US3676110A - Chromium base alloys having excellent corrosion resistance and workability - Google Patents

Chromium base alloys having excellent corrosion resistance and workability Download PDF

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Publication number
US3676110A
US3676110A US96220A US3676110DA US3676110A US 3676110 A US3676110 A US 3676110A US 96220 A US96220 A US 96220A US 3676110D A US3676110D A US 3676110DA US 3676110 A US3676110 A US 3676110A
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workability
alloys
alloy
chromium
manganese
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Expired - Lifetime
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US96220A
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Satoru Mito
Kazumi Shimotori
Mituo Kawai
Kanzi Kawaguchi
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Toshiba Corp
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Tokyo Shibaura Electric Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
    • C22C27/06—Alloys based on chromium

Definitions

  • the present invention relates to chromium-nickel alloys and more particularly to Cr-Ni alloys prepared by adding manganese and, if required, carbon or nitrogen to an alloy mainly consisting of chromium and nickel so as to elevate corrosion resistance and workability.
  • a thermal reactor intended to detoxicate gasoline engine exhaust by combustion is operated at elevated temperature, so that rapid corrosion results from lead oxide (PbO), a combustion product of tetraethyl lead contained in gasoline.
  • PbO lead oxide
  • Cr-Ni alloys for example, 50 Cr-SO Ni alloy in particular, can Withstand the aforementioned corrosion, they have the drawbacks that they present diificulties in forging and though casting may be available to Work them, the resulting product has little ductility and is likely to be broken due to brittleness.
  • chromium base alloys indeed present higher resistance to oxidation and corrosion with increasing chromium content, but become brittle to render forging difficult, possibly resulting in breakage due to said brittleness.
  • the object of the present invention is to provide Cr-Ni alloys free from the above-mentioned shortcomings, prominently resistant to corrosion, readily forged and, what is better, sufficiently ductile to be saved from breakage due to brittleness.
  • the object of the invention is to provide Cr-Ni alloys having excellent workability and corrosion resistance which consist of 40-70% chromium, 27% manganese and nickel as the remainder.
  • workability and corrision resistance there may be added to said alloys, if necessary, 0.5 wt. percent max. carbon or 0.2 wt. percent max. nitrogen alone or in combination.
  • FIG. 1 is a 300-fold magnified microscopic photograph of the crystal structure of Cr-Ni alloys prepared by the prior art process
  • FIGS. 2 and 3 are 300-fold magnified microscopic photographs of the crystal structure of Cr-Ni alloys prepared by the present invention.
  • FIG. 4 is a photographic presentation comparing the deformation of prior art Cr-Ni alloys caused by hammering with that of the present invention.
  • FIG. 5 is a curve diagram comparing the tensile strength and ductility at elevated temperatures of Cr-Ni alloys according to the present invention in comparison with that of the prior art.
  • manganese has been found to help chromium base alloys to have greater resistance to corrosion by, for example, V 0 and PbO and particularly good workability. While the proportion of chromium is less than 40 percent by weight, the crystal structure of Cr-Ni alloys exhibits a v-phase, so that addition of manganese is not significant. However, if the content of chromium rises higher, the alloy assumes an phase. Accordingly, there should be added at least 2 percent by weight of manganese so as to broaden the v-phase for easy forging.
  • manganese leads to decreased oxidation resistance, depending on interrelationship with the chromium content. Therefore it is preferred that the upper limit to addition of manganese be set at 7 percent by weight.
  • a particularly preferable range of Mn addition is between 4 and 6 percent by weight.
  • Nickel like chromium, constitutes the matrix of the subject alloy, and helps its structure to assume a 'y-phase. Therefore, its too small content causes the alloy to present an ot+'y phase, resulting in degraded workability. n the other hand, its too large proportion decreases the chromium content by that extent to reduce resistance to oxidation and corrosion. Further, the amounts of impurities, for example, -Fe and Co unavoidably entrained with the alloy should preferably be less than 1 percent by weight.
  • FIGS. 1, 2 and 3 indicate the crystal structure at 1200 C. of the alloy samples Nos. 4 and 6 of Table 1. These figures show that while an 52 Cr alloy (FIG. 1) without Mn presented the prominent presence of an ot-phase (black dots scattered over the matrix), 48.3 Cr alloy (FIG. 2) containing 2.3 wt. percent and 51.7 Cr alloy (FIG. 3) containing 5.1 wt. percent Mn had the 'y-phase considerably broadened (white region) and that increased addition of Mn noticeably enlarged the 'y-phase. Said increased 'y-phase is considered to elevate the ductility, extensibility and workability of the alloy. This is also supported by the results of the later described tests on Workability and high temperature tensile strength.
  • Table 2 shows the resistance of the samples of Table 1 to oxidation and corrosion.
  • the sample numbers correspond to those of Table 1.
  • the oxidation test was conducted by cutting all the alloy samples into pieces 5 mm. x 10 mm. x 20 mm, exposing the pieces 30 hours to an atmosphere at 1200 C. and after cooling determining weight change by a chemical balance. Said weight change is presented on unit area basis.
  • Table 2 shows that a Cr-Ni alloy containing Mn did not appreciably decrease in oxidation resistance but presented substantially the same degree of said resistance as that without Mn, whereas, with respect to corrosion by V 0 and P130, the Mn bearing alloy exhibited a several times stronger resistance than the latter alloy, and that a Cr-Ni alloy containing C or N indicated the same result.
  • Table 3 represents the results of a hammering workability teSt on the alloy samples of Table l as well as of determination on their resistance to deformation by Dynapak and maximum strain.
  • the workability test was conducted by heating the alloy samples to 1200 C., forging them by hammering and qualitatively deciding workability from the condition of cracks appearing therein and the extent of deformation with respect to deformation resistance and maximum strain, determination was made by subjecting the sample to simple compression applied at a pressure of 4 kg. m./cm. in the axial direction using the Dynapak While maintaining the sample at 1200 C.
  • FIG. 4 shows the deformation of the samples Nos. 2, 4 and 6 when they were forged under the same conditions. Table 3 above and FIG.
  • the Cr-Ni alloy containing Mn according to the present invention is Well adapted not only for forgings but also for castings.
  • Cr-Ni alloys having excellent corrosion resistance and workability consisting on a weight basis of to chromium, 2 to 7% manganese, 0 to 0.2% nitrogen, 0 to 0.5% carbon and the remainder nickel.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
US96220A 1969-12-09 1970-12-08 Chromium base alloys having excellent corrosion resistance and workability Expired - Lifetime US3676110A (en)

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JP44098281A JPS4923450B1 (enrdf_load_stackoverflow) 1969-12-09 1969-12-09

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4025314A (en) * 1975-12-17 1977-05-24 The International Nickel Company, Inc. Nickel-chromium filler metal
US4088479A (en) * 1976-01-16 1978-05-09 Westinghouse Electric Corp. Hot corrosion resistant fabricable alloy

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4025314A (en) * 1975-12-17 1977-05-24 The International Nickel Company, Inc. Nickel-chromium filler metal
US4088479A (en) * 1976-01-16 1978-05-09 Westinghouse Electric Corp. Hot corrosion resistant fabricable alloy

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JPS4923450B1 (enrdf_load_stackoverflow) 1974-06-15

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