Product Code Database
Alloy steel is steel that is Alloy with a variety of elements in amounts between 1.0% and 50% by weight, typically to improve its mechanical properties.
The simplest steels are iron (Fe) alloyed with (0.1% to 1%) carbon (C) and nothing else (excepting slight impurities); these are called Carbon steel. However, alloy steel encompasses steels with additional (metal) alloying elements. Common alloyants include manganese (Mn) (the most common), nickel (Ni), chromium (Cr), molybdenum (Mo), vanadium (V), silicon (Si), and boron (B). Less common alloyants include Aluminium (Al), cobalt (Co), copper (Cu), cerium (Ce), niobium (Nb), titanium (Ti), tungsten (W), tin (Sn), zinc (Zn), lead (Pb), and zirconium (Zr).
Although alloy steels have been made for centuries, their metallurgy was not well understood until the advancing chemical science of the nineteenth century revealed their compositions. Alloy steels from earlier times were expensive luxuries made on the model of "secret recipes" and forged into tools such as knives and swords. Machine age alloy steels were Tool steel and Stainless steel.
Because of iron's Ferromagnetism properties, some alloys find important applications where their responses to magnetism are valued, including in electric motors and in transformers.
| + Principal low-alloy steels ! width="125" | SAE designation !Composition |
| 13xx | Mn 1.75% |
| 40xx | Mo 0.20% or 0.25% or 0.25% Mo & 0.042% S |
| 41xx | Cr 0.50% or 0.80% or 0.95%, Mo 0.12% or 0.20% or 0.25% or 0.30% |
| 43xx | Ni 1.82%, Cr 0.50% to 0.80%, Mo 0.25% |
| 44xx | Mo 0.40% or 0.52% |
| 46xx | Ni 0.85% or 1.82%, Mo 0.20% or 0.25% |
| 47xx | Ni 1.05%, Cr 0.45%, Mo 0.20% or 0.35% |
| 48xx | Ni 3.50%, Mo 0.25% |
| 50xx | Cr 0.27% or 0.40% or 0.50% or 0.65% |
| 50xxx | Cr 0.50%, C 1.00% min |
| 50Bxx | Cr 0.28% or 0.50%, and added boron |
| 51xx | Cr 0.80% or 0.87% or 0.92% or 1.00% or 1.05% |
| 51xxx | Cr 1.02%, C 1.00% min |
| 51Bxx | Cr 0.80%, and added boron |
| 52xxx | Cr 1.45%, C 1.00% min |
| 61xx | Cr 0.60% or 0.80% or 0.95%, V 0.10% or 0.15% min |
| 86xx | Ni 0.55%, Cr 0.50%, Mo 0.20% |
| 87xx | Ni 0.55%, Cr 0.50%, Mo 0.25% |
| 88xx | Ni 0.55%, Cr 0.50%, Mo 0.35% |
| 92xx | Si 1.40% or 2.00%, Mn 0.65% or 0.82% or 0.85%, Cr 0.00% or 0.65% |
| 94Bxx | Ni 0.45%, Cr 0.40%, Mo 0.12%, and added boron |
| Eglin steel | Ni 5%, Cr 2%, Si 1.25%, W 1%, Mn 0.85%, Mo 0.55%, Cu 0.5%, Cr 0.40%, C 0.2%, V 0.1% |
| + Properties ! Property !! Elements !! Mechanism |
| remove dissolved oxygen, sulfur and phosphorus |
| form solid solutions in ferrite |
| form second-phase Carbide |
| Zirconium, cerium, and calcium |
| +Principal effects of major alloying elements for steel !Element !Percentage !Primary function | ||
| Aluminium | 0.95–1.30 | Alloying element in nitriding steels |
| Bismuth | — | Improves machinability |
| Boron | 0.001–0.003 | (Boron steel) A powerful hardenability agent |
| Chromium | 0.5–2 | Increases hardenability |
| 4–18 | (Stainless steel) Increases corrosion resistance | |
| Copper | 0.1–0.4 | Corrosion resistance |
| Lead | — | Improved machinability |
| Manganese | 0.25–0.40 | Combines with sulfur and with phosphorus to reduce brittleness. Also helps to remove excess oxygen. |
| >1 | Increases hardenability by lowering transformation points and causing transformations to be sluggish | |
| Molybdenum | 0.2–5 | Stable Carbide; inhibits grain growth. Increases the toughness of steel, thus making molybdenum a very valuable alloy metal for making the cutting parts of Machine tool and also the turbine blades of Turbojet engine. Also used in Rocket motor. |
| Nickel | 2–5 | Toughener |
| 12–20 | Increases corrosion resistance | |
| Niobium | — | Stabilizes microstructure |
| Silicon | 0.2–0.7 | Increases strength |
| 2.0 | Spring steels | |
| Higher percentages | Improves magnetic properties | |
| Sulfur | 0.08–0.15 | Free-machining properties |
| Titanium | — | Fixes carbon in inert particles; reduces martensitic hardness in chromium steels |
| Tungsten | — | Also increases the melting point. |
| Vanadium | 0.15 | Stable carbides; increases strength while retaining ductility; promotes fine grain structure. Increases the toughness at high temperatures |
In one approach steel is heated to a high temperature, cooled somewhat, held stable for an interval and then quenched. This produces islands of austenite surrounded by a matrix of softer ferrite, with regions of harder bainite and martensite. The resulting product can absorb energy without fracturing, making it useful for auto parts such as bumpers and pillars.
Three generations of advanced, high-strength steel are available. The first was created in the 1990s, increasing strength and ductility. A second generation used new alloys to further increase ductility, but were expensive and difficult to manufacture. The third generation is emerging. Refined heating and cooling patterns increase strength at some cost in ductility (vs 2nd generation). These steels are claimed to approach nearly ten times the strength of earlier steels; and are much cheaper to manufacture.
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