US2129382A

US2129382A - Method of centrifugally casting pipes in chilled molds

Info

Publication number: US2129382A
Application number: US86751A
Authority: US
Inventors: Piwowarsky Eugen
Original assignee: Individual
Current assignee: Individual
Priority date: 1935-07-01
Filing date: 1936-06-23
Publication date: 1938-09-06
Anticipated expiration: 1955-09-06

Description

Patented Sept. 6, 1938 METHOD OF CENTRIFUGALLY CASTING PIPES IN CHILLED MOLDS Eugen Piwowarsky, Aachen, Germany No Drawing. Application June 23, 193G, Serial No. 86,751. In Germany July 1, 1935 2 Claims. (Cl. 148-3) The present practice in producing cast-iron pipes centrifugally, preferably in cooled molds,

is the use oi cast-iron which contains ordinarily over 3% of carbon with a corresponding propor- 5 tion of silicon. Such centrifuged pipes, which may if necessary be annealed after the centrifuging operation, have good strength combined with high resistance to corrosion.

In order to produce centrifugally-cast pipes which have extremely high strength and an unusually high resistance to shock, according to the present invention it is proposed to use a cast iron of which not only the carbon content but also the total content of carbon and silicon to- 0 l5 gether is maintained low. Thus very good results have been obtained by using cast-iron containing less than 2.4% of carbon and in which the sum of C+Si varies between 3 and 4%. Experiments have shown that by using this cast-iron according to the invention, itis possible to obtain centrifugally cast pipes which have after the known annealing operation good resistance to corrosion and high coefficient of resistance to shock of over 3 mkg.

Furthermore it has been found that the tensile strength, and more particularly the resistance to shock, can be still increased in the pipes produced from the cast-iron according to the invention by subjecting them after the known annealing operation to an additional improving heat treatment carried out at temperatures lying between 200 and 600 0., preferably between 250 and 350 C.

This improving heat treatment may either be efiected on the pipes already cooled after the annealing operation. It may also be carried out after the completion of the known annealing operation, by first quenching the pipes by air, oil or water, from temperatures of about 20 to 80. C. above the conversion point A 1, 2, a, whereupon the improving heat treatment according to the invention follows. Centrifugally cast-pipes subjected to this improving heat treatment possess not only high strength but also high coefficient of resistance to shock of over 4 mkg.

The invention is not confined to the application of this improving heat treatment to centrifugally cast pipes made from cast-iron according to the invention containing less than 2.4% of carbon, and having a content of C+Si of from 3 to 4%, but extends also to the application of the improving heat treatment to centrifugally cast pipes made of cast-iron in which the carbon content is a little higher, but is under 3%, and the content of C+Si is likewise a little higher, that is to say, up to about 5.5%, as an appreciable increase in the resistance to shock of centrifugally-cast pipes in the production of which such cast-iron is used, is produced by the improving heat treatment according to the invention.

Furthermore, when using an alloyed castiron to which are added alloying constituents producing white iron, the carbon content and the sum of the contents C+Si may be correspondingly higher than first indicated, when subjected to the improving heat treatment.

What I claim 1S1 to impact shocks is produced.

2. The method claimed in claim 1, in which said pipe is reheated, after the annealing step, at temperatures ranging between 200 and 600 6., whereby the shock resistance of said pipe is further increased.

EU GEN PIWOWARSKY.