GB2171941A

GB2171941A - Treatment of cast iron melt prior to casting

Info

Publication number: GB2171941A
Application number: GB08605039A
Authority: GB
Inventors: Anton Alt
Original assignee: Georg Fischer AG
Current assignee: Georg Fischer AG
Priority date: 1985-03-05
Filing date: 1986-02-28
Publication date: 1986-09-10
Also published as: IT8619630A1; GB2171941B; IT1188416B; ES552623A0; DE3605200C2; CH668722A5; IT8619630A0; GB8605039D0; SE8600980D0; AT396658B; ATA50586A; SE8600980L; FR2578459A1; DE3605200A1; ES8703315A1

Abstract

The melt is treated in a treatment chamber (4, 5) with an agent (2a) which promotes the formation of spheroidal or vermicular graphite, and is then introduced into a mould cavity (8). The agent (2a) comprises an alloy based on magnesium and/or rare earth metals, and is placed in a recess (2) in the base of the treatment chamber. Above the recess (2) there is arranged a dividing element (3) which acts as a flow resistance and ensures an intense reaction of the melt with the alloy. During the pouring-in process, a pouring gate (7), which communicates the treatment chamber with the mould cavity (8), is closed by means of a plug (6), whereby the melt is dammed-up for a short time before the plug (6) is opened thereby allowing the mould cavity (8) to be filled with treated melt. Thus, the melt is in contact with the agent for a sufficient period until the necessary reaction time has expired and the reaction products separate and a complete blending of the melt is achieved, prior to introduction of the melt into the mould cavity. <IMAGE>

Description

SPECIFICATION Process and device for the production of cast pieces of cast iron with spheroidal or vermicular graphite in a casting mould The present invention relates to a process and a device for the production of cast pieces of cast iron with spheroidal- or vermicular graphite in a casting mould, and the use of this process.

It is known, in the production of cast pieces, to carry out the treatment of the cast iron melt in the casting mould. The best known process in this connection is the so-called Inmould process, in which a closed chamber is formed-out in the casting mould and this chamber contains the treatment agent. The inflowing cast iron melt is treated continuously on its way into the mould.

The disadvantage with this process is on the one hand the continuous treatment of the melt flowing into the mould. A result of this may be a different modification of the graphite which can lead, for example in the case of a casting cluster with several moulds, to cast pieces of varying quality.

A further disadvantage with this process is the forming-out of the additional closed chamber which eventually can not be coated with cast metal and therefore is uneconomical.

Another process with which the melt is dammedup by means of a sheet metal probe, has the disadvantage that the sheet metal probe melts uncontrollably before the blending of the sample takes place.

The present invention therefore seeks to remove these disadvantages and to propose a process which economically and accurately permits a uniform treatment of the pieces to be cast and hence leads to reproducible quality characteristics.

According to one aspect of the invention there is provided a process for the production of cast iron with spheroidal or vermicular graphite in a casting mould, in which: a cast iron melt is pre-treated in a treatment chamber with a predetermined amount of an agent which promotes the formation of spheroidal or vermicular graphite, and is then introduced into a mould cavity; and the flow of the melt in the treatment chamber is controlled so as to achieve contact with the agent until the necessary reaction time has expired and the reaction products are separated and a complete blending of the melt is achieved, prior to introduction of the melt into the mould cavity.

According to a further aspect of the invention there is provided a casting mould for the production of cast iron with spheroidal or vermicular graphite and comprising: a mould cavity; an open pre-treatment chamber for receiving a cast iron melt; means provided in the chamber for contacting the cast iron melt with a predetermined amount of an agent which promotes the formation of spheroidal or vermicular graphite; a pouring aperture communicating the chamber with the mould cavity; and closing means for closing said aperture for a predetermined period so as to enable a necessary reaction time to expire for contact between the agent and the cast iron melt and for reaction products to be separated, prior to introduction of the treated melt into the mould cavity.

An embodiment of the invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 is a section through a casting mould of the invention, and Figure 2 is a plan view of the upper catchment area of the casting mould of Figure 1.

Figure 1 shows a horizontally split casting mould 1 in whose upper half an upper catchment area (4, 5) is milled. A chamber 2, which is used as a treatment chamber, is formed-out in the base of the upper catchment area. This chamber runs transversely to the longitudinal axis of the upper catchment area and is rranged there to pass through from one edge to the other of the upper catchment area. There is further provided in the upper catchment area a pouring gate 7 which provides access to a mould cavity 8. With the aid of a plug 6 this access can be closed or opened. A dividing element 3, preferably in the form of a Croning core, is arranged over the treatment chamber in such a way that this core divides the upper catchment area into two areas 4 and 5. This core is shaped substantially so that its height corresponds more or less to the depth of the upper catchment area.As regards width the core does not quite correspond to the width of the treatment chamber 2, as can be seen from Figure 2. Thus the core is used as a flow resistance for the melt which is poured into the upper catchment area so that the melt has to flow through the treatment chamber 2, and over pre-alloy treatment agents 2a in the chamber 2 which are based on magnesium and/or rare earth metals.

Instead of using the upper catchment area as a treatment area it is possible to place a treatment chamber onto the casting mould. This would be particularly advantageous with vertically divided casting moulds.

The presse is as follows: A plug 6 is pressed into the pouring gate 7. Then the liquid iron in the area 4 flows under the dividing element 3 and over the agents 2a, and then towards the end wall la of the upper catchment area. The requirement is cast iron with spheroidal graphite or with vermicular graphite. The emptied-in melt is so measured that the amount is sufficient for the casting provided. If the entire amount provided is emptied into the upper catchment area then both areas 4 and 5 are filled with iron melt.

