FI85507B - FOERFARANDE FOER FRAMSTAELLNING AV PERLITISKA GJUTJAERNSSORTER. - Google Patents

Description

1 85507

The method inherited from Iitti Sten for the production of cast iron grades

The invention relates to a process for the production of cast iron grades such as GG, GGG and GGV.

One hitherto possible possibility for the production of perlite GG, GGG and GGV is to charge a heritic stabilizer, e.g. copper, in a melting furnace or to add it to the molten iron melt in the ladle. This is especially the case when the treated cast iron is cast from an automatic casting furnace or plug bucket directly into a casting mold. However, this method causes difficulties when using the same melting furnace for both ferritic and peritite alloys. For example, cleaning a pressurized gas-fired casting furnace from debris requires a lot of time, and can result in the entire casting line stopping. Nevertheless, there are risks associated with any change from peritol to ferritic cast iron grade, as any perlite stabilizer impurities that may remain in the furnace feed may adversely affect subsequent ferritic cast iron grade.

This is solved according to the invention by means of the characterizing part of claim 1.

Other preferred embodiments of the method of the invention will be apparent from the claims.

The process of the present invention is based on the addition of at least one perlite stabilizer to molten iron in a casting furnace or ladle during pouring into a mold. The addition of perlite stabilizer is preferably performed in the casting stream. Thus, the melting and / or swimming devices are not exposed to contamination of the perlite stabilizer.

When the perlite stabilizer 2 85507 to be added to the inoculum must not cause an excessive thermal load on the casting stream, tin (Sn) or antimony (Sb) are used instead of copper (Cu) to a substantially lesser extent than the dosed copper. This ensures that the added inoculant and perlite stabilizer melt immediately and evenly in the casting stream. This is further aided by the lower melting temperatures and lower specific temperatures of Sn and Sb compared to Cur.

Example 1:

In order to produce GGG 50 grade graphite wax, it is usually alloyed with 0.3% Cu in addition to obtain the required perite content. Provided that the copper content of the base iron (scrap) is less than 0.1% Cu, only 0.015% Sn is required instead of 0.2% Cu.

Example 2:

To produce GGG 60 grade graphite wax, it is usually alloyed with 0.5-0.7% Cu. Under the same conditions as in Example 1, then 0.4-0.6%, on average 0.5% Cu, to be replaced, only 0.015% $ 1 of li is required.

The addition of perlite stabilizers, such as Sn and / or Sb, can take place e.g. in powder, wire or 1. in the form of a powder surrounded by a metallic or non-metallic sheath in the form of. Sn or Sb may be added in combination with an inoculant (FeSi and the like), e.g. in the form of a powder mixture (by blowing in), as an alloy, e.g. in the form of a wire, the wood blood mixture being surrounded by a metallic or non-metallic sheath. The powdered inoculum may be surrounded by a metallic sheath which is internally or externally terminated with tin or antimony. If the addition takes place in the form of a wire, the shell of the powdered inoculant may be Sn or Sb. The wire may also be fitted with a powdered seed. in which case the sheath may be of metallic or non-metallic material. The addition of Sb is particularly advantageous because Sb 3 85507

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the boiling point is 1440 C, i.e. lower than the heat of the melt before treatment. Thus, a circulating raw material from peritite to ferritic cast iron grades can be used, since any Sb therein evaporates during smelting.

One particular advantage of the described method is the possibility to produce ferritic and traditional cast iron grades in the same smelting and siling machine without interrupting production for the complete emptying of these equipment. In addition, the risk inherent in the known process that residues of perlite stabilizers remaining in the feed system will interfere with the subsequent production of ferritic cast iron is avoided. The addition of Sn or Sb in the form of yarn described with the inoculant is quite advantageous, since thus accurate dosing of Sn or Sb is achieved.

Claims (10)

1. A process for the production of ferritic and perlite cast iron varieties the latter in the form of GG, GGG or GGV using the same casting furnace, respectively. casting furnace from which the cast iron melt is poured through an outlet into a mold, wherein during the manufacture of a perlitic cast iron to the cast iron melt, at least one perlite stabilizing element is characterized, the perlite stabilizing element possibly being added with a grafting iron to is found in the molten state between the outlet and the interior of the mold. Method according to claim 1, characterized in that the pearlite stabilizing element is added to the casting beam. Method according to claim 1 or 2, characterized in that tin (Sn) or antimony (Sb) is added as perlite stabilizing element. Method according to any of claims 1-3, characterized in. ···. by adding the perlite stabilizing element with a graft portion such as an alloy. 6 Ö 5 507 Process according to any one of claims 1-3, characterized in that the pearlite stabilizing element is added as a tree or as a powder. 6. A process according to claim 5, characterized in that the pearl stabilizing element is added in tree form such as powder sheathed with a non-metallic sheath. Process according to claim 6, characterized in that the pearl stabilizing element and the inoculant are added in tree form such as powder sheathed with a non-metallic sheath. Method according to any one of claims 1-3, characterized in that the perlite stabilizing element is added in the form of a sheath of a powdered grafting agent. Method according to any of claims 1-3, characterized in that the perlite stabilizing element is added as a layer applied to the outer or inner surface of a metallic sheath of a powdered grafting agent. Method according to any one of claims 1-3, 5 and 6, characterized in that the pearl stabilizing element is added as a tree embedded in powdered, with a non-metallic sheath wrapped grafting agent.