possesses high strength properties and resistance to elevated temperatures. It also demonstrates remarkable protection against corrosion and oxidation. Its ability to withstand high stress and a wide range of temperatures, both in and out of water, as well as being able to resist corrosion while being exposed to highly acidic environments makes it a fitting choice for nuclear and marine applications.

Inconel ASTM A312 was developed in the 1960s with the purpose of creating a material that

could be used for steam-line piping. Some modifications were made to its original

composition that have enabled it to be even more creep-resistant and weldable.

2.Chemistry

Some chemical properties of Inconel ASTM A312 include:

Inconel ASTM A312 was designed as a solid solution strengthened material with no significant

microstructure. This holds true at low and high temperatures, but there is a region

(923 to 1148 K) where precipitates form that are detrimental to the creep properties,

and thus the strength, of the alloy. Under any creep conditions (high temperature

with an applied stress), M23C6-type carbides form at the grain boundaries. When

tested at 973 K, γ” precipitates begin forming. These γ” phase precipitates are

ordered A3 B type with a composition of Ni3(Nb, Al, Ti) and a tetragonal crystal structure.

They form a disk-shaped morphology and are coherent with respect to the matrix.

When tested at 998 K, a δ-phase precipitate begins forming which consist of Ni3(Nb, Mo)

in an orthorhombic crystal structure. They form in a needle-like morphology and are

incoherent with the matrix. Both of these precipitates can be completely dissolved back

into the matrix when the sample is heated 1148 K. This leads to the ability to recover creep

properties of the alloy to prolong the materials lifetime.

3.ASTM (American Society for Testing and Materials) for various products made

out of Inconel ASTM A312 are as follow:

4.specifications

Specifications and certifications include:

• AMS: 5599, 5666
• MS: 5837
• ASME: SB 443 Gr 1, SB 446 Gr 1
• ASTM: B 443 Gr 1, B 446 Gr 1
• EN: 2.4856
• ISO: 15156-3
• NACE: MR0175-3
• UNS: N06625
• Werkstoff: 2.4856

5.Heat Treatment

Heat Treatment Inconel 725 is usually strengthened by cold work, with annealing at

temperatures between 1,700 and 1,900F as required to remove the effects of cold work.

Although nominally a solid-solution alloy containing intergranular and intragranular

carbide precipitates, Inconel 725 is not responsive to strengthening heat treatments.

Solution heat treating at 2000 to 2200F dissolves almost all of the secondary carbides.

The major effects of short-time annealing of hot-rolled bar of standard composition are

to affect reductions in tensile strength and hardness.Typically, the annealing heat

treatment most utilized for Inconel 725 is at 1800F.

The mild annealed low carbon ASTM A312 has been widely used in the chemical

process industry. Its good corrosion resistance and high strength make it a thinner

structural component.The ASTM A312 alloy can be used in contact with sea water and under

high mechanical stress.Typical applications:

1. Components of the chlorinated organic chemical process, especially in the use

of acidic chlorides catalysts.

2. Used for cooking machines and bleaching ponds in the pulp and paper industry

3. Absorption tower, reheater, flue gas inlet baffle, fan (moist), agitator, guide plate

and flue pipe in flue gas desulfurization system.

4. Equipment and components for manufacturing applications in acidic gas environments

5. Acetic acid and acetic anhydride reaction generators

6. Sulfuric acid condenser