US3443934A

US3443934A - Steel alloys resistant to sulfuric acid and containing small quantity of alloying elements of copper,chromium,and tin or antimony

Info

Publication number: US3443934A
Application number: US540343A
Authority: US
Inventors: Hirovuki Kubota; Tohru Mimino; Yuh Fukuda; Yoshio Ishizu; Toshio Nago
Original assignee: Nippon Kokan Ltd
Current assignee: JFE Engineering Corp
Priority date: 1965-04-12
Filing date: 1966-04-05
Publication date: 1969-05-13
Anticipated expiration: 1986-05-13
Also published as: GB1101728A; DE1533332B1; DE1783151A1; DE1783151C3; DE1783151B2

Description

y 1969 HIROYUKI KUBOTA T L 3, 34

STEEL ALLOYS RESISTANT TO SULFURIC ACID AND CONTAINING SMALL QUANTITY OF ALLOYING ELEMENTS OF COPPER. CHROMIUM. AND

we on ANTIMONY Filed April 5. 1966 I Sheet o! 6 I I I I I Solubilug I I I I I I I l I I l l I 1 BY YUII rum, yoslno 130/10 rosmo Inna WM M 1% May 13, 1969 HIROYUKI KUBOTA ET AL STEEL ALLOYS RESISTANT 'ro SULFURIC ACID AND cou'ruumc SMALL QUANTITY OF ALLOYING ELEMENTS OF COPPER. CHROMIUM. AND TIN OR ANTIMONY Filed April 5, 1966 Sheet :2 0f 6 HIROYUKI KUBOTA ET AL May 13, 1969 3,443,934

STEEL ALLOYS RESISTANT TO SULFURIC .ACID AND comuuma SMALL QUANTITY OF ALLOYING ELEMENTS OF COPPER. CHROMIUM. AND

TIN on ANTIMONY Filed April 5. 1966 Sheet ,3 of 6 B 05 \o S EM: w

7 50/. wo-c- 130C INVENTORj TOH-Ku MIN/4'0 1 WWW rsmzo d I Tvsma N66 0 I wear 0 y 3, 1969 HIROYUKI KUBOTA ET AL 3,443,934

STEEL ALLOYS RESISTANT TO SULFURIC ACID AND CONTAINING SMALL QUANTITY OF ALLOYING ELEMENTS OF COPPER, CHROMIUM. AND TIN OR ANTIMONY Filed April 5, 1966 Sheet ore COMPARED MATERIALS A (Cu-Cr$b) COMPARED MATERIALS I (l-"" ""TA|NLEss) May 13, 1969 HIROYUKI KUBOTA ET AL 3,443,934

STEEL ALLOYS RESISTANT T0 SULFUR-1C ACID AND CONTAINING SMALL QUANTITY OF ALLOYING ELEMENTS OF COPPER, CHROMIUM. AND TIN 0R 'ANTIMONY Filed April 5. 1966 Sheet 5 of 6 INVENTIONED STEEL F (cucr Ni sb-Sm May 13, 1-969 UK KUBOTA ET AL 3,443,934

STEEL ALLOYS RESISTANT To suLFuRIc ACID AND CONTAINING SMALL QUANTITY OF ALLOYING ELEMENTS OF COPPER, CHROMIUM. AND

TIN on ANTIMONY Filed April 5, 1966 Sheet 6 of 6 30c 50C 30C 149% 20% 9% THIS INVENTION PRIOR ART |ooc 50C 193 80% THIS INVENTION PRIOR ART United rates 3,443,934 STEEL ALLOYS RESISTANT T SULFURIC ACID AND (JONTAINING SMALL QUANTITY OF AL- LOYING ELEMENTS OF COPPER, CHROMIUM, AND TEN 0R ANTIMONY Hiroynlri Kuhota, Tohru Mimino, Yuh Fukuda, Yoslno Ishizu, and Toshio Nago, Kawasaki-ski, Kanagawa-lren, Japan, assignors to Nippon Kokan Kabushikl Kalsha, Tokyo, Japan Filed Apr. 5, 1966, Ser. No. 540,343 Claims priority, application Japan, Apr. 12, 1965, iii/21,173; Aug. 27, 1965, til/52,245; Oct. 4, 1965, til/60,675

Int. Cl. C22c 39/26, 39/22 US. Cl. 75-125 8 Claims ABSTRACT OF THE DISCLOSURE A steel resistant to sulfuric acid consists essentially of carbon less than about .15 silicon less than about .40%, manganese in an amount less than about .50% phosphorus in an amount less than .03, sulfur in an amount less than about .03, copper in an amount of about .2.6%, chromium in amount 0.30.9% at least one substance selected from the group consisting of antimony and tin in an amount of about .050.5% and the balance iron.

