US2532117A - Nickel steel alloys - Google Patents

Description

Patented Nov. 28, 1950 Harold D. Newell, Beaver Falls, -Pa., assignor to The Baboock & Wilcox Tube Company, West Mayiield, Pa., a corporation of Pennsylvania No Drawing. Application September 17, 1946,- Serial No. 697,5"l

Claims. (01. -125 This invention relates to improved nickel alloy steel compositions and more particularly to nickel alloy steels resistant to certain corroding influences and having good toughness characteristics with ductility and resistance to impact at sub-zero temperatures.

Heretofore, it has been customary to use nickel steels for machine parts, for automotive parts, for carburized roller bearings and for other purposes in the usual form of SAE or NE grades with nickel contents up to 5% or thereabouts. Steels with up to this amount of nickel are also combined with small quantities of chromium, molybdenum, vanadium, silicon or other alloying ingredients, and the carbon content is adjusted to suit the end use or requirement for hardness, strength or other properties. High nickel steel alloys containing 30% or more nickel are also well known and have been used for their special properties of electrical resistance, low expansion rates or other features. Commercial steels, exclusive of stainless steels, have not been made and used containing more than about 5.25 per cent nickel and-this is especially so of steels containing between about 7 per cent and 12 per cent nickel because such steels are hard and martensitic in character and lack ductility and are difllcult to anneal so as to soften them for machining, expanding, bending or other forming operations. Consequently, such steels have previously not been available in tubing or pipe or other articles as they were considered to be laboratory curiosities not usable commercially because of their peculiar properties.

. The present invention makes available nickel in welded constructions by the use of well-known welding methods if certain practices are followed as to preheating and postheating the metal following the welding operations.

The main object of the present invention is to provide a new series oinickel alloy steels which may be varied as to composition to provide various properties of corrosion resistance to atmosphere, to alkaline solutions or mild organic acid conditions (pH 2.0 to 6.0), to chloride and sulphide solutions, or other forms of corrosion where presently available lower alloy content steels, including the commercial nickel steels,

' are not adequate or economical because of their lack of corrosion resistance or unsuitable physical properties for special fields of service. Another and more specific object is to' provide for the manufacture of articles requiring steels having toughnessv and ductility such as tubes, pipe, rods, containers, valves and fittings, and other formed appurtenances for industrial use as in 0115111 use.

The new series of nickel alloy steels made in accordance with the present invention have in general the following composition:

Per cent Carbon 0.03to 0.20 Manganese 0.20 to 1.00 Silicon 0.03to 0.40 Nickel 7.50 to 12.00 Chromium 0.02to 6.00 Copper 0z.05:t0 $00 Molybdenum 0.03to 2.00

Titanium, columbium, zirconium or vanadium singly or in combination 0.0 to 1.00 with the balance substantially all iron.

a 3 ingots, blooms, bars or, tubes should be low in sulphur for best results.

The steels should be thoroughly deoxfdized, usually with one to two pounds or more of aluminum per ton to produce steels with fine grained characteristics having high toughness and ductility. This is necessary for retention of impactstrength at low temperature and such thorough deoxidation has the further advantage of stimulating reaction rates during annealing and reducing strain-aging properties. Silicon is preferably kept below 0.25 per cent and the steels should be poured into hot-topped molds.

With respect to composition, the nickel content, although not limited thereto, is usually ranged between a and per cent in a low carbon base, the carbon being restricted in most cases to 0.12 per cent maximum and, where maximum ductility and softness is required in the finished product, as in tubes for bending or ex-- carbon is limited to .20 per cent maximum, or more often is restricted to .12 per cent or less, the hardenability of the steel is reduced and the working, annealing and machining of these nickel steels is greatly improved. However, to further reduce hardenability and to provide easy workability, good ductility and ease of annealing, such as necessary in the manufacture of ductile seamless tubes suitable for expanded Joints or bends,

panding, the carbon should be under 0.10 per cent, i. e. about 0.06 to 0.09 per cent. Even lower carbon may be advantageous in certain circumstances to avoid formation of a hard martensitelike constituent which has heretofore been characteristic of alloy steels having a nickel content I have found it desirable to incorporate one or more strong carbide formers to tie up carbon and render it ineifectlv'e in forming and retaining the hard and brittle martensite-like constituent.

This is accomplished by adding titanium up to the eyuivalent of four or more times the carbon content. -When columbium is added up to ten times the carbon content, it has an equal eifect in suppressing hardenability. Zirconium and/or vanadium may also be used for their effects of this kind. For this purpose, zirconium may be added in a ratio up to 8-10 times the carbon content and vanadium up to 4 or more times the carbon content, depending on whether it is in the range disclosed. Copper is usually added to the composition for "its beneficial efl'ect in creating better corrosion resistance toward the atmosphere and other corrosive media including alkalies and mild acids. The usual addition is 0.20 to 0.40 per cent copper. Where high ultimate strengths are required the copper ,may be raised to 1.00 per cent or more and this adds further to the corrosion resistant properties of the alloys, at the same time permitting agehardening reactions to occur in the steel upon tempering treatments, with decided improvement in physical properties. In fact, carbon can be kept very low in my allow steels, and copper may be used to strengthen them by precipitation hardening on applying appropriate heat treatments. Such heat treatments consist of normalizing or quenching from above the A3 point and thereafter tempering between about 850 F and 1100 F.

