US3555236A - Corrosion resistant boiler tube for chemical recovery vapor generating unit - Google Patents

Corrosion resistant boiler tube for chemical recovery vapor generating unit Download PDF

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Publication number
US3555236A
US3555236A US790182*A US3555236DA US3555236A US 3555236 A US3555236 A US 3555236A US 3555236D A US3555236D A US 3555236DA US 3555236 A US3555236 A US 3555236A
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United States
Prior art keywords
steel
tube
boiler tube
corrosion
percent
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Expired - Lifetime
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US790182*A
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English (en)
Inventor
Tsuneto Hayashi
Hidejiro Kinoshita
Koji Iwahashi
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Mitsubishi Heavy Industries Ltd
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Mitsubishi Heavy Industries Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
    • B23K35/24—Selection of soldering or welding materials proper
    • B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550 degrees C
    • B23K35/3053—Fe as the principal constituent
    • B23K35/308—Fe as the principal constituent with Cr as next major constituent
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L58/00—Protection of pipes or pipe fittings against corrosion or incrustation
    • F16L58/02—Protection of pipes or pipe fittings against corrosion or incrustation by means of internal or external coatings
    • F16L58/04—Coatings characterised by the materials used
    • F16L58/08—Coatings characterised by the materials used by metal
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12771—Transition metal-base component
    • Y10T428/12861—Group VIII or IB metal-base component
    • Y10T428/12951—Fe-base component
    • Y10T428/12958—Next to Fe-base component
    • Y10T428/12965—Both containing 0.01-1.7% carbon [i.e., steel]

