US3370934A - Iron alloy - Google Patents

Description

United States Patent 3,370,934 IRON ALLOY Bud R. Smith, Muncie, Ind., assignnr to Ball Brothers (Iompauy incorporated, Muncie, Ind., a corporation of Indiana No Drawing. Continuation of application Ser. No. 373,-

090, June 5, 1964. This application June 5, 1967, Ser. No. 643,736

5 Claims. (Cl. 65-374) ABSTRACT OF THE DISCLOSURE Glass molding equipment formed of a ductile iron alloy including, by weight, 2.5% to 3.5% carbon, 1% to 3.5% silicon, 1% to 1.25% nickel, 0.35% to 0.5% chromium, 0.3% to 0.6% molybdenum and iron, said alloy combining machineability with impact resistance at high temperatures.

This application is a continuation of copending U.S. application Ser. No. 373,090, filed June 5, 1964, entitled Iron Alloy by Bud R. Smith and now abandoned.

This invention relates to a novel alloy and more particularly to a new and improved metal alloy which is useful for forming equipment in glass forming machines.

In the past, glass forming equipment, such as blank molds, blow molds, neck rings, plungers, bafiles, bottom plates, etc., have largely been made of cast iron, and usually some type of gray cast iron. Gray cast iron is an alloy consisting primarily of iron, carbon, and silicon with small amounts of sulfur and phosphorus. Since the maximum solid solubility of carbon in iron, or more specifically, ferrite, is 0.025%, all of the carbon above 0.025% will be present as free graphite or combined to form carbides with other elements that may be present. It is well known that the graphite structure is the most predominant strength-controlling constituent of cast iron.

Although gray cast iron is still extensively used in forming equipment, changes in the industry have brought attention to many of its disadvantages. For example, the nature of gray cast iron is such that its structure, and mechanical and thermal properties are contingent upon the foundry practices employed in manufacturing forming parts. Thus, since foundrymen do not have complete control of the melting practice, casting temperatures, and cooling rates, it is impossible to consistently produce the graphite flake size, shape and distribution that will produce an alloy having the desired properties.

It is inherent in glass forming processes that molds are subjected to cyclic heating and cooling so that after relatively short periods of use, the gray cast iron molds have exhibited extensive fire cracks. Furthermore, gray cast iron is normally a relatively soft metal and is subject to wear, vapor blasting and polishing, and wears quickly outside of dimensional specifications, resulting in inaccurately formed ware. Finally, forming machines have operated in recent years at much higher speeds than in the past, and as a result, the forming parts incorporated therein have been required to undergo tremendously higher impact loads while at a relatively high temperature (900 to 1000 R), such as when the baflle plate strikes the blank mold. The operating life of forming parts subjected to such treatment has been reduced due to wear and breakage. It is well known that gray cast iron has a very low impact strength at temperatures above 800 F., accounting for the resulting undue damage and breakage of forming parts under such conditions.

In view of the numerous difiiculties and shortcomings of previous gray cast iron alloys used in forming equipment, it was totally unexpected to discover a new cast iron alloy which retains the favorable qualities of gray cast 3,370,934 Patented Feb. 27, 1968 ice iron such as case of machinability, ease of casting, good ability to be polished to a mirror finish, low cost, and resistance to oxidation at elevated temperatures, yet avoids the above-mentioned disadvantages of gray cast iron.

The metal alloy of the present invention can be easily and consistently reproduced by foundrymen under con ventional, controlled casting procedures. Therefore, consistently improved mechanical and thermal properties can be achieved such as a higher impact strength at temperatures above 800 F., a high resistance to thermal'fatigue and fire cracking, a stable metallic structure resistant to growth caused by cyclic heating and cooling, and better resistance to wear, vapor blasting and polishing.

The novel cast iron alloy of the present invention comprises a type of cast iron which has been alloyed with between about 0.9% and 2.35% by weight of nickel, chromium, and molybdenum. Even better results have been obtained with the use of a ductile cast iron in which the graphite is present in a spheroidal shape rather than a flake along with between about 0.9% and 2.35% by weight of the above-mentioned alloying elements.

In ductile cast iron, the graphite is usually formed into a spheroidal shape by alloying the metal with a small percentage of magnesium. The small amount of magnesium present in the metal alloy does not affect the physical properties as a normal alloying element might, but instead acts as nuclei or seeds around which the graphite grows into spheroids. Then the other alloying elements are added in their described proportions.

Good results have been obtained with cast iron having the following ranges of alloying elements: between about 2.5% and 3.5% by weight carbon, between about 1.0% and 3.5% by weight silicon, between about 0.5% and 1.25% by weight nickel, between about 0.1% and 0.5% by weight chromium, and between about 0.3% and 0.6% by weight molybdenum. Even more preferable are alloys in which the alloying elements are within the following more specific ranges: between about 1.0% and 1.25% by weight nickel, between about 0.35% and 0.5% by weight chromium, and between about 0.35% and 0.5% by weight of molybdenum.

By agglomerating the free graphite and alloying the matrix of the iron, the alloy of the invention has a more dense grain structure in addition to increased dimensional stability. Also, the strength, thermal resistance and hardness are all increased. In addition, the alloy exhibits a higher ability to be polished to a mirror finish on the mold cavities, which is an important feature of a glass mold. Good resistance to wear and vapor erosion are also demonstrated.

