Iron, Mild Steels, and Low Alloy Steels -____._
C. P. LARRdBEE AND S . C . SKYDER Carnegie-Zllinois Steel Corporation, Pittsburgh, Pa.
T
HIS paper summarizes information published since the previous articles were written (16, 17). IRONS
Cast iron finds many uses in the chemical industry. Its relatively low cost.per ton makes it a desirable constructional material for many environments. T h e cast irons containing varying amounts of alloying elements are coming into greater use as the distinctive properties of each become known. Heineniann (10) points out that cast-iron pipe has been used satisfactorily for 14 years for handling brine. For the storage of strong salt brine, steel tanks are entirely satisfactory, if provision is made to protect the water line. Guniting or painting the tank walls in this region is beneficial, as is the use of a floating layer of heavy oil on the brine surface. Cast iron is used for handling ammoniated brine a t elevated temperatures. -is an inhibitor, sulfides introduced as hydrogen sulfide or sodium sulfide are used in ammoniated brines. Cast iron is superior t o steel for handling crude amnioniacal liquor. Steel, coated with gunite, is used for tanks handling this liquor. Large tonnages of cast iron and unalloyed steel have been used in the sulfuric acid indust'ry. For concentrated acid (98 t o 1 0 0 ~ o H2S04) a t temperatures up to 140" F., Spitz ( 2 3 ) states that steel is the recommended constructional material. Steel is not suitable for use with sulfuric acid between 100 and l027,, but m-hen the concentration is over l02%, the use of steel beconies satisfactory again. *it high velocities of flow, acid of any of the above strengths attacks steel rapidly. Sulfuric acid between SO and 90% is reasonably noncorrosive to steel or iron but below 80% neither material is suitable. Kaplan and Andrens (1 3) state that, in red fuming nitric acid and mixed acids, unalloyed steels and irons are seriously corroded. Stainless steels and duriron have superior resistance t o these acids. Good abrasion resistance is a desirable property of metals used in construction of certain equipment. Hawort,h (9) states shat the abrasion resistance of cast irons containing chromiuni improved with increasing amounts of alloy up to 7%. Six dry materials were used separately as abrasives in this investigation. It is reported (2) that abrasion resistance of hardened cast-iron rolls is increased tn-o to five times by the additions of about 4.5% nickel and 1.5% chromium. Rolls of this type are used in the chemical, cement, and coal industries. T h e use of silicon t o replace additions of more costly alloys in order to improve cast iron for high temperature service is recommended by SThite and Elsea ( 2 4 ) . Reduced cost and increased availability are t!ic principal reasons for the change. Reese (20)gives a summary of several uses where certain alloy cast irons can be employed to advantage; specific examples are for large gas engines, piston rings, and One of ihc n c ~ c cieveiopiiicnts r in the cast iron field is that of spheroidal cast iron. It is reported (4)that this material n-ill fill numerous rieccl q. However, until the patent situation is clearer, few commercial applications !\-ill be made of this significantly higher streagth i y ~ i i : . 2122
C4RIZU3 STEELS
Severv localized vorrosion, commonly referred to a$ ring-worm attack, frequently occurs in service on t,he upset end of oil well tubing. Manuel (15) has shown that,, unless the upset tubing is subsequently normalized, it will be subject to localized attack iIi those areas where the carbides are in the spheroidal form. Most molten metals and many molten salts seriously attack steel and other constructional materials. Data on these corrosion rates, too extcmsive for reproduction here, are made availabie by Morral (19). Corrosion rates are also given for several niistures of molten salts. hccording to Black (6), the well kno\Tn corrosion-resistant properties of aluminum in many environments may be imparted to steel by the calorizing process, which is described in some detail. Enhanced corrosion resistance is claimed for calorized steel in oil refining equipment such as tube stills, valves, retorts, and condenser parts, as Tell as in conveyers, stackers, roasters, and kiln parts. .i more specific example of improved service life by plating steel with aluminum is described by Schulze ( 2 2 ) . In the synthesis of terLiary alkyl mercaptans, fractures of relief valve springs made from carbon steel were troublesome until aluminum-platfd springs were installed. -411 the other equipment m s of steel: allommces lor corrosion losses \\-ere included in the design. Nonmetallic coatings (paints) are probably the most common method of protecting steel surfaces. The great importance of proper surface preparation before application of any paint is emphasized by Hudson and Banfield ( 1 2 ) . Results of a &year atmospheric csposure test. show that