1. Material Specification 
2. Material Grade

For Example, In SA 106 Gr.B the “SA106” is the material specification, and “Gr.B” is the grade of the material.

Please note that for a particular specification there may be more than one grade. For example, SA106 has three grades i.e. Grade A, Grade B, and Grade C.

In this article, The Material Specification & Grades has been explained, as per ASME Sec II, for the following Items/commodities;

1. Pipes

2. Tubes

3. Forgings

4. Castings

5. Fittings

6. Valves

7. Nuts and Bolts

ASME Material Specifications for Pipes:

1. SA 53: Hot-dipped, Zinc-coated, Welded, And Seamless Pipes

2. SA 106: Seamless Carbon Steel Pipe For High-temperature Service

3. SA 312: Seamless, Welded, And Heavily Cold Worked Austenitic Stainless Steel Pipes

4. SA 333: Seamless And Welded Steel Pipe For Low-temperature Service And Other Applications With Required Notch Toughness

5. SA 335: Seamless Ferritic Alloy-steel Pipe For High-temperature Service

6. SA 358: Electric-fusion-welded Austenitic Chromium-nickel Stainless Steel Pipe For High-temperature Service And General Applications

7. SA 376: Seamless Austenitic Steel Pipe For High-temperature Central-station Service

8. SA 409: Welded Large Diameter Austenitic Steel Pipe For Corrosive Or High-temperature Service

9. SA 672: Electric-fusion-welded Steel Pipe For High-pressure Service At Moderate Temperatures

Popular Grades for Pipes:

Material Specifications for Tubes:

1. SA 179: Seamless Cold-drawn Low-carbon Steel Heat-exchanger And Condenser Tubes

2. SA 192: Seamless Carbon Steel Boiler Tubes For High-pressure Service

3. Sa 209: Seamless Carbon-molybdenum Alloy-steel Boiler And Superheater Tubes

4. SA 210: Seamless Medium-carbon Steel Boiler And Superheater Tubes

5. SA 213: Seamless Ferritic And Austenitic Alloy-steel Boiler, Superheater, And Heat-exchanger Tubes

6. SA 249: Welded Austenitic Steel Boiler, Superheater, Heat-exchanger, And Condenser Tubes

7. SA 556: Seamless Cold-drawn Carbon Steel Feedwater Heater Tubes

8. SA 688: Seamless And Welded Austenitic Stainless Steel Feedwater Heater Tubes

Popular Grades for Tubes:

Material Specifications for Plates:

1. SA 240: Chromium And Chromium-nickel Stainless Steel Plate, Sheet, And Strip For Pressure Vessels And For General Applications

2. SA 299: Pressure Vessel Plates, Carbon Steel, Manganese-silicon

3. SA 302: Pressure Vessel Plates, Alloy Steel, Manganese-molybdenum And Manganese Molybdenum-nickel

4. SA 387: Pressure Vessel Plates, Alloy Steel, Chromium-molybdenum

5. SA 515: Pressure Vessel Plates, Carbon Steel, For Intermediate-And Higher-temperature Service

6. SA 516: Pressure Vessel Plates, Carbon Steel, For Moderate- And Lower-temperature Service

7. SA 517: Pressure Vessel Plates, Alloy Steel, High-strength, Quenched And Tempered

8. SA 204: Pressure Vessel Plates, Alloy Steel, Molybdenum

9. SA 225: Pressure Vessel Plates, Alloy Steel, Manganese-vanadium-nickel

10. SA 283: Low And Intermediate Tensile Strength Carbon Steel Plates

11. SA 285: Pressure Vessel Plates, Carbon Steel, Low- And Intermediate-tensile Strength

12. SA 353: Pressure Vessel Plates, Alloy Steel, Double-normalized And Tempered 9% Nickel

13. SA 455: Pressure Vessel Plates, Carbon Steel, High-strength Manganese

14. SA 533: Pressure Vessel Plates, Alloy Steel, Quenched And Tempered, Manganese molybdenum And Manganese molybdenum-nickel

