US2165553A - Alloy steel - Google Patents

Description

Patented July 11, 1939 2,165,553

UNITED STATES PATIENT OFFICE ALLOY STEEL Daniel E. Krause and Clarence H. Lorig, Columbus, Ohio, aasignors to Battelle Memorial Institute, Columbus, Ohio, a corporation of Ohio No Drawing. Application September 7, 1937,

' Serial No. 162,695

Claims. (01. 15-425) Our invention relates to alloy steels. It has to In spite of the rather remarkable influence of do, more particularly, with alloy steels which small amounts of phosphorus on the mechanical contain phosphorus and vanadium. properties and corrosion resistance, as shown in The effect of phosphorus on corrosion and the above tables, phosphorus by itself may be mechanical properties of carbon steels and various objectionable in some cold-forming and coldalloy steels is well known. Its influence on drawing. steels because it increases their hardatmospheric corrosion and corrosion in other ness. Furthermore, in excess amounts it induces media is regarded as very beneficial. By itself, cold-shortness, increases the size of the grain, or in combination with other elements, it funclowers the ductility and causes segregation in the tions as an alloy and strengthening element and, ingots into which the steels are cast. as such, produces high yield strength and yield One of the objects of our invention is to proratio. For the above reasons, many of the newly vide low alloy, high strength steels having greatly developed low-alloy, high yield strength strucimproved mechanical properties, reduced grain tural steels contain substantial percentages of size, increased ductility, and increased corrosion phosphorus. resistance to the atmosphere.

The remarkably great effect upon mechanical Other objects will be apparent from the followproperties and corrosion resistance conferred on ing description of our invention. steels by small additions of phosphorus is demon- We have found that additions of vanadium to strated by results obtained on a series of very low Phosphorus Steels greatly improve t e mechanicarbon steels containing increasing percentages .cal properties, reduce theirgrain size, increase of phosphorus. Normalized bar stock of these their ductility, very materially increase their steels had mechanical properties shown in th corrosion resistance to the atmosphere, and in following table: other ways improve the phosphorus steels by 5 Base combo8ition 0 03% C, 010% Mn, 0 01% Si suppressing some of the detrimental influences o 047 S of excess phosphorus. Grain size reductions and its control by the use of vanadium in phosphorus steels assist in producing better steels of more 32, 31 $321,, gigg uniform properties and with less segregation.

cent lb./sq. in. lbJsq. in. 2" 1.255% a. lb. As illustrative of the grain size reduction brought about in phosphorus steels by vanadium, two

annealed sheet steels, each containing 0.12% car- .1, 8:92 {3% 3 3; g ban and 0.17% phosphorus, one without vanadium 2 %,:g 42,000 40 7s 54 and one containing 0.20% vanadium, had grain 5 2g 2-, i" counts of 4,000 and 36,000 grains per sq. in., re-

spectively. Thus, a great decrease in grain size 35 Thus the abdve results indicate phosphorus results from the use of vanadium in phosphorus h k Steels. x 2 5 eflect the mechanical We have found that steels containing less-than In 1 form 0.5% carbon, up to about 0.5% phosphorus and dicated steels s v vid igsizs fi xifiu z tie to about 05% vanadium readily workable atmosphere for 6 d 12 months as follows: 7 both hot and cold and have decidedly better properties than steels of the same carbon and phosphorus content but containing no vanadium. For best resistance to corrosion, the carbon con- I tent should be less than 0.25% and preferably 3,33 :33:25 it should be under 0.15%. The carbon content may be as low as 0.01 per cent. The amount of phosphorus is limited only by its deleterious influences on other properties required of the steels.

Weight loss mgJcm.

O lbWNbass ss QWGOIOQ sass? QQQNN vanadium overcome to a degree these deleterious influences and therefore allow higher phos- Thus, the above results indicate that an inphorus contents tobe used. While the resistan'e crease in the phosphorus content results in an into corrosion of steels is greatly improved if they crease in the corrosion resistance of the steel. contain from 0.08% to 0.50% phosphorus, we 55 Lower carbon contents and the presence of prefer to use from 0.08% to 0.25% phosphorus.

