Why Maraging steel was replaced with Alloy steel in Agni missile?

alloy steel uses

Maraging steel is known for superior strength and hardiness without being deprived of ductility. It is a special class of low carbon that obtains strength from precipitation of intermetallic compounds. However, it is proposed that Fe-12%Ni steels alloyed with 1-2% Al and Mo may offer a steel competitive in toughness although at ⅓ cost of alloy. Alloy steel is steel that is alloyed with heterogeneous elements in order to upgrade its mechanical properties. It consists of Iron and carbon depending upon the type. Alloy is considered to be superior to Maraging steel. Several reasons lie behind replacing it with the later while building the Agni missile. 

Alloy steel plays a crucial role in the construction industry. The most important aspect is the composition and proportion of alloying elements in order to determine its properties. There are around 3,500 grades of steel and each of its unique offers environmental, chemical and physical properties. When supplementary elements consisting of metals and non-metals are added to carbon steel, alloy steel is produced. 

Properties of Alloy Steel:

Alloy Steel consists of Mechanical properties and surafce properties. 

The behaviour of materials under external load defines their mechanical properties. Mechanical hardness could be connected to the yield stress splitting the elastic and plastic regions, aloft which a substantial dislocation activity develops. Besides the bulk parameters, the formation energies of two-dimensional defects are also dominant in narrating the mechanical characteristics of solids.  

Surface properties incorporate a metallic primary solid solution, made up of components which are immiscible at low temperature, is thermodynamically volatile when quenched from high temperature and phase separation takes place during aging or annealing.


Types of Alloy Steel:

High alloy steels are defined by a greater percentage of alloying elements in them. The most common one would be stainless steel. It contains 12% of chromium and is split into 3 basic types – ferritic, austenitic and martensitic. Ferritic steel contains around 12-27% of Chromium and usually utilized in Industrial equipment. Austenitic steel contains high levels of nickel, manganese and nitrogen. They are often used to store mining and corrosive liquids.Martensitic steel contains the least amount of chromium compared to the others and are typically utilised in making cutlery.

Low alloy steel features a comparatively less percentage of alloying elements upto 1-5%. These steels are contrasting with regards to strength and uses depending on the chosen alloy. Dinesh Tube India is one such Manufacturer that produces large diameter flanges, plates, round bars and fasteners using these alloys due to specific mechanical properties required. 

Other elements that provide varied properties include titanium, cobalt, boron, sulfur, nitrogen, lead, selenium, tellurium and zirconium that can be used individually or in various combinations considering the properties desired.

Composition of Alloy Steel:

 The alloy steel composition represents a relatively recent development in steelmaking. It is achieved as a high strength alloy steel with a yield stress level of 90-100 ksi and is available only in plate form upto 6 inches thick. Carbon is by far the most important chemical element present in steel. Higher strength and lower ductility is observed when carbon content is increased. Aluminium is a crucial deoxidizer that helps to form fine-grained crystalline microstructure which is typically found in combination with silicone to obtain semi/fully killed alloy steel. Manganese, too, has similar effects to those of carbon and is necessary for the process of hot rolling of steel with the combination of oxygen and sulphur. 

Other chemical elements also include chromium, columbium, copper, molybdenum, nickel, phosphorus, silicon, vanadium and titanium.

Grades of Alloy Steel:

The most commonly used Grades for Alloy steel are-

Uses of Alloy Steel:

The area of application for alloy steel is broad since it encompasses numerous sorts of steel. Low alloy steels are applicable in a wide range of industries due to their maximal strength, availability and cost-effectiveness. They are established in military vehicles, ships, construction equipment, pipelines and other structural components that include examples of HY80 and HY100.

High alloy steel, however, is often exorbitant to manufacture and back-breaking to process. Nevertheless, their distinguished toughness, hardness and corrosion resistance makes it absolute for automotive applications, chemical processing, structural components and power generating equipment that include examples of HE, HF, HH, HI, HK, and HL grades.

The Alloy Steel Plant came up with an alternative to Maraging Steel that was used previously in the outer motor casing of Agni missiles. Local companies like Dinesh Tube India cater to high quality Alloy steel pipes and tubes. Not only does it save valuable foreign exchange but also increases indigenous capability in India. Since ultra-high-strength and toughness was required for missile manufacture the alternative was developed.

As we can observe from the foregoing, alloy steels play an important role in the building and construction industry along with other industries. Alloy steels offer economy, high performance under harsh conditions, resistance, durability, corrosion, high strength and a wide variety of products to compliment most applications.



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