15. SA 537: Pressure Vessel Plates, Heat-treated, Carbon-manganese-silicon Steel

16. SA 542: Pressure Vessel Plates, Alloy Steel, Quenched-and-tempered, Chromium-molybdenum, And Chromium molybdenum-Vanadium

Popular Grades for Plates:

Material Specifications for forgings:

1. SA 105: Carbon Steel Forgings, For Piping Applications

2. SA 181: Carbon Steel Forgings, For General-purpose Piping

3. SA 182: Forged Or Rolled Alloy And Stainless Steel Pipe Flanges, Forged Fittings, And Valves And Parts For High-temperature Service

4. SA 266: Carbon Steel Forgings For Pressure Vessel Components

5. SA 336: Alloy Steel Forgings For Pressure And High-temperature Parts

6. SA 350: Carbon And Low-alloy Steel Forgings, Requiring Notch Toughness Testing For Piping Components

7. SA 372: Carbon And Alloy Steel Forgings For Thin-walled Pressure Vessels

8. SA 723: Alloy Steel Forgings For High-strength Pressure Component Application

Popular Grades for Forgings:

Castings Material Specifications:

1. Sa 216: Steel Castings, Carbon, Suitable For Fusion Welding For High-temperature Service

2. Sa 217: Steel Castings, Martensitic Stainless And Alloy, For Pressure-containing Parts, Suitable For High-temperature Service

3. Sa 351: Castings, Austenitic, Austenitic-ferritic (Duplex), For Pressure-containing Parts

4. Sa 352: Steel Castings, Ferritic And Martensitic, For Pressure-containing Parts, Suitable For Low-temperature Service

Popular Grades for Castings:

Material Specifications for Fittings:

1. SA 234: Piping Fittings Of Wrought Carbon Steel And Alloy Steel For Moderate And High-temperature Service

2. SA 403: Wrought Austenitic Stainless Steel Piping Fittings

3. SA 420: Piping Fittings Of Wrought Carbon Steel And Alloy Steel For Low-temperature Service

Material Specifications for Flanges:

1. SA 105: Carbon Steel Forgings, For Piping Applications

2. SA 182: Forged Or Rolled Alloy And Stainless Steel Pipe Flanges, Forged Fittings, And Valves And Parts For High-temperature Service

3. SA 350: Carbon And Low-alloy Steel Forgings, Requiring Notch Toughness Testing For Piping Components

Material Specifications for Valves:

1. SA 216: Steel Castings, Carbon, Suitable For Fusion Welding For High-temperature Service

2. SA 217: Steel Castings, Martensitic Stainless, And Alloy, For Pressure-containing Parts, Suitable For High-temperature Service

3. SA 352: Steel Castings, Ferritic And Martensitic, For Pressure-containing Parts, Suitable For Low-temperature Service

4. SA 182: Forged Or Rolled Alloy And Stainless Steel Pipe Flanges, Forged Fittings, And Valves And Parts For High-temperature Service

Material Specifications for Nuts and Bolts:

1. SA 193: Alloy-steel And Stainless Steel Bolting For High-temperature Or High-Pressure Service And Other Special Purpose Applications

2. SA 194: Carbon And Alloy Steel Nuts For Bolts For High Pressure Or High-Temperature Service, Or Both

3. SA 320: Alloy-steel And Stainless Steel Bolting For Low-temperature Service

• Plates
• Bars
• Shapes (beams, channels, angles, etc.)

In this article following topics will be covered;

1. Mechanical Properties of ASTM A36 steel

2. Chemical Properties of ASTM A36 steel

3. A 36 Steel Equivalent

4. Other properties of A 36 steel such as Density, Melting Point, Modulus of elasticity (Young’s modulus), Shear modulus, Poisson’s ratio, etc. 