We have discovered that in the presence of phosphorus, vanadium adds greatly to the resistance to corrosion of steels. While we may use percentages of vanadium as high as 0.5%, the cost of the element in some instances renders its use to this extent inadvisable. We have found that in the less costly steels, vanadium in percentages from 0.025% to 0.25% is satisfactory.

The remaining constituents of the steels, aside from iron, are those incidental to their manufacture. The sulphur is maintained low, preferably not more than 0.20%, though steels containing more than this are within the scope of our invention. The manganese is maintained under 1.5%. The preferred percentage of manganese is from 0.2% to 0.8%.

The following tables illustrate examples of steels made in accordance with the present invention and compare them with other steels. The mechanical properties were obtained on bar stock after normalizing and after annealing and the atmospheric corrosion losses were obtained on 22 gauge sheet.

decidedly beneficial, although this amount of copper does not measurably increase the strength or raise the yield point. When the loss in mechanical strength, which would accompany a decrease in vanadium content, is not of serious consequence in the use of the steel, then it becomes possible to replace some of the much more costly vanadium with copper without impairing the resistance to corrosion. In this case, the use of 1 to 2 times as much copper as the vanadium which it replaces would not'less'en the resistance to corrosion. On the other hand, 0.1% to 0.5% copper, in addition to the indicated vanadium content, can be used to further enhance the resistance to corrosion that resultsfrom the joint use of phosphorus and vanadium.

When the strength and yield point of steels having combinations of carbon, phosphorus, vanadium and copper which are particularly satisfactory are to be raised, we prefer to obtain the increased strength and yield point by the use of more copper rather than by the use of additional amounts of one or more of the other three elements. This preference lies in the fact that cop- Tensile Yield Elong. Red. 01 Charpy C, P, V, Cu, B 1 percent percent percent percent Condition 151:5151; 106 :3611; tfi b f L- 03 21 Normalized 55,000 32, 500 44 75 67 2- 03 21 Annealed 52, 500 29, 500 44 75 7 3 .12 .17 63,000 39,500 38 67 30 4-.-- .12 31 76, 000 51, 500 34 01 10 5 .25 .18 77,250 42,500 30 49 14 6. 14 17 65,000 40, 000 3s e5 34 7 .14 .17 80,000 50,000 29 57 4 5 a at: a z; s 3 9- 12 .004 000 9,

10... 12 16 79,000 56,500 34 65 30 ll .12 I .16 73,000 50,000 34 65 29 12 .03 .006 34,500 25,000 48 83 42 13--- 13 .008 50,250 32,000 42 72 51 14--. .06 .25 .19 1.5 79, 100 63,300 67 31 15- 06 25 19 1. 5 Annealed- 78, 000 62, 300 32 67 30 (0 Atmospheric corrosion weight loss mg/cm 0, P, V, Cu, percent percent percent percent Condition 6 months 12 months exposure exposure 1-... .03 .21 17.6 25.8 2.--- .03 .21 14.0 25.8 3 .12 .31 16.8 23.6 4 12 31 14.0 21. 7 5---. .25 .18 17.2 21.2 8---- .14 .17 16.3 22.2 7--.- .14 .17 16.0 22.7 8.--- .12 .004 21.0 31.0 it" '15 '32 it? 24. 8 ML 11... .12 .10 13.1 21.4

The vanadium-phosphorus steels, having a substantial content of both elements, are characterized by having very high tensile and yield strengths relative to the tensile andyield strengths of the phosphorus steels containing only traces of vanadium or the vanadium steels low in phosphorus. They are extremely ductile. In resistance to corrosion, the vanadium-phosphorus steels are superior to the copper-phosphorus steels of the very high phosphorus types.

