US3100729A - Stainless steel product and method - Google Patents

Description

to the production of and tough, and readily lends itself to weaving into beltas a few months as a maximum, pending upon the United States Patent 3,100,729 STAINLESS STEEL PRGDUCT AND li/EETHOD George N. Goller, Towson, Md, assignor to Armco Steel Corporation, Middletown, Ohio, a corporation of Ohio No Drawing. Filed Apr. 27, 1961, tier. No. 105,378 15 Claims. (Cl. 148-125) My invention relates to stainless steel products such as sheet, strip, rods and wire and to wire belting, particularly the wire belting for Fourdrinier paper-making machines.

One of the objects of the invention is sheet, strip and wire which fatigue in use and especially to wire which is well suited woven belts, which wire is strong the provision of ing and to brazing in forming the completed belt.

Another object is the provision of a woven wire belt which is resistant to wear and abrasion; which is resistant to corrosion; and which is resistant to fatigue under the conditions of vibration, wear, corrosive attack and the like, all as encountered in actual practical use.

A further object of my invention is the provision of a method for making a wire belt and to the wire employed therein, in which method there is enjoyed a simplicity of procedure in combination with an assurance of a belt possessing a long and useful life under the many varying conditions of actual use.

Other objects of my invention in part will be apparent to one reading this specification and in part more particularly pointed out.

Accordingly, my invention will be seen to reside in the composition of ingredients, in the combination of procedu'ral steps, and in the relation of each of the same to one or more of the others all as described herein and particularly set forth in the claims at the end of this specification.

As conducive to a better understanding of my invention, it may be noted that in the art of paper-making there conventionally is employed a Fourdrinier machine with woven wire belting on which paper pulp for processing and elimination of moisture. In these machines the wire belts employed commonly range up to a width of 350 inches and a length up to 180 feet or more. The mesh size of the belts is on the order of some 40 to 90 per lineal inch, the particular mesh depending upon the particular type-of paper to be made. And the Wire size employed in these belts ranges from .005 to .016 inch diameter. As a matter of further information, the belts weigh anywhere from 400 pounds to 3,000 pounds apiece. And they are "driven at speeds up to 3,000 feet per minute. 7

At present, the Fourdrinier wire warp wire of the grade C Phosphor bronze (92% copper and 8% tin) and cross or shute wires of brass. These warp wires have a tensile strength of about 72,000 p.s.i., a yield strength of 50,000 p.s.i., and an elongation in 10 inches which is somewhat better than: 50%.

A belt lasts only fromabou-t days to perhaps as much the life generally debelts are made with type of paper of operation, and the type of equipment employed. For example, in making paper board'the Fourdrinier wire belt may last about seven days, for newsprint about seven to fourteen days, and for special papers using slow speed operation they may last three months. The principal causes of belt failure are mechanical wear and mechanical fatigue.

The known Fourdrinier wire belts are costly, perishable and replaceable only at substantial loss of machine time.

is particularly resistant to is charged being processed, speed 3,100,729 Patented Aug. 13, 1963 1n the operation of the Fourdrinier machine it is noted that the belt rides over and is in friction with a number of suction boxes. These conventionally are made of a hard Wood such as maple. And it is not infrequently found that particles of silica and china clay become embedded in the surfaces of the box with which the belt comes in contact. As a result loss of the metal of the belt because of friction, wear and abrasion becomes considerable. A belt then customarily is withdrawn from service when the diameter of the warp wires has been reduced by some 40% of the original diameter. Use beyond this would court the hazard of belt breakage in use and under load, all at great cost in equipment and in machinery shut-down, this coming at a bad time; in planned replacement the paper-making machine is shut down over the weekend or even a holiday in order to prevent loss of a working day.

A further necessity for belt replacement is a failure of the belt as a result of fatigue, particularly the fatigue of the warp wires of the belt. Most of these failures occur at the edges of the belt where there is a certain amount of flapping in high speed belt movement. It is found, for example, that at a speed of some 2,800 feet per minute a failure occurs after about 630,000 cycles of belt operation.

And where some mechanical damage occurs in use, such as the formation of dents, wrinkles, or the like, the life of the belt is substantially lessened because such damaged areas quickly wear through, giving holes in the belt which cannot be repaired. Further use of a belt in such condition runs the risk of producing an inferior paper and sudden breakage with inconvenient and expensive shut-down of the entire machine as well.