Blending takes place by the flow conditions occurring in the upper catchment area during the pouring-in process and by the short-term holding or damming-up of the melt by the dividing element 3. Blending of the same takes place with the prealloy agents 2a, so as to promote the formation of spheroidal or vermicular graphite, and the reaction process is then over. The plug 6 is withdrawn and the treated iron can flow into the mould 8 through the gate 8 and the catchment system.

By means of the measured dosage both of the treatment agent and the melt, with this process the quality of the cast pieces can be controlled.

Through the steel, slag particles can be segregated, which leads to a further improvement in quality. It is also possible to use the described process for stack moulds and to cast severai cast pieces at the same time with constant quality.

The process is also economical because a better yield and a better mould surface coating can be achieved.

The pre-alloy agents can be individually selected for each casting. All known pre-alloys can be considered as pre-alloys, and hence FeSiMg for example.

Thus, there is disclosed herein a process for the production of cast pieces of cast iron with spheroidal or vermicular graphite in a casting mould. A cast iron melt is pre-treated in a treatment chamber (4, 5) with a predetermined amount of an agent (2a) which promotes the formation of spheroidal or vermicular graphite, and is then introduced into a mould cavity (8). The treatment chamber is either placed onto a casting mould (1) or is formed-in in the mould. The agent (2a) comprises a pre-alloy based on magnesium and/or rare earth metals, and is introduced into a recess (2) in the base of the treatment chamber.When the cast iron melt is poured into the treatment chamber, a reaction with the pre-alloy takes place, and the flow of the melt in the treatment chamber is controlled so as to achieve contact with the agent for a sufficient period until the necessary reaction time has expired and the reaction products can be separated and a complete blending of the melt achieved, prior to introduction of the melt into the mould cavity.

Above the recess (2) there is arranged a dividing element (3) which on the one hand is used as a flow resistance to the cast iron melt, and on the other hand ensures an intense reaction of the melt with the pre-alloy. During the pouring-in process, a pouring gate (7), which communicates the treatment chamber with the mould cavity (8), is closed by means of a plug (6), whereby the melt, which is introduced in measured quantities, is dammed-up for a short time before the plug (6) is opened thereby allowing the mould cavity (8) to be filled with treated melt. The process provides economic advantages, as well as providing reproduceable quality of cast pieces and a better yield and better mould coating.

Claims

1. A process for the production of cast iron with spheroidal or vermicular graphite in a casting mould, in which: a cast iron melt is pre-treated in a treatment chamber with a predetermined amount of an agent which promotes the formation of spheroidal or vermicular graphite, and is then introduced into a mould cavity; and the flow of the melt in the treatment chamber is controlled so as to achieve- contact with the agent until the necessary reaction time has expired and the reaction products are separated and a complete blending of the melt is achieved, prior to introduction of the melt into the mould cavity.

2. A process according to claim 1, in which the amount of the agent is adapted to the piece to be cast.

3. A process according to claim 1 or 2, in which the controlled flow of the melt is effected by means of a mechanical device which closes a through-aperture from the treatment chamber to the mould cavity.

4. A process according to any one of the preceding claims, in which the treatment chamber is an open chamber having a recess in its base in which the agent is located, and in which a core is arranged in the chamber so as to direct the flow of the melt over the agent.

5. A process according to any one of the preceding claims, in which the agent comprises a prealloy based on magnesium and/or-rare earth metais.

6. A process according to a- FeSiMg pre-alloy.

7. A casting mould for the production of cast iron with spheroidal or vermicular graphite and comprising: a mould cavity; an open pre-treatment chamber for receiving a cast iron melt; means provided in the chamber for contacting the cast iron melt with a predetermined amount of an agent which promotes the formation of spheroidal or vermicular graphite; a pouring aperture communicating the chamber with the mould cavity; and closing means for closing said aperture for a predetermined period so as to enable a necessary reaction time to expire for contact between the agent and the cast iron melt and for reaction products to be separated, prior to introduction of the treated melt into the mould cavity.

8. A casting mould according to claim 7, in which the open pre-treatment chamber is placed on the casting mould.

9. A casting mould according to claim 7, in which the pre-treatment chamber is formed-out in the casting mould, whereby the casting mould has an upper catchment area in which a recess is provided for said agent, and in which a pouring gate is arranged to form said pouring aperture.

10. A casting mould according to claim 9, in which a dividing element is arranged over said recess and along its path.

11. A casting mould according to any one of claims 7 to 10, in which the pre-treatment chamber is milled-out or formed-out.

12. A casting mould according to claim 10, in which the dividing element is arranged to sub-divide the chamber.

13. A casting mould according to claim 12, in -which the height of the dividing element corresponds at least to the depth of the pre-treatment chamber.

14. A casting mould according to claim 12 or 13, in which the dividing element comprises a Croning core.

15. Use of the process according to any one of claims 1 to 6, for the casting of cast pieces of GGG (cast iron with spheroidal graphite) or GGV (cast iron with vermicular graphite) in moulds arranged on top of each other in a stack.

16. A process according to claim 1 and substantially as hereinbefore described with reference to, and as shown in the accompanying drawing.

17. A casting mould according to claim 7 and substantially as hereinbefore described with reference to, and as shown in the accompanying drawing.