Mechanical Properties of ASTM A36 steel:

The mechanical properties such as Ultimate tensile strength, Yield stress, and % Elongation of A36 steel plates, shapes (beams, channels, angle, etc.), and bars are given in the below table;

NOTE:

1. For wide flange shapes, having flange thickness more than 75 mm (3 in), minimum % elongation in 50 mm (2 in.) will be 19 % and the 550 MPa (80 ksi) maximum tensile strength will not apply

2. For plates with a thickness of more than 200 mm (8 in.), the minimum yield stress value will be 220 MPa (32 ksi)

3. For plates with a width of more than 600 mm (24 in), the minimum % elongation requirement will be reduced to two percentage points.

Chemical Properties of ASTM A36 steel:

The chemical properties of A36 steel plates, shapes (beams, channels, angle, etc.), and bars are given in the below table;

Note: For shapes with flange thickness more than 75 mm (3 in.) – Manganese content required 0.85–1.35 % and silicon content required 0.15–0.40%.

A 36 Steel Equivalent:

Due to the varying amounts of chemical and mechanical properties, It is very hard to come to a conclusion for an equivalent of A36 steel from other standards. However, in general, the following steel properties are very near to A36 steel and hence can be considered comparable to A36 steel;

• European Standard (EN 10025-2:2004): Equivalent Grade – S235JRG2
• Canadian Standard (CSA G40.21-13): Equivalent Grade 260W
• German Standard (DIN 17100): Equivalent Grade – St 37-2
• Japanese Standard (JIS G3101): Equivalent Grade – SS400
• Indian Standard (IS2002): Equivalent Grade – E250
• Chinese Standard (GB 700-88): Equivalent Grade – Q235B
• ISO Standard (630:1995 A1:2003): Equivalent Grade E 235 (Fe 360)

Other properties of A 36 steel:

Density:  7.85 g/cm³ (0.284 lb/in³)  

Melting Point: 1425-1538 °C (2,600-2,800 °F)

Modulus of elasticity (Young’s modulus): 200 GPa (29000 ksi)

Bulk Modulus: 140 GPa (20300 ksi)

Shear modulus: 79.3 GPa (11500 ksi)

Poisson’s ratio: 0.260

• What is stainless steel?

• Types of stainless steel.

• Is stainless steel magnetic?

• Stainless steel welding and weldability.

• How to select the welding rod or filler wire?

we will start this article with the first topic/question i.e what is stainless steel?

WHAT IS STAINLESS STEEL?

Stainless steels (SS) are essentially iron base alloy steels containing at least 10.5 % Chromium. Other important alloying elements that may be present in stainless steel are carbon, Nickel, Manganese, etc.

“SS’ is an abbreviation used for stainless steel in the industries.

Due to the presence of chromium, a very thin chromium-rich oxide layer is formed on the outer surface of stainless steel. This chromium-rich oxide layer has two unique features;

1. Passive layer: Due to passive (inactive) in nature, this layer does not reacts with the environment (especially oxygen – the major cause of rusting) and prevents oxidation hence the stainless steel remains safe and free from rust.

2. Self-repairable: Whenever the chromium-rich oxide layer is damaged, a new layer is formed quickly. Hence, the stainless steel will remain rust-free. However, the rate at which the chromium oxide passive film is developed depends on its chromium content.

Polished stainless steel remains bright under most environmental conditions.

TYPES OF STAINLESS STEELS

There are five main types (or grades) of stainless steel, these are the following;

1. Austenitic stainless steel – FCC (face-centered cubic) crystal structure
2. Ferritic stainless steel – BCC (body-centered cubic) crystal structure
3. Martensitic stainless steel – BCT (body-centered tetragonal) crystal structure
4. Duplex stainless steel – FCC + BCC i.e. mixture of Austenite and Ferrite
5. Precipitation-hardening (PH) stainless steel

Out of these five types, the first four i.e. Austenitic, Ferritic, Martensitic, and duplex are categorized according to their crystal structure and if they are additionally strengthened by the precipitation hardening process then the product obtained is known as Precipitation-Hardening (PH) stainless steel.