In some instances the operational life of the papermaking belt is shortenedas a result of corrosion-fatigue, that is, fatigue compounded by corrosive attack of. the metal. In those operations where pulp with corrosive waters is to be encountered it is customary to use a belt made up of wires which have been tinned or nickelplated. The tinning or nickel-plating of the wires, of course, is doneprior to their being woven into belting.

In order to obtain greater belt life under the conditions encountered in use, the art has tried belts fashioned of Inconel wire (80% nickel, 14% chromium and 6% iron). These shortly failed as a result of fatigue. An effort also has been made to employ belts fashioned of stainless steel of different grades. But all of those belts failed to achieve the success hoped for, failure through fatigue occurring within several days of usage. As a consequence, it is the known Phosphor bronze-brass tional life as compared to those of the prior art, all at minimum cost in intial investment, assuring freedom from sudden breakage and at substantial savings in machine shut-down time. 1

Referring now more particularly to the practice of my 1' invention, I proved a woven wire belt for a Fourdrinier paper-making machine, the belt being fashioned of a chromium-nickel stainless steel wire severely and critically cold-drawn to particular amount and then tempered within a critical range of heat-treatment. In broad terms, the stainless steel wire employed in the warp essentially conof 16% to 18% chromium,

are also had where the warp wire sists of about 16% to 26% chromium, about 6% to 22% nickel, carbon up to about .25%, with remainder substantiallyall iron. Where desired, and especially in certain paper-making applications, the warp wire includes molybdenum, this in the amount of some 2% to 3%; For other applications the warp wire includes one or more of titanium and columbium, this in the amounts up to about 8% for the titanium and up to about 1.2% for the columbium. As representative of the grades of chromiumnickel stainless steel employed are the American Iron and SteelInstitute types Nos. 302 (17% to 19% chromium, 8% to 10% nickel, .08% to .20% carbon, and remainder iron), 304 (18% to 20% chromium, 8% to 11% nickel, carbon 0.08% max, and remainder iron), 304L (analysis of 304 except with carbon .03% max), 305 (17% to 19% chromium, 10% to 13% nickel, carbon 0.12% max, and remainder iron), I308 (19% to 21% chromium, 10% to 12% nickel, carbon 0.08% max, and remainder iron), 309 (22% to 24% chromium, 12% to 15% nickel, carbon 0.20% max, and remainder iron), 310 (24% to 26% chromium-19% to 22% nickel, carbon 0.25% max, and remainder iron), 316 and 316L (16% to 18% chromium, 10% to 14% nickel, 2% to 3% molyb denum, carbon 0.10% max, for the type 316, and carbon 0.03% max. for the type 316L, and remainder iron), 317 (18% to 20% chromium, 11% to 14% nickel, 3% to 4% molybdenum, carbon 0.10% max, and remainder iron), 321 (17% to 19% chromium, 8% to 11% nickel, carbon 0.08% max., titanium a minimum of times the carbon content, and remainder iron), and the type 347 (17% to 19% chromium, 9% to 12% nickel, carbon 0.08% max., with titanium a minimum of times the carbon content, and remainder iron).

Of the several grades indicated above, I find best results are achieved with warp wire essentially consisting 10% to 14% nickel, 2% to 3% molybdenum, carbon 0.03% maximum, and remainder substantially all iron. -It will be understood in this remainder there is included manganese 2% max., silicon 1% max, phosphorus 0.040% max. and sulphur 0.030% max. This is the type 316L. Excellent results is of like analysis but content, that is, the max., this being the type 316.

with greater tolerance for carbon carbon content being 0.10%

' Good results are also achieved with wal p wine essentially consisting of 18% to 20% chromium, 8% to 11% nickel, carb0n 0.08% max, with. manganese 2% max., silicon 1% max, phosphorus 0.040% max., sulphur 0.030%

max, and remainder iron, this being type 304. And for shute Wire satisfactory results are had with stainless steel essentially consisting of 17% to 19% 10% nickel, carbon 0.08% max, silicon 1%- chromium, 8% to to 0.20% manganese 2% max, phosphorus 0.040% max, sulphur 0.030% max, and remainder iron, this being type 302. Other grades of stainless steel may be employed in the shute Wire where desired, although generally it is felt that no benefit is had by employing the more costly grades of higher chromium and nickel contents.

