DECEMBER, 1936
INDUSTRIAL AND ENGINEERISG CHEMISTRY
Thompson, J. F., Kent's Mech. Engrs. Handbook, 10th ed., pp. 529-34, New York, John Wiley & Sons, 1923. (29) Vanick, J. S., paper presented before Am. Foundrymen's Assoc., Birmingham, Ala., 1935. ( 3 0 ) Vanick, J. S., and Merica, P. D., Trans. A m . SOC.Steel Treating, 18, 923-34 (1930). (31) Wadhams, 9.J., Metals Handbook, pp. 1236-9, .4m. Soc. Metals, 1936; Wise, E. M., Ibid.,p. 1272. 3 3 ) Worthington, R., Intern. Nickel Co., Inc., Tech. Bull. T-1 (1932). (33) Worthington, R., Ji'arl'ne Eng. & Shipping B g e , Sept., 1931. (3i) Forthington, R., X e t n l P r o g r e s s , 24, No. 1, 20-4 (1933). (28)
RECEIVEDOctober i , 1936.
..
WROUGHT COPPER BASE ALLOYS D. K. CRAMPTON Chase Brass & Copper Company, Waterbury, Conn.
Discussion I. B. McCORKLE National Tube Company, Pittsburgh, Pa.
I
S ADDITION to problems of corrosion resistance of ferrous
materials and their ability to give satisfactory service a t elevated temperatures, the chemical engineer a t times must employ his materials a t subzero temperature. In general, steels become stronger and less ductile as the temperature is lowered. -Also, as the temperature is lowered, steels in the notched condition show a rapid drop in their ability to absorb energy in the impact test. In the unnotched condition, there is apparently little if any embrittlement due to low temperatures. However, all commercial materials are more or less notched owing to euch causes as threads, too sharp fillets, pitting from corrosion, or even carelessness in handling. Unfortunately there is no way to translate impact values directly into design, so that the engineer in his selection of materials must set himself a more or less arbit,rary value. The minimum acceptable value must be the result of experience. Some designers of low-temperature equipment consider as satisfactory a minimum of 10 foot pounds at the working temperature. Until recently this value could not be met consistently at -50 F., for example, even with soft steel, unless it were quenched and tempered. Aside from the expense, heat treating is often impracticable. It has been found that' alloying with nickel will affect considerable improvement. The recent development of the so-called fine-grained steels has led to remarkable improvement in plain carbon steels with respect to low-temperature impacts. There is also indication that the improvement effected by nickel is further enhanced by the fine-grain treatment. For example, t,est results on a 0.15 carbon-0.50 chromium steel showed less than 10 foot pounds a t -50" F., whereas a steel similar in composition, but differing in that it was of the fine-grain type, gave over 120 foot pounds. Considerable advances in the ability to produce steels with good impact properties at low temperatures may be expected in the next few years. O
RECEIVED October 9, 1936.
1397
Copper tubes are being increasingly used for all water supplies, for pulp lines in the paper industry, air lines, oil supply lines, vapor lines, etc. Red brass is the preferred material from the corrosion standpoint for most corrosive waters. In the condenser tube field the cupronickels are gaining ground. The silicon bronzes are being increasingly applied in many diverse fields-for instance, tanks, kettles, evaporators, bolts, springs, agitators, etc. One of the latest applications in the paper industry is for Fourdrinier wire. Some of the newer alloys comprise aluminum brass for condenser use and particularly the recent modification containing both tin and aluminum. Antimony is being used in many brasses t o prevent dezincification. An alloy of great promise is nickel-aluminum bronze of rather high nickel and aluminum content. In the welding field, coated rod for metallic arc-welding and nonfuming brazing rod are important accessories t o fabrication of chemical equipment. A recent development is that of composite tubes for withstanding serious corrosion in oil refinery tubes. EVELOPMENTS in alloys as with other products usually take place over a period of years, and startling innovations are seldom brought forth in a short time. Some of the comparatively recent copper alloy developments have to do with extended uses of the well-known established alloys and others are of the nature of new materials. A few examples from each field will be described.