In addition to the above-mentioned types, some advanced types (or specialty grades) of stainless steels are also being used in the industries, these are;

• Superaustenitic Stainless steel
• Superferritic stainless steel
• Supermartensitic stainless steel
• Superduplex stainless steel

The austenitic stainless steel can be further divided into two types;

1. Austenitic stainless steel containing Chromium and Nickel as the main alloying elements (In addition to Iron) – These are identified as AISI 300 Series types.
2. Austenitic stainless steel containing Chromium, Nickel, and Manganese as the main alloying elements (In addition to Iron) – These are identified as AISI 200 Series types.

Ferritic stainless steels contain chromium as the major alloying element and are identified as AISI 400 series types.

Martensitic stainless steels also contain chromium as the main alloying element (In addition to Iron and Carbon) and identified are AISI 400 series types.

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A very important question, which comes to our mind, is;

Is stainless steel magnetic?

In general, the Austenite stainless steels are non-magnetic, a term paramagnetic is also used for non-magnetic elements. Hence, we can say that Austenitic stainless steels are paramagnetic. This concept will be discussed later on in this article.

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Table 1, gives a general summary of types of Stainless steel and their corresponding identification No. (As per the AISI Classification system), detrimental alloying elements, Main types/grades, and P Numbers (As per ASME Sec IX).

Table – 1

Now, we shall discuss the three important types of stainless steel i.e Austenitic, Ferritic, and Martensitic stainless steel, properties & grades, weldability, and suitable filler metal/electrodes.

1. AUSTENITIC STAINLESS STEEL:

Austenitic stainless steels are the most widely used stainless steel in the world. They have a face-centered cubic (FCC) crystal structure and are nonmagnetic (also known as paramagnetic) in the annealed condition. However, the magnetic properties of austenitic stainless steel can be increased by cold working.

The chromium content is generally above 16% in austenitic stainless steels and total chromium, nickel, manganese, and silicon content over 25% by weight, They are popular among industries for;

• Good ductility
• Excellent strength
• Good corrosion resistance
• High toughness
• Excellent cryogenic properties
• Excellent strength and oxidation resistance at high temperatures.

Austenitic stainless steel based mainly on the Iron-Chromium-Manganese-Nitrogen is identified by a three-digit number system starting with 2, such as 201 and 202. Whereas, alloys based on the Iron –Chromium-Nickel-Carbon are also identified by a three-digit number system but starting with 3 for example, 304 and 309, etc.

Due to face-centered-cubic (FCC) crystal structure, austenitic stainless steels have better toughness and ductility than carbon steels and alloy steels. The notch toughness at cryogenic temperatures is also excellent.

Type 316H stainless steels possess the best stress-rupture behavior of the Series 300 austenitic stainless steel.

Weldability of austenitic stainless steel:

Austenitic stainless steels possess higher thermal expansion than ferritic or martensitic stainless steels.

Distortion or warping occurs during the welding of austenitic stainless steel due to it’s high coefficient of thermal expansion and low thermal conductivity.

Austenitic stainless steel is susceptible to solidification and liquation cracking. Hence, proper care to be given while selecting filler material and welding process.

Submerged arc welding (SAW) is not preferred when a fully austenitic stainless steel or low ferrite content weld deposit is required.

Table – 3, gives a guide for the selection of proper filler wire or welding rods as per the base material (for austenitic stainless steel).

Table – 3

Where,

• N – Addition of Nitrogen
• H – High Carbon content
• L – Low Carbon content

2. FERRITIC STAINLESS STEEL:

Ferritic stainless steels are essentially iron-chromium-carbon alloys with a nominal of 11% to 30% chromium along with other ferrite stabilizers, such as molybdenum, aluminum, niobium, or titanium.

They possess a body-centered cubic (BCC) crystal structure. These steels exhibit good ductility and have good resistance to stress corrosion cracking, pitting, and crevice corrosion.