In accordance with the teachings of my invention, the warp wires are severely cold-drawn, this to the extent of a cold reduction exceeding 8 0%, and generally amounting to a figure exceeding on up to as much as 95% reduction in area. The cold-drawn Wire had is about 0.006 to 0.013 inch in diameter. The particular wire size: is dependent upon the specific requirements. In general, however, the cold-drawn Wire ranges between the values indicated. The cold-drawn wire has a tensile tial loss in tensile strength, shows a great improvement in ductility. Thus, with the tempering treatment the tensile strengths of 250,000 to 300,000 p.s.i. are lowered to some 110,000 to 140,000 p.s.i. The elongation in 10 inches, however, is greatly increased, this to a value of some 20 to 40 percent. I find that the grain structure of the drastically cold-drawn and tempered wire is fine and equiaxed, about ASTM size 10 to 12.

It is this drastically cold-drawn and tempered wire which is the Warp wire which is woven into belting material. In the belting of my invention the shute Wire is preferably in the annealed condition because, as suggested above, it is Warp wire rather than shute wire which is subjected to greatest Wear and fatigue. Actually, the woven wire belting appears to be a wire cloth. The mesh size is on the order of some 40 to mesh to the lineal inch. Most of the'belts for the Fourdrinier paperrnaking machine are of 50 to 60 mesh to the lineal inch.

As to specific examples of the warp wire of my invention, one analyzes about 1 7% chromium, 12% nickel, 2% molybdenum, carbon not exceeding .03% max. and remainder substantially all iron. cold-drawn to the extent of 82% reaching a size of 0.0107" in diameter. Another analyzes about 18% chromium, 8% nickel, canborl 0.08% to 0.20%, and remainder substantially all iron. This example has been cold-drawn to the extent of about 90%, arriving at a diameter of 0.0087. The mechanical properties ot the wire of these two examples is given in Tables 1(a) and 1(1)) lbelow. Samples of each of these example have been tempered at temperatures ranging from some 1200 F. up to 1900 F. The tre-atment accorded the various wire samples, the mechanical properties had and the fatigue performance for the two specific examples are given in the Tables I(a) and 1(1)) below.

TABLE I(a) Mechanical Properties and Fatigue Performance for the Cold-Drawn and Tempered Wire of 0.0107" Dlameter Percent Avera e Fatl 0 Condition cold-drawn 82% U.T. S. .2% Y .S., elongafatigui tes t s Load,

p.s.l. p.s.l. tlon cycles averaged lbs. V m 10" Above only 245, 000 232, 000 .4. Ab no. 1 262,000

ovep us mm 10,44 Above plus 1,300 F. 11, 758 2 8 Above lus 1,400 F. 11,718 4 0' Above plus 1, 450 F. 11, 651 4 0' Above plus 1,500 F.- 11, 749 4 0' Above plus 1,5s0 F. 8,072 a 0' Above plus 1,s00 F. r 8,031 4 0' Above plus 1,700 F. 110, 000 40, 500 33. 0 7,105 4 of Above lus 1,so0 F. 5 103, 000 40, 000 so. 0 6,996 a 0 0. Above plus l,900 F. 5 mm.. 100, 000 43, 000 36.0 5, 920 5 0 Above plus 1,400 F.44/mln. 122, 000 37. 0 Above plus 1,400 F. 9471111111.. 142, 000 2s. 0 10, 550 1 ii "0. 1

l Furnace length 12 it.

This example has been It is noted from Table 1(a) above that severely colddrawn wire with an ultimate tensile strength of some 245 000 to 262,000 p.s.i. is brought to an ultimate tensile strength of some 110,000 to 140,000 p.s.i. through tempering, respectively, at 1700 F. for live minutes for the lower tensile figure and 1400 F. for five minutes for the higher tensile figure. correspondingly, however, the elongation in 10 inches is brought up to 33% for a strength of 110,000 p.s.i. and 18% for the 139,000 p.s.i. figure. The average number of cycles for the fatigue test ranges from 7,105 for the specific sample with tensile strength Off 110,000 p.s.i. and elongation of 33%, to 11,- 718 for the specific example with tensile strength of 139,- 000 p.s.i. and elongation of 18%. In all cases several fatigue tests were taken and the figures given are averages for these several tests.