Extended Uses of Older Alloys COPPERTUBES.The metal copper has found many new and enlarged fields of use. With the advent of suitable fittings of the flared or sweated type, copper tubes are more widely utilized than formerly. I n the plumbing field this product is highly suited t o most 71-ater conditions and combines all of the
Frouxu 1 (Above). Sscwolr T ~ R O U O I I I)EEI.*.CIPIED ALPHA 8R:kSs ( X 75), ORIOIN.%LSTRUCTURE BELOW, I)ERINCIFIF:D PLUQ ABOVE Fiiiiiti~ 2 (Below). PITTEDCopma Tiinhi ( X 7.5)
qualities necessary for successful application. It is law i n cost, easy to install. neat in appearance, light i n welglit, excellent in corrosion rcsistance, and high in strength and resistance t o damage lroiii UJC or abuse. Copper tubcs are being extensively utilized for oil and gasoline supply lines, compressed air lines, etc. Similarly, copper tubcs in the form of special coils of all types and sizes are being rrseci more and more for heater coils, heat exchanger coils in air-conditioning apparatus, eto. I n considering this product x i t h sweated joints a question might well be raised as t o whether accelerated corrosion woold be experienced at the point of contact between the copper and the solder. Laboratory tests, supplemented by service records, indicate that this need not be a matter for a p p w hension. I n particular, one series of accelerated tests shows interesting results. A line composed of many short lengths of tube sweated together with various commercial solders has been under test with severe conditions for more than three years with no sign of corrosion. In this test a very corrosive saline water is being circulated continuously through the line by means of an air lift which at the same time thoroughly aerates the solution. The whole line is submerged in a constant-temperature water bath held a t 60' C., the combined conditions giving much more drastic exposure than would normally be experienced in commercial installations. A similar line, dismantled and thoroughly examined a t the end of two years, showed no attack a t the joints. An interesting use for copper water tube and sweat fittings in chemical plants is for experimental set-ups. Because of its ease of bending, assembly, etc., and the relatively good resistance t o most solutions, this makes a n ideal piping rnaterial for experimental and pilot plant use. Copper water tube is being used increasingly for gas lines bot here its use is recommended only with qualifications. It is well suited for distribution of natural gases and manuSactured gas of low sulfur content. Ilowever, with manufactured gas of relatively high sulfur cont.ent, there is a superficial siilfur attack. The slight corrosion product so formed may get into delicate valve mechanisms and cause clogging and malfunctioning. For gafi supply lines conta.inina sulfur, tinned copper is satisfartory where bare copper wonld not be.
11 C o ~ i ~ s n .Consirlcrsirle t.iirned copper 118s bee11 iised for years in the brewing iniinstry, but reccnt exhaustiye t,rsts liavc shown that, cont,rnry to prcvioiis ideas, bare c q q c r . ' 'ctuaily bctter suitcd for such use than tinned copper. ts ninde on tlic effect of various metals on taste, odor, arid appetirance of beer showed conclusively that bare clean copper had no adverso effect. Surprisingly, block tin and both hot tinned and electrolytically tinned copper had 3 serions adverso effect on taste, odor, and appearance. REDBRASS.An older alloy which is gaining rapidly in use is red brass. As a result of extensive laboratory tests, as well as service tests over a period of years, this alloy, containing 85 per cent copper and 15 per cent zinc, appears to be the most corrosion-resistant of any of the ordinary copper alloys snitable for fabrication into pipe or tube. The older pipe alloys comprising yellow or high brass and Muntz metal, although well suited for many waters, are particularly vulnerable to the dezincifioation type of attack. This is part.icularly true in hot water lines, and the copper content at which immunity t o soah action occurs increases with the temperature of the water. Figure 1 shows the typical appearance of alpha brasses which have suffered dezincification attack. Red brass containing about 85 per cent copper and 15 per cent zinc cannot he dezincitied under any conditions found in domestic water supplies. On the other hand, pnre copper is somewhat subject to a pitting type of attack in many waters and the red brass is distinctly superior in resisting this attack. Figure 2 shows typical pits on 3 corroded copper tnbe. As a result of its resistance to both types of attack, red brass is today the preferred alloy for pluinbing and for all uses, both in pipe and tube form, for contact wit.11 corrosive watcrs. C U P ~ O ~ I C K EIn L . the field of condenser tubes, seventl improved alloys have been available for several years. OF these, the cupronickels containing 20 to 30 per cent nickel, up to 5 per cent zinc, and the balance mainly copper have been the most successful. These alloys are highly resistant to all types of attack, including impingement, water line, and deposit types found in condensers either in fresh or salt, waters. They are, in addition, immune to dezincification and corrosion cracking. They are being specified in increasing proportion wherever severe corrosion conditions exist. SILICONBRONZES. Other well-known alloys which COLItinue t o find new a.pplications are the silicon bronzes. These comprise a considerable number of alloys of slightly varying composit.ion. The most commonly used is the 3 per cent silicon type containing lesser amounts, of one or more ,of several other elements--for instance, zmc, manganese, tm, iron, aluminum, etc. The physical and chemical properties