Molybdenum may be added as required to the extent of upwards of 2.00 per cent to benefit corrosion resistance particularly under mild acid corrosion conditions. When used, a preferred amount is approximately 0.50 per cent molybdenum. Chromium, when added to my nickel steels, is used for improvement of corrosion resistance. It also alters physical properties. Approximately 5 per cent chromium may be added although a lesser amount has a beneficial effect. For resist-' ance to alkalies or for good toughness at low temperature, chromium is not required and is not incorporated in my preferred alloy.

Manganese is incorporated as in good alloy steel practice and may be present between about 0.20 and 1.00per cent. About 0.30/0.60 per cent is the usual addition. Phosphorus is generally low and for maximum softness, silicon can be ranged near the low limit or about 0.20-0.05 per cent.

The usual nickel alloy steels having a nickel content of about 5.0 to 12.0 per cent or more tend to be hard and brittle due to the characteristic formation of a martensite-like constituent which is difficult to break down to ferrite and carbides even on extended annealing. cycles. When the alloying constituents previously described are combined in the proportions disclosed, and the desired to fairly fully suppress or only partially suppress hardening reactions. These carbide forming elements may be used singly or together corporated in the steels upto a total of not exceeding 1.00 per cent construed as coming within the scope of the invention. The titanium, vanadium, columbium and/or zirconium may be added in the form of the usual ferro-alloys as metals, or special deoxidizers or reduced into the metal from their oxides or, other compounds. Titanium is the preferred addition because of the low ratio required for carbide formation and because it is most economical. Other advantages accrue from using these carbide formers in my alloys as they tend to suppress caustic embrittlement and they reduce strain-aging effects in the metal.

As is disclosed, several'variations of my alloy may be used depending upon exact use. My preferred range for general use is:

with the balance substantially all iron.

Typical heats of this nickel steel alloy made for use as tubes in alkali evaporators had analyses and grain sizes as follows:

TableI McQuaidgfij 0 Mn Si 01' Ni Cu Mo Ehn Grain Size pering, after normalizing, the impact strengths improved greatly as may also be noted in the same table.

. s Table Ila-impact properties Standard Charpy specimen .394" s pare-drilled ke hole notch. Values shown are average of three spec mens of each eat at'each temperature. All tests made on specimens taken longitudinal to rolling direction. I

Other alloys coming within the scope of the invention are disclosed as to composition in Table III. Usual heat treatments applied consist of normalizing at about 1575 F., or double normalizing and tempering at about 1050 F. ,Witl'. selection of composition and treatment, wide range of physical properties may be provided. Typical properties obtained on my alloys in these circumstances may be noted in Table IV. In surveying these values, it may be noted that titanium additions are useful for softening and reduction of silicon content is also helpful toward that end where maximum ductility might be required in the article.

Theiareferred double normalizing heat treatment consists in first normalizing at a temperature of approximately 1625 F. and a second normalizing at a temperature of approximately 1450 F.

Table IIL-Chemical analysis Using the compositions set forth, I am able to provide corrosion resistance in a variety of media which exceeds that available in the usual structural nickel steels, particular-advantage being securedwhen articles of my alloys are exposed to alkaline media. Good resistance is also secured under mildly acidic conditions.

Physical properties may be altered in my steels by variation within the range of composition set forth to obtain high strength with reasonable ductility, or softer more ductile material may be provided as required. Mypreferred alloy composition offers high impact strength and retains its toughness to much lower temperatures than any of the lesser alloy content engineering steels and consequently may be employed to replace stainlss austenitic steels or non-ferrous metals in equipment intended for sub-zero service. It is especially useful when service temperatures fall below about minus 1'75 F.

My alloys may be rolled -or manufactured into useful industrial articles such as tubing and pipe for conveying fluids, into sucker rods, valve parts, oil well appurtenances, bearings for carburizing and into other articles as desired. Ordinary equipment usually available in steel mills may be used to convert the metal from ingot to other wroughtforms. My alloy steels can be substituted for steels having lesser corrosion resistance or inferior physical properties at moderate increase in cost over those presently available commercially and at much lower cost than for the high chromium-nickel stainless steels.

The analyses given in Table III are illustrative and the objects of the present invention may be realized by altering the composition within the ranges set forth in the claims made hereinafter.