In the fatigue testing the various strands of wire undergoing test are suspended into vertical position and are wrapped once around a cluster of 4 rolls each of 1 inch diameter, with the diameter of the cluster amounting to 4 inches, the wire being held taut by a weight of 0.4 lb.

And in the tempering treatment I find that excellent results are had with short time treatment at substantial temperatures, this permitting use of a strand furnace for heating the wire at high speed of travel. In the last two examples given in Table 1(a) the wire travelled respectively at 44 feet/min. and 94 feet/min, this through the furnace of 12 foot length maintained at 1400 F. The duration of treatment then amounted to about /4 minute and about /s minute, respectively. Good results are had even at greater speeds of travel and shonter times of treatment but in somewhat higher temperatures. example, I find good results are achieved in a 12 toot furnace maintained at 1520 F. with a wire speed of 118 feet/minute, this giving a time of treatment amounting to of a minute.

In my invention. the time of treatment is very short and the temperatures are high, for I find than with this combination recrystallization is achieved after the'severe oold-reduotion and yet no objectionable grain growth follows the recrystallization. Apparently, with the tempering treatment the metal fast recovers from the drastic cold-reduction. Then, withthe continued heating, the grains nucleate around the original grain boundaries where grains meet (triple points). And following this the grains will begin to grow.- In my method the tempering is interrupted in advance of objectionable grain growth. In this way I preserve remnants of the coldworking and pick up new grains to give maximum formability.

TABLE 1(b) Mechanical Properties and Fatigue Performance for the 90% Co d-Drawn and Tempered Wire 0.0087 Inch.

Diameter 0.2% Percent 1 Condition colddrawn U.T.S., Y.S., elonga- Fatigue Load,

(app. 90%) p.s.i. p.s.i. tion cycles lbs.

Above only 319, 000 319, 000

Above plus 1,200 F. 5 min 202,000 202,000 Do 202, 000 202, 000 Above plus 1,280 13. 30 min 151, 000 141, 000 Above plus 1,505 F 5 min 150,000 02, 500 130---. 146, 000 84, 000 Above plus 1,615 F. 5 1

min 143, 000 75, 000 37 .5 Do 141, 500 79, 000 37 .5 Above plus 1,675 F.

min 147,000 40 .5 14, 480 0 .4 Do 147, 000 77, 500 42 .5 14, 140 0 .4 Above plus 1,675

min 143. 000 70, 000 38 .5 12, 380 0 .4 D0 143, 000 70, 500 38 .5 12, 760 0 .4 Above plus 1,700 F. 1 r 1 min 146, 000 73, 750 40 .0

For

TABLE I b --Continued 0.2% Percent Condition cold-drawn U.T.S Y.S., olouga- Fatigue Load,

(app. p.s.i. p.s.i tion cycles lbs.

Above plus 1,700 F. 5

14, 828 0 .4 Do 13, 908 0 .4 Above plus 1,700 F. 5

min. plus pickled... 13.140 0 .4 Do 13, 428 0 .4

134, 500 47, 000 43 .5 7, 608 0 .4 129. 500 50, 500 37 .5 6, 260 0 .4 Do 1... 6,016 0.4 Above plus 1,000 F. 5

min 133,. 000 48, 000 43 .5 3, 948 0 .4 Do 133, 000 48, 750 46 .0 4. 700 0 .4

As noted from the mechanical properties given in Table 1(1)), the severely cold-drawn wire with an ultimate tensile strength of 319,000 p.s.i. is bound to have a tensile strength on (the order of 150,000 p.s.i. with 10 inch elongation of about 26.8% as a result of tempering treatment at 1510 F. for 5 minutes. With tempering at 1750 F. for 5 minutes the ultimate tensile strength is lowered to 140,000 p.s.i. and the elongation in 10 inches is-inereased to 40.5%. Somewhat greater elongation, with further lowering of tensile strength, is bad with tempering at 1900 F. for both 2 minutes and 5 minutes, the elongation arnounting to about 43.50% and the ultimate tensile strength about 133,000 p.s.i.

The'tatigue performance for the examples, given in Table 1(b) average some 11,000 to 14,000 cycles for the examples tempered at 1725 F. and 1675 F., respectively. Here it is noted that in the fatugue testing the wires were loaded to theextent of 0.4 lb. except where otherwise indicated.

