Sleeve, procedure for the manufacture thereof and mixture for the production of said sleeve

Abstract

Procedure for the production of sleeves for mini-deadheads and an economical method of casting incorporating the use of said sleeves. A fluoride-free mixture, consisting of microspheres of aluminium silicate, an oxidizable metal, such as powdered aluminium, an oxidizable agent, magnesium as initiator element of the exothermic reaction, are introduced by blowing in a mould fitted with two cores to produce a sleeve provided with two openings, one of which is closed with a plug before being used.

1 . A procedure for the production by blowing and cold box curing of an exothermic sleeve for foundry moulds which comprises:
 (A) introducing, by blowing, in the space defined by a sleeve mould and two cores, a mixture for the production of an exothermic sleeve, to obtain an uncured sleeve that is formed as a single piece and having an opening at both ends, one opening having an internal double chamfer, whilst the other opening is normally flat, said mixture for the production of exothermic sleeves comprises:   a. a fluoride-free composition for the production of sleeves which comprises:   a.1) an insulating or refractory material;   a.2) an exothermic mixture based on an oxidizable metal, an oxidizing agent capable of producing an exothermic reaction and magnesium as initiator element of the reaction;   b. a binding agent for cold box curing;   (B) putting the uncured sleeve prepared in (A) with a catalyst for curing said uncured sleeve;   (C) leaving the sleeve resulting from (B) to be cured;   (D) removing the cured sleeve from the mould, the sleeve having an inner surface adapted to contact molten material to be supplied to foundry moulds; and   (E) locating a plug in opening opposite the end with the internal double chamfer.   
     
     
         2 . A procedure according to  claim 1 , wherein said insulating material with refractory properties (a.1) is aluminium silicate in the form of hollow microspheres. 
     
     
         3 . A procedure according to  claim 1 , wherein said oxidizable metal is aluminium, or a mixture of fine and coarse aluminium powder. 
     
     
         4 . A procedure according to  claim 1 , wherein said oxidizing agent is selected from the group consisting of salts of alkaline metals, salts of alkaline earths, metallic oxides, and mixtures thereof. 
     
     
         5 . A procedure according to  claim 1 , wherein said oxidizing agent is selected from the group consisting of nitrates, chlorates of alkaline metals, permanganates of alkaline metals, chlorates of alkaline earths, permanganates of alkaline earths, iron oxide, manganese oxide, and mixtures thereof. 
     
     
         6 . A procedure according to  claim 1 , wherein said exothermic material (a.2) is in non-fibrous form, that is, in blowable form. 
     
     
         7 . A procedure according to  claim 1 , wherein said cold box curing binding agent is selected from the group consisting of phenol resins, phenol-urethane resins, acrylic resins, alkaline phenol resins, and resins of silicates. 
     
     
         8 . A procedure according to  claim 1 , wherein said cold box curing binding agent is selected from the group consisting of acrylic resins activated by SO 2  (gas) and phenol-urethane resins activated by amine (gas). 
     
     
         9 . A procedure according to  claim 1 , wherein, in step (B), the uncured sleeve prepared in step (A) is put in contact with a catalyst in the gaseous phase suitable for curing said sleeve. 
     
     
         10 . A procedure according to  claim 1 , wherein said catalyst for curing the uncured sleeve is a catalyst in the gaseous phase selected from the group consisting of: a gaseous amine to activate phenol-urethane resins; SO 2  (gas) to activate acrylic resins; CO 2  (gas) or methyl formate (gas) to activate alkaline phenol resins; and CO 2  (gas) to activate sodium silicate resins. 
     
     
         11 . A procedure according to  claim 1 , wherein the cured sleeve comprises on one end an opening for supplying molten material to a cast piece as the cast piece contracts, said opening comprising a double chamfer part adapted to provide a rut or slot in a deadhead, to facilitate the removal of the deadhead from the cast piece, and the opening at the other end of the sleeve is closed with a plug of plastic, wood, sawdust, sand or the material forming the sleeve. 
     
     
         12 . A procedure according to  claim 4 , wherein said oxidizing agent is selected from the group consisting of nitrates, chlorates of alkaline metals, permanganates of alkaline metals, chlorates of alkaline earths, permanganates of alkaline earths, iron oxide, manganese oxide, and mixtures thereof. 
     
     
         13 . A method of economically producing a cast piece in a mould having a mould cavity, comprising the steps of:
 (a) fitting over the mould cavity a single-piece, fluoride-free exothermic sleeve designed for high exothermic loads having a first opening at a first end and a second opening at a second end, the first opening having an internal double chamfer in direct communication with the mould cavity, the second opening being fitted with a plug, said sleeve comprising insulating or refractory material; an exothermic mixture based on an oxidizable metal; an oxidizing agent capable of producing an exothermic reaction; magnesium as an initiator element of the reaction; and, a binding agent;   (b) pouring molten metal into the mould so that it overflows into the sleeve through the first opening;   (c) allowing the molten metal to solidify;   (d) removing the mould and sleeve;   (e) locating a cutting line at a slot formed by the double chamfer;   (f) removing from the cast piece, at the cutting line, any mini-deadhead that may have formed in the sleeve.   
     
     
         14 . A method according to  claim 13 , wherein said insulating or refractory material is aluminium silicate in the form of hollow microspheres. 
     
     
         15 . A method according to  claim 13 , wherein said oxidizable metal is aluminium, or a mixture of fine and coarse aluminium powder. 
     
     
         16 . A method according to  claim 13 , wherein said oxidizing agent is selected from the group consisting of salts of alkaline metals, salts of alkaline earths, metallic oxides, and mixtures thereof. 
     
     
         17 . A method according to  claim 16 , wherein said oxidizing agent is selected from the group consisting of nitrates, chlorates of alkaline metals, permanganates of alkaline metals, chlorates of alkaline earths, permanganates of alkaline earths, iron oxide, manganese oxide, and mixtures thereof. 
     
     
         18 . A method according to  claim 13 , wherein said oxidizing agent is selected from the group consisting of nitrates, chlorates of alkaline metals, permanganates of alkaline metals, chlorates of alkaline earths, permanganates of alkaline earths, iron oxide, manganese oxide, and mixtures thereof. 
     
     
         19 . A method according to  claim 13 , wherein said binding agent is selected from the group consisting of phenol resins, phenol-urethane resins, acrylic resins, alkaline phenol resins, and resins of silicates. 
     
     
         20 . A method according to  claim 13 , wherein said binding agent is selected from the group consisting of acrylic resins activated by SO 2  (gas) and phenol-urethane resins activated by amine (gas). 
     
     
         21 . A method according to  claim 13 , wherein said plug is selected from the group consisting of plastic, wood, sawdust, sand and the material forming the sleeve.