Alloy Steel Types, Properties and Uses

Alloy steel is a steel that has had small amounts of one or more alloying elements (other than carbon) such as such as chromium, manganese, silicon, nickel, titanium, copper and aluminum added. Nickel is an important alloying addition to low-alloy steels. Alloy steels grade P91 is mainly used for power industry. Many of industry are depend on Alloy Steel because of their economical cost, wide availability, ease of processing, and good mechanical properties.

Alloy steels are generally more responsive to heat and mechanical treatments than carbon steels. For welded construction, the ASME Boiler and Pressure Vessel Code limits the carbon content to less than 0.35%. Alloy Steel is strong, tough and wear resistant and also has vastly improved hot hardness over regular carbon steel. HSLA stands for high-strength low-alloy steel.

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  • 389  Isothermal Transformation Diagrams of Nickel Alloy Steels
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  • 4419  18% Nickel Maraging Steel – Engineering Properties
  • 1278  IN-787 – A Precipitation Hardening Alloy Steel, Properties and Applications
  • 1238  Low-Temperature Properties of Nickel Alloy Steels
  • 1203  Six Reasons for Specifying Nickel Carburizing Steels
  • 1108  Nickel Alloy Steel Plates
  • 447  Alloy Steel Compositions
  • 479  Nickel Alloy Nitriding Steels
  • 472  Nickel Alloy Tool Steels
  • 392  Hardenability of Nickel Alloy Steels

Alloy steel is ideally suited for applications that require higher strength, improved toughness or better wear resistance than standard carbon steel grades. Alloy Steels are used in boiler construction because they are inexpensive, readily available, easily formed and welded to the desired shape and, within the broad limits, are oxidation- and corrosion-resistant enough to provide satisfactory service for many years to many industries.

Alloy Steel is used across a range of highly demanding applications within the aerospace and power (nuclear) industries. Alloy Steel is also found in applications where its response to magnetism is important, in transformers and electric motors for example.

It is the addition of other elements that makes Alloy Steel extra strong. The elements such as silicon and manganese through heat treatment makes Alloy Steel with improved characteristics and additional benefits, such as increased corrosion resistance or improved weldability. The mechanical properties achievable are dependent on the addition of elements such as nickel, chromium, molybdenum and vanadium.

Most Frequently Used Steels

ALLOY SPECIFICATION MAXIMUM USEFUL
TEMPERATURE
Carbon-steel SA178, SA192,
SA210, SA106,
SA515, SA516
850°
Carbon-1/2
Molybdenum
SA209 900°
1 1/4 Chromium-
1/2 Molybdenum
SA213 T-11
SA335 P-11
1025°
2 1/4 Chromium-
1 Molybdenum
SA213 T-22
SA335 P-22
1075°
18 Chromium-
10 Nickel
SA213 TP304(H),
321(H), 347(H)
1500°

There are 5 five alloys (mentioned in above table) cover probably 85% to 90% of the steels used of the many acceptable grades listed in the Code. There are others that may find specific applications, for example 1/2 Chromium-1/2 Molybdenum alloy SA213 T-2, 9 Chromium-1 Molybdenum alloy SA213 T-9, and corrosion-resistant, high-temperature alloys of nickel and chromium, SB-407.

Low Alloy steel grades 4130, 4140, 4145 and 1/4 Cr – 1Mo F22 type.

ASTM A213 / A213M – 17:

Standard Specification for Seamless Ferritic and Austenitic Alloy-Steel Boiler, hpw Superheater, and Heat-Exchanger Tubes

ASTM A335 / A335M – 15a:

Standard Specification for Seamless Ferritic Alloy-Steel Pipe for High-Temperature Service