FIGURE
3. EFFECTOE?
SILICON CONTENT SlLrcon- B R O S Z E STnlp
ON
ROLLI,:~
DECEMBER, 1936
INDUSTRIAL .4ND ENGINEERING CHEMISTRY
1399
Newer Allovs
FIGURE 4 (Above). SILICON BRONZE BOLTS, COLD-HEADED FROM HIOH-STRENGTHCOLDDRAWNWIRE FIQURE 5 (Left). CORRODED CONDENSER TUBE SHOWING PITS DUE TO IMPINGEMENT ATTACK
In addition tCJ the extended uses cf older materisk already mentioned, in the lsst two or three years a number of new alloys and products of considerable promise have appeared. I n the field of condenser tubes one of the most frequent causes of failure is attack caused by the impingement of entrained air bubbles on the wall of the tube near the inlet end, Figure 5 illustrates the appearance of a tube which has suffered such attack. Aluminum brasses containing up t o about 2 per cent aluminum have been on the market for several years and have demonstrated extraordinary resistance to impingement type of attack in condenser tubes. However, these alloys under certain conditions have been found to be quite susceptible t o dezincification and have, therefore, not been entirely satisfactory. A still later development is a modification of such alloys with the inclusion of tin; these modified alloys show the same high resistance to impingement but in addition are immune to dezincification under practically all conditions. The following figures show the difference in type and degree of attack suffered by admiralty brass, ordinary aluminum brass, and the improved tin-bearing aluminum brass :
are almost entirely determined by the silicon content so that even with all of these minor modifications they are considered rn belonging to the one group. The pronounced Original Original Streneth Eloneation effect of the silicon content on the tensile strength Lo& LZst Copper Aluminum Tin Zinc by by of these alloys is well shown in Figure 3. Content Content Content Content Corroeion Corrosion Type of Attack No other copper base alloys show so good a com% % % % % % bination of as large a number of desirable proper29 6 25 Layer type derinoi70 1 fication ties as do the silicon bronzes. They make excel76 2 22 45 79 Plug type derincifilent castings, can be readily and e x t e n s i v e l y cation 17 1 14 General thinning 2 1 worked either hot or cold, show unusual strength, This *tlloy ia the subjeot of U.9. Patent 1,938,172(Dea. 15, 1933). have great resistance t o fatigue, season cracking, and stress corrosion cracking, are highly resistant to all waters and many chemical solutions, and are particularly These figures are the result of water line tests carried out well suited to welding by practically all commercial methods. on a number of samples of each alloy, using dilute sea water As a result, they have gained wide acceptance in quite diverse for 100 days a t 60" C. They were designed particularly to fields. show resistance to dezincification and had no bearing on r e They are today the preferred material for welded tanks of sistance to impingement type of attack. all shapes and sizes for water and for many chemical solutions. Recently it was found that small amounts of antimony They have been used extensively for household refrigerator are particularly effective in combating dezincification in evaporators where their welding properties are of paramount various brasses. Brasses which readily deeincify under importance. The silicon bronzes are gaining increased apvarious conditions, when modified by the addition of antiplication for springs of many types where they are replacing mony show in some cases complete resistance and in others a the older and somewhat more expensive phosphor bronzes marked reduction in degree and type of attack. The data with excellent results. There is an increasing tonnage of these in Table I show clearly the marked effect of antimony adalloys used annually for high-strength bolts where a material ditions on three different brasses, resistant to corrosion and season cracking is desired. I n this connection a silicon bronze cold-drawn to a strength of TABLE 1. EFFECT O F ANTIMONY ON TYPE AND DEGREEOF 90,000 pounds per square inch can be readily headed and CORROSION OF BRASS roll-threaded, and after such cold working is still so tough Original Original that it cannot be fractured by any kind of abuse. Figure Tensile Elongatlon Copper Antimony Stren th Lost 4 illustrates the abuse such a cold-drawn and cold-headed ConConLost%y by bolt will withstand without cracking or other failure. I n of Attack tent tent Corrosion Corrosion Type ~. addition, these alloys are highly resistant to season and cor% % % % 65 42 68 Layer type dezincification rosion cracking. 