DE2740716A1 - Spheroidal graphite cast iron - is produced by adding solid cast iron of high magnesium content to the iron melt - Google Patents

Abstract

Spheroidal graphite cast iron is produced by melting an Fe charge having a C content >2 wt % and adding solid cast iron which contains a spheroidal graphite-forming element such as Mg and/or Ce in 4-10 times the amt. necessary to form spheroidal graphite in the final cast iron product. The solid cast iron may be added in the form of scrap of normal spheroidal graphite content together with casting risers and gates. Method is simple and reduces losses in spheroidal graphite forming elements while at the same time utilising cast iron scrap.

Description

PROCESS FOR CONTINUOUS MANUFACTURING VCN

BALL GRAPHITE CAST IRON The preliminary invention relates to Process for the production of spheroidal graphite cast iron in foundry furnaces.

E3 a process for the periodic production of nodular cast iron is known, that in meltdown of an iron and more than 2% by weight of carbon Feed material in an Ofczi, subsequent tapping of the molten @@ - metal in a pan and treatment of the metal derin with spheroidal graphite - formers such as magnesium, Cerium or Yttrium consists, so performing this process presupposes the presence not only ahead of the furnace, but also with a vessel in which the Cast iron melt treated with a ball graphitbildrer. This treatment of the Cast iron smelter, which has a high temperature, is having a pyogenic effect, a intense cooking of the metal and large quantities of flue gas connected, which pollute the air in the foundry and thus for the operating personnel are annoying.

For this reason, tightly closed pans were also used, but they are also unable to eliminate the undesired cooling of the melt, and with them, too, the trial continues to be periodic.

At Ze @@ you put the spheroidal graphite former in the Pfan @@, wor @ uf this is filled with metal, or one sets the melt poured into the ladle the spheroidal graphite formers too. The spheroidal graphite to be added is more formative than Bars, chains, chips or balls. Sometimes you bring the spheroidal graphite former into the pans at their bottom through an opening in the pan (or oven) wall a.

With all these modifications of the process, the cooling remains the cast iron melt when it is treated with the spheroidal graphical agent, after which you cannot heat them up again, so that you overheat the cast iron, i.e. the melt in the furnace to higher temperatures of the order of 1500 ° C must bring.

It is the temporary effectiveness of spheroidal graphite formers, the strong pyre effect and the increased consumption of expensive spheroidal graphite formers, which is why the production of nodular cast iron encounters greater difficulties.

It is also a process for the continuous production of spheroidal graphite Cast iron confesses according to which one is melted the previous @@ in the furnace and the above described m pans treated Cast egg @@@ in an induction furnace s @ mmelt, which you seal and in which you create a N @ utralatm @ sphärt or a layer of slag can be ignited on the melt. But here, too, there is still a need a previous batch treatment of the melt in pans placed in them from the individual ovens with subsequent collection of their contents in the induction oven be stabbed.

The known processes for the production of spheroidal gr @ h @ t cast iron are expensive, because they cause great losses of spheroidal graphite formers their evaporation and oxidation upon introduction into the melt characterize, which arise because the cast iron melt from the grounds of compensating their cooling in the pan while it is being cooked and the temperature is maintained the treatment in which the metal is thin enough to be too thin Castings of complex configuration to be forgotten at high temperatures is heated. Here you have to have a part of the metal, which is due to cooling is no longer glorious, in order to avoid Fenlabgussen @ thin-walled castings to broken cast. This in turn leads to considerable losses of metal and Spheroidal graphite formers.

This is not the only reason for broken castings such as sprues, risers and faulty casts, which make up 40% of the use, but also that with the spheroidal graphite former treated cast iron that is too cold to be remelted. When remelting goes the spheroidal graphite contained in this cast waste formers completely er @ er @ er.

At de @ known process for the production of spheroidal graphite cast iron you have to have a strong pollution of the ambient air and an additional space requirement for the bulky auxiliary equipment in purchase nchzon.

In view of the constantly growing demand for K @@ elgraphit cast iron, which has to be forgiven for the last few years is the problem of a major one Improvement of the process for its continuous production as a prerequisite for meeting the current requirements of mechanical engineering for thin-walled Castings of complex configurations were created.

The purpose of the present invention is to eliminate the listed Trouble.

The invention is based on the object of a method for continuous Manufacture of spheroidal graphite cast iron with this type of operation and such additives to sharpen for the Flüzsig @ etall, where the technological process is easier gestaltca and the working conditions for the operating personnel improve permit.

This task is achieved by a process for continuous production solved by spheroidal graphite cast ice @@@, the melting down of a ferrous Insert with a carbon content of not less than 2 wt .-%, in the introduction of Cast iron in a solid state in the furnace chamber 2/3 filling primary Melt until the furnace space is filled and the secondary ones are subsequently heated There is melt in the furnace up to the tapping temperature, according to the invention the added cast iron in the solid state forms at least one spheroidal graphite in a 4 to 10 times the C @@ old of normal spheroidal graphite cast iron on bat @@ ffenden element contains excess quantity or it including casts made of spheroidal cast iron with a normal content of spheroidal graphite former is added as a return flow will.

