Low-alloy steel
Low alloy steels are usually used to achieve better harden ability, which in turn improves its other mechanical properties. They are also used to increase corrosion resistance in certain environmental conditions.With medium to high carbon levels, low alloy steel is difficult to weld. Lowering the carbon content to the range of 0.10% to 0.30%, along with some reduction in alloying elements, increases the weld ability and form ability of the steel while maintaining its strength. Such a metal is classed as a high strength low alloy steel.
Alloying elements are added to achieve certain properties in the material. As a guideline, alloying elements are added in lower percentages (less than 5%) to increase strength or harden ability, or in larger percentages (over 5%) to achieve special properties, such as corrosion resistance or extreme temperature stability.
Manganese, silicon, or aluminum are added during the steel making process to remove dissolved oxygen from the melt. This understates the case because manganese also serves to remove sulfur and phosphorous from the molten steel.
Manganese, silicon, nickel, and copper are added to increase strength by forming solid solutions in ferrite. Chromium, vanadium, molybdenum, and tungsten increase strength by forming second-phase carbides. Nickel and copper improve corrosion resistance in small quantities. Molybdenum helps to resist embitterment. Zirconium, cerium, and calcium increase toughness by controlling the shape of inclusions.meganese sulphide, lead, bismuth, selenium, and tellurium increase Mach inability.
Carbon steel
Carbon steel, also called plain-carbon steel is steel where the main alloying constituent is carbon. The (AISI) defines carbon steel as: "Steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt, columbium, molybdenum, nickel, tit, Tungsten, vanadium or zirconium, or any other element to be added to obtain a desired alloying effect; when the specified minimum for copper does not exceed 0.40 percent; or when the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65, silicon 0.60,copper 0.60.
Muhammad Naveed Sabir
QA/QC Inspector Mechanical
Moody International pvt Ltd.
cell:+92-307-7005422
--Can anyone advise me where I can find the definition for CARBON STEEL and LOW ALLOY CARBON STEEL (Preferably an explicit definition by ASTM and the relevant standard number/description).
Form a web search I have found the following definitions :
AISI defines carbon steel as follows: Steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt, columbium [niobium], molybdenum, nickel, titanium, tungsten, vanadium or zirconium, or any other element to be added to obtain a desired alloying effect; when the specified minimum for copper does not exceed 0.40 per cent; or when the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65, silicon 0.60, copper 0.60.
Alloy or alloyed steels are defined by the ISO specification 4948/1 in the following manner. Alloy steels are those containing any element listed below in a quantity equal to or greater than the quantity for that listed element: aluminium 0.10%, boron 0.008%, bismuth 0.10%, chromium 0.30%, cobalt 0.10%, cupper 0.40%, manganese 1.65%, molybdenum 0.06%, lead 0.40%, selenium 0.10%, silicon 0.50%, tellurium 0.10%, titanium 0.05%, tungsten 0.10%, vanadium 0.10%, zirconium 0.05%, Lanthanides (each) 0.05%, other specified elements (except carbon, sulphur, phosphorus, nitrogen) 0.05% [Ref 1].
Various attempts have been made to distinguish 'low' and 'high' alloy carbon steels, but the definitions vary between countries and between standard-setting organisations. As a general indication, low alloy steel can be regarded as alloy steels (by the ISO definition) containing between 1% and less than 5% of elements deliberately added for the purpose of modifying properties.
However, AISI defines low alloy steels as a constitute to 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% chromium.
Regards
Barry Gideon
ARV Offshore Co., Ltd.
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