0 1bb7 8 19 Layer type dezincifioation 0.02 5 15 An increasing amount of silicon bronze is being used in General thinning 0.09 4 6 General thinning tanks, kettles, evaporators, digesters, and similar chemical 70 ... 45 77 Plug type dezincification 0 . 0 6 5 9 General thinning equipment handling a great variety of materials. The greater 75 ... 30 62 Layer type depincification strength, corrosion resistance, and adaptability for welding 0.06 3 3 General thinmng indicate that such uses will increase still further. A recent field of application of silicon bronze is the Fourdrinier wire in paper making. Here a combination of severe These data are the result of water line tests conducted in a corrosion. excessive abrasion, and repeated flexing causes solution of 0.5 per cent sodium chloride and 0.5 per cent rapid failure. I n the relatively short time these materials malic acid a t 60' C. for 30 days. The effect of antimony have been uqed. they have shown phenomenal performance, on dezincification is analogous to that of arsenic which has and their use n-ill ~undouhtedlyevtend rapidly. been described in the literature for some years. However,
ISDUSTRIAL A I D EXGIhEERIhG CHEMISTRY
1400
\OL. 78, >\to. 12
solution potential. Also, in productioii no particular annealing, pickling, or scrap dispohal probRocklems arise. Temp. well BriConThe nickel-aluminum bronzes are relatively of B ne11 Elongatrac.4ging (2 Hard- HardYield Tensile tion in tion of new; the precipitation hardening type is particuAlloy Hr.) ness ness Strength Strength 2 In. Area larly useful. Two such alloys are available. I”. Poundslsquare inch % % One contains about 91 per cent copper, 7.5 per 91 Cu, 7.5 Ni, 1.5 91 Not aged 13 cent nickel, and 1.5 per cent aluminum, and 900 87 71,000 99,000 19 40 1000 92 160 t h e o t h e r 82 p e r c e n t copper, 15 per cent 1100 94 165) nickel, and 3 per cent aluminum. The first 82 Cu, 15 Ni,3 A1 Not aged 95 165) so0 102 210 alloy can be extensively worked either hot or 900 104 220 100,000 140,000 5 6 cold and is also capable of considerable precipi1000 tation hardening as shown by the figures in Table 11. It finds auulication in uroueller shafts and s i m i l a r s t r u c t u r e s where a-hard, highan important difference in the action of these two elements strength, tough, corrosion-resistant alloy is necessary. The alloy containing 15 per cent nickel and 3 per cent has only recently been appreciated. When arsenic is added to brasses for dezinciiication resistance, a severe intercrysaluminum is readily hot-worked but can be cold-worked talline type of attack is a p t to result which may be as serious relatively little and then only with difficulty. It is hard and as the dezinci5cation. On the contrary, antimony shows no strong and is quite susceptible to precipitation-hardening such tendency and is, therefore, a safer and more effective treatment. The excellent properties which can be developed remedy than arsenic. These antimony-bearing alloys are are shown in Table I. This alloy finds logical application to the subject of a U. S.patent (allowed but not yet issued). parts of such size and form as to lend themselves to fabrication A recent development appears in connection with condenser hot and where a material is desired with great strength, and heat exchanger tubes in oil refineries where oil or vapor hardness, abrasion resistance, and corrosion resistance, along with ability to be age-hardened. is in contact with one side of the tube and water in contact with the other. A difficult problem results. Extensive An important innovation in the welding field is that OF