Steel alloy for compound tubes

• US 6,296,953 B1
• Filed: 04/06/2000
• Issued: 10/02/2001
• Est. Priority Date: 08/12/1997
• Status: Expired due to Term

• Current Assignee: Sandvik Intellectual Property AB (Sandvik AB)
• Original Assignee: Sandvik AB
• Inventors: Lindén, Johan, Forsberg, Urban
• Primary Examiner(s): Koehler, Robert R.
• Application Number:
  US09/485,120
• Time in Patent Office: 544 Days
• Field of Search: 428/681, 428/682, 428/683, 428/684, 428/685, 428/686, 428/924, 428/925, 138/143, 420/40, 420/43, 420/44, 420/46, 420/47, 420/48, 420/50, 420/51, 420/52, 420/53, 420/54, 420/55, 420/56, 420/57, 420/59, 420/62, 420/63, 420/67, 420/68, 420/69, 420/70, 420/77, 420/78, 420/79, 420/80, 420/81, 420/83, 420/103, 420/104, 420/105, 420/108, 420/109, 420/110, 420/111, 420/112, 420/117, 420/118, 420/119, 420/120, 420/123, 420/124, 420/125, 420/126, 420/127, 420/128, 420/583, 420/584.1, 420/586.1, 420/588, 148/325, 148/327, 148/331, 148/333, 148/334, 148/335, 148/336, 148/337, 148/442, 148/909, 148/519, 148/590, 148/592
• US Class Current: 428/681
• CPC Class Codes: B32B 15/011 all layers being formed of iron alloys or steels
• CPC Class Codes: F16L 9/02 of metal F16L9/16 - F16L9/22 take precedence
• CPC Class Codes: Y10S 428/924 Composite
• CPC Class Codes: Y10S 428/925 Relative dimension specified
• CPC Class Codes: Y10T 428/12951 Fe-base component
• CPC Class Codes: Y10T 428/12958 Next to Fe-base component
• CPC Class Codes: Y10T 428/12965 Both containing 0.01-1.7% carbon [i.e., steel]
• CPC Class Codes: Y10T 428/12972 Containing 0.01-1.7% carbon [i.e., steel]
• CPC Class Codes: Y10T 428/12979 Containing more than 10% nonferrous elements [e.g., high alloy, stainless]
• CPC Class Codes: Y10T 428/12986 Adjacent functionally defined components

Abstract

A compound tube comprises a layer of a Fe—Cr—Al-alloy and a layer of a load-carrying component and optionally one or several additional layers. The Fe—Cr—Al-alloy has the following analysis in weight-%: carbon<0.3, chromium 5-30, nickel<10, manganese<5, molybdenum<5, aluminium 3-20 , silicon<5, nitrogen<0.3, cerium+bafnium+yttrium<1.0, titanium 0.005-1.0, zirconium 0.005-1.0, niobium 0.005-1.0, the remainder iron, and naturally occurring impurities. These tubes are very resistant towards carbonization and “metal dusting” and are being used to advantage for bayonet tubing, superheat tubing and reformer tubing in steam formation.

Claims

1. A method of use of an iron chromium alloy with a ferritic microstructure, the iron chromium alloy includes in weight-%:

carbon;

<

0.3,

chromium;

5-30,

nickel;

<

10,

manganese;

<

5,

molybdenum;

<

5,

aluminum;

3-20,

silicon;

<

5,

nitrogen;

<

0.3,

cerium+lanthanum+hafnium+yttrium;

<

1.0,

titanium 0.000-1.0,

zirconium;

0.000-1.0,

vanadium;

0.000-1.0,

niobium;

0.000-1.0, and

the rest iron, apart from naturally occurring impurities;

wherein the method comprises forming a compound tube comprising a layer of a load carrying material and a layer of the iron chromium alloy.

2. Use according to claim 1, where the chromium content is 15-25 weight-%.

3. Use according to claim 1, where the nickel content is <

5 weight-%.

4. Use according to claim 1, where the aluminium content is 3-7 weight-%.

5. Use according to claim 1, where the silicon content is <

2 weight-%.

6. Use according to claim 1, where Ce+La+Hf+Y is <

0.5 weight-%.

7. Use according to claim 1, where Ce+La+Hf+Y is between 0.01 and 0.5 weight-%.

11. Compound tube according to claim 6, in the form of bayonet tubing, superheater tubing, or reformer tubing.

8. Compound tube including at least one layer of an iron chromium aluminium alloy, and at least one layer of a load carrying component, wherein the iron chromium aluminium alloy has the following composition in weight-%:

carbon;

<

0.3,

chromium;

5-30,

nickel;

<

10,

manganese;

<

5,

molybdenum;

<

5,

aluminum;

3-20,

silicon, <

5,

nitrogen;

<

0.3,

cerium+lanthanum+hafnium+yttrium;

<

1.0,

titanium;

0.000-1.0,

zirconium;

0.000-1.0,

vanadium;

0.000-1.0,

niobium;

0.000-1.0, and

the rest iron, apart from naturally occurring impurities.

9. Compound tube according to claim 8, wherein the outer diameter of the tube is between 15 and 200 mm and that it has a total wall thickness of between 2 and 20 mm.

10. Compound tube according to claim 8, wherein the layer of the iron chromium aluminium alloy mentioned constitutes 20-50% of the total wall thickness.