Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys

Definitions

• the present invention relates to a nitrogenous additive based on calcium cyanamide.
• nitrogen is nowadays incorporated in a variety of steel qualities to improve the material properties, in particular strength and toughness.
• alloying is carried out with gaseous nitrogen, which is introduced into the liquid steel melt, or nitrogen-containing alloys or compounds of the steel melt are added.
• nitrogen-containing compounds or alloys are usually used.
• the usual alloys here are embroidered ferromanganese or ferrochrome with low nitrogen contents of 4 to 6%. This can be used to alloy relatively accurately, but the amounts of nitrogen that can be introduced into the molten steel are very often limited by the manganese or chromium content of the steel analysis. In addition, these alloys are comparatively expensive as embroidery agents.
• Lime nitrogen is also known as a cost-effective nitrogen additive for N-alloyed steels in the steel industry, with the lime nitrogen being introduced into sacks or buckets when tapping into the pan.
• this method still has serious disadvantages.
• the calcium cyanamide introduces considerable amounts of carbon into the steel melt, which is almost 100% absorbed by the melt.
• the present invention was therefore based on the object of developing a nitrogen-containing additive based on calcium cyanamide which does not have the disadvantages of the prior art mentioned, but which enables a substantially higher and more uniform nitrogen output.
• the additive is used in the form of a filled wire, consisting of a metallic sheath and finely divided calcium cyanamide as filler.
• the nitrogen-containing additive according to the present invention is in the form of a cored wire consisting of a metallic sheath and finely divided lime nitrogen as the filler material, which is sheathed by the sheath.
• the diameter of the entire cored wire can be varied within wide limits, but in practice a diameter range from 5 to 20 mm, preferably from 9 to 13 mm, has proven to be particularly advantageous.
• the filler material of the wire consists of technical lime nitrogen (N content 20 to 26%), which should be in the finest possible form in order to enable a largely homogeneous distribution of the treatment agent in the steel melt.
• the particle size of the calcium cyanamide used should therefore preferably be less than 1 mm.
• the amount of calcium cyanamide used per cored wire length unit depends essentially on the diameter of the cored wire and is usually between 50 and 250 g calcium cyanamide per meter of cored wire.
• the jacket material should be selected so that it dissolves in the steel melt relatively quickly with the release of the treatment agent, without this jacket material or its residues introducing undesirable components into the steel melt. In practice, unalloyed steel casings have proven particularly useful.
• the thickness of the jacket is usually 0.1 to 1 mm, preferably 0.2 to 0.6 mm.
• the preparation of the additive according to the invention is unproblematic and is carried out by customary methods and methods.
• the lime nitrogen if necessary after it has been crushed to the desired grain size range, is poured into the wires, which are then closed by folding or welding and wound up on coils.
• the steel treatment with the additive proposed according to the invention can be carried out safely and without problems.
• 0.1 to 10 kg of cored wire are used per ton of molten steel to be treated, with winding speeds of 50 to 180 m / minute, in particular 100 to 150 m / minute, having proven successful.
• the cored wire is preferably injected 1 to 1.5 m deep into the molten steel.
• fine-grained lime nitrogen decomposes in the steel melt, so that the nitrogen is released in the deeper bath layers and dissolves.
• An 80 t batch of molten steel with an 18/8 stainless steel quality should be embroidered from 240 ppm [N] to 500 to 600 ppm [N].
• the nitrogen content was 520 ppm, which corresponded to a nitrogen output of 95%.
• the carbon uptake was only 0.02%.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• Treatment Of Steel In Its Molten State (AREA)
• Continuous Casting (AREA)
• Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 1987
  • 1987-11-19 DE DE19873739156 patent/DE3739156A1/de not_active Withdrawn
• 1988
  • 1988-11-14 US US07/270,749 patent/US4897114A/en not_active Expired - Fee Related
  • 1988-11-17 EP EP88119148A patent/EP0316920A1/fr not_active Withdrawn
  • 1988-11-18 JP JP63290336A patent/JPH01162717A/ja active Pending

Patent Citations (4)

Non-Patent Citations (2)

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