METHOD OF CASTING A DIRECTIONALLY SOLIDIFIED ARTICLE HAVING A VARIED COMPOSITION

• US 3,847,203 A
• Filed: 06/22/1972
• Issued: 11/12/1974
• Est. Priority Date: 06/22/1971
• Status: Expired due to Term

• Current Assignee: James Edward Northwood
• Original Assignee: James Edward Northwood
• Inventors: Northwood, James Edward
• Primary Examiner(s): Overholser, J. Spencer
• Assistant Examiner(s): Roethel, John E.
• Application Number:
  US05/265,251
• Time in Patent Office: 873 Days
• Field of Search: 164/60,95,96 416/241,241A
• US Class Current: 164/96
• CPC Class Codes: B22D 27/045 Directionally solidified castings
• CPC Class Codes: B22D 27/15 by using vacuum

Abstract

A first molten alloy is poured into a mould and progressively cooled to produce a vertical columnar crystal growth. A second molten alloy is then poured in while the surface of the first alloy is still liquid. The progressive cooling is then continued. A suitable mould is made of ceramic material and has an overflow tube formed in the wall of the mould so that any excess of the first alloy will run off. Two pairs of alloys, suitable for casting turbine blades, are described. The advantage of this method is that different parts of the casting can be formed from different alloys and that the known advantages of controlled columnar crystal growth are substantially maintained right across the join.

Claims

1. A METHOD OF CASTING A METAL ARTICLE COMPRISING THE FOLLOWING STEPS:

A. INTRODUCING A FIRST MOLTEN ALLOY INTO A MOULD HAVING AN OVERFLOW MEANS UNTIL MOLTEN ALLOY OVERFLOWS INTO THE SAID OVERFLOW MEANS;

B. PROGESSIVELY COOLING THE MOULD TO PRODUCE CONTROLLED CRYSTAL GROWTH IN THE FORM OF A VERTICAL COLUMNAR STRUCTURE IN THE MOLTEN ALLOY;

C. INTRODUCING A SECOND MOLTEN ALLOY COMPATIBLE WITH THE FIRST MOLTEN ALLOY INTO THE MOULD WHILE MAINTAINING THE SURFACE OF THE FIRST ALLOY IN A LIQUID STATE;

AND D. PROGRESSIVELY COOLING THE MOULD TO PRODUCE CONTROLLED GROWTH IN THE FORM OF A VERTICAL COLUMNAR STRUCTURE IN THE SECOND MOLTEN MOLTEN ALLOY.

2. A method of casting a metal article comprising the following steps:

a. introducing a first molten alloy into a mould;

b. progressively cooling the mould to produce controlled crystal growth in the form of a vertical columnar structure in the molten alloy;

c. introducing a second molten alloy compatible with the firs molten alloy into the mould while maintaining the surface of the first alloy in a liquid state; and

d. progressively cooling the mould to produce controlled growth in the form of a vertical columnar structure in the second molten alloy;

said alloys having the compositions;

3. A method of casting a metal article comprising the following steps:

a. introducing a first molten alloy into a mould;

b. progressively cooling the mould to produce controlled crystal growth in the form of a vertical columnar structure in the molten alloy;

c. introducing a second molten alloy compatible with the first molten alloy into the mould while maintaining the surface of the first alloy in a liquid state; and

d. progressively cooling the mould to produce controlled growth in the form of a vertical columnar structure in the second molten alloy;

said alloys having the compositions;

4. A method as claimed in claim 1, wherein casting is carried out in an atmosphere which is chemically inert with respect to the alloys to be cast.

5. A method as claimed in claim 1 including the step of introducing a third molten alloy compatible with the second molten alloy into the mouled while maintaining the surface of the second alloy in a liquid state, and subsequently cooling the mould.

6. A method as claimed in claim 5 in which the first and third molten alloys are identical.