It has been found that by using the alloy of the invention in the fabrication of forming tools for glass forming machines, which tools are subjected to very high wear, cyclical temperatures, and high impact stresses, the usable life of such forming tools and forming equipment is greatly extended. The types of forming means which most greatly benefit from the alloy of the invention are those tools or parts of the forming equipment which directly contact the hot glass such as the molds, plungers, etc. For example, blank molds used to form a parison from a molten gob of glass are normally subjected to very high temperatures and wide temperature extremes, fire cracking and thermal fatigue. However, when blank molds are constructed of the novel alloy of the present invention, they have a much longer life and show much less fire cracking, breakage and other damage. More importantly, when the metal alloy of the present invention is used to form parts which must "be dimensionally accurate at all times and yet resist high impact stresses and wear in forming equipment, such as the neck ring portion of the mold, the amount of Wear and breakage is drastically reduced. Furthermore, this reduces the overall cost of 3 these parts relative to the total number of articles produced.

The increase in toughness and resistance to fatigue associated with ductile cast iron, as distinguished from normal gray cast iron, adds to the advantages attained by the use of the above-mentioned alloying elements to produce a metal alloy which is even better able in certain applications to resist thermal fatigue and fire cracking. It is preferable to employ this latter type of metal alloy in cases where it is desirable for the ambient temperature to run at a slightly higher temperature than normal.

The invention will be described in greater detail with reference to the following examples. It is intended that the-examples be illustrative of the invention and not limit the invention to the specific details as set forth. In the examples, percents are by weight.

EXAMPLE I Six neck ring molds made of an alloyed ductile iron containing 3.3% total carbon, 0.24% combined carbon, 0.16% manganese, 0.027% phosphorus, 0.006% sulfur, 3.34% silicon, 0.80% nickel, 0.23% chromium, and 0.43% molybdenum were used on the front and back, respectively, of three sections of a Hartford-Empire individual station glass forming machine in a regular production line for manufacturing -ounce vegetable jars. Each section produced such articles at the rate of approximately 14 pieces of ware per minute. After allowing time for the operating conditions to stabilize, 1275 pieces of ware produced over a thirty-minute period. This ware was examined to determine the number of finish defects. Only 10 defects were discovered in the ware produced by these molds during that interval of time.

Simultaneously, a similar production run was made on three additional sections of the same glass forming ma chine in which the conditions were the same as above, except that the six neck ring molds were made of normal gray cast iron. In 1-275 pieces of ware produced by these molds, 26 finish defects were found.

The above figures show that alloyed ductie iron neck ring molds of the present invention produce ware with less than 50% of the finish defects than do molds made with common gray cast iron.

EXAMPLE II In another test, two sets of molds were used in the regular production of glassware to determine the operational life of the molds. Again, neck ring molds were employed to subject the mold parts to high stress and rapid wear. The composition of the two types of molds in this test was similar to those used in Example I. The average life of the alloyed ductile iron neck ring mold was approximately 194 hours as compared with an average life for the gray cast iron neck ring of about 84 hours. These tests showed that on the average, the life of an alloyed ductile iron neck ring mold of the invention is more than twice the life of a gray cast iron neck ring mold.

EXAMPLE III Tests similar to those conducted in Examples I and II were run with neck ring molds made from an alloyed cast iron having 3.2% carbon, 3.2% silicon, 1.2% nickel, 0.4% chromium, and 0.4% molybdenum. Improved results were obtained by the use of this alloy, comparable to those described in Examples I and II. 7

It can be seen from the above discussion and examples that the metal alloy of the present invention greatly increases the operational life of glass forming equipment as well as the quality of ware produced. In addition, the alloy of the invention has increased dimensional stability, resistance to wear and vapor erosion, and does not exhibit evidence of fire cracking or thermal fatigue after relatively long periods of use in production. Furthermore, such a metal alloy clearly overcomes serious problems experienced by the use of prior metal alloys, such as gray cast iron, in glass forming equipment, as described above.

It will be apparent from the above description that various modifications in the formulations ad procedures described may be made within the scope of the invention. Therefore, the invention is not intended to be limited to the specific details described herein except as may be required by the following claims.

What is claimed is:

1. In glass molding equipment having members therein which contact and form molten glass to a desired shape, the improvement wherein said members are made of a ductile iron alloy consisting essentially of between about by weight 2.5% and 3.5% carbon; 1% and 3.5% silicon; 1% and 1.25% nickel; 0.35% and 0.5% chromium; 0.3% and 0.6% molybdenum; not more than trace amounts'of sulfur and phosphorus and the balance being constituted of iron, the free carbon having been agglomerate in spheroidal form by a nodulizing addition of magnesium, said members having high impact resistance at elevated temperatures and being readily machined to shape.

2. An improvement as claimed in claim 1 wherein said glass contacting members are blank molds, blow molds, neck ring molds, plungers, bafiies, or bottom plates.

3. An improvement as claimed in claim 1 wherein said glass contacting member is a neck ring mold.

4. An improvement as claimed in claim 1 wherein said glass contact member is a blank mold.

'5. An improvement as claimed in claim 1 wherein said glass contactingmember is a blow mold.

References Cited UNITED STATES PATENTS 1,391,215 9/1921 Speer -128 1,948,246 '2/1934 Seaman 75128 XR 2,171,082 8/1939 Ervin 75128 XR 2,455,183 11/1948 Lobdell 75128 XR 2,485,760 10/1949 Millis et al 75-1-23 2,485,761 10/1949 Millis et al 75123 2,804,414 8/1957 Moss et al 75-128 XR DAVID L. RECK, Primary Exar'nine'r.

P. WEINSTEIN, Assistant Examiner.