Definitions

  • the disclosure relates to a corrosion resistant boiler tube for chemical recovery vapor generating units, in which a boiler tube of carbon steel or low alloy Cr-M. steel has weld deposited on its exterior surface a coating of high chromium steel containing 13-26 percent Cr and 0.51.5 percent Cb.
  • BACKGROUND OF THE INVENTION ln the production of paper pulp, useful chemicals are recovered and steam power requirements are supplied, at least in part, by burning the waste liquor, used for digestion of the pulp, in a chemical recovery vapor generating unit.
  • a chemical recovery vapor generating unit may be used to recover soda smelt as well as to generate steam for the production of electric current and for the steam requirements of the pulp production plant.
  • the chemical recovery unit or boiler the organic ingredients of the waste liquor, such as lignin and sugars, are burned. During combustion, the inorganic components, such as principally sodium carbonate and sodium sulfate, are melted and the resulting soda smelt is recovered at the base of the combustion chamber of the recovery unit.
  • boiler tubes of carbon steel or low alloy Cr-Mo steel corrosion due to the attack by soda smelt occurs in those tubes which are located in the combustion chamber at and near to the inlet for the introduction of primary air, which is the location of highest temperature. Such corrosion also occurs preferentially in tubes located in the lower bent portion of the super heater.
  • the rate of corrosion of the boiler tubes is of the order of 1 mm. per year in a unit operating under pressure of 100 kg./cm.
  • the wall thickness of a boiler tube in the combustion chamber is normally from 5 to 6 mm., the useful life of boiler tubes in the combustion chamber is usually about 4 to 5 years.
  • the first process mentioned above has the drawback that the studs corroded and reduced in length in a relatively short time, and to the extent that the anticorrosive material applied in the interspaced is liable to fall out.
  • this material is adhered only mechanically to the tube walls, and there is therefore the disadvantage that the anticorrosive material has a tendency to strip off from the tube walls.
  • the third process mentioned above there is the hazard that the tube can be cracked owing to the difference in thermal expansions between the protecting material of stainless steel and the base material of the tube, if the protectingmaterial is inadequately secured to the base material of the tube.
  • This third method has the further disadvantage, among others, that the heat efficiency of the recovery unit is reduced.
  • This invention is directed to boiler tubes for use in chemical recovery vapor generating unitsand, more particularly; to such boiler tubes having improved resistance to corrosion and suitable, for example, fo'r'use in a chemical recovery vapor generating unit used to recover soda smelt?"
  • a boiler tube, for use in a chemical recovery vapor generating unit is provided in which the aforementioned disadvantages are avoided.
  • inexpensive high Cr steel containing Cr and Cb is weld deposited on the exterior surface of the wall of a boiler tube of carbon'st eel or low alloy C r-Mo steel.
  • the weld deposited material riot only has physical properties similar to those of the basem'aterial of thetube, but also has mechanical properties superior to those of the base material. Thus, the weld deposited material hasa substantially higher resistance to attack by soda smelt than does the base material, and moreover can be readily welded to the base material.
  • the material weld deposited on a base material of carbon steel or low alloy Cr-Mo steel comprises a high chromium steel containing 13-26 percent Cr and 0.5--l.5 percent Cb.
  • a boiler tube in accordance with the present invention has a remarkably high resistance to corrosion, due to the particular coating weld deposited on the surface of the base material. With the boiler tube of the present invention, the anticorrosive deposited layer can neither drop off nor strip off the base material, because the weld deposited material has weldability so good that the weld deposited layer can-be adhered strongly and closely to the base material of theboiler tube.
  • the weld deposited material has physical properties very similar to those of the base material of the boiler tube.
  • An additional advantage is that the weld deposited material, in the case of a boiler tube embodying the present invention, is less expensive than Cr-Ni stainless steel. Consequently, the overall expense of the boiler tube is reduced while the boiler tube still has a long useful life since it exhibits a combination of the abovementioned advantages and also has a high resistance to corrosion due to soda smelt.
  • Boiler tubes embodying the present invention may be formed by weld depositing high Cr steel, containing a specific proportion of Cb, onto the base material by a hand welding method orby s a submerged arc welding method.
  • the weld depositing of the protective material onto the base material is effected at those portions of the surface of the basic tube where corrosion is likely to occur due to attack by soda smelt.
  • the thickness of the weld deposited layer should be l mm or more. In practice, it is preferred, from the standpoint of economics, that the thickness of the weld deposited layer be up to 5 mm.
  • Each tube may have a coating weld deposited thereon while i it is still in the form of a single tube, the distortion of the tube may then be corrected by suitable measures, a number of the coated tubes may thereafter be assembled in a panel, and the assembly may then be annealed to eliminate stress in the assembly.
  • the weld depositing of the coating may be effected after a group of tubes have been assembled into a panel.
  • the high Cr steel used as the weld deposited protective coating in the tube of the present invention should contain the specific proportions of Cr and Cb, because the percentages of Cr and Cb in the high Cr steel are critical as will be made apparent hereinafter.
  • an object of the present invention is to provide an improved corrosion resistant tube for use in waste recovery vapor generating units.
  • Another object of the invention is to provide such a tube comprising a base material having a high Cr steel weld deposited on its exterior surface.
  • a further object of the invention is to provide such a tube in which the base material is carbon steel or low alloy Cr-Mo steel and the protective coating weld deposited thereon is a high Cr steel including a specific proportion of C b.
  • Still another object ofthc invention is to provide such a tube formed of carbon steel or low allow Cr-Mo steel and having weld deposited on its outer surface a coating of high chromium-steel containing l-3-26 percent Cr and 0.5-1.5 percent Cb.
  • a further object of the invention is to provide such a boiler tube which is particularly resistant to corrosion due to attack by soda smelt,
  • Another object of the invention is to provide such a tube including a base material having weld deposited thereon a corrosion resistant material, and in which the corrosion resistant material has physical properties similar to those of the base material but corrosion resisting properties very substantially in excess of those of the base material.
  • FIG. I is a graph which shows a relation between the Cr content of Cr steel and the rate of corrosion of the Cr steel due to the attack of soda smelt;
  • FIGS. 20 and 2b are microphotographic views of the deposition welded layer of 18 Cr-l Cb steel on the boiler tube of the present invention and of the weld deposited layer of 18 Cr steel;
  • FIG. 3 is a graph which shows the results of tests determining the rates of corrosion of various steel materials weld deposited on the surface of the boiler tube;
  • FIGS. 4 and 5 are graphs showing the physical and mechanical properties of various steel materials to be weld deposited on the surface of the boiler tube.
