Method for casting objects with an improved riser arrangement
A method of casting an object, usually a railroad wheel, is provided. A graphite mold having a drag section and a cope section requires a plurality of riser openings in the cope section to ensure proper dimensional accuracy of the cast railroad wheel by allowing molten metal to continue to feed downwardly through the riser openings to the cast wheel cavity during initial cooling. The riser openings are lined with an improved insulating material in an accurate manner such that the insulating material is added between a machined riser opening in the graphite cope mold section and a mandrel inserted in the riser opening.
1. A method of lining riser openings in a graphite mold comprising the steps of:
providing a graphite mold cope section having a plurality of riser openings, each of the riser openings having an inner surface,
inverting the cope section such that a top of each riser opening faces downwardly, and that a bottom of each riser opening faces upwardly,
inserting a mandrel into the upwardly facing bottom of each riser opening, the mandrel having an outer surface and each riser opening having an inner surface and sealing the downwardly facing top of each riser opening,
placing a vented plate assembly adjacent the upwardly facing bottom of each riser opening in the cope section,
injecting an insulating material through the vented plate assembly between the outer surface of the mandrel and the inner surface of each riser opening,
and injecting a curing agent to contact the insulating material to form a layer of cured insulating material on the inner surface of each riser opening.
2. The method of claim 1
wherein the insulating material is injected through a blow tube,
the mandrel interacts with the blow tube when the mandrel is inserted into the riser opening,
and the insulating material surrounds the blow tube to form a sprue opening in the insulating material lining each riser opening.
3. The method of claim 1
further comprising the steps of forcing the insulating material between the mandrel and the riser openings with pressurized air,
venting air from the riser openings after the insulting material is injected,
and injecting the curing agent as a gas catalyst to contact the insulating material.
4. The method of claim 1
wherein the mandrel insertion depth can be adjusted such that the mandrel is held at a predetermined distance from the downwardly facing top of each riser opening.
5. A method of casting a railroad wheel comprising the steps of
providing a graphite mold having a drag section and a cope section,
providing a plurality of riser openings in the cope section, each riser having an inner surface,
inverting the cope section such that a top of each riser opening faces downwardly and a bottom of each riser opening faces upwardly,
inserting a mandrel into the upwardly facing bottom of the riser opening, the mandrel having an outer surface, the mandrel sealing the downwardly facing top of the riser opening,
injecting an insulating material downwardly between the outer surface of the mandrel and the inner surface of the riser opening,
wherein the insulating material is injected through a blow tube,
the mandrel interacts with the blow tube when the mandrel is inserted into the riser opening,
the mandrel is supported and positioned by contacting a mandrel support inserted into the downwardly facing top of the riser opening,
and the insulating material surrounds the blow tube to form a sprue opening in the insulating material lining the riser opening,
injecting a curing agent to contact the insulating material and cure the insulating material to form a layer of cured insulating material on the inner surfaces of the riser opening,
assembling the cope section and drag section to form a completed graphite mold,
and pouring molten steel into the completed graphite mold to cast a railroad wheel.
6. The method of claim 5
wherein each riser opening is of a generally cylindrical shape,
and the mandrel is of a generally cylindrical shape generally smaller radially than the riser opening such that a generally hollow, generally cylindrical space is formed between the mandrel outer surface and the inner surface of the riser opening,
the insulating material being formed on the inner surface of the riser opening to form a lined riser opening of a generally cylindrical shape and wherein the cured insulating material generally conforms to the space between the mandrel outer surface and the riser inner surface.
7. The method of claim 6
wherein the riser opening is of a diameter of about 5 inches, the cured insulting material is of a thickness of about 0.5 inches and the lined riser opening is of a diameter of about 4 inches.
8. The method of claim 6
wherein the lined riser opening is of a diameter of about 4 inches.
9. The method of claim 5
wherein the insulating material is a resin coated sand and the curing agent is a gas catalyst.
10. A method of lining riser openings in a graphite mold comprising the steps of:
providing a graphite mold cope section having a plurality of riser openings, each of the riser openings having an inner surface,
inserting a mandrel into the upwardly facing bottom of each riser opening, the mandrel having an outer surface and each riser opening having an inner surface and sealing the downwardly facing top of each riser opening,
placing a vented plate assembly adjacent the upwardly facing bottom of each riser opening in the cope section,
injecting an insulating material through the vented plate assembly between the outer surface of the mandrel and the inner surface of each riser opening.
11. The method of claim 10
further comprising injecting a curing agent to contact the insulating material to form a layer of cured insulating material on the inner surface of each riser opening.
12. The method of claim 10
wherein the cope section is inverted prior to the insertion of the mandrel such that a top of each riser opening faces downwardly.