investigation in the field as well as in the laboratory shows nonfuming brazing rod. For many years large amounts of that any alloy with high resistance t o aqueous corrosion is Muntz metal type rod have been used for brazing, since it i.: particularly well adapted to joining and repairing cast-iron intrinsically vulnerable to attack by sulfur in oils and vice parts. A former objection to the use of this material was the versa. No single alloy appears to be well suited to withstand both types of attack. High-copper alloys, for instance, show excessive amount of zinc fume produced which frequently resulted in considerable discomfort to the welder. Recently excellent resistance t o aqueous attack whereas the low-copper it has been found possible, by the addition of either beryllium brasses have relatively poor resistance, especially a t the temor silicon to these alloys, to suppress these objectionable peratures involved in oil refinery practice. On the other hand, fumes almost entirely, making the use of such alloys a inore these low-copper brasses have the best resistance to sulfur pleasant and less troublesome occupation. Silicon is mor? attack of any of the copper alloys. effective than beryllium in certain ways and is being used To combat this condition, composite tubes have been deextensively in commercial work. veloped with one layer of composition suitable for water Many other new developments in the copper alloy industry resistance and the other suitable for oil resistance. A typical are still in the laboratory stage or a t least not ready for combination now being tested in the field has commercial general exploitation. Time and money are being constantly bronze for the water side and admiralty brass for the oil side. directed to such activities, and the indications are that during This combination of two brasses has certain important adthe next few years even more new and worth-while developvantages for such applications over similar combinations of ments will be brought out than in any similar period in the past. any two less similar materials. For instance, there is only a slight difference in the coefficient of thermal expansion or RECEIVED September 12, 1936. TABLE
11.
PROPERTIES O F NICKEL-.kLUMINUM
RROSZES
*.*.
Discussion W.H.BASSETT, JR. Anaconda Wire and Cable Company, Hastings-on-Hudson, N. Y
T
HE chemical industry uses a wide variety of copper base materials, ranging from copper to the ternary alloys, and those containing more than 3 elements. In general these materials fall within eight groups: ( 1 ) electrolytic and deoxidized copper, (2) copper-zinc alloys, (3) copper-nickel-zinc and coppernickel alloys, (4) copper-silicon group, (5) copper-tin alloys, (6) copper-aluminum group (copper-aluminum-iron and copperaluminum-iron-nickel), (7) copper-zinc-aluminum, copper-zinctin, and other special copper-zinc alloys, (8) precipitation hardening alloys, such as copper-nickel-silicon, copper-beryllium, and copper-beryllium-nickel. The increase in the use of some of the older alloys has resulted in great measure from the improvements in the casting and fabricating departments. The use of larger melting units, the improved control during the melting and casting, and the increase
in the weight of the cast bars have resulted in more uniform products generally. Metallurgical control during the rolling and annealing operations has also resulted in the general improvement in the quality of the finished product. These changes have been definitely reflected in the service records of the materials in question. In some cases the same alloy has shown marked increase in its useful life, because of the improved metallurgical practice instituted during the past 15 years. Among the newer alloys, Crampton mentioned the addition of aluminum and tin to an 80-20 copper-zinc alloy. These metals combined with copper have been used successfully for almost every major railroad electrification in the United States. The alloy contains approximately 2.25 per cent aluminum, 1.75 per cent tin, and 96 per cent copper. One of the first installations was that of the Cleveland Union