  • the proportion of Cb in the high Cr steel should be within the range of 0.5 to 1.5 percent in accordance with the present invention, because the content of Cb less than 0.5 percent is not effective in making the grains of the Cr steel finer and because a content of Cb more than 1.5 percent is neither economical nor can it produce any further improvement in the mechanical properties of the Cr steel.
  • FIG. 2a which is a microphotographic view of an 18 Cr-l Cb steel as the weld deposited material in accordance with the invention
  • FIG. 2b which is a microphotographic view of an 18 Cr steel used as a reference material
  • the grains in the Cbcontaining Cr steel are very much finer than those in the reference Cr steel.
  • Curve I represents the results obtained with a tube formed of carbon steel STB 35
  • Curve ll represents the results obtained with a tube of 9 Cr-l Mo steel
  • Curve III represents the results obtained with a protecting material of 18 Cr-8 Ni stainless steel
  • Curve IV represents the results obtained with a tube formed of carbon steel STB 35 having weld deposited on its outer surface 18 Cr-l Cb steel in accordance with the present invention.
  • the resistance to smelt corrosion of a tube having a coating of 18 Crl Cb weld deposited thereon is 12 times higher than that of the tube of carbon steel STB 35 and that of the tube of 9 Cr-l Mo steel at a relatively moderate test temperature of the order of 350 C.
  • the difference in the corrosion-resistance of a holder tube in accordance with the present invention from the corrosionresistance of reference materials is greater as the test temperature is increased.
  • the corrosion-resistance resistance of a boiler tube formed in accordance with the present invention is not much different from that of a reference boiler tube of 18 Cr-8 Ni stainless steel at test temperatures in the vicinity of 350 c., but at higher temperatures, the resistance of the reference boiler tube of 18 Cr-8 Ni stainless steel is substantially lower than that of a boiler tube of the present invention.
  • a 13 Cr-l Cb steel which may be used as the weld deposited corrosion-resistance coating within the scope of the present invention, shows a more or less lower resistance to smelt corrosion than does the 18 Cr-l Cb steel, but its corrosion-resistance may still be sufficient for certain uses within the scope of the present invention.
  • the coating of 26 Cr-l Cb steel has a further improved resistance to smelt corrosion as compared to that of the 18 Cr-l Cb steel.
  • Table 2 shows that the average coefficient of thermal expansion of the 18 Cr-l Cb steel in a temperature range of 100 C. to 500 C. is ll.0 X [0- and is slightly smaller than the average value 13.0 X l0--") of the carbon steel STB 35 in the same range of temperature. Since the weld deposited layer of 18 Cr-l Cb steel on the surface of the boiler tube of the present invention, which contacts with the gases at higher temperature has a coefiicient of thermal expansion smaller than that of the base material of the tube, it is clear that the boiler tube of the invention can resist heat-stress with safety.
  • the 13 Crl Cb steel has a slightly lower coefficient of thermal expansion than the 18 Cr-l Cb steel, the boiler tube with this 13 Cr-l Cb steel weld deposited thereoncan also resist heat-stress with safety. It may be appreciated that the 26 Cr-l Cb steel has a coefficient of thermal expansion,
  • Thermal conductivity of the 18 Cr-l Cb steel is somewhat lower than that of the carbon steel STB 35, but this does not produce trouble in the operation of the boiler tube of the present invention.
  • Thermal conductivity of the 13 Crl Cb steel and of the 26 Cr-l Cb steel is substantially of the same order as that of the 18 Cr-l Cb steel and is better than that of 'l8 Cr-8 Ni stainless steel, though the table does now show photographic view in FIG. 6A.
  • those tubes The 18 Cr-l Cb steel exhibits higher yield points and higher tensile strengths, but somewhat lower elongation and lower contraction of area, than the carbon steel STB 35, though it has a strength and toughness sufficient to be used as the weld deposited coating material according to the present invention.
  • Both the 13 Cr-l Cb steel and .the 26 Cr-l Cb steel similarly have mechanical properties sufficient for use as the weld deposited material according to the present invention.
  • the 18 Cr steel however, clearly cannot be used as the weld deposited coating material, as it has a very much lower elongation and contraction of area than does the 18 Cr-l Cb steel. It is apparent that the 18 Cr-l Cb steel exhibits a lower yield point than does the carbon steel STB 35 at higher temperatures, and that the 18 Cr-l Cb steel, as well as the 13 Cr-l Cb steel and 26 Cr-l Cb steel, show higher tensile strengths than does the carbon steel STB 35 at higher temperatures.
  • the 18 Cr-l Cb steel has a more or less lower contraction of area than the carbon steel STB 35 and that the 18 Cr-l Cb steel as well as the 13 Cr-l Cb steel and 26 Cr-l Cb steel exhibit somewhat lower elongations than the carbon steel STB 35.
  • these Cb-containing steels still retain a toughness sufficient to be used as the weld deposited material with advantage.
  • Table 3 there are shown the mechanical properties of the conventional carbon steel STB 35 as well as of the 18 Cr-l Cb steel, the 13 Cr-l Cb steel and the 26 Cr-l Cb steel which are used as the weld deposited coating material for the boiler tube according to the present invention.
  • the mechanical properties shown in Table 3 have been determined at normal temperature.
  • the graph of FIG. 4 includes curves which represent the variations of tensile strength of the different steels at higher temperatures, as well as curves which represent the variations of yield point of the steels at higher temperatures.
  • the upper group of curves in the graph of FIG. 5 represents the variation of sinking-workability of the steels at higher temperatures, and the lower group of curves represents the variation of elongation of the steels at higher temperatures.
  • boiler tubes formed in accordance with the present invention have a durable life of several times to 10 times that of conventional boiler tubes, because the high chromium steel containing 13-26 percent Cr and 0.5-1.5 percent Cb deposited as a surface layer on the boiler tube is highly resistant to attack by soda smelt.
  • the high chromium steel, containing 13-26 percent Cr and 0.5l.5 percent Cb, weld deposited as the surface layer of boiler tubes in accordance with the invention exhibits physical properties very much similar to those of the carbon steel which is the base material of the tube, and moreover it has stronger mechanical properties than does the carbon steel.
  • These properties of the Cr steel containing Cb, and having high resistance to corrosion provide a tube formed in accordance with the invention with a toughness so high that a recovery unit can be operated at higher temperatures and pressures with greater efficiency than prior recovery units.
  • it is not necessary to use an expensive Cr-Ni stainless steel. Accordingly, the tube in accordance with the invention has very substantial advantages from the economic standpoint.
  • a method of forming a boiler tube resistant to corrosion by soda smelt, when used as the tube of a chemical recovery vapor generating unit comprising, forming a tubular body of a material selected from theigroup consisting of carbon steel and low alloy Cr-Mo steel; and fusion weld depositing, on the exterior surface of said tubular body, a high chromium steel consisting of l326 percent Crand 0.5-1.5 percent Cb, balance Fe and the usual impurities.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Rigid Pipes And Flexible Pipes (AREA)
  • Arc Welding In General (AREA)
US790182*A 1966-09-29 1968-09-26 Corrosion resistant boiler tube for chemical recovery vapor generating unit Expired - Lifetime US3555236A (en)