This invention relates to steel alloys containing a relatively small quantity of alloying elements and more particularly to steel alloys containing a small quantity of carbon, copper and chromium, wherein antimony or tin or both of them is incorporated in the steel alloys for the purpose of greatly improving the corrosion resistance of the alloys against sulfuric acid.

Usual iron and steel materials which do not contain any special elements and are not subjected to special surface treatments are readily corroded by and dissolved in liquid sulfuric acid of a concentration of less than 60%. With a concentration of more than 60%, corrosion proceeds violently when the sulfuric acid is heated. Consequently, the usual life of ordinary iron and steel is very short when the same are used under such circumstances wherein they are contacted with sulfuric acid or with a corrosive gas which forms sulfuric acid upon condensation, and hence the loss of steel and iron due to such corrosion is very large. While considerable efforts have been made in the past regarding researches for metal materials which are resistant to the corrosive action of sulfuric acid, most materials which have been developed concern pure metals or steels containing large quantities of expensive alloying elements and low price steel alloy containing lesser amounts of alloying elements are not yet readily and widely available. We have made exhaustive research with regard to the effect of Various elements upon corrosion resistance of various types of steel against sulfuric acid or corrosive gasses of the same series and found low cost steel alloys containing lesser quantities of alloying elements and exhibiting extremely high resistance against sulfuric acid under circumstances mentioned above.

More particularly, we have made many investigations for the purpose of obtaining low price steel alloys which contain small quantities of alloying elements and are suitable for use for such structures as steel tubes used in the low temperature sections of heavy oil burning boilers, for example, under circumstances containing or forming corrosive sulfuric acid. As is well known in the art, such elements as nickel, chromium, copper and the like are commonly recognized as suitable elements to impart resistance against sulfuric acid to steel alloys but their effect is very small and is not determinative. We have found that by incorporating and causing to co-exist a suit- 3,443,934 Patented May 13, 1969 f" I re able quantity of antimony, or tin, or both, in a base steel material containing a small quantity of chromium, copper and carbon, practical steel alloys which exhibit excellent corrosion resistant property under circumstances containing sulfuric acid or corrosive gasses of the same series are provided. We have also found that the corrosion resistant property of this improved steel alloy can be further increased by adding thereto a relatively small amount of nickel, for example, from 0.30 to 0.80%. While the latter steel alloy containing nickel has a considerable resistance against the corrosive effect of sulfuric acid, we have found that this steel alloy is also suitable for use as welding electrode or wire.

It is therefore the principal object of this invention to provide improved steel alloys which contain a relatively small amount of alloying elements and which have a high resistance to the corrosive eifect of sulfuric acid.

Another object of this invention is to provide an improved welding material which can produce welded articles having high resistance to sulfuric acid.

According to one embodiment of this invention, the novel steel alloy consists of less than 0.15 of carbon, less than 0.40% of silicon, less than 0.50% of manganese, less than 0.03% of phosphorus, less than 0.03% of sulfur from 0.2 to 0.6% of copper, from 0.3 to 0 .9% of chromium, from 0.05 to 0.5% of antimony or tin or both, and the balance of iron and impurities.

In the modified form, the novel alloy further contains from 0.30 to 0.80% of nickel in addition to various ingredients mentioned above.

According to another feature of this invention, this last mentioned steel alloy which contains nickel is utilized as welding electrodes or welding wires.

