Low-alloy Steels
Steels can be classified in a variety of different ways depending on their composition (carbon, low-alloy or stainless steel), manufacturing methods, finishing method (such as hot rolling or cold rolling), product form (bar,sheet, tube, etc), heat treatment (such as annealing, quenching and tempering), required strength level as specified in ASTM standards) and others. Because of the wide variety of chemical compositions possible and the fact that some steels are used in more than one heat-treated, condition, some overlap exists among the alloy steel classifications.
There are different alloy steel grades derived from the different compositions of alloys (i.e the % weight of alloying materials used) but basically alloy steels are divided into two subgroups (high and low alloy steels) as a result of higher or lower participations of alloying materials in their chemical composition. Low-alloy steels constitute a category of ferrous materials that exhibit mechanical properties superior to plain carbon steels as the result of additions of alloying elements such as nickel, chromium, and molybdenum. Total alloy content can range from 2.07% up to levels just below that of stainless steels, which contain a minimum of 10% Cr. For many low-alloy steels, the primary function of the alloying elements is to increase hardenability in order to optimize mechanical properties and toughness after heat treatment. In some cases, however, alloy additions are used to reduce environmental degradation under certain specified service conditions.
Different low-alloy steel grades include: SAE AISI(*) 4130 (G41300**), 4140 (G41400**), 4330 (G43300**) and 4340 (G43400**).
As with other steels, low-alloy steels can be classified according to:
- Chemical composition, such as nickel steels, nickel-chromium steels, molybdenum steels, chromium-molybdenum steels
- Heat treatment, such as quenched and tempered, normalized and tempered, annealed.
Alloy steel applications range over a variety of industrial, domestic and commercial uses, from household and kitchen accessories to larger industrial machine parts.
AISI 4130/4140 Low-alloy Steels
SAE AISI 4130 and 4140 low-alloy steels have the same elemental composition, with common elements being carbon, molybdenum, chromium. They are popular steel materials due to properties such as toughness, high fatigue strength, and strength. Both grades do not have anti-rust properties. To make them stronger they need to be subjected to heat treatment such as annealing, cold working, etc.
AISI 4130, also known as Chromoly or Chrome Moly after the 2 key elements of its composition, chromium, and molybdenum, is a general-purpose alloy steel widely used by the aviation and motorsports industries due to its weldability, fabrication, and mild hardenability in all offered forms (tubes, bars, sheets and plates). 4130 alloy steel (Chrome Moly) have been for years the standard of the aircraft industry.
AISI 4140 is harder than normal steel remaining unbroken in heavy loading conditions. It is susceptible to rust although it is highly resistant to corrosion. 4140 steel also has good machinability but it has to be subjected to heat treatment. Often used for gears, crankshafts and other parts.
In terms of weldability and machinability, AISI 4130 is a preferred choice because it has a lower carbon content than 4140.
They are available in two different material states (Normalized and Annealed) depending on the process of how the material is heated and cooled. The Normalized condition (sometimes referred to as "Condition N") is the harder and stronger condition and is best used when forming is not needed. Normalizing relieves internal stress on steel and improves toughness in steels that may harden after the cold working process. The Annealed condition (sometimes referred to as "Condition A") is the softer and formable condition and is best used when forming is needed. Annealing relieves internal stresses, softens and makes the material more ductile.
Sourced from quality producers, AISI 4130/4140 steel sheets/plates are offered as part of our own branded (AVIATIONEU NEW ERA) product lines in different specifications and pre-cut or cut-to-oder dimensions, depending on the order requirements. They can be furnished in two different conditions, Normalized and Annealed when forming is required. Annealing creates a softer more formable sheet allowing a tighter bend radius.
For additional information please refer to the individual product presentations.
(*) Society of Automotive Engineers (SAE), American Iron & Steel Institute (AISI)
(**) Unified Numbering System ( UNS) Number. UNS is an alloy designation system for Metals & Alloys providing a means of correlating many internationally used metal and alloy numbering systems administered by their producers, societies, trade associations, and individual users.