some paint systems applied t o pickled steel surfaces gave good protection, but the same paint systems applied to rusted steels after cleaning with a wire brush failed in 1.6 years. The escellent service that can be expected from vitreous enameled coatings in either severe industrial or marine atmospheres is also demonstrated esperimentally by the same authors. The cleaning of boilers is sometimes accomplished hy hydrochloric acid inhibited with some proprietary compound. Khcther such procedure resuits in serious attack was studied by Cardxell and Martinez (8) n-ho found t,hat the loss was beloiy 0.03 pound per square foot per day (0.0007 inch). It was also reported that annealing of carbon steels reduced the attack by inhibited acid, whereas increasing the carbon or silicon contents of the steels increased the corrosion rates. Further work will be done on the effects of alloying elements on corrosion rates in inhibited acids. HIGH STRENGTH, LOW ALLOY STEELS
For most applications, the high strength, lorn alloy steels are used in plate, structural, or sheet form. The expanding uses for this class of steels are frequently the results of trial installations, the majority of which do nor. appear in the literature. Sometimes, however, use is sufficiently novel to warrant a description. For instance, a 42-inch diameter welded pipe was made from nickelcopper-chromium steel plate and used to transport highly corrosive gas ( 3 ) . Hudson ( 1 1 ) describes tests which show that wires made of high
October 1949
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
strength, low alloy steel last considerably longer than wires of plain or copper steel when exposed to severe industrial atmosphere. Use of the high strength, low alloy steel wire will thus result in either longer life for equal sized wires or the same life for thinner wires. ALLOY STEELS
2123
Steels for use in steam lines a t 1000" F. are discussed by Rotinson (21). As a result of long-time creep and rupture test results on molybdenum-vanadium pipe material in comparison with low chromium-molybdenum compositions, it is stated that molybdenum-vanadium compositions show superior long-time strength a t high temperatures (1000" F.). Alany of the uses of alloy steels are a t temperatures too high for successful applications of carbon steels. The data published by Miller (18) are of interest, since he lists the elevated temperature properties of most of the alloy steels used in the petroleum industry. Before alloy steels can be specified for use a t elevated temperatures, their internal and external stability a t those tcmperatures should be known. Kilder and Light ($5) give the results of their work on tven:y alloy and stainless steels after heating 10,000 hours a t goo", 1050", and 1200" F. Graphite was observed in steels of three types-that is, zirconium, molybdenum, and zirconium-rnolybdenurii, but graphite was not found in the titanium-molybdenum or cobalt-zirconium steels. Lustman (14) has shown that maximum temperature of surface stability in oxidizing atmospheres of steels increases with chromium cont'ent-that is, iron begins to scale a t 930" F.; 4 to 6% chromium steel resists scaling up to 1200' f..; and a steel containing 6.5 to 8.5% chromium? 1.2 to 2.0% alurninilm, or 1.0% silicon is stable up to 1650' F. Higher chromium and chromium-nickel alloys have correspondingly higher t,rmaeraturee of surface stability.
Zapffe ( 2 7 )has published a brief history of the development of these grades of steel. Their use in oil-field equipment is described by Adams (1). He points out that without alloy steels, oil wells could be drilled to only a fraction of the present attainable depth (20,000 feet). Formerly, slush pumps were built largely of cast iron. Iiow the cylinders are of cast steel with valves, valve seats, cylinder liners, and piston rods of forged alloy steels (A.I.S.I. 4820, 4150, 5060, and 4140, respectively). Several grades of drill pipe are used depending on the depths of the holes to be drilled. Grade E (-4.P.I.)drill pipe is specified as having a minimum yield strength of 75,000 pounds per square inch, necessitating an alloy steel, such as A.I.S.I. 4340, which has a minimunl. vield sirennth of 105.000 w u n d s Der *quare inch in the norni:&d arid tempered condition. Casing pipe is oftell made of low alloy steels and Some A.I.S.1. 4340 (1.75qib nickel, 0.80% chromium, and 0.25% molybdenum) normalized and tempered pipe has been employed. Couplings between sections of drill pipe (tool joints) were formerly untreated carbon steel, but are now heat treated alloy steels of a variety of compositions, such as '4.I.S.I. 8645. For the dwpest drilling, 4340 is employed. Alloy steels are also used for drill collars (4140) and shafting (4340). Brake rims are being made from heat treated seamless chromium-molybdenum forgings. Sprocket chains for driving oil-field equipment are made of alloy steel. For sucker rods, II.I.S.1. 