A more complete understanding of our invention may be had from the following description considered together with the accompanying drawings wherein:

FIG. 1 shows the manner of dissolving of ordinary steel in hot sulfuric acid;

FIG. 2 is a chart that shows the result of corrosion test in hot sulfuric acid made on the novel steel alloys containing lesser quantities of alloying elements and on control samples;

FIG. 3 shows the relation between piercing temperature and limiting reduction percentage;

FIG. 4 shows the test results of corrosion by hot sulfuric acid made on the novel steel alloy and on contrast material;

FIG. 5 are photographs showing macro-structure of the contrast material caused by piercing test;

FIG. 6 are photographs showing macro-structures of the steel alloy according to this invention caused by piercing test and FIG. 7 are photographs which show the results of comparison tests utilizing hot sulfuric acid made on welds prepared by the novel welding rod and conventional welding rod.

Referring now to the accompanying drawings, the manner of dissolving of a common steel in hot sulfuric acid is generally shown by the solubility cure shown in FIG. 1. Although this solubility curve varies in a complicated manner as the conditions of the test are varied, it is convenient to consider it by dividing it into four consecutive sections or regions I, II, III and IV. In accordance with this invention, in order to decrease the resistances against corrosion in respective regions, there is proposed a basic steel alloy consisting of less than 0.15% of carbon, less than 0.40% of silicon, less than 0.50% of manganese, less than 0.03% of phosphorus, less than 0.03% of sulfur, from 0.2 to 0.6% of copper, from 0.3 to 0.9% of chromium, from 0.05 to 0.5% of antimony and the balance of iron and impurities, said basic steel alloy being characterized by its low contents of alloying 3 4 elements and high resistance against the corrosive effect corrosion resistance property of the steel alloy in the of sulfuric acid. If desired, tin may be substituted for anregion IV shown in FIG. 1, The cumulative effect timony in the above mentioned composition, in which caused by the coexistence of tin and antimony is more case the steel alloy consists of less than 0.40% of silicon, effective than the incorporation of either tin or antimony.

less than 0.50% of manganese, less than 0.03% of phos' 5 The reason for setting the sum of tin and antimony in the phorus, less than 0.03% of sulfur, from 0.2 to 0.6% of range of from 0.05 to 0.5% is that below the lower limit copper, from 03 to 0.9% of chromium, from 0.05 to of 0.05% it is diflicult to provide a satisfactory corrosion 0.5 of tin and the balance of iron and impurities. Furresistant property while above the upper limit of 0.5

ther, in the two types of steel alloys just mentioned antithe hot workability becomes poor.

mony or tin may be substituted by the same amount of As a result of many experiments we have found that the sum of antimony and tin. elements that impart a remarkable corrosion resistant With regards to respective elements utilized in the alloy property in regions I, II, III and IV, respectively, shown steels of this invention, carbon, when used in excess of in FIG. 1 can be tabulated as shown in Table 1.

0.15%, not only deteriorates the anti-corrosion property but also results in an undesirable increase in strength due to the co-existence of other elements. Ranges of silicon and manganese of less than 0.4% and of les h 050%, TABLE 1.EFFECTIVE ADDITIVE ELEMENTS IN VARIOUS respectively, are the ranges of deoxrdizlng agents re- REGIONS quired to be used in the process of steel manufacturing. 1 n In W Upper limits of 0.03% for prosphorus and 0.03% for sulfur represent the limits below which it is difficult to Efiecfiveaddime918mm,, SB reduce the quantity of these elements in steel manufac- Sb Sn +Sn) turing art. Further, since phosphorus has a tendency of promoting corrosion, it is essential to limit its upper range to the prescribed value. While copper is an element effective to impart a corrosion resistant property, incorporation thereof of less than 0.2% is not effective and Table 2 below Shows ypi l Chemical compositions of copper in excess of 0.6% results in difiiculties in the steel samples of steel alloys of this invention and those of conmanufacturing process. Chromium in the range of from trol samples and Table 3 shows the results of immersion 0.3 to 0.9% exhibits a corrosion resistant property when tests in hot sulfuric acid.

TABLE 2.CHEMICAL COMPOSITIONS OF SAMPLES OF THIS INVENTION AND THOSE OF CONTRAST SAMPLES A B C D E F G H TABLE 3.THE RESULT OF IMMERSION TEST IN HOT SULFURIC ACID MADE ON SAMPLE EMBODYING THIS INVENTION AND CONTROL SAMPLES Test condition, mg./cm. /5 h.

