Refractory materials consisting of grains bonded by a binding phase based on aluminum nitride containing boron nitride and/or graphite particles and process for their production
AssigneeSavoie Refractaires
InventorsJacques P. R. Schoennahl, Michel Dussaulx
Life of this patent
Estimating the term…
Abstract
The invention relates to refractory materials which comprise: (A) grains of at least one refractory material whose melting point and thermal decomposition temperature are higher than 1700.degree. C.; (B) a binding matrix which binds these grains together and predominantly consists of aluminum nitride AlN of hexagonal structure and/or of at least one of the polytypes of AlN; and (C) hexagonal boron nitride particles and/or crystalline graphite flakes dispersed in the binding matrix. Applications in iron and steel metallurgy, in particular as plates in a slide closure device.
Claims9
A refractory material which comprises, in % by weight
- (A) 32-85% of grains of at least one refractory material whose melting point and thermal decomposition temperature are higher than 1700.degree. C.;
- (B) 10-40% of a binding matrix produced in situ which bids these grains together, said matrix comprising a major proportion of at least one member of the group consisting of at least one of the polytypes of AlN designated in the Ramsdell notation by 2 H, 27 R, 21 R, 12 H and 15 R, and the mixtures thereof with AlN of hexagonal structure, as determined from an X-ray diffraction pattern;
- and
- (C) 3-42% of a dispersed phase selected from the group consisting of hexagonal boron nitride particles, crystalline graphite flakes, and mixture thereof, said phase being dispersed in the binding matrix;
- said refractory material exhibiting resistance to corrosion by molten steel at 1700.degree. C.
A process for the production of a refractory material, which comprises:
- (1) preparing a batch comprising a mixture of the following constituents in the indicated proportions:
- a) 35 to 80% by weight of grains, at least 90% of which are between 50 .mu.m and 5 mm in size, these grains consisting of a refractory material whose melting point or thermal decomposition temperature are higher than 1700.degree.0 C.;
- b) 9 to 25% by weight of particles at least 90% of which are smaller than 50 .mu.m in size, these particles consisting of a refractory material identical to or different from that of the grains (a), with the exception of magnesia, the melting point or thermal decomposition temperature of said refractory material being higher than 1700.degree. C., on condition that the sum of the ingredients (a) and (b) does not exceed 88% by weight;
- c) 7 to 30% by weight of aluminum powder, at least 90% of the particles of which are smaller than 80 .mu.m in size;
- d) from 3 to 45% by weight of hexagonal boron nitride particles or crystalline graphite flakes or a mixture of these, at least 80% of the graphite flakes being larger than 100 .mu.m in size;
- e) 0 to 3% of a dried and ground refractory clay, with the proviso that the starting batch contains a mixture of fine alumina particles smaller than 20 .mu.m in size and silicon powder in a ratio by weight of Si/Al.sub.2 O.sub.3 of less than about 1:3, it being possible for the proportion of silicon powder to be up to about 35% of the weight of aluminum, and the sum of the proportion of silicon powder and aluminum powder not exceeding 30% of the weight of ingredients (a) to (e), the alumina powder being regarded as being part of constituent (b).
- the sum of the ingredients (a) to (e) making up 100%;
- and
- f) a temporary binder;
- (2) shaping the resulting mixture into a shape by pressing;
- (3) drying the shaped mixture;
- and
- (4) firing the shaped and dried mixture under a nitrogen atmosphere at a temperature of 1300.degree. C. to 1600.degree. C.
Dependencies are inferred from the claim text.