The method according to the invention allows the casting @@ enschmelse by adding spheroidal graphite formers below the liquid metal level in the furnace and to be treated at a lower temperature, which is in contrast to the Treatment of the melt in the pans No more burn-off of the spheroidal graphing agent gives.

In the process, the melting is also compatible Cast iron added to the melt in the solid state with the excess content on the spheroidal graphite formed in the melt with the heating up to the Tapping temperature. The metal therefore does not need to be heated up to higher temperatures and therefore the energy consumption cannot be so high.

Since the treatment of molten cast iron with spheroidal graphite bildner takes place in the furnace, the @@@ necessary for conventional processes are no longer necessary Auxiliary equipment for the foundries, namely the vessels in which otherwise the spheroidal graphite formers are introduced.

In the process according to the invention, the air is in the foundry and the working conditions f @@ the @@ d @ en a ung @@ ute to a degree better that one then get by without powerful ventilation systems and the process is continuous can run.

material means that the contents of the casting waste form spheroidal graphite are now not lost, but used for the spheroidization of the graphite will.

Magnesium and / or cerium are expediently used as spheroidal graphite formers used. The elements mentioned are besendcrs effective and suitable for the Mass production.

In the following, the method according to the invention is illustrated by implementation examples explained.

Example 1 In a neutral lined induction oven weighing 30 kg Capacity was melted 20 kg of normal foundry iron, with the melt filled the oven space 2/3 full. The furnace was then refilled by using the Melt solid copper iron except for an additional magnesium content of 0.2 to 0.5% by weight (i.e., 4 to 10 times as much as in normal spheroidal graphite cast iron) the same chemical composition in @ blocks added. After melting the cast iron and heating the secondary melt to a tapping temperature of 1380 to 14030C the melt was one third (10 kg) and placed in a pan for pouring in Stitched shapes in the oven 10 kg solid cast iron with 0.3 to 0.5 wt .-% Magne @ ium added again. Replenishing the furnace with cast iron in the solid state, the melting dca insert and the heating of the secondary melt in the oven go on without pyogenic effects and smoke development. The process is on as quietly as with the normal remelting of cast iron. The continuity of the process was maintained within 5 hours.

The remaining magnesium content remained during the entire melting process (0.08 to 0.12 wt%) unchanged and there was graphite in spherical shape in the casts obtain. The mechanical one.

properties of cast iron such as tensile strength #b and elongation # were after brief annealing at #b = 65 kp / mm2 and # = 7 to 8%.

Example 2 To accelerate the start of melting, an induction furnace was used with a capacity of 60 kg, a primary cast iron postmol that fills 2/3 of the furnace space which has been treated in a conventional manner by adding cerium. Of the The melt in the induction furnace was then placed in cast iron blocks with 0.2 to 0.5% by weight cerium and normal nodular cast iron as broken pieces (Steiger, sprues) in a tight fit that makes up the remaining 30% of the oven's capacity. That The result of the continuous metal melting was similar to that of Example 1.

Example 3 28 kg of starting material were made from normal foundry iron melted down in a 50 kg induction furnace. In the melt Zaan then brought solid cast iron with 0.2% by weight of cerium and magnesium of the same chemical composition in blocks. After the cast iron has become liquid with the increased cerium and magnum content and filling the furnace chamber with the This melt was heated to 134,000, whereupon it was placed in molds under low pressure was cast to cast parts with 2 to 20 mm thick walls.

Then cast iron blocks with 0.2 Ges magnesium and cerium and 25 % By weight normal spherical cast iron introduced into the furnace as return matorial, with the Addition took place below the liquid metal level. The process was stable, The testing of the samples showed mechanical properties as in Example 1. As spheroidal graphite former Yt @@@@@ can also be used.

For castings at higher temperatures (1450 ° C), solid cast iron was melted with 0.8 wt .-% magnesium in an induction furnace. In this case they were themselves forming grephite balls smaller and the plastic properties of cast iron (: 10 to 12%) better.

The tests confirm the advantages of the method according to the invention compared to the known method. For example, it was found that the treatment of the primary cast iron melt by adding @ solid cast iron an increased content of eugelgraphite formers in the furnace below the liquid metal level at a relatively low temperature of the melt a smaller power consumption and brings with it smaller losses of spheroidal graphite formers.

In addition, the nodular cast iron melting process is continuous in front of him, runs calmly, without pyroofing and thus creates on the basis of the lesser Accumulation of flue gases polluting the air in the foundry, but also the elimination of them The creation of auxiliary equipment provides better working conditions for the operating personnel.

Claims (2)

PATENT CLAIMS 1. Verrahren for the continuous production of Nodular cast iron, which is used in melting down a ferrous insert with a Kon @ ensto @@ content of not less than 2 wt .-%, in the introduction of cast iron in solid state into the primary melt, which fills 2/3 of the furnace space, until it is filled of the furnace room and subsequent heating of the secondary melt in the furnace until insists on the tapping temperature that there is no indication that the added cast iron in the solid state at least one ball of graphite in a 4 to 10 times the content of normal nodular cast iron in the relevant Element contains excess amount or it together with castings made of ductile iron with a normal content of spheroidal graphite bilaner is added as return material. 2. The method of claim 1, d a d u r c h g e -k e n n z e i c @ n e t that as a spheroidal graphite former Magne. sium and / or cerium can be used.