Ferritic stainless steels with Low chromium (Approx 11%) such as Type 409, are commonly used in automotive exhaust systems. Ferritic stainless steel alloys having an intermediary level of chromium content (16% to 18%) are often used in food handling and automotive trim applications. High chromium content ferritic stainless steel with additions of molybdenum (often referred to as superferritic stainless steels) are commonly used in applications that require high levels of oxidation and corrosion resistance such as heat exchangers and piping systems for seawater.

Types 430, 442, and 446 are referred to as the first-generation ferritic stainless steels. They contain mainly chromium as a ferrite stabilizer along with relatively high carbon content.

They often require PWHT otherwise intergranular corrosion may occur. They also exhibit low toughness.

Whereas, Types 405 and 409 are referred to as the second-generation ferritic stainless steels. They have lower chromium and carbon content but contain ferrite formers.

These steels are also referred to as pseudoferritic because they require other ferrite formers in addition to chromium.

They are comparatively less costly, possess good fabrication characteristics, and have useful corrosion resistance than the first-generation ferritic stainless steels but they often possess low toughness.

Weldability of ferritic stainless steel:

Generally, fewer precautions are required during welding because they cannot be hardened by quenching. Hence, the chances of martensite formation are less during the cooling of weld metal. However, Types 430, 434, 442, and 446 are exceptional cases due to the presence of both high chromium and high carbon content. The risk of hydrogen-induced cracking during cooling is more in these alloys especially when welding is carried out under high restraint conditions such as heavy weldments or surfacing welds on carbon steel. To minimize residual stresses that contribute to weld, preheating of 150°C (300°F) or higher can be used.

Chances of Hydrogen embrittlement increases in ferrites stainless steel when martensite is present along ferrite grain boundaries in the weld metal or HAZ. However, Ferritic stainless steels are less susceptible to hydrogen embrittlement if compared to martensitic stainless steel.

The risk of solidification cracking in ferritic stainless steels is comparatively very less because the primary solidification phase is ferrite. However, Alloys with additional alloying elements like titanium and niobium or high impurity levels are more susceptible to solidification cracking

Ferritic Stainless Filler Metals:

To weld ferritic stainless steels with ferritic stainless steels or to any dissimilar steel, Filler metal/welding electrode of the following types can be selected;

1. Filler metals with compositions approximately matching to those of the base metals
2. Austenitic stainless filler metals (Types 309 and 312)
3. Nickel-alloy filler metals (ERNiCr-3, ENiCrFe-2, or ENiCrFe-3)

Filler metals/welding rods matching Types 409 and 430 stainless steels (base metal) are widely available. However, whenever ferritic stainless steels are used as filler metal, the resulting welds lack in toughness properties in both the weld metal and the HAZ

Filler metals made up of Austenitic stainless steel such as Types 309 and 312 or nickel-alloy filler metals such as ERNiCr-3, ENiCrFe-2, or ENiCrFe-3 often are selected for joining ferritic stainless steels to ferritic stainless steels or any dissimilar metals.

Type 444 stainless steel can be welded to matching steel with Type 316L weld metal and Type 430 steel can be welded with E308 and E308L.

when welding ferritic stainless steels to ferritic stainless steels or mild or low alloy steels, nickel alloys, and copper-nickel alloys, Nickel-alloy filler metal, such as ERNiCr-3, ENiCrFe-2, or ENiCrFe-3, can be used which produce sound weld joints.

However, Austenitic stainless steels are generally less resistant to stress corrosion cracking (SCC) than ferritic stainless steel alloys. Hence, proper consideration must be given before choosing filler metals.

To weld Low-chromium ferritic stainless steels, such as 405 and 409 with mild steel, carbon steel filler metals can be used with proper care to avoid excessive dilution.

Preheat and PWHT requirements:

The preheating requirements are determined largely by job thickness, chemical composition, desired mechanical properties, and restraint conditions.

Ferritic stainless steels with low chromium or high-carbon content can be preheated within the range of 150°C to 230°C (300°F to 450°F).