Sample 0.49%+30 C. 0.20%+30 C. %+50 C. %+60 C. %+75 C. 70%+100 C. 80%+130 C. 90%+160 C.

0. 8 2. 2 2 43. 6 16. 8 8. 3 l2. 8 46. 1. 3 3. 2 11. 4 40. 8 19. 9 0. 9 14. 9 48. 0. 8 2. 7 15. 8 50. 7 16. 4 8. 0 18. 2 34. 1. l 2. 4-. 12. 5 48. 2 l6. 5 6. 6 10. 6 29. 0. 6 2. 7 21. 8 67. 2 17. 8 0. 6 15. 2 38. 2. 3 13. 2 119. 0 239. 0 13. 2 7. 4 1.5. 5 54. 19. 5 15. 3 248. 0 380. 6 20. 6 8. 3 20. 4 65. 0. 04 2. 0 65. 7 229. 6 176. 2 I79. 6 208. 7 42.

it co-exists with copper, but chromium of less than 0.3% 60 In these tables samples A to E inclusive represent the does not impart a corrosion resistant property. Further, novel steel alloys whereas samples F to H represent conchromium in excess of 09% causes poor workability. As trol samples. FIG. 2 shows the test result shown in Table pointed out before, this invention is characterized by in- 3.

corporating tin or antimony or both for the purpose of Although steel alloys having compositions referred greatly improving the corrosion resistant property in reto above exhibit a high resistance against the corrosive spective regions I, II, III and IV. Antimony content of effect of sulfuric acid it was found that the hot workmore than 0.5% lowers the melting point of the material ability and processability of steel alloys containing elethus imparing its hot workability, while antimony conments which are effective to impart the corrosion resisttent of less than 0.05% does not result in the increase in ance property at their upper limits have lowered slightly the corrosion resistant property. The range of tin of from so that it is difiicult to produce products required to have 0.05 to 0.5 is determined by the same reason as that accurate dimensions. We have endeavoured to develop for antimony. Thus a tin content of above 0.5% greatly improved alloy steels containing lesser quantities of alimpairs the hot workability while a tin content of less loying elements, having good resistance against corrosion than 0.05% does not contribute to increase the corrosion and being suitable for precise hot working. The improved resistant property. Co-existence of tin and antimony in the steel alloy satisfying these requirements consists of less range of from 0.05 to 0.5% is intended for improving the than 0.15% of carbon, less than 0.40% of silicon, less than 0.50% of manganese, less than 0.3% of phosphorus, less than 0.03% of sulfur, from 0.20 to 0.60% of copper, from 0.30 to 0.90% of chromium, from 0.30 to 0.80% of nickel, from 0.05 to 0.50% of the sum of antimony and tin, and the balance of iron and impurities.

The modified embodiment is characterized by containing from 0.30 to 0.80% of nickel in addition to the various elements employed in the first embodiment. Incorporation of nickel in the range specified hereinabove 6 interfaces, thus forming cracks there and causing poor hot workability. However, incorporation of Ni has an efiect of preventing easy oxidation of iron. Further, Cu, Sb and Sn which are precipitated and accumulated at the interfaces of grains will be mixed with nickel and form compounds of high melting points which contributes to preserving good hot workability.

Chemical compositions of typical samples of this embodiment and those of control samples are shown in the does not materially affect the corrosion resistant property 10 following Table 4.

TABLE 4.-CHEMICAL COMPOSITIONS 0F TYPICAL SAMPLES OF THIS INVENTION AND THOSE OF CONTROL SAMPLES Chemical composition Samples C S1 Mn P S Cu Cr Ni Sb Sn A control 0.12 0.21 0.40 0.017 0.015 0.34 0.54 0.48 B this invention" 0.09 0.24 0.38 0.017 0.015 0.41 0.68 0.58 0.25 C this invention" 0. 11 0. 28 0. 35 0. 018 0. 015 0. 30 0. 48 0. 64 0. 42 D control 13 0. 30 0. 38 0. 020 0. 017 0. 42 0. 53 0. 0. 11 Ethls invention 0.13 0.31 0.42 0.019 0.014 0.41 0.53 0.54 0.17 0.12 F this invention 0. 09 0. 24 O. 46 0. 016 0. 015 0. 39 0. 52 0. 40 0. 0. 11 G control 0.13 0.19 0.45 0.012 0.015

