Alloy composition and process for the manufacture of glass making moulds

Abstract

An alloy comprising: (i) 0.5-5 % by weight of one or more carbide formers selected from Molybdenum, tungsten and vanadium; (ii) 0.3 to 1.5 % by weight silicon; (iii) 5 to 40 % by weight chromium; (iv) 0.5 to 5 % by weight nickel; (v) 0.5 to 3.5% by weight boron; (vi) 0.1 to 0.5 % by weight of carbon; (vii) 0 to 2% by weight of manganese; (viii) 0 to 0.1% by weight of sulphur, (ix) 0 to 0-1% by weight of phosphorous; (x) 0 to 3.0% by weight of copper; and (xi) iron providing the balance of the alloy by weight

1 . An alloy comprising: 
 (i) 0.5-5% by weight of one or more carbide formers selected from Molybdenum, tungsten and vanadium;    (ii) 0.3 to 1.5% by weight silicon;    (iii) 5 to 40% by weight chromium;    (iv) 0.5 to 5% by weight nickel;    (v) 0.5 to 3.5% by weight boron;    (vi) 0.1 to 0.5% by weight of carbon;    (vii) 0 to 2% by weight of manganese;    (viii) 0 to 0.1% by weight of sulphur;    (ix) 0 to 0.1% by weight of phosphorous;    (x) 0 to 3.0% by weight of copper; and    (xi) iron providing the balance of the alloy by weight.    
   
   
       2 . An alloy according to  claim 1  wherein said alloy comprises 0.3-1.5% by weight of said one or more carbide formers.  
   
   
       3 . An alloy according to  claim 1  wherein said alloy comprises 0.5 to 1.5% by weight silicon.  
   
   
       4 . An alloy according to  claim 1  wherein said alloy comprises 5 to 20% by weight chromium.  
   
   
       5 . An alloy according to  claim 1  wherein said alloy comprises 1 to 1.5% by weight nickel.  
   
   
       6 . An alloy according to  claim 1  wherein said alloy comprises 1.8 to 2.2% by weight boron.  
   
   
       7 . An alloy according to  claim 1  wherein said alloy comprises 0.18 to 0.3% by weight of carbon.  
   
   
       8 . An alloy according to claim I wherein said alloy comprises 0.4 to 1.5% by weight of manganese.  
   
   
       9 . An alloy according to  claim 1  wherein said alloy comprises 0.2 to 1.0% by weight of copper.  
   
   
       10 . A process of making a blank mould including the step of: 
 (i) melting an alloy which is preferably an alloy of the first aspect;    (ii) confirming that the alloy composition has a predetermined ratio of elements by comparison with appropriate standards using a technique selected from XRF (X-Ray Fluorescence) and AES (Atomic Emission Spectroscopy) characterised in the case of boron that a plurality of boron standards are used with the lowest standard corresponding to 0.5% boron or less and the highest boron standard corresponds to 3.5% boron or more;    (iii) casting the molten alloy from step (i) to form the blank mould;    (iv) heating said casting to about 880-1000° C.;    (v) cooling said casting to a temperature of 200° C. or less wherein the casting has a hardness of 50-60 Rockwell C;    (vi) softening the casting to a hardness required for machinery by heating the casting to 700-750° C. for 34 hours to attain a hardness of 30-38 Rockwell C;    (vii) re-hardening the casting by heating the casting to 880-1000° C. so that the casting has a hardness of 50-60 Rockwell C; and    (viii) reducing the hardness of the casting to 40-47 Rockwell C by heating the casting to an optimum temperature range within 480-700° C.    
   
   
       11 . A process as claimed in  claim 10  wherein in step (i) a charge material is discharged to a furnace having (a) 600-680 kg of steel scrap; (b) 80-120 kg of ferro-boron; (c) 200-230 kg of fee chromium; (d) 12-18 kg of nickel; (e) 6-10 kg of ferro-molybdenum, and ferro-tungsten or ferro-vanadium, (f) 11-15kg of ferro-silicon and (g) 1.5-2.0 kg of carbon, wherein amounts (a), (b), (c), (d) and (e) are based on 1000 kg of charge material.  
   
   
       12 . A process as claimed in  claim 11  wherein the charge material contains 640 kg of steel scrap, 100 kg of ferro-boron, 214 kg of ferro-chromium, 15 kg of nickel, 8 kg of ferro-molybdenum, ferro-tungsten or ferro-vanadium, 13.3 kg of ferro-silicon and 1.8 kg of carbon.  
   
   
       13 . A process as claimed in  claim 11  wherein the charge material also contains 24 kg of copper and 5-7 kg of ferro-manganese.  
   
   
       14 . A process as claimed in  claim 13  wherein the charge material contains 6 kg of ferro-manganese and 3.5 kg of copper.  
   
   
       15 . A process as claimed in  claim 10  wherein step (viii) is carried out by heating the casting to an optimum temperature or temperature range within 480-700° C. which optimum temperature or temperature range can be determined having regard to a specific alloy composition by plotting temperature against hardness in terms of Rockwell C in relation to samples of the specific alloy composition which have already been subject to steps (i), (ii), (iii), (iv) and (v).  
   
   
       16 . A process as claimed in  claim 10  wherein in step (iv) the casting is heated to 900-950° C.  
   
   
       17 . A process as claimed in  claim 10  wherein in step (v) the casting is cooled to room temperature.  
   
   
       18 . A process as claimed in  claim 10  wherein in step (v) the casting has a hardness of 55 Rockwell C.  
   
   
       19 . A process as claimed in  claim 10  wherein in step (vi) the casting has a hardness of 32-35 Rockwell C.  
   
   
       20 . A process as claimed in  claim 10  wherein in step (vii) the casting is heated to 900-950° C.  
   
   
       21 . A process as claimed in  claim 10  wherein in step (vii) the casting has a hardness of 55 Rockwell C.  
   
   
       22 . A process as claimed in  claim 10  wherein after step (viii) the hardness of the casting is 42-45 Rockwell C.