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JP9121466 1966-09-29

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US00003573A Expired - Lifetime US3712317A (en) 1966-09-29 1970-01-08 Corrosion resistant boiler tube for chemical recovery vapor generating unit

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FI (1) FI47601C (enrdf_load_stackoverflow)
SE (1) SE318582B (enrdf_load_stackoverflow)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3696228A (en) * 1970-09-24 1972-10-03 Arcos Corp Pressure vessel and method of making
US4049186A (en) * 1976-10-20 1977-09-20 General Electric Company Process for reducing stress corrosion in a weld by applying an overlay weld

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3775194A (en) * 1970-12-21 1973-11-27 Texas Instruments Inc Composite material, tubing made from the material, and methods for making the material and tubing
US3867212A (en) * 1972-03-16 1975-02-18 Texas Instruments Inc Composite material, tubing made from the material, and methods for making the material and tubing
US3997373A (en) * 1975-01-13 1976-12-14 Allegheny Ludlum Industries, Inc. Ferritic stainless steel having high anisotropy
SE468209B (sv) * 1991-08-21 1992-11-23 Sandvik Ab Anvaendning av en austenitisk krom-nickel-molybden- jaernlegering foer tillverkning av kompoundroer foer anvaendning som bottentuber i sodahuspannor
US5275893A (en) * 1991-12-11 1994-01-04 Nippon Steel Corporation Line pipe having good corrosion-resistance and weldability

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2050043A (en) * 1936-04-07 1936-08-04 Vulcan Alloy Corp Weld rod
US2164072A (en) * 1937-02-25 1939-06-27 George G Kitzeman Basting device for cooking meats, vegetables, and the like
US3185814A (en) * 1961-12-30 1965-05-25 Siemens Ag Method and apparatus for overlay welding
US3476909A (en) * 1965-06-17 1969-11-04 Mitsubishi Heavy Ind Ltd Method of deposit welding chromium steels

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2963129A (en) * 1954-12-09 1960-12-06 Babcock & Wilcox Co Dissimilar metal welded joint with protective overlay
US3288575A (en) * 1962-10-01 1966-11-29 Murex Welding Processes Ltd Welded nickel steel article

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2050043A (en) * 1936-04-07 1936-08-04 Vulcan Alloy Corp Weld rod
US2164072A (en) * 1937-02-25 1939-06-27 George G Kitzeman Basting device for cooking meats, vegetables, and the like
US3185814A (en) * 1961-12-30 1965-05-25 Siemens Ag Method and apparatus for overlay welding
US3476909A (en) * 1965-06-17 1969-11-04 Mitsubishi Heavy Ind Ltd Method of deposit welding chromium steels

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3696228A (en) * 1970-09-24 1972-10-03 Arcos Corp Pressure vessel and method of making
US4049186A (en) * 1976-10-20 1977-09-20 General Electric Company Process for reducing stress corrosion in a weld by applying an overlay weld

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FI47601B (enrdf_load_stackoverflow) 1973-10-01
US3712317A (en) 1973-01-23
SE318582B (enrdf_load_stackoverflow) 1969-12-15
FI47601C (fi) 1974-01-10

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