H controL.-- 0.07 0.42 0.50 0.083 0.010

I control 0. 07 0. 55 0. 98 0. 036 0. 010

of the steel alloy. Nickel also prevents accumulation of additive elements effective to impart the desired corrosion resistant property at interfaces between crystalline particles which is caused by the selective oxidation of the iron component at the time of hot working. In order to impart satisfactory hot workability under severe operating conditions it is necessary to select the lower limit of 0.30%, whereas when the upper limit of 0.80% is exceeded the corrosion resistant property of the steel alloys decreases gradually. This range of nickel is also suitable Each of these samples were immersed for 5 hours in sulfuric acids of diiferent concentrations and maintained at different temperatures to test its corrosion, and the results are tabulated in the following Table 5. As can be noted from this table samples of this invention, namely samples, B, C, E and F each containing nickel showed lesser corrosion than control samples. In Table 5, percentages show the concentration of sulfuric acid, C. indicates the temperature of sulfuric acid and other numerical data represent corrosion expressed in term of mg./cm. /5 hrs.

TABLE 5.IMMERSION TESTS BLADE ON SAMPLES OF THIS INVENTION AND CONTROL SAMPLES Test conditions Samples 0.49%, 30 C. 20%, 30 C. C. 50%, C. 60%, C. 70%, 100 C. 130 C. 160 C.

A control 0. 7 2. 1 17. 5 37. 5 13. 2 8. 2 12. 4 44. 7 B this invention- 0. 6 1. 6 12. 1 33. 4 l5. 0 7. 4 13. 7 45. 4 0 this invention 1. 1 2. 4 19. 7 42. 2 14. 3 8.2 15.6 48.1 D con trol 0. 7 2. 8 16.0 40. 6 18. 4 7. 0 14. 8 35. 9 E this invention 1. 0 3. 2 19. 1 50. 2 15. 6 6. 9 10. 3 32. 0 F this invention--- 0. 8 2. 4 l7. 2 48. 1 17. 0 9. 2 18. 0 37. 6 G control 2. 2 12. 6 19. 3 241. 2 13. 5 7. 0 14. 5 60. 2 H control..- 19. 5 15. 3 248. 0 380. 6 20. 6 8. 3 20. 5 65, 2 I control 0. 04 2. 0 65. 7 6 176- 2 179. 6 208. 7 42. '7

for establishing adequate balance with regard to the ranges of other elements incorporated.

Incorporation of a small amount of nickel prevents lowering in the hot workability and processability of the steel alloy caused by the addition of elements which are effective to impart the desired corrosion resistant property so that it makes it possible to prepare various steel articles including special steel plates, structural steels, steel tubes et cetera which are strictly required to have precise dimensions. Further, according to this modification, these products can be produced in mass production scale by similar procedures as usual hot worked products, thus reducing their cost of manufacture.

When elements such as Cu, Sb and Sn are incorporated according to the first embodiment, these elements will form a solid solution in ferrite and when the ferrous component oxidizes in preference to these elements, the concentration of solid solutions with Cu, Sb and Sn will increase, thus resulting in the precipitation and accumulation of these elements at the interfaces of grains. It is presumed that this will cause lowering of the melting point at these These results are plotted as a set of curves in FIG. 4.

With regard to more specific characteristics of steel alloys of this modification, in order to determine the lim iting reduction percentage, we have adopted a method of working a test piece wherein the test piece was put in a Mannessman piercing machine without utilizing a mandrel and the ratio of the length of the test piece in which no crack was noted to the total length of the test piece was determined as the limiting reduction percentage. With the roll gap of the Mannessman piercing machine adjusted to 20 mm., a frustoconical test piece having a diameter of 25 mm., at one end, a diameter of 30 mm. at the opposite end, and a length of 150 mm., was put in the roll gap and worked. The limiting reduction percentage at the time when there was no crack was taken as and the limit of reduction percentage was calculated by expressing the quotient in percents obtained by deviding the difference between the total length of the test piece and the length of cracked portion with the total length. By using this method, samples C and F embodying this invention and control samples A and I shown in 7 Table 4 were perforated at 1150 C., 1200 C., respectively, to test their effectiveness with respect to hot workability and the results of the tests are shown in Table 6 and FIG. 3 of the accompanying drawing.