In some instances, part of the vanadium may be replaced by copper or the corrosion resistance and mechanical properties of the steels may be enhanced by the use of copper in addition to the vanadium content indicated above. .For corrosion resistance, the use of 0.1% to 0.5% copper,

76 in addition to the indicated vanadium content, is

per decreases the ductility'far less for a given increase in strength and yield point than does additions of carbon or phosphorus in steels already containing carbon and phosphorus. In the presence of substantial amounts of phosphorus, more carbon is deleterious as it induces brittleness, while in a steel already containing substantial amounts of phosphorus, an increase of phosphorus very seriously eiIects the impact resistance and ductility. The use of vanadium merely to strengthen the steels, in most instances, is inadvisable because of its cost.

We have found that 1% copper will increase both the strength and yield point of the steels from 5,000 to 20,000 lb./sq. in. depending upon the heat treatments given them, and that additional increases of the same magnitude may be obtained through precipitation hardening. The latter may be effected with normalized steels containing 0.7%

to 3% copper by holding them in, or cooling very slowly through the precipitation hardening temperature range of 750 degrees to 1050 degrees F.

The. preferred range of copper for improved strength and yield point'is about 0.50% to 3%.

Our steel has an advanta in welding. On welding thehardening in the adjacent to the weld is not apprecia a. One of the secondary advantages of the v um in the steel is that it prevents a martensitic zone-from forming in the steel near the weld. Another function of the vanadium isto prevent grain .growth in the overheated zone adjacent to the weld. Phosphorus steel without vanadium will be coarse grained in this zone.

It will be apparent from the above description that we have provided phosphorus-vanadium steels having greatly -improved mechanical prop erties, reduced grain size, increased ductility and increased corrosion resistance. The steel will have a yield strength in therolled, normalized and annealed conditions of more than 40,000'lhs./sq. in, a ductility at least equal to that of plain carbon steel of equal strength, a small grain structure, and a resistance to atmospheric corrosion that is greater than that of either plain phosphorus steel of hire phosphorus content or phosphorus-copper steel of like phosphorus and copper content.

The phosphorus-vanadium steels with or without copper, of the type disclosed herein, having high physical properties as well as high resistance to corrosion may be made into castings orcan-be fabricated into rough articles such as structural shapes, sheet, plate, wire and tubing which are to be used where resistance to corrosion, as well as high physical properties are desired.

Having thus described our invention, what we claim is:

1. An alloy, steel consisting of fr m 0.01% to ne immediately 0.5% carbon, from 0.025% to 0.5% vanadium,

from 0.08% to 0.5% phosphorus, from 0.2% to 1.5% manganese, copper in an amount not over 3%, and not over 0.20% sulphur, the balance being substantially all iron. v

I 2. An alloy steel consisting of from 0.01% to 0.25% carbon, 0.025% to 0.25% vanadium, 0.08%

'to 0.25% phosphorus, 0.2% to 0.8% manganese,

copper in an amount not over'3%, and not over 0.20%'sulphur, the balance being substantially all iron.

3. An alloy steel consisting of from 0.01% to 0.25% carbon, 0.025% to 0.25% vanadium, 0.08% to 0.25% phosphorus, 0.2% to 0.8% manganese,

0.10% .\to0.5% copper, and not more than 0.20% sulphur, th balance being substantially'all iron. 4. An allo steel containing from 0.01 .per cent to 0.5 per cent'carbon, from 0.025 per cent to 0.5 per cent vanadium,from 0.08 per cent to 0.5 per cent phosphorus, from 0.2 per cent to 1.5 per cent 20 manganese, copper in an amount not over 3 per cent, and not over 0.20 per cent sulphur, the phosphorus being present for the purpose of enhancing the corrosion resistance and mechanical properties of the steel and not merely as an impurity-and 25.

the vanadiumbeing present to oflset the embrit-- tling eifect of phosphorus, the balance being substantially all iron, the steel having a yield strength in the rolled, normalized and annealed conditions of more than 40,000 pounds per square inch and e ductility at least equal to that of plain carbon steelpf equal strength.

I ,5. An alloy steel consisting of from 0.01% to