The fatigue performance had with the severely colddrawn and tempered stainless steel wire of my invention compares well with the fatigue performance had with the bronze wire employed in the prior art. Thus, where the steel wire of my invention, as noted above, achieves a value of some 11,000 cycles in an average of four tests as noted in Table 1(a) and some 11,000 to 15,000 cycles in Table 1(1)), one sample of bronze wire of .008 inch diameter had an average fatigue life of 11,600 cycles in six tests. And another bronze Wire of .0076 inch had a t fatigue life of some 12,120 to 13,128 cycles, both under test conditions. identical with those reported in Tables 1(a) and -I(b). i

And the values of tensile strength and yield strength are very much in favor of my severely cold-drawn and tempered stainless steel wire. For while the two bronze wires respectively referred to above had average tensile strengths of 70,000 p.s.i. and 75,000 p.s.i. with yield strengths of about 35,000 p.s.i. and 37,000 p.s.i. the average tensile strength of my wire is on the order of 110,000 to. 150,000 p.s.i. with yield strengths of 50,000

i to 120,000 p.s.i. The'ductility of the bronze wire substantially exceeds that of the severely cold-drawn and tempered wire of my invention but, as noted above, the ductility of any wire is adequate for the purpose and the great increase in strength had over that of the bronze .wire of the prior art gives much greater wear and durabili- -ty under the conditions of use.

In making up a woven wire belt according to my invention, I employ warp knives of about .006 to .013 inch diameter of the character particularly set forth above, i.e., wire essentially consisting of about 16% to 26% chromium, about 6% to'22% nickel, carbon about .25% mate, with remainder substantially all iron (the preferred warp U wire analyzes about 16% to 18% chromium, about to 14% nickel, about 2% to 3% molybdenum, carbon not exceeding about .03% max, and remainder substantially all iron), which wire has been cold-drawn to at least about 80% and then tempered at a temperature of about 1200 to 1750 F., more particularly l400 to 1700- F, and

preferably 1615 to 1750 'F. for types 302 and 304 for example, and preferably 1400 to 1600 F. for the types 316, 3161. and 305. For the shute wires, i.e., the cross wires, I preferably employ a wire slightly larger in diameter than for the warp wire, essentially consisting of about 17% to 19% chromium, about 10% to 13% nickel, carbon not exceding about .l2%, and remainder substantially all iron (type 305), this in the annealed condition, -i.e., heated at a temperature of some 1850 to 2050 F. and cooled rapidly.

Woven wire belting in accordance with the teachings of my invention in strips up to 350 inches wide and several hundred feet long is readily fabricated into a belt for Fourdrinier paper-making machines simply by welding or brazing together the two ends of the strip. For this purpose there conveniently is employed a silver solder as in the prior art as applied to the Phosphor bronze belts.

Thus it will be seen that I provide in my invention stainless steel wire possessing the surprising combination of .good Wear resistance with good resistance to fatigue. Also that I provide a woven wire belt for the Fourdrinier paper-making machines which is strong, tough, corrosionresis-tant, as well as resistant to wear, abrasion and fatigue under the conditions encountered in actual practical paper-making operation. The wire and belting of my invention outlast the wire and belting of the prior art. And substantial savings are had in the cost of belts for the Fourdrinier paper-making machines, this in terms of initial investment and in terms of maintenance, upkeep and replacement.

While the wire and-belting of my invention is particularly suited to the Fourdrinier paper-making machines, it will be understood that the wire and belting are suited to other applications where strength, corrosionvresistance, resistance to wear and abrasion and resistance to fatigue are called into play. For example wires of about .006 to A", or even to /2" diameter, particularly .006 to A inchdiameter are bad with severe coldreduction (exceeding 80%) and then tempered at 1200 to 1750 -F. Also it is understood that my invention embraces strip as well as wire which is first severely cold-reduced, that is, an amount exceeding 80%, and

especially exceeding 85% and on up to about 95%, and then tempered at about 1200 to 1750 F., particularly 1400 to 1700 F.

Accordingly, it is to be understood that the description of the wire, strip and belt of my invention as given above is ,to be interpreted as illustrative and not as a limitation.