4620 (nickel-molybdenum) has given satisfactory results in many oil fields. The use of alloy steels in oil refineries is described by Braun ( 6 ) . Twenty-five years ago, carbon steel was virtually the only material of construction in the petroleum refining industry. Today alloy steel has largely replaced carbon steel in refinery processing applications. Chromium steels played an important part in enabling the oil industry to process the corrosive Paper >rill Sulfite Digester M a d e of Low Carbon Steel sour crudes from west Texas. Nickel-chromium Containing 2.75% Nickel steels (such as S.A.E. 3130) were found to be relatively satisfactory for cast valves and fittings handling the less corrosive crudts. These are now being raplsctd At very 1017' temperatures, there are considerable differences t)y 5% chromium-1% tungsten and 5% chromium4 5% molybin the properties of various steels; moreover, the change from the denum steels. For still tubes and piping, 5% chromium-O.5g properties a t room temperature to those a t low temperatures molybdenum steel is very satisfactory for handling sour crude; varies widely from steel to steel. The mechanical properties For sweet crudes, steels containing 1 to 3% chromium and 0 5 1 1 ) including the fatigue of aircraft alloys a t very low temperatureq 1% molybdenum (A.S.T.M. A200) are useful. is given by Zambrow and Fontana (26). ThLy state that among Both 7 and 9% chromium steels (with molybdenum) are used other steels, S.A.E. 2330. S E. 8630, and an 8.5% nickel steel were subjected to mechanical tests in the temperature range to in refinery applications. The 7% chromium steel is about twice as corrosion resisrant and the 9% chromium steel is about four -253" C. -111 steels shoved a n increase in fatigue strength, tensile strength, and yield strmgth with falling temperature. times as corrosion resistant as the 5 % chromium steel. Bolts are A.I.S.I. 3130, 3140, and 4140 in th.: quenched and tempered The reduction of area decreased with falling temperature with the exception of the 8.57, nickel steels which shor;ed a slight condition, as described in A.S.T.M. Specification A193 Throughout the refinery industry, a t least half the alloy steei increase in reduction of area a t -78" C. over that obtained a t room temp-rature. is 5 % chromium-molybdenum, the rest being lower alloy chromium-molybdenum steels or 18-8. Considerable interest has been shown in the 8 to 10% nickel For steam boiler tubes, and to a lesser extent for refinery equip\[eel. Its metallography and heat treatment are given by Brophy ment, 0.5% molybdenum steels are employed. For high temand Miller ( 7 ) . As a result of an investigation including steels perature steam piping, steels containing 0.5 to 1.0% chromium from 3 to 15% nickel, it was determined that the optimum comwith 0.5% molybdenum are now being employed. posiiion for service at -320' F. w a s 0.125'4 maximum carbon,
Vol. 41, No. 10
INDUSTRIAL AND ENGINEERING CHEMISTRY
2124
0.35 to 1.0% manganese, 0.15 to 0.30% silicon, 0.04% maximum 0*040Jo phosphorus’ and to lo%
’
Optimum properties were developed by double normalizing followed by reheating t o a temperature within the range between the true and conventional Acl temperatures to convert carbides to high carbon, nickel austenite. ( h c l is the temperature a t which austenite begins t o form during heating. ) LITERATURE ClTED
.%dams.€1. L., Metal Progress. 54, 468 (1948). Anon., 12’ickeZ Topics, I, No. 5 (1948). Ibid., 2,No. 1 (1948). Ibid., No.3 (1948). Black, Geo., Am. Machinist, 92,No. 23 (1948). Braun. F.C.,Metal Progress, 54, 471 (1948). Brophy, G.R.,and Miller, A. J., Trans. Am. Soc. M&ds, XLI, 1185 (1949).
Cardwell, P. H., and Martincz, S. J., IND. ENG.CHEM.,40, 1950 (1948).
Hawoith, 11. D., J r . , Trans. Am. SOC.Metals, XLI, 819 (1949). Heinemann, Gustave, Corrosion. 4, 519 (1948). Hudson, J. C.,J . Iron SteelInst , 160, Part 3,276 (1948).
(12) Hudson, J. C.,and Banfield, T. .%.,Ibid., 151, Part 1, 99-110 (1948). (13) Kaplan, Nathan, and Andrews, K. J . , ISD. ENG. CHEY., 40, 1946 (1948). (14) Lustman, Benjamin, Materialu and Methods, 28, No. 6 , 97 (1948). (19 Manuel, R W., Steel, 121, No. 16, 82 (1947). (16) Mears, R . B.,and Sjnder, S. C’,, IVD. ESG.CIIiEsf., 39, 1219 34 (1947). (17) I b k ] 40, 1798-800 (1948). (18) Miller, R. F..Prtroleum Enyr., 19,KO.-1. 1T8 (1948). (19) Morral, F. It., Wire and Wire Products, 23, 484-9; 571--!l (1948). (20) Reese, D. J., Metal Progress, 53, No. 4,539 (1948). (21) Robinson, E. L., Trans. Am. SOC.Mech. Engrs., 70, 855 (1948). ( 2 2 ) Schulze, W.A , , Lyon, J. P., and Short, G . H., IND.ESG. CHEY.. 40, 2308 (1948). (23) Spitz, A.W., Chem. Eng., 55, Xo. 5,235 (1948). (24) White, W. H., and Elsea, A . It., I r o n A g e , 162, No. 19, 106 (1948). ( 2 5 ) Wilder, A. B., and Light, J. O . , Trans. Am. SOC.Metals, XLI, 141 (1949). (26) Zambrow, J. L., and Fontana, M.G., Ibid., p. 480. (27) Zapffe, C. A., M e t a l P r o g r e s s , 54, 459 (1948). RECEIVKD Jiily 23, 1940.