PWHT for first-generation ferritic stainless steels (Types 430, 442, and 446) can be conducted at temperatures ranging from 700°C to 840°C (1300°F to 1550°F). These temperature ranges help prevent further grain coarsening.

Whereas, PWHT for Second-generation ferritic stainless steels (Types 405 and 409) can be conducted at higher temperatures up to at least 1040°C (1900°F)

3. MARTENSITIC STAINLESS STEEL

Martensitic stainless steels were the first stainless steel to be produced in the world. As mentioned above they are essentially iron-chromium-carbon alloys with a nominal of 11.5% to 18% chromium.

They are hardenable by appropriate heat treatments and can also be hardened by cold working.

Martensitic stainless steel can be transformed into austenite when heated beyond 1010°C (1850°F). However, rapid cooling from this temperature will again result in a martensitic microstructure.

These steels are popular for

• Relatively low cost.
• Moderate corrosion resistance,
• Oxidation resistance,
• Lacks toughness and require tempering for adequate toughness
• Ability to develop a wide range of mechanical properties

Martensitic stainless steels are used to fabricate a variety of products, for example, Low and medium carbon martensitic stainless steels are typically used in jet engines, steam turbines, and gas turbines. High carbon martensitic stainless steels are used for gears, shafts, cams, ball bearings, and valves, etc.

Weldability of Martensitic stainless steel:

Martensitic stainless steels often produce hardened HAZs, and as the hardness of HAZ increases, it’s toughness decreases, and susceptibility to Hydrogen induced cracking increases.

As a general practice, post weld heat treatment (PWHT) is given to martensitic stainless steel welded joints, to improve the weld properties.

It’s weldability, in general, increases when an austenitic type filler metal or welding rod is used.

Since Martensitic stainless steels are subject to hydrogen-induced cracking hence proper precautions must be taken in the selection of welding process, handling, and storage of the filler metal and cleanliness to avoid hydrogen from entering into the weld metal.

Following Welding processes can be employed to weld Martensitic stainless steel

1. Arc Welding

• Shielded Metal Arc Welding (SMAW) or stick welding
• Gas Metal Arc welding (GMAW) or MIG Welding
• Gas Tungsten Arc Welding (GTAW) or TIG welding
• Flux Cored Arc Welding (FCAW)
• Plasma Arc Welding (PAW)
• Submerged Arc welding (SAW)

2. Resistance Welding

• Resistance Spot Welding
• Resistance Flash Welding

3. Electron beam welding

4. Laser beam welding

5. Friction welding

6. High frequency welding

Filler metal/Welding Rod for martensitic type stainless steels:

The three most commonly used filler metal grades for martensite stainless steel are;

• E410/ER410
• E410 NiMo /ER410 NiMo
• E420/ER420

Filler metal type 410 (E410/ER410) can be used to weld the following martensitic stainless Types;

• 403
• 410
• 414
• 420

Type 410 NiMo filler metal is used to weld Type CA-6NM castings (cast martensite stainless steel)

Filler metal ER420 is used to weld type 420 stainless steel when the main goal is matching the carbon content of base metal with filler metal. This filler metal may also be used for surfacing of carbon steels to provide good corrosion and wear resistance.

However, martensitic stainless steel welding lacks good toughness properties (except for ER410NiMo), hence PWHT is carried to achieve good toughness (If required).

To achieve good weld metal toughness property, austenitic stainless steel filler metal type 308 (E308/ER308) & 309 (E309/ER309) can also be used to weld martensitic stainless steels to martensitic stainless steels or any other types of stainless steels.

For Types 416 and 416Se steels that are free-machining grades, E312-15 austenitic stainless steel filler metal may be used for welding.

Preheat and PWHT requirements:

Preheat and post weld heat treatment (PWHT) requirements for martensitic stainless steel are given in Table – 2.

Table – 2

What is Steel?