I claim:

Alloy I o I Mn I s1 I Ni 011 Mo v Ti Cr 40 1. A forgeable and machinable alloy steel characterized by high resistance to alkali and ,mild 0.12 0.05 0.15 3.01 0.05 0 m 0.50 acidic corrosion, said steel having the folio 31% 3120 8153 01% 0.55 composition 4 .21 9.32 0.38 3.53 3.34 8.50 9.21 0.22 from 0.03 to 0.20% carbon M0 M3 from 0.20 to 1.00% manganese 0.08 0.45 0.20 9.50 0.81 0.58 5.50 0.10 0.00 0.38 9.40 0. 48 0.5a 0.21 5.53 from 0. 2 to 0. 0% silicon 906 M7 from 7.50 to 12.00% nickel from 0.20 to 2.00% copper Table IV .---Physical properties Elong. 11011.01 Ultimate Yield Impact Allo Condition 1 Per Cent Area. BHN Y p. s. 1. p. s. 1. m Ft. Lbs.

Normalized 185,750 151,000 13.0 47.2 307 18.5 .50 C1- 7 Double Normalized 191, 200 159, 250 11.5 44. 4 408 18. 5 Double Normalized and Tempered.. 1 250 117, 750 20. 0 60. 1 285 32. 5 Normalized 139, 000 113, 000 15. 0 55.5 287 25. 0 .20 Mo 8 {Double Normalized" 131, 000 108, 800 15.0 49. 9 309 27. 0 Double Normalized and Tempered 120, 750 109, 150 20. 0 57. 7, 265 36. 5 Normalized 147,000 125, 100 15.5 I 57.3 305 9 Double Normalized; 500 110, 500 17. 0 58. 4 278 25. 0 Double Normalized and Tempered- 106, 300 90, 250 22. 0 65. 8 230 41. 0 Normalized 135, 200 115, 000 17. 0 59. 6 305 26. 5 10 {Double Normalized 122, 500 102, 000 19. 0 07. 3 263 37. 0 Double Normalized an 122, 800 109, 000 20.0 67. 4 275 41. 0 orm zed 104, 750 83,600 24.0 67.9 229 53.5 11 {Double Normalized 108, 000 81, 250 26. 0 67. 8 228 54. 5 Double Normalized and Tempered- 90, 000 79, 750 26. 0 68. 2 227 56.5 Normalized 142, 400 118, 900 15.0 54.4 307 22. 0 12 {Double Normalized 137,000 114, 200 26. 0 45. 8 293 20. 5 Double Normalized and empered-- 133,000 1 500 18.0 51. 5 300 33. 0 Normalized 180,500 147, 050 15.0 53.7 387 21.5 13 {Double Normalized 192,000 153, 500 12. 0 47.0 427 15.0 Double Normalized and Tempered 152, 250 142, 000 18.0 59. 4 342 21. 5 Normalized 107,000 158,000 13.5 50.8 301 14 Double Normalized 202, 500 154, 300 12. 5 44. 2 385 26.5 Double Normalized and Tempered 167, 200 105, 500 13. 0 51.2 303 43. 0 Normalized -1 144, 000 119, 750 15. 0 53. 3 312 18. 0 15 Double Normalized 138, 800 119, 300 17. 0 58. 9 299 21. 5 Double Normalized and Tempered... 137,1110 124, 800 21. 0 01. 2 303 31. 5

. incidental impurities.

\ balance iron and incidental impurities.

up to 8.00% chromium up to 2.00% molybdenum and up to 1.00% of a carbide former selected from the group consisting of titanium, columbium, zirconium and vanadium; balance iron and 2. A iorgeable and machinable alloy steel characterized by hi h resistance to alkali and mild acidic corrosion, said steel having the 101 lowing composition up to 0.12% carbon from 0.40 to 0.60% manganese from 8.00 to 10.00% nickel from 0.05 to 0.25% silicon from 0.20 to 2.00% copper balance iron and incidental impurities 3. A iorgeable and machinable alloy steel characterized by high resistance to'alkali and mild acidic corrosion, said steel having the following composition from 0.06'to 0.09% carbon from 0.40 to 0.50% manganese from 8.80 to 9.20% nickel from 0.15 .to 0.25% silicon from 0.20 to 0.40% copper from 0.03 to 0.11% chromium from 0.04 to 0.07% molybdenum 4. A torgeable and machinable alloy steel characterized by high resistance to alkali and mild acidic corrosion, said steel having theiollowing composition up to 0.12% carbon from 0.30 to 0.60% manganese from 8.00 to 10.00% nickel up to 0.25% silicon from 0.20 to 0.40% copper up to 0.50% molybdenum and titanium up to 4 times the carbon content; balance iron and incidental impurities.

5. A nickel steel alloy tubular article composed of the alloy steel defined in claim 1; said article having been normalized and tempered.

' HAROLD D. NEWELL.

REFERENCES crrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS

Claims (1)

1. A FORGEABLE AND MACHINABLE ALLOY STEEL CHARACTERIZED BY HIGH RESISTANCE TO ALKALI AND MILD ACIDIC CORROSION, SAID STEEL HAVING THE FOLLOWING COMPOSITION