TABLE 6.LIMITING REDUCTION PERCENTAGE These results clearly indicate that incorporation of nickel to the first embodiment of this invention which contains various elements including antimony eifective to impart corrosion resistant property greatly improves the hot workability of the teel alloys.

Macro-structures of test pieces which have undergone the above test are shown by photographs in FIGS. 5 and 6 which clearly show excellent internal characteristics of the steel alloys embodying this invention. The internal flexibility of each of the test pieces shown in FIGS. 5 and 6 becomes lost as the temperature of the test piece is decreased, thus obscuring the interfaces between grains. This condition is more prominent in the control sample shown in FIG. 5, especially so in 18-8 stainless steel (FIG. 5B). The sample shown in FIG. 5, which contains antimony, shows fairly good internal characteristics at a temperature of 1250 C., which is the appropriate temperature for piercing, but its limiting reduction percentage was 50%. On the other hand, FIG. 6 shows the internal characteristic of samples C and F which are incorporated with nickel in accordance with this invention. As can be noted from this figure internal characteristics as well as the limiting reduction percentage have been greatly improved. (The limiting percentages being 90 and 63%, respectively for samples C and F.)

As mentioned above, steel alloys according to the first embodiment of this invention are suitable for use as steel tubes or steel plates at low temperature portions of boilers burning heavy oil wherein a circumstance in which corrosion by sulfuric acid prevails. According to the second embodiment of this invention, a relatively low amount of nickel is added to the composition of the first embodiment whereby hot workability and processability of steel alloys are greatly improved, thus making it possible to prepare at lower cost such steel products as special steel plates, structural steel members, steel tubes and the like which are vigorously required to have precise dimensions. These products find their use in steam power plants, petroleum refining plants, city gas refining plants, synthetic chemical industry, and various chemical plants for manufacturing ethylene, olefines and derivatives thereof.

We have also found that steel alloys containing nickel and prepared according to the second embodiment of this invention also suitable for use as welding rod or wire for oxygen or acetylene gas welding. Such welding rod or wire can also be used in consumptive or non-consumptive welding, such as TIG (tungsten inert gas) Welding. Corrosion of steel or steel alloys due to sulfuric acid or an atmosphere containing corrosive gas which forms sulfuric acid is more severe at welds due mainly to metallurgical structure and construction thereof. In prior art, it has been impossible to utilize weld rods or wires which form welds resistant to corrosive action of sulfuric acid.

Welding rods or Wires of this invention are especially suitable for welding together mother metals having high resistance to corrosion caused by sulfuric acid, such as those having compositions according to the above described first and second embodiments, whereby the Welded article will have homogeneous metallurgical structure. Thus, it becomes possible to make such welded products as steel plates, structural steels, steel tubes and the like. These products can be welded and treated in the same manner as the case wherein ordinary welding rods available on the market are utilized. As has been already pointed out, when elements such as Cu, Sb, Sn, et cetera are incorporated in steel alloys, these elements will form solid solutions in ferrite. However, when the alloys are heated to high temperatures it is expected that ferrous components will be oxidized in preference to these elements and Cu, Sb and Sn will be precipitated and accumulated at interfaces between grains, thus decreasing the mechanical strength at these interfaces. However, nickel contained in the welding rods or wires of this invention will mix with Cu, Sb and Sn which are precipitated and accumulated at interfaces between grains, thus increasing the melting point while still maintaining the Weldability at high values. Table 7 below illustrates a preferred composition of the welding rod according to this invention.

Table 7.Chemical composition of the welding rod In order to investigate the ability and characteristics of the novel welding rod, two types of welding rods were prepared, i.e. one being a gas welding rod GA 43) having a tensile strength of more than 44 kg./mm. and an elongation of more than 20%) for mild steels prepared in accordance with Japanese Industrial Standards (JIS) Z 3201 and the other being the novel welding rod, each having a diameter of 3.2 mm. Two sheets of 5 x 100 x 200 mm. steel plates having high resistance against sulfuric acid were prepared each consisting of 0.08% of carbon, 0.19% of silicon, 0.47% of manganese, 0.012% of phosphorus, 0.013% of sulfur, 0.42% of copper, 0.50% of chromium, 0.35% of nickel and 0.11% of antimony. These plates were then butt welded with 60 V shaped groove provided at their center by means of one pass manual welding procedure utilizing oxygen and acetylene gas test pieces of the dimensions of 3 x 20 x 40 mm. thus obtained was finished by machining, and tested their corrosion by immersing them for 5 hours in sulfuric acids of various concentrations and maintained at different temperatures. The result of the test is shown in Table 8 below and attached photographs denoted by FIG. 7. The table and photographs show that welds obtained by using the novel welding rod have sufiicient corrosion resistance.