Steel is an alloy of Iron and the principal (main) alloying element is Carbon. However, there are some exceptions to this definition like interstitial-free (IF) steels and type 409 ferritic stainless steels, in which carbon is considered as an impurity.

What is an Alloy?

When different elements are mixed in smaller quantities in the base element, the resulting product is called an alloy of the base element. Hence steel is an alloy of Iron because Iron is the base element (main constituent) in steel and the principal alloying element is Carbon. Some other elements such as Manganese, Silicon, Nickel, Chromium, Molybdenum, Vanadium, Titanium, Niobium, Aluminum, etc. are also added in varying quantities to produce different grades (or types) of Steel.

What Are the Different Types Of Steel?

Based on the chemical compositions, Steel can be categorized into four (04) basic types:

• Carbon Steel

• Stainless Steel

• Alloy Steel

• Tool Steel

1. Carbon Steel:

Carbon steel is the most utilized steel in the industries and accounts for more than 90% of the total steel production. Based on the carbon content, Carbon steels are further classified into three groups.

• Low Carbon Steel/Mild Steel

• Medium Carbon Steel

• High Carbon steel

Carbon content is given in the table below:

2. Stainless Steel:

Stainless steel is an alloy steel that contains 10.5% Chromium (Minimum). Stainless steel exhibits corrosion resistance properties, due to the formation of a very thin layer of Cr2O3 on its surface. This layer is also known as the passive layer. Increasing the amount of Chromium will further increase the corrosion resistance of the material. In addition to Chromium, Nickel and Molybdenum are also added to impart desired (or improved) properties. Stainless steel also contains varying amounts of Carbon, Silicon, and Manganese.

Stainless steels are further classified as;

1. Ferritic Stainless Steels

2. Martensitic Stainless Steels

3. Austenitic Stainless Steels

4. Duplex Stainless Steels

5. Precipitation-Hardening (PH) Stainless Steels

Ferritic Stainless Steel: Ferritic steels consist of Iron-Chromium alloys with body-centered cubic crystal structures (BCC). These are generally magnetic and cannot be hardened by heat treatment but can be strengthened by cold working.

Austenitic Stainless Steel: Austenitic steels are most corrosion-resistant. It is non-magnetic and non-heat-treatable. Generally, austenitic steels are highly weldable.

Martensitic Stainless Steel: Martensitic stainless steels are extremely strong and tough but not as corrosion-resistant as the other two classes. These steels are highly machinable, magnetic, and heat-treatable.

Duplex Stainless Steels: Duplex stainless steel consists of a two-phase microstructure consisting of grains of ferritic and austenitic stainless steel (i.e Ferrite + Austenite). Duplex steels are about twice as strong as austenitic or ferritic stainless steels.

Precipitation-Hardening (PH) Stainless Steels: Precipitation-Hardening (PH) Stainless Steels possess Ultra high strength due to precipitation hardening.

3. Alloy Steel:

In alloy steel, varying proportions of alloying elements are used, to achieve desired (improved) properties such as weldability, ductility, machinability, strength, hardenability and corrosion resistance, etc. Some of the most used alloying elements and their effects are as follows;

Manganese – Increases strength and hardness, decreases ductility and weldability

Silicon – Used as deoxidizers used in the steel making process

Phosphorus – Increases strength and hardness and decreases ductility and notch impact toughness of steel.

Sulfur –Decreases ductility, notch impact toughness, and weldability. Found in the form of sulfide inclusions.

Copper – improved corrosion resistance

Nickel – Increases hardenability and Impact strength of steels.

Molybdenum – Increases hardenability and enhances the creep resistance of low-alloy steels

4. Tool Steel:

Tool steels have high carbon content (0.5% to 1.5%). Higher carbon content provides higher hardness and strength. These steels are mostly used to make tools and dies. Tool steel contains various amounts of tungsten, cobalt, molybdenum, and vanadium to increase the heat and wear resistance, and durability of the metal. This makes tool steels very ideal for use as cutting and drilling tools.