Lead and Its Alloys -
G . 0. HIERS,
__
AVationnl
Lead Company, Brooklyn, .V. Y
S
IXCE publication of tho previous revicw of literature on lead (IO), the first issue of “The Corrosion Handbook” ( 2 2 )
appeared. The corrosion rcsistance of lead is discussed gencrally in many other chapters, but particularly in the following chapters: 1. Corrosion in Liquid Media, the Atmosphere, and Gases 2. Corrosion of Lead and Lead-Alloy Cable Sheathing 3. Corrosion Protection by Lead Coatings
T h e follon-ing is quoted from “Protective >Ieasures” from this
book: T o prolong the useful life of a lead installation or to u5e it to the best advantage, the following measures have been employed: ( a ) Lime or sodium silicate treatment ( p H 8 to 9 ) of potable waters which promotes formation of protective coatings on lead and generally prevents dangrrous plumbo solvencv ( 1 6 ) . ( b ) Coating of sheet lead and pipe with tar, asphaltum, or bituminous paint ( 6 ) or waterproof membrane to prevent corrosion due t o contact with aerated seepaqe waters through fresh concrete. After aging 1 year, the free lime in concrete is usuallv sufficiently carbonated to eliminate the danger. However, continued seepage of water through some concrete stiuctures ma\ he a source of corrosion for a longer time. (c) Use of acid brick linings for chemical equipment to prevent erosion effects. They a190 may lower the lead temperature and reduce burkling of the sheet lead, ( d ) Avoidance of large soil particles around hear lPsd pipe buried underground in certain soils ( 8 ) . ( e ) Use of automatic steam piessure regulation fol iiqe with lead heating coils. T h e steam should be turned on graduxlly ii needle valve mav often be used (i,Avoidance of quick-shutting valves in lead pipc2 handling liquids prevents failure from watei hammer. ( 9 ) Adoption of lead welding, commonlv called biuning, is the preferred method of making joints in le:td chemical equipmrnt. For such purposes, the burning or welding bars should be of the same composition as the material being joined. I n the same book there is a chapter entitled “Chemical Resistant Materials.” This relates to the corrosion ratings of various metals and alloys including lead, togrther with common chemicals of different strengths and temperatures. Such prrsrntations are difficult and somctimes cumbersome. Anothcr type of tabulation
wa5 used in the second Materials of Construction Review ( 1 1 ) which gives mechanical and physical propertirs also. This represents a n attempt toward a satisfactory punched card class tion. During 1948 a long overdue issue of the “>Cletals Handbooh” ( 1 ) was published. I t contains a chapter on “The Rc~istanceof Lead and Lead rlllovs to Corrosion.” Therein is a list of chemicals compatible with lead and much detailed information on thc use of lead and lead alloys. The mechanical and physical propnrties are numbered for coordinating purposes and mostly appear III other chaptcrs. Additional chapter5 deal M ith casting, soldering, and welding. A completely revised edition of the ‘.Welding Handbook” is to appcw this year. Lead and lead d o v s are discussed in some drtail but it must be admittrd that good welders (lead burners) brcome so onlv through training and experience. Although somr large chemical plants use sufficient lead equipment to warrant their continuous employment of some lead burners, they r r c nevertheless apt to employ more euperiencrd lead w I d i n g contractors (specialists) for installing or building new rquipmcnt. The 1949 spring meeting of the Sationnl hssociation of Coirosion Engineers had a n exhibition at which tivo of the large l t d product manufacturers gave literaturr and information about . Irad equipment for the chemical industrv. Evhibits and R ~ Tcrtising drew attention to: lead and Irad coverrd equipment, valves, pumps, pipe and fittings, cquipintmt for t h r r(mve1v of sulfuric acid, sheet lead, and lead pipe,. Xt the same convcntion there \vas a symposium on the chemical industry. Kempton I f . Roll, of the Lead Industries Association, presented a p‘iper on “Phvsical and Chemical Charactt.iistics of Lrad in the Chrmicltl Industry” (20). h thorough discussion of Irsd’s usc and pcrforniance in the chemical industry is givcn. He mentions a n apparentlv new type of heat exchanger as a doublr-action heating and cooling devicr. An inner lead pipe with round holr and sixpointrd star outer cross section is so designed that when ccmtcvd in a round lead encasing pipe the cross-srctional area of thtl space between pipes about equals t h r cross-srctional area of the bore of
