Difference Between Duplex and Super Duplex Stainless Steel

 

What is the Difference Between Duplex and Super Duplex Stainless Steel?

Significant difference between Super Duplex Stainless Steel and Duplex Stainless Steel. Super Duplex variants are characterized by a higher alloying addition of 25% chromium, in contrast to Duplex Stainless Steels with 22% chromium. Elevating the chromium content enhances the resistance to pitting corrosion. It’s important to note that these factors are not the sole determinants; other variables also play a role.

Price Difference Between Duplex and Super Duplex Stainless Steel

Super duplex materials, owing to their higher chromium, nickel, and molybdenum content, are more expensive compared to the standard duplex grades. Within both standard duplex and super duplex categories, various grades exist, each with its distinct material composition. As a result, the prices differ based on these compositions. Generally, a super duplex is pricier than the standard duplex grades due to its enhanced alloy content and superior properties.

Welding Duplex And Super Duplex Stainless Steel

One of the significant challenges when welding metallic components involves dealing with chromium carbide precipitation. This phenomenon can lead to intergranular corrosion and localized corrosion over the long term. Because both duplex and super duplex stainless steel include a high chromium concentration, they are susceptible to chromium carbide precipitation.

However, the extent of carbide precipitation is also influenced by the carbon content present in these materials. To mitigate this issue, proper preheating prior to welding is essential, followed by post-weld heat treatment. Fortunately, due to their inherent resistance to corrosion, both these materials are viable for welding, provided that the appropriate procedures are meticulously followed, and the correct parameters are diligently maintained.

Duplex And Super Duplex Corrosion Resistance

As previously said, integrating chromium, nickel, molybdenum, nitrogen, and tungsten into their alloys improves their corrosion resistance. Pitting resistance can reach amazing values of up to 45. Furthermore, these alloys may be used at high temperatures without oxidation damage. They are also extremely resistant to different alkaline, acidic, and neutral solutions.

Duplex & Super Duplex Stainless Steel Cutting Speed

Cutting through duplex and super duplex stainless steel can be a challenge, but fear not! We’ve got you covered. Achieving the perfect cutting speed is crucial for efficient machining.

Duplex grades can be cut and machined faster than super duplex due to their composition. Super duplex, with its higher chromium, nickel, and molybdenum content, demands more precision and patience.

To tackle these materials like a pro, you’ll need top-notch tools and a slower cutting pace. Luckily, there are tests like the turning, chip formation, and drilling tests to help determine the ideal cutting speeds for various grades.

With the right approach, you’ll be cutting through duplex and super duplex stainless steel like a hot knife through butter!

Duplex Stainless Steel Chemical Composition

Grade	C	Mn	Si	P	S	Cr	Mo	Ni	N	Fe
S31803	0.030 max	2.00 max	1.00 max	0.030 max	0.020 max	22.0 – 23.0	3.0 – 3.5	4.50 – 6.50	0.14 – 0.20	63.72 min
S32205	0.030 max	2.00 max	1.00 max	0.030 max	0.020 max	21.0 – 23.0	2.50 – 3.50	4.50 – 6.50	0.8 – 0.20	63.54 min

2205 Duplex Stainless Steel Equivalent

S31803 / S32205	Density	Melting Point	Yield Strength (0.2%Offset)	Tensile Strength	Elongation
7.8 g/cm3	1350 °C (2460 °F)	Psi – 80000 , MPa – 550	Psi – 116000 , MPa – 800	15 %

Mechanical Properties of UNS S31803 Duplex 2205

STANDARD	WERKSTOFF NR.	UNS
Duplex 2205	1.4462	S31803 / S32205

Super Duplex SS 2507 Equivalent

Grade	UNS	EN	W-Nr	DIN	AFNOR	SS
Duplex 2707 HD Bars	S32707	–	–	–	–	–
Duplex 2507 Bars	S32750	1.4410	–	X 2 CrNiMoN 25 7 4	–	2328

Super Duplex 2507 Chemical Composition

C	Si	Mn	P	S	Cr	Ni	Mo	N	Cu
≤0.030	≤0.8	≤1.2	≤0.035	≤0.015	25	7	4	0.3	≤0.5

Mechanical Properties of Super Duplex UNS S32750

Proof strength	Tensile strength	Elong.	Hardness
Rp0.2a)	Rm	Ab)	Rockwell C
ksi	ksi	%
≥80	110-135	≥25	≤28