Abstract A means and method are provided for extruding compositions, particularly for extruding mixes of carbon and/or graphite particles and carbonizable binder. The means and method can additionally be employed to control the orientation of acicular particles in a composition during the extrusion thereof so as to control the properties of the extruded product. In all cases, the extrusion die''s internal configuration is defined by at least three sections comprising first a converging section, then a diverging section and then a final section of substantially constant cross-section. A section of substantially constant cross-section may also sometimes follow the converging section. When employed in the extrusion of a carbonaceous mix containing needle-like carbon particles, dies of the present invention of appropriate design can be used to produce stock which after baking and graphitizing is characterized by having a transverse to longitudinal average coefficient of thermal expansion (CTE) ratio considerably less than that characteristic of corresponding stock in which the particles are all axially aligned.
A method according to claim 1 wherein the sections of said forming die are coaxially aligned.
Claim 2
Dependent Claim
31 words
A method according to claim 1 wherein the average angle of divergence in the diverging section is between about 15* and about 45* with respect to the axis of the die.
Claim 3
Dependent Claim
23 words
A method according to claim 1 wherein said converging section is followed by a section of substantially constant cross-section before the diverging section.
Claim 4
Dependent Claim
24 words
A method according to claim 1 wherein the cross-section of the mix being extruded at any location in each of the sections is circular.
Claim 5
Dependent Claim
31 words
A method according to claim 1 wherein the cross-sectional area of the final section of the forming die is about 2 1/2 times the minimum cross-sectional area of the converging section.
Claim 6
Independent Claim
104 words
An apparatus for extruding comprising a cylindrical chamber into which the material to be extruded is charged, a conventional hydraulically or mechanically actuated ram press for forcing the extrudable material through the apparatus, and a forming die leading from the outlet of the cylindrical chamber, said forming die being characterized by being free from any obstructions and by possessing at least three sections defined by the walls of the die comprising first a converging section, then a gradually diverging section possessing no abrupt contour changes, and then a final section of substantially constant cross-section, but whose length is not less than twice its diameter.
Claim 7
Dependent Claim
16 words
An apparatus according to claim 7 wherein the sections of said forming die are coaxially aligned.
Claim 8
Dependent Claim
27 words
An apparatus according to claim 7 wherein said converging section of the forming die is followed by a section of substantially constant cross-section before the diverging section.
Claim 9
Dependent Claim
38 words
An apparatus according to claim 8 wherein said coaxially aligned sections of the forming die are each also characterized by possessing smooth interior contours and wherein a cross-section at any location in each of the sections is circular.
Claim 10
Dependent Claim
31 words
An apparatus according to claim 7 wherein the cross-sectional area of the final section of the forming die is at least 1.2 times the minimum cross-sectional area of the converging section.
Claim 11
Dependent Claim
31 words
An apparatus according to claim 11 wherein the cross-sectional area of the final section of the forming die is about 2 1/2 times the minimum cross-sectional area of the converging section.