TABLE 8.-IMMERSION TEST OF THE WELDS Samples for immersion test 0.49%, 30 C. 20%, 30 C. 40%, 50 C. 50%, 60 C. 60%, C. 70%, 100 C. 130 C. C

ii r%f?ii 'liilf 5. 2 2. e 9. s 18. 5 22. 0 s. 0 17. s 32 t-"fiiiliiiliiffifflilf---. 1 4 6 11 13 15 18 20 Welds formed with conven- 5. R 2. 4 14. 8 47. 0 1R. 8 7. 8 l0. 0 31. 9 No ofphotogruphs shown in 5 U H w H m Remarks.In Table 8 percentages show the percentages of sulfuric acids which are heated to respective temperatures designated and the numerical data represent the quantity of corrosion in terms of mg./cm. /5 hrs.

Generally, steel alloys of the type used herein exhibit a high value of corrosion at test conditions of about 40%, 50 C. and 50%, 60 C., so that corrosions under these conditions are most important. Conventional mild steel generally shows values of corrosion of approximately from 100 to 400 mg./cm. /5 hrs. under these test conditions, so that numerical data shown in the above Table 8 prove that the novel welding electrode has made a great advance in the Welding art.

It is to be understood that above described numerical data refer to the entire body of the test piece and that the data regarding weld only are greater than the data shown in the Table 8.

While the invention has been described in connection with preferred embodiments thereof it should be understood that various changes may be made therein without departing from the true spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. Sulfuric acid-resistant steel alloy consisting essentially of carbon in an amount less than about 0.15%, silicon in an amount less than about 0.40%, manganese in an amount less than about 0.50%, phosphorus in an amount less than about 0.03%, sulfur in an amount less than about 0.03%, copper in an amount of about 0.2- 06%, chromium in an amount of about 03-09%, at least one substance selected from the group consisting of antimony and tin in an amount of about 0.05-0.5%, and the balance iron.

2. Alloy according to claim 1 wherein said substance is antimony alone.

3. Alloy according to claim 1 wherein said substance is tin alone.

4. Alloy according to claim 1 wherein said substance is a mixture of antimony and tin.

5. Sulfuric acid-resistant steel alloy consisting essentially of carbon in an amount less than about 0.15%, silicon in an amount less than about 0.40%, manganese in an amount less than about 0.50%, phosphorus in an amount less than about 0.03%, sulfur in an amount less than about 0.03%, copper in an amount of about 0.2- 06%, chromium in an amount of about 03-09%, at least one substance selected from the group consisting of antimony and tin in an amount of about 0.050.5%, nickel in an amount of about 0.3-0.80%, and the balance iron.

6. Elongated welding material formed of an alloy consisting essentially of carbon in an amount less than about 0.15%, silicon in an amount less than about 0.40%, manganese in an amount less than about 0.50%, phosphorus in an amount less than about 0.03%, sulfur in an amount less than about 0.03%, copper in an amount of about 02-06%, chromium in an amount of about 03-09%, at least one substance selected from the group consisting of antimony and tin in an amount of about 0.050.5%, nickel in an amount of about 0.3-0.80%, and the balance iron.

7. Elongated welding material according to claim 6 and wherein said iron includes impurities.

8. Welding material according to claim 6 wherein said Welding material is in the form of a wire.

References Cited UNITED STATES PATENTS 2,013,600 9/1935 Carius.

2,150,342 3/1939 Saklatwalla -425 2,867,531 1/1959 Holzwarth.

3,177,070 4/1965 Wacquez 75125 HYLAND BIZOT, Primary Examiner.

US. Cl. X.R.