What Is The Difference Between Stainless Steel And Duplex Stainless Steel
Any steel that is stainless is referred to as stainless steel. The content of the material must include at least 10% chromium for it to be considered stainless. There are grades of austenitic and ferritic stainless steel. The 400 series and 300 series, respectively, contain these. Austenitic steels are not magnetic, whereas ferritic steels are magnetic. Their metallurgic microstructures differ. The metallurgical microstructure of duplex steels, which combine the greatest qualities of ferritic and austenitic steel grades, contains both ferritic and austenitic phases. Duplex steels are robust and resistant to corrosion. Modern duplex grades are utilised in place of more expensive, more conventional metals. Standard duplex and super duplex are two of the three main types of duplex steel.
Although stainless steels may tolerate some corrosion, they are not very effective against extremely corrosive substances. The austenitic stainless steel grades like 316 can withstand high chloride concentrations but not acids. Duplex grades are more resistant to corrosion when exposed to acids, reducing agents, oxidising agents, and chlorides. The various duplex grades offer greater corrosion resistance than the majority of austenitic stainless steels. Much more adaptable materials, including hastelloys, are employed in highly corrosive applications like acid production facilities.
The procedures of pickling and passivation increase a material's ability to resist corrosion. The pickling process involves cleaning the surface of any metal to get rid of contaminants. Before being used in delicate applications like food grade applications and chemical applications, pipes and tubes must be cleaned of inorganic pollutants and stains. The process of passivation renders the surface of the material inactive. An acid bath removes the iron and oxides from the surface. For items that will be utilised in acidic applications and applications with other oxidising agents, the passivation process is very beneficial. To achieve the greatest results and completely clean the surface, metals are often pickled, machined, and then passivated.
Stainless steels are unquestionably less expensive than duplex grades. The stainless steels are widely utilised and are easily accessible on the market. They were easily machined, cut, moulded, and welded. The market does not have easy access to the duplex steel grades. Since they are less common than stainless steels, they must be ordered and specified. Additionally, due to the higher alloying content in the composition, duplex steel prices are higher. Specific welding techniques are required for the different duplex steel grades, such as preheating to a predetermined temperature before welding and post-weld heat treating. However, despite their increased cost, duplex steels are still preferred for applications that call for strength, corrosion resistance, and high temperature resistance.
| EUROPE EN | BRITISH BS | AISI | DIN | SS | TYPICAL COMPOSITION (%) | ||||
|---|---|---|---|---|---|---|---|---|---|
| C | CR | NI | MO | OTHER | |||||
| 1.4362 | X2CrNiN23-4 | 2327 | 0.03 × | 22 | 4 | 0.4 | 0.4 Cu | ||
| 1.4410 | 2328 | 0.03 × | 24 | 6 | 3 | ||||
| 1.4460 | 329 | X4CrNiMoN27-5-2 | 2324 | 0.05 × | 25 | 5 | 1.5 | ||
| 1.4462 | X2CrNiMoN22-5-3 | 2377 | 0.03 × | 22 | 5 | 3 | |||
| 1.4501 | 318S13 | 0.03 × | 24 | 6 | 3 | 0.5 W | |||
| 1.4507 | 0.03 × | 24 | 6 | 3 | 1.0 Cu | ||||
| DUPLEX TYPE | PREN |
| Standard | Approximately 35 |
| Lean | 25-30 |
| Duplex | Above 40 |
| AUSTENITIC STAINLESS STEEL | FERRITIC STAINLESS STEEL | MARTENSITIC STAINLESS STEEL | DUPLEX STEEL | |
|---|---|---|---|---|
| Formability | M/H | L/M | L | L/M |
| Oxide Resistance | M | H | - | M |
| Weldability | M/H | M/H | L | M |
| Toughness | H | L/M | M | M |
| Room Temp. Strength | M/H | M | VH | H |
| Corrosion Resistance | H | M/H | M | M/H |
| Strength at Temperature | H | L/M | - | H |
| Price Comparison | H | M | M | H |
| GRADES | TEMPERATURE | YOUNG'S MODULUS | THERMAL EXPANSION COEFFICIENT | SPECIFIC HEAT CAPACITY | THERMAL CONDUCTIVITY | ||
|---|---|---|---|---|---|---|---|
| C | F | GPA | 10−6K1 | J KG−1 K−1 | WM−1 K−1 | ||
| Ferritic | A516* | 20 | 68 | 205 | 12.5 | 450 | 60 |
| S43000 | 20 | 68 | 205 | 10 | 480 | 22 | |
| S44700 | 20 | 68 | 205 | 10 | 480 | 21 | |
| Auslenitic | S30400 | 20 | 68 | 205 | 16 | 520 | 16 |
| N08904 | 20 | 68 | 205 | 16 | 544 | 15 | |
| Duplex | S31803 | 20 | 68 | 200 | – | 470 | 14 |
| 100 | 212 | 190 | 13 | 500 | 15 | ||
| 200 | 392 | 180 | 14 | 530 | 17 | ||
| 300 | 572 | 170 | 14.5 | 560 | 18 | ||
| S32304 | 20 | 68 | 200 | 13 | 470 | 16 | |
| Superduplex | S32750 | 20 | 68 | 200 | 13 | 470 | 14 |
| S32760 | 20 | 68 | 190 | 12.8 | 482 | 12.9 | |
| S32520 | 20 | 68 | 205 | 13.5 | 450 | 17 | |
| 100 | 212 | 195 | 14 | 500 | 18 | ||
| 200 | 392 | 185 | 14.5 | 530 | 19 | ||
Duplex stainless Steel:
Austenitic Stainless Steel:
Precipitation Hardened Stainless Steel:
Martensitic Stainless Steel:
Ferritic Stainless Steel:
