US2746861A - Ternary zirconium base alloy containing sn and ti - Google Patents

Description

TERNARY ZIRCONIUM BASE ALLOY CONTAINING Sn AND Ti Walston Chubb, Jr., and Lyle L. Marsh, Jr., Columbus,

Ohio, assignors to the United States of America as represented by the United States Atomic Energy Commission No Drawing. Application July 17, 1253, Serial No. 376,279

1 Claim. (Cl. 75-177) This invention deals with a zirconium-base alloy, and in particular with a ternary zirconium-tin alloy.

It is an object of this invention to provide an alloy which has high tensile strength at elevated temperature.

It is also an object of this invention to provide an alloy which is characterized by a high degree of ductility.

Alloys which have the above-mentioned properties are being used as construction material, for instance, for equipment which is subjected to high temperatures.

The objects of this invention are accomplished by providing zirconium-tin-titanium alloys. Although the desirable properties are obtained with practically all titanium contents, it is preferable to restrict the titanium content to a content of 6% by weight. The tin content should not exceed 4% if the alloys are to be fabricated. The alloy of this invention thus preferably contains from 0.5 to 4% by weight of tin and from 2 to 6% of titanium, the best alloy containing about 4% of either component.

The alloys may be produced by any method known to those skilled in the art. For the experiments described below the alloys were prepared by drilling holes into pieces of metallic zirconium, putting suitable quantities nited States Patent For the hardness tests, the ingots of the alloys were first upset-forged'and then hot-rolled at 1000 C. to yield Aa-inch thick slabs. Then about 0.01 inch of the slabs was shaved ofl? from the surface on each side in order to remove any gaseous contaminants. These scalped" slabs were then cold-rolled in reductions of approximately 0.002 inch per pass until a total reduction of from 20 to 30% had been obtained. The cold-rolled alloys were then annealed for one hour at 700 C. in a straightening press. The sheets resulting thereby were again scalped 0.01 inch on each side and cut into testing specimens. The hardness was determined at three stages of the alloys, namely, as cast, cold-rolled, and annealed. In addition to these, the hardness was also determined in some instances after the alloys had been heated to 955 C. and brine-quenched.

For the tensile strength tests, the specimens were taken parallel to the rolling direction. The specimens were 5 inches long and inch wide; they had a l /z-inch long reduced section which was 0.5 inch wide and from 0.04 to 0.08 inch thick. The tensile strength was tested in an argon atmosphere at 500 C. with the head of the testing machine traveling at 0.02 inch per minute. The yield strength was determined as the 0.02% offset yield strength, which is the stress developed in tension producing an offset of 0.2% from the original modulus line.

Determination of the elongation was carried out by punching bench marks in the tensile specimens before testing. These bench marks were one inch apart before testing. After testing, the two halves of the broken specimen were placed together and the distance between the bench marks was measured. The increment in distance between the marks was an indication of the elongation of the specimen.

In the following table the properties of some of the alloys of this invention are summarized.

0.68% Sn, 2% Sn, 3.9% Sn, 8.9% Sn, 3.9% Sn, Components of Zirconium Alloy 3.3 T1 4.5% Ti 1.2% Ti 1.6% T1 4.2% Ti 0.2% ofiset yield strength at 500 C., p. S. l 24, 000 25, 600 25, 400 28, 100 32, 000 Ultimate strength at 500 0., p. s. i 44, 000 42, 400 38, 800 42, 600 50, 000 Elongation in 1 at 500 0., percent 22 28 29 35 18 Reduction of area at 500 0., percent 28 34 35 34 22 Hardness as cast, Rockwell A 54 52 53 56 Hardness, cold-rolled, Rockwell A 60 62 60 60 63 Hardness, cold-rolled and annealed 1 h 0.,

Rockwell "A" 1 56 58 58 57 60 Hardness after brine-quenched from 955 0.,

Rockwell 21" 63 54 55 68 1 This alloy was annealed for 3 hours at 700 C.

of tin and titanium thereinto, and then sealing the holes with zirconium chips. These zirconium pieces were then heated in a graphite crucible by high-frequency induction at an absolute pressure of less than 10 microns of mercury. A charge of about 200 grams was melted in each case; the crucible was first charged with about half of this quantity, and only after this first portion had melted was there added the remainder of the charge. The melted alloys were then allowed to cool slowly. The ingots obtained thereby weighed between and grams, part of the material having been taken up by the graphite of the crucible. In some instances, the alloys were produced in an arc melting furnace, and satisfactory results were then also obtained. It will be understood that, instead of melting the materials in two installments, the entire charge may be placed into a crucible at the beginning.

The alloys produced were tested as to hardness, tensile strength, and elongation, the characteristics primarily of interest for construction materials.

These results show that titanium increases the yield strength of a zirconium-tin alloy and also that a tin content improves the yield strength of a zirconium-titanium alloy. The 0.2% ofiset yield strength for pure zirconium was found to range between 4000 and 11,000 p. s. i., which is considerably less than that found with the alloys. Stainless steel 347, which is a steel containing from 17 to 19% chromium and from 9 to 12% nickel, has a yield strength of 31,000 p. s. i. at 500 C.

The microstructure of these alloys was determined on sections of the alloys, which had been annealed for three hours at 700 C.; these sections were polished by hand to 4/0 paper and etched with a 2% ammonium bifiuoride- 2% ammonium persulfate solution. The alloys were found to consist of one single phase with the exception of minor carbide particles which were formed from a low contaminating carbon content.

The alloys of this invention are used advantageously as construction materials in the chemical industry where the equipment has to undergo temperature increases.

It will be understood that this invention is not to be OTHER REF REN ES limited to the details given herein but that it may be modified within the scope of the appended claim. Anderson et Preliminary Survey Of Zirconium wh i l d i Alloys, Bureau of Mines Rept. of Investigations 4658, A ternary zirconium-base alloy containing about 4% 5 March 1950, 43 Pages, Particularly P g 40-43.

h wei t of tin and about 49 b wei t of titanium.

y gh y gh 1138-1140.

References Cited in the file of this patent UNITED STATES PATENTS 2,490,571 Anicettic Dec. 6, 1949 Schwope et aL: Journal of Metals, Nov. 1952, pages