Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D3/00—Diffusion processes for extraction of non-metals; Furnaces therefor
  • C21D3/02—Extraction of non-metals
  • C21D3/08—Extraction of nitrogen
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D3/00—Diffusion processes for extraction of non-metals; Furnaces therefor
  • C21D3/02—Extraction of non-metals

Definitions

• the invention concerns a process for the reduction of free nitrogen in steel to a very low level.
• effervescent, or rimmed steel has the advantage over killed steel that at a lower cost, a higher output of the former is obtainable.
• effervescent steel in general has the disadvantage of having no ageing resistance.
• the ageing of effervescent steel decreases in the course of time, which is a consequence of the presence of free nitrogen in this steel.
• additives are added to the steel in a liquid condition, which additives have the property of forming nitrides to bind the free nitrogen.
• the nitrogen present in the steel is in a dissolved state and subject to a partial nitrogen pressure.
• iron forms a nitride which, however, has a relatively high partial ni trogen pressure, so that at low nitrogen levels in the steel the iron nitride decomposes easily.
• An object of the invention is to provide a method in which the nitrogen content of the efiervescent steel is reduced to such an extent that the steel becomes ageing resistant, the method being less expensive than known ones.
• the effervescent steel sheet is brought in close contact or substantially in close contact with a substance (solid or liquid) having a low partial pressure of nitrogen.
• the nitrogen in the substance may be present in a dissolved state, or the substance may form nitrides.
• Another object of the invention is to provide a method wherein steel sheet containing an impurity is brought into contact with a steel sheet having a lower partial pressure of this impurity during annealing. After annealing, the properties of the steel sheet having the lower partial pressure of the impurity are not changed appreciably.
• an effervescent steel sheet may be annealed in contact or substantially in contact with an aluminum-killed steel sheet.
• an excess of [aluminum is present in the form of a solid solution in the steel.
• the partial nitrogen pressure of aluminum nitride is much lower than the partial nitrogen pressure of free nitrogen in steel. By this means the nitrogen is bound by the metallic aluminum in the aluminum-killed sheet.
• Tests have been run with effervescent steel sheet and aluminum-killed steel sheet in close contact, the sheets having been clamped together. Tests have also been run with similar steel sheets, a gap of approximately 0.04 inch being left open between the sheets. The results of the two tests did not show significant differences between them. The importance of this feature lies in the fact that the nitrogen, or other impurity capable of migrating through the steel is in a gaseous state.
• Bringing the sheets close together may be done by composing a pile of alternating effervescent and alumimum-killed steel sheets and clamping these sheets together,
• the temperature preferably chosen lies close to the transition temperature of austenitic to ferritic steel.
• Tests have also been run coating effervescent steel sheet in some cases with zinc and in other cases with magnesium. Results obtained are fully comparable with results obtained using aluminum-killed steel.
• Second test In an annealing charge of cold-rolled eifervescent extra deepdraw steel in the form of sheets (thickness 0.9 mm.) a few aluminum-killed deepdraw steel sheets were inserted in the middle of the pack. The effervescent sheets, clamped each time between two aluminum-killed sheets, served as test sheets; a few sheets from the other part of the pile served as blanks. Annealing time 17 hours at 660680 C. Test sheets and blank sheets were coldrolled once again; elongation about 1%. Again a part was tested at once, another part afted induced ageing (15 /2 hours at 60 C.).
• a process for reducing the nitrogen content of rimmed steel sheet by annealing the said steel sheet substantially in contact with a solid having a lower partial nitrogen pressure than the said steel, so as to promote migration from the said steel sheet to the said solid.
• a process for reducing the nitrogen content of rimmed steel sheet by annealing the said steel sheet substantially in contact with a solid containing at least one nitride forming element, the nitride having a lower partial nitrogen pressure than the free nitrogen in the said steel.
• a process for reducing the nitrogen content of rimmed steel sheet by annealing the said steel sheet substantially in contact with a solid containing an element of the group consisting of aluminum, chromium, titanium, boron, vanadium, silicon, zinc and magnesium.
• said solid comprises a second steel sheet containing an amount of material selected from said group effective for reducing the nitrogen content of said rimmed steel.
• a process for producing ageing resistance steel sheet in which no more than half the production is aluminum-killed sheet sheet, the. remainder being rimmed steel sheet, the sheets being annealed in alternating contact with each other, so that the rimmed steel sheet becomes ageing resistant and the aluminum-killed steel sheet does not lose its ageing resistance.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)

Applications Claiming Priority (1)

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ID=19753457

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Citations (2)

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• 1962
  • 1962-11-26 BE BE625302D patent/BE625302A/fr unknown
  • 1962-11-27 US US240457A patent/US3203837A/en not_active Expired - Lifetime
  • 1962-11-29 LU LU42778D patent/LU42778A1/xx unknown
  • 1962-11-29 FR FR917068A patent/FR1341091A/fr not_active Expired
  • 1962-11-30 GB GB45373/62A patent/GB1023505A/en not_active Expired
  • 1962-11-30 DE DEK48341A patent/DE1245402B/de active Pending

Patent Citations (2)

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