I claim as my invention:

1. In the production of stainless steel of good fatigue, resistance, the art which comprises providing steel not exceeding /2" thickness and essentially consisting of about 16% to 26% chromium, about 6% to 22% nickel,

*carbonup to about .25% maximum, with remainder substantially all iron; cold-reducing the same, without benefit of intermediate anneal in an amount exceeding about 80% and giving a tensile strength of about 250,000 p.s.i. or more; and then tempering the same at a temperature of about 1-200 to 1750 F. for about to 30 minutes to give an elongation of about 20% to 40% with a tensile strength ofabout 110,000 to 140,000 p.s.i.

. and fine equiaxed grain structure.

2. in the production of stainless steel wire and strip of about .006 to /2 inch thickness and of good fatigue resistance,"the art which comprises providing wire or strip essentially consisting of about 16% to 26% chromium, about 6% to 22% nickel, carbon up to about .25 maximum,

with remainder substantially all iron; cold-reducing the same, without benefit of intermediate anneal, in an amount exceeding 85% and giving a tensile-strength of about 250,000 p.s.i. or more; and then tempering the same at a temperature of about 1400 -F. to 1700 for about A to 5 minutes to give an elongation of about 20% to 40% with a tensile strength of about 110,000 to 140,000 psi. and line equi-axed grain structure.

3. In the production of stainless steel Wire of about .006 to /8 inch diameter and of good fatigue resistance, the ant which comprises providing wire essentially consisting of about 16% to 26% chromium, about 6% to 22% nickel, carbon up to about .25 maximum, with remainder substantially all iron; cold-drawing thesarne, without benefit of intermediate anneal, to an amount exceeding and up to about 95%; and then tempering the same at a temperature of about 1200" F. to 1750 F. for about A to 30 minutes, giving a line equi-axed grain structure.

4. In the production of stainless steel wire of about .006 to .013 inch diameter and of good fatigue resistance, the art which comprises providing wire essentially consist ing of about 16% to 18% chromium, about 10% to 14% nickel, about 2% to 3% molybdenum, carbon not exceeding about 03%, and remainder iron; cold-drawing the same, Without benefit of intermediate anneal, in an amount exceeding and on up to and tempering the same at a temperature of about 1400 F. to 1600 F. for a period of time not exceeding about A minute, giving a fine equi-axed grain structure.

5. Stainless steelwire and strip of good fatigue resist I ance, said wire or strip essentially consisting of about 16% 2% to 3% molybdenum, carbon not exceeding about .03 and remainder substantially all iron and having a fine equi-axed grain structure.

7. In the production of stainless steel wire of good fatigue resistance, the art'which comprises providing wire essentially consisting of about 18% to 20% chromium, about 8% to 11% nickel, carbon not exceeding about .03%, and remainder substantially all iron; cold-drawing thesame, without benefit of intermediate anneal, in an amount exceeding 80% and on up to about 95%; and tempering at about 1615 F. to 1750 F., giving a fine equi-axed grain structure.

8. In the production of stainless steel wire of about .006 to .013 inch diameter and of good fatigue resistance,

the art which comprises providing wire essentially con-. sisting of about 17% to 19% chromium, about 8% to 10% nickel, about 08% to .20% carbon, and remainder substantially all iron; cold-drawing the same, without benefit of intermediate anneal, in an amount exceeding and tempering at about 1615 F. to 1750 F., giving a fine equi-axedgrain structure.

9. A woven wire belt, the warp wires of which are of stainless steel of about .006 to Vs inch diameter and essentially consisting of about 16% to 26% chromium,

about 6% to 22% nickel, carbon not exceeding about 7 ;-.25%,-and remainder substantially all iron and having a uniform fine equi-axed grain structure.

10. A woven wire belt, the warp wires of which are of stainless steel essentially consisting of about 16% to 18% chromium, about 10% to 14% nickel, about 2% to 3% molybdenum, carbon not exceeding about .03 and remainder substantially all iron and having a fine ,equi-axed grain structure.

11. A woven wire belt having stainless steel warp wires of about .006 to .013 inch diameter and essentially con sisting of about 16% to 18% chromium, about 10% to 14% nickel, about 2% to 3% molybdenum, carbon not exceeding about 03%, and remainder substantially all iron, and having a fine equi-axed grain structure; and having stainless steel shute wires essentially consisting of about 17% to 19% chromium, about 10% to 13% nickel, carbon not exceeding about .12%, and remainder substantially all iron in the fully annealed condition.

