DE717450C - Process for casting chilled cast iron rolls - Google Patents

Description

Process for casting chilled cast iron rolls With chilled cast iron rolls, which are standing from bottom to top. are cast, there are extraordinarily large differences in temperature during casting and thus also differences in cooling and, as a result, also in the course of the shrinkage over time. The hot iron, which enters the shock bowl through the tangential incision in a strong turning movement, cools down so much during the ascent due to the great heat extraction that there is between the temperature of the last iron poured in and that of the iron arriving in the upper spigot, i.e. between the Temperatures at the top and bottom of the ball, a difference of over 100 ' can exist. The resulting varying degrees of shrinkage and the premature freezing of the top pin are the causes of the dreaded hot cracks.

In the case of chilled cast iron rolls made from an alloy with the usual shrinkage coefficient are produced, experience has shown that to avoid cracks it is sufficient to add more iron to use than is necessary to fill the mold, and the excess iron to overflow. This measure has, however, been particularly strong in the case of dwindling Alloys proved to be inadequate. By pouring it up, iron becomes higher Temperature pushed down from below, but this reduces the mentioned Temperature difference not or only insignificant.

The invention is based on a known casting process in which To prevent hot cracks, insert the hot iron into the from below and from above standing roll form is poured. In this process, the casting takes place First, roll from below. As soon as the iron reaches the upper end of the roll barrel has reached, the pouring is stopped from below and now only Cast iron from above. However, this measure does not result in prevention Sufficient temperature equalization achieved from hot cracks.

According to the invention, therefore, hot ice sets of the same alloy are used Poured in from below and above at the same time. I find it useful to do this at the same time Pouring the iron from below and from above only takes place after that of Iron fed in from below has exceeded the lower edge of the roll and the iron level is on the way to the top of the ball. This procedure enables it, including high-quality rolls that are particularly sensitive to hot cracks, e.g. B. such with low C and very low P content, cast with success. For pouring If necessary, a special pouring pipe can be known per se from above Kind be used.

One known method for casting dense blocks is Material poured in from above only when the material fed in from below pods has flowed in for a while. This procedure is for the purpose of To avoid the formation of cavities in steel blocks. In the method according to the invention on the other hand, it is about the prevention of cracks on the ball surface of Sohalen chilled cast iron rolls. When casting such rolls, a layer of white is formed on the shock pan Iron, which is about 201, disappears, while the inner core is gray iron with about i '/' curvature of sight freezes. Since the gray iron is when entering later If solidification also expands at first, then instead of a void there is a Overpressure that becomes so strong that the already solidified white coat rips open again, when the iron cannot ascend through the top tenon into the overhead.

It is also already known to roll chilled cast iron using what is known as the composite casting process to pour, with for the working surface of the roller on the one hand and for the core and the cones, on the other hand, are fundamentally different, namely hard and soft materials be used. 'For example, after solidification. The shell of a roller the still liquid, hard material is blown off through the lower end of the casting mold and at the same time poured in from above to replace soft core material. at Another type of casting is only the casting mold with the hard material for the outer The shell is fully cast from below, then immediately about as much soft Iiertiwerkstof, how the contents of the lower spigot and the pouring tube correspond; into the sprue refilled and after the shell has solidified the still liquid part of the material, drained and replaced by glcichz @@ ai @ from above poured soft material.

According to an earlier proposal, a reverse casting process is used Use is not permitted, however, this is in contrast to the aforementioned procedures 711m yaw from: i composite chill cast rollers always use the same yaw. at the reverse casting process is, as in the process according to the invention, also the Purpose; -success-t. Alen otherwise occurring Temperatiiru.iterscliie # 1 between the The lower and upper ball edges should be aligned to avoid hot cracks. That Process according to this proposal can be carried out in various ways as follows: After pouring the mold up to the top, a drainage nozzle is opened. As a result, the level of the iron in the fornt lowers. As soon this has reached the lower edge of the bale, the drainage nozzle is closed again and poured hot iron of the same alloy type through the overhead.

The shape can also be used with gesclile, sseiieiii drainage nozzle from below First of all, it must be poured full up to the top of the ball, whereupon it is poured through the overhead the upper cone shape is filled. In doing so, what is in the mold sinks Iron and rises in the sprue to the level of the overhead. Now the drain socket opened so that the iron level both in the form and in the sprue again sinks. As soon as the iron level is in both parts: in the holic of the upper edge of the ball of the foot has sunk. the drain nozzle is closed and iron again through the Overhead after - 1-poured. Both processes can also take place at the same time or each other overlap.

These proposed procedures guarantee a far-reaching one Temperature equalization, however, is with their implementation eiii heavy consumption liquid iron required. This is done when applying the @ method according to the Erfin-Jung is limited to what is absolutely necessary for the production of a roller. da lii @ i-liei in contrast to the known or previously proposed methods the iron poured into the roller mold remains in it.

On the drawing is to explain de method according to the invention a Giellvorrichtung shown in vertical section, for example.

To pour the iron @leiit the 1 - Cingußrohr z, that with the lower Molding box -connected. This forms the shape for the cones below - der Wa lz @ find t _- =: @; t die Schrecl; shells. @ and for education of ZValzenballens 6. The overhead pin 7 - the roller 'is pushed into the panic by one 5 inserted or attached to this form ä formed on which a special Form 9 is put on for the so-called overhead. The top edge of the barrel of the roller is marked with io, the lower ball edge with i i.

When pouring the iron through molds S and 9, high drop heights easily form splash balls that affect the structure. To this This pouring can be avoided by a special one inserted into the mold Casting pipe are made. The pouring pipe can be used accordingly during pouring the rise of the iron level in the form can be moved upwards: but it can also be made of thin sheet metal and remain in the mold when poured, so that it is melted by the rising iron column.

Claims (1)

PATENT CLAIM: Process for casting chilled cast iron rolls, at the hot iron from below and from above to prevent hot cracks in the standing shape is poured, characterized in that to achieve a Temperature equalization between the lower and upper part of the roller, in particular of the roll barrel, hot iron of the same alloy at the same time from below and is poured in from above.