15CDV6 Alloy Steel 15CDV6 is a low carbon steel with very good yield strength. It also has very good toughness and excellent weldability. Welding can be achieved without subsequent heat treatment and with negligible loss of properties.
300M Alloy Steel 300M is a low alloy, vacuum melted, steel of very high strength. Essentially it is a modified AISI 4340 steel with silicon, vanadium and slightly greater carbon and molybdenum content than 4340. 300M has a very good combination of strength (1900-2100 MPA after final heat treatment), toughness, fatigue strength and good ductility. 300M is a through hardening alloy.
4130 Alloy Steel Bar & Tube 4130 is a through hardening low alloy steel containing molybdenum and chromium as strengthening agents. 4130 responds well to nitriding for very good wear and abrasion resistance.
4130 Alloy Steel Sheet & Plate 4130 is a through hardening low alloy steel containing molybdenum and chromium as strengthening agents. 4130 responds well to nitriding for very good wear and abrasion resistance.
4340 Alloy Steel 4340 Alloy Steel (AMS 6414, AMS 6415).
52100 Alloy Steel 52100 Alloy Steel Metal (AMS 6440, AMS 6444)
S99 Alloy Steel 5S99 Alloy Steel (W.Nr 1.6745)
EN14 W.Nr 1.1160, 150M19
EN16 Alloy Steel EN16 Alloy Steel (605M36)
EN19 Alloy Steel EN19 Alloy Steel Metal (W.Nr 1.7225, 708M40)
EN24 Alloy Steel EN24 Alloy Steel (W.Nr 1.6565, 817M40)
EN36 Alloy Steel EN36 Alloy Steel (W.Nr 1.5752, 655M13)
EN39 Alloy Steel EN39 Alloy Steel (835M15)
HY-TUF Alloy Steel HY-TUF Alloy Steel (AMS 6418, ASTM A322)
S156 Alloy Steel S156 is a high strength VAR steel with a tensile strength of between 1320-1520 MPa. Material is supplied in the normalised and softened / annealed condition and develops a hard wear resistance case after surface treatment.
T45 Alloy Steel T45 Alloy Steel

Alloy Steel Elements & Their Benifit

  • Chromium – Adds hardness. Increased toughness and wear resistance.
  • Cobalt – Used in making cutting tools; improved Hot Hardness (or Red Hardness).
  • Manganese – Increases surface hardness. Improves resistance to strain, hammering & shocks.
  • Molybdenum – Increases strength. Improves resistance to shock and heat.
  • Nickel – Increases strength & toughness. Improves corrosion resistance.
  • Tungsten – Adds hardness and improves grain structure. Provides improved heat resistance.
  • Vanadium – Increases strength, toughness and shock resistance. Improved corrosion resistance.
  •  Chromium-Vanadium – Greatly improved tensile strength. It is hard but easy to bend and cut.

Alloy steel is one of the most versatile steels in the world, with a diverse range of elemental properties and specifications used in a variety of exotic mission-critical applications that demand superior performance under high pressure environments.

Low-alloy Steels

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.

Alloy Steel is used by many Industries include:

  • Agriculture
  • Bearings
  • General engineering
  • Automotive
  • Hydraulics
  • Railway
  • Mining
  • Construction
  • Aerospace
  • Windpower
  • Chemical
  • Medical
  • Defense

Alloy Steel Grades

CHEMICAL COMPOSITION OF A335 ALLOY PIPES

A335 Alloy Pipe
Grade

UNS

equiv.

C≤ Mn P≤ S≤ Si≤ Cr Mo
P1 K11522 0.10~0.20 0.30~0.80 0.025 0.025 0.10~0.50 0.44~0.65
P2 K11547 0.10~0.20 0.30~0.61 0.025 0.025 0.10~0.30 0.50~0.81 0.44~0.65
P5 K41545 0.15 0.30~0.60 0.025 0.025 0.5 4.00~6.00 0.44~0.65
P5b K51545 0.15 0.30~0.60 0.025 0.025 1.00~2.00 4.00~6.00 0.44~0.65
P5c K41245 0.12 0.30~0.60 0.025 0.025 0.5 4.00~6.00 0.44~0.65
P9 S50400 0.15 0.30~0.60 0.025 0.025 0.50~1.00 8.00~10.00 0.44~0.65
P11 K11597 0.05~0.15 0.30~0.61 0.025 0.025 0.50~1.00 1.00~1.50 0.44~0.65
P12 K11562 0.05~0.15 0.30~0.60 0.025 0.025 0.5 0.80~1.25 0.44~0.65
P15 K11578 0.05~0.15 0.30~0.60 0.025 0.025 1.15~1.65 0.44~0.65
P21 K31545 0.05~0.15 0.30~0.60 0.025 0.025 0.5 2.65~3.35 0.80~1.60
P22 K21590 0.05~0.15 0.30~0.60 0.025 0.025 0.5 1.90~2.60 0.87~1.13
P91 K91560 0.08~0.12 0.30~0.60 0.02 0.01 0.20~0.50 8.00~9.50 0.85~1.05
P92 K92460 0.07~0.13 0.30~0.60 0.02 0.01 0.5 8.50~9.50 0.30~0.60