12. In the production of stainless steel of good fatigue resistance, the art which comprises providing steel not exceeding /2" thickness and essentially consisting of about 16% to 26% chromium, about 6% to 22% nickel, carbon up to about .25% maximum, with remainder substantially all iron; cold-reducing the same, without benefit of intermediate anneal, in an amount exceeding about 80% and giving a tensile strength of at least about 250,000 psi; and then tempering the same at a temperature of at least about 1200 F. for at least about 1 minute to give an elongation of at least about 20% with a tensile strength not exceeding about 140,000 p.s.i. and fine equi-axed grain structure.

13. In the production of stainless steel wire of good fatigue resistance, the art which comprises providing wire essentially consisting of about 16% to 26% chromium, about 6% to 22% nickel, carbon up to about .25% maximum, with remainder substantially all iron; cold-reducing the same, Without benefit of intermediate anneal, in amount of about 80% to 95% reduction in area and giving a tensile strength of at least about 250,000 p.s.i.; and then tempering the same at a temperature of at least about 1400" F. to give an elongation of at least about 18% with a tensile strength not exceeding about 150,000

psi. and with fine equi-axed grain structure.

14. In the production of stainless steel of good fatigue resistance, the art which comprises providing steel not exceeding /2" thickness and essentially consisting of about 16% to 26% chromium, about 6% to 22% nickel, carbon up to about .25 maximum, with remainder substantially all iron; cold-reducing the same, without benefit of intermediate anneal, in an amount exceeding about and giving a tensile strength of .at least about 250,000 p.s.i.; and then tempering the same at a temperature of about 1200 F. to 1900 F., with tempering at a temperature of at least about 1400 F. for a reduction of 82% or more and at least 1280 -F. for a reduction of or more, giving a steel of at least 16% elongation and fine equiaxed grain structure.

15. In the production of stainless steel wire of good fatigue resistance, the art which comprises providing wire essentially consisting of about 16% to 26% chromium, about 6% to 22% nickel, carbon up to about .25% maximum, with remainder substantially all iron; coldreducing the same, without benefit of intermediate anneal, in an amount of about 80% to reduction in area; and then tempering the same at a temperature of about 1400 F. to 1900 F., with tempering at about 1700 F. to 1900 F. for reductions exceeding about 80%, and at about 1500 F. to 1900 F. for reductions exceeding about 90% to give steel of at least 30% elongation and line equi-axe-d grain structure.

References Cited in the file of this patent UNITED STATES PATENTS 2,088,449 Specht July 27, 1937 2,527,521 Bloom Oct. 31, 1950 2,578,782 Campbell Dec. 18, 1951 2,590,074 Bloom Mar. 25, 1952 2,598,760 Cobb June 3, 1952 2,686,116 Schernpp et al. Aug. 10, 1954 2,795,519 Angel ct al June 11, 1957 2,815,273 Moore Dec. 3, 1957 2,851,233 Hayden Sept. 9, 1958

Claims (1)

1. IN THE PRODUCTION OF STAINLESS STEEL OF GOOD FATIGUE RESISTANCE, THE ART WHICH COMPRISES PROVIDING STEEL NOT EXCEEDING 1/2" THICKNESS AND ESSENTIALLY CONSISTING OF ABOUT 16% TO 26% CHROMIUM, ABOUT 6% TO 22% NICKEL, CARBON UP TO ABOUT .25% MAXIMUM, WITH REMAINDER SUBSTANTIALLY ALL IRON; COLD-REDUCING THE SAME, WITHOUT BENEFIT OF INTERMEDIATE ANNEAL IN AN AMOUNT EXCEEDING ABOUT 80% AND GIVING A TENSILE STRENGTH OF ABOUT 250,000 P.S.I. OR MORE; AND THEN TEMPERING THE SAME AT A TEMPERATURE OF ABOUT 1200*F. TO 1750*F. FOR ABOUT 1/10 TO 30 MINUTES TO GIVE AN ELONGATION OF ABOUT 20% TO 40% WITH A TENSILE STRENGTH OF ABOUT 110,000 TO 140,000 P.S.I. AND FINE EQUI-AXED GRAIN STRUCTURE.