Types of

Properties and Applications

Austenitic stainless steels

The most common types are AISI 304, 304L, 316, 316L, 310 and 317L. The basic properties are: excellent corrosion resistance, excellent hygiene factor - cleaning, easy to process, excellent weldability, are not hardened by heat treatment, they can be used both at cryogenic temperatures and elevated temperatures.

Main applications: Household utensils and equipment, and hospital use in the food industry, tanks, pipes, etc

- AISI 304: The steel major application, containing chromium and nickel, it resists very well corrosives and having high ductility can be cold worked by various procedures used in the food industry and has application in the chemical, textile industry etc.

- AISI 304L: The low carbon content, which allows for greater resistance to intergranular corrosion.

- AISI 316: The addition of molybdenum in these stainless steels considerably improve corrosion resistance, especially under adverse conditions, as in the case of high pressures or high temperatures.
This steel is used for elements of machinery and dedicated facilities to the pulp industry and paper with good results in concentrations of acetic acid, phosphoric and the like acids.

- AISI 316 L: The low carbon content which gives it greater resistance to intergranular corrosion.

- AISI 317L: This type of steel improves resistance to corrosive attack type, pitting and corrosion CCheck because it contains more of molybdenum, to counteract the tendency to the formation of ferrite during the preparation of this steel is added as much nickel, resulting in an overall improvement of corrosion resistance.

- AISI 310: It's a refractory high alloy steel, used to work at high temperatures, the contents of chromium and nickel give the steel excellent corrosion resistance and high strength at high temperatures, they are used to manufacture air heaters, equipment heat treatment (all accessories), chemical process equipment etc.

- AISI 310S: Version of AISI 310 low carbon, its use is recommended when there is potential for intergranular corrosion effect of high temperature process.

- AISI 309:- They possess high strength, toughness and excellent resistance to oxidation at temperatures up to 1000 ° C.
Air heaters, chemical processing equipment, parts of burners in gas turbines and heat exchangers are process, parts of gas burners and heat exchangers turbines are some of the most common applications made from this steel.

- AISI 321: This is a type titania used with AISI 304 steel version; This type of steel is recommended when going to work at high process temperatures (500 to 700 ° C approx) giving even greater resistance to intergranular corrosion type.

Ferritic stainless steels

Ferritic stainless steels are characterized may have a chromium content higher than other types of families of steel, combined together with low presence in carbon percentage (in fact they are known as stainless steels direct chromium). Thus in this family steels the chromium content occupies a margin width can vary from 10.5% (AISI 409) or percentage of 30% (AISI 448) while the carbon content is limited to a maximum of carbon 0.12% which makes the ferrite phase is only stable throughout the temperature range.

Generally ferritic stainless steels have higher weldability than martensitic types, although lower than the austenitic grades, because ferritic stainless steels are magnetic.

In terms of its corrosion resistance it is generally good and is linked to the presence of chromium in its composition.

Steels (AISI 430, 434, 436) generally have excellent corrosion resistance, so they are widely used in the manufacture of household utensils and cooking for his brilliant and mirrored color.

Martensitic stainless steels

Martensitic stainless steels were first developed commercially (as cutlery) and have a relatively high carbon content (0.1% 1.2) compared with other stainless steels. basically contain chromium in percentage between 12/18%

Its basic properties are hardenable by heat treatment, have moderate corrosion resistance, weldability and are less magnetic (taking the magnet).

It is used in knife blades, surgical instruments, springs, axles etc.

The most common degrees ASIS 410 (CA15) and AISI 420.

The CA6NM is an alloy of Fe-Cr-Ni-Mo-based hardenable 13% chromium (this replaces the steel alloy CA15).

With the addition of molybdenum and nickel improve impact properties, resistance to corrosion by salt water rise the addition of these two elements, the welding conditions are favorable and requires less preheating temperatures.

Their most used applications are impellers, valve bodies, components of water turbines etc.

ASTM-A351 CF3 (AISI 304L) ASTM-A351 CF3M (AISI 316L)
ASTM-A351 CF3MN (AISI 316LN) ASTM-A351 CF8 (AISI 304)
ASTM-A351 CF8C (AISI 347) ASTM-A351 CK20 (AISI 310)
ASTM-A351 CF8M (AISI 316)
ASTM A217 C12 ASTM A743 CA40
ASTM-A487 CA15 (AISI 410) ASTM-A487 CA6NM

Properties and Applications

Duplex stainless steels

Duplex stainless austenitic-ferritic or structure steels combine the differentiating characteristic and families instead of austenitic and ferritic steels aspects. As the steels of the ferritic family show good resistance to stress corrosion cracking in media containing chlorides, also duplex stainless steels have a ductility and intermediate tenacity between families and an appreciably higher yield strength than ferritic steels and austenitic.

Duplex steels have biphasic ferrite and austenite structures whose properties will depend on the proportions between the two phases, the ferrite content is between 40 and 60%.

Alloys are duplex grades S 2001, S 2304, S 2205 and is most commonly used alloy 2205 (UNS 31803).

Its resistance to pitting corrosion is generally very good by virtue of its composition, in this type of duplex steels a commonly known is used to define the resistance to pitting corrosion will stainless steels (especially in media containing chlorides ) is the "PRE" (Pitting Resistance Equivalent) which takes into account the presence of those chemical elements which protect against this eventuality:
PRE = % CR + 3.3 % Mo + 16% N

Duplex steels generally have higher tensile strength and yield point than austenitic steels and ferritic, duplex normally used in a temperature range between -45 and 260 ° C.

Pipes used in heat exchangers, piping for conducting oil platform overseas, gas wells, line pipes, valve bodies for handling seawater or casting pumps etc.

ASTM-A890-1B - 25 Cr-5Ni-Mo-Cu (CD4MCu)
ASTM-A890-3A - 25 Cr-5Ni-Mo-Cu (CD6MCu)
ASTM-A890-4A - 22 Cr-5Ni-Mo-Cu (CD3MCu)
ASTM-A890-5A - 25 Cr-7Ni-Mo-N (CE3MN)

Properties and Applications

Carbon steels

When iron is alloyed with carbon in proportions lower than 2% of carbon, it is called carbon steel..

The proportion of carbon and the heat treatment of the steel determine the properties of the steel, in terms of hardness and mechanical resistance.

According to the amount of carbon, steels can be classified as follows:

  • - Low carbon steels (less than 0.30%)
  • - Medium carbon steels (between 0.30 / 0.50%)
  • - High carbon steels (more than 0.50%)

Mechanical properties vary according to the composition and heat treatments that can be performed.

ASTM-A217 C5 ASTM-A217 WC9
ASTM-A487 2C ASTM-A487 4C
ASTM-A915 SC 4140 API-36K