Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium

Definitions

• Field of invention relates to an improved chromium steel and to the method of producing same whereby the finished strip form of said steel exhibits non-ridging characteristics. More specifically, the invention is concerned with improvements on ferritic chromium steels such as A.I.S.I. Type 430, whose general composition limits are as follows:
• Ridging is a defect which should be distinguished from the phenomenon of stretcher straining. This problem, which appears as elongated markings on drawn articles, is a function of yield-point elongation and can be alleviated or eliminated by temper rolling the sheet stock be fore drawing the articles. Ridging cannot be so eliminated or minimized. Stretcher straining, moreover, occurs in about the first five percent of the elongation due to drawing, and then disappears, while ridging becomes noticeable first at about this point and increases to a maximum just before the failure of the metal in tension.
• the normalizing treatment was found effective in producing low ridging quality. However, this procedure involves tight controls in melting the alloy, and was not sufficient to substantially reduce or eliminate the phenomenon without deleteriously afiecting other properties such as hardness and formability.
• the present invention shatters or at least modifies the concept that ridging is associated with the banded microstructure after hot rolling.
• a more definite concept has now been established by the present development. That is, the removal of carbon from the alloy system results in the elimination of ridging. While a banded micro structure after hot rolling was observed in some low carbon steels of this invention, ridging was not found. On the other hand, in one comparison alloy investigated during the development of this invention ridging was found without banding in the hot rolled structure.
• Ni varied between .42 and .56%.
• nitrogen can be present in an amount between about .04-09% by weight. It has been determined that the substantial reduction of caubon in the alloy system, from the typical initial value of 0.06%, results in the elimination of ridging.
• austenite is present as a high temperature phase at the iron-rich end of the system.
• the austenite region is further characterized by a two-phase band or region surrounding same, and separating it from the chromium enriched phase of ferrite. This two-phase region is austenite and ferrite.
• This two-phase region is austenite and ferrite.
• Table II shows the mechanical properties and ridging quality of the several alloys treated in the manner above.
• this invention contemplates and includes carbon levels as high as .01 by weight.
• a process of eliminating ridging in a ferritic chromium stainless steel containing about 1418% by 'Weight chromium, upon drawing from strip form which process comprises selecting a chemistry for said steel with a carbon content no greater than about .006% by weight, and subjecting said steel to a sequence of heat treating and rolling operations, which operations include hot and cold rolling, annealing and normalizing, suitable for reducing said steel to strip form.
• a non-rdiging ferritic chromium stainless steel containing about 14-18% by weight chromium, carbon no greater than about .006% by weight, and the balance essentially iron.

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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 Sheet Steel (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=25292134

Family Applications (1)

Country Status (9)

Cited By (1)

Families Citing this family (2)

• 1969
  • 1969-07-23 US US844213A patent/US3674467A/en not_active Expired - Lifetime
• 1970
  • 1970-06-26 CA CA086656A patent/CA930982A/en not_active Expired
  • 1970-07-07 GB GB3291070A patent/GB1313896A/en not_active Expired
  • 1970-07-21 DE DE19702036138 patent/DE2036138A1/de active Pending
  • 1970-07-22 BE BE753733D patent/BE753733A/fr unknown
  • 1970-07-22 FR FR7027000A patent/FR2055461A5/fr not_active Expired
  • 1970-07-22 SE SE7010130A patent/SE382469B/xx unknown
  • 1970-07-23 JP JP6400370A patent/JPS5517097B1/ja active Pending
  • 1970-07-23 ES ES382073A patent/ES382073A1/es not_active Expired

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