US2182135A - Alloy steel - Google Patents

Description

Patented Dec. 5, 1939 UNITED STATES ALLOY STEEL Gustav A. Reinhardt, Youngstown, Ohio, assignor to The Youngstown Sheet and Tube Company, Youngstown, Ohio, a corporation of Ohio No Drawing. Application February 12, 1937, Serial No. 125,425

3 Claims. (Cl. 75125) This steel falls within that group of steels containing carbon, manganese, nickel and copper which have appreciably greater tensile strength and resistance to corrosion than ordinary steels 5 of similar carbon content and is characterized by properties which permit it to be readily and satisfactorily welded either electrically or by other usual methods. It is therefore particularly valuable for conditions of use in which a strong relatively non-corrodible steel of good weldability is desirable, especially as it readily lends itself to the usual manufacturing operations such as rolling, forging or the like.

I am aware that because of their strength and corrosion resistant properties steels of this general group, particularly those containing chromium, have been widely used for many purposes, but as far as I have been able to ascertain these steels do not readily submit to welding and may therefore be considered as of low or poor weldability as after welding they have a tendency to crack either in or adjacent the weld. In an effort to overcome this tendency it is therefore the usual practice to heat the part or parts just prior to welding to about 150 F. or more over the entire area within a foot or so of the intended seam and, after formation of the weld, to subject this area as well as the weld itself to a heat treatment commonly known as a stress relieving treatment. This practice necessarily involves considerable expense and loss of time, while frequently because of the size or location of the parts or for other reasons the heat treatments either cannot be performed at all or can be performed only with difilculty,so that in such instances the poor weldability of the steel makes it virtually impossible to turn out a satisfactory welded job irrespective of its cost.

The principal object of the invention therefore is the provision of an alloy steel having good rolling and forging qualities, good weldability and greater corrosion resistance and strength than ordinary carbon steels of similar carbon content.

A further object of the invention is the provision of an alloy steel of the copper-nickel group which can be welded by any of the methods of welding commonly in use without the necessity for preliminary or subsequent heat treatments of the work designed to obviate or minimize cracking in or in the vicinity of the weld.

Other objects, purposes and advantages of the invention will hereafter more fully appear from the following description during which reference will be made by way of example to certain alloys of specific compositions, it being understood,

Per cent Carbon 0.00-0.20 Silicon 0.10-0.25 15 Copper 0.90-1.10 Nickel 1.80-2.20

It may also be desirable, depending to some extent upon the purpose for which the steel is to be 20 used, to include in it sulphur up to 0.10% since its presence enhances machineability. Furthermore if it is desired to enhance the hardness and brittleness of the steel a small percentage of phosphorus may be included without materially .25

affecting its qualities in other respects.

The steel may also contain manganese in an amount requisite to maintain suitable malleability, ductility, rolling and other generally similar properties, but not in excess of 0.70% although at 30 least about 0.35% of this element may advantageously be present.

Several other elements which are customarily found in many kinds of steel may incidentally occur in very small quantities and are not ap- .35 preciably inimical, but it is preferable that chromium and tungsten be wholly absent and that "boron, molybdenum, tantalum, uranium and vanadium be kept as low as possible since the presence of any of these in appreciable amounts 40 may impair the characteristics of the steel;

however, a trace of aluminum resulting from this metal being used for killing the steel during or after pouring, or from other causes, is not particularly inimical. 45

When the ratio of nickel to copper is maintained at approximately 2:1 within the limits stated and the other elements named kept within the range hereinabove set forth, the resultant alloy steel possesses corrosion resistant qualities 50 in a ratio of 5:1 and strength in a ratio of 1.5:1 as compared to ordinary carbon steels of like carbon content, while its weldability is distinctly better than that of any other steels of the coppernickel group of which I am aware.

Within or substantially'within the foregoing range of permissive analyses for carbon, manganese, silicon, copper and nickel, a large number of alloy steels may be made, each difiering in specific analysis and perhaps slightly in other respects from the others yet each of good weldability,.great strength and high-corrosion resistance, qualities not concurrently found in such other steels of the copper-nickel group.

In view of the desirability of maintaining the steel free or substantially free from the several rare elements as above stated, namely chromium, tungsten, boron, molybdenum, tantalum, uranium and vanadium, it is usually preferable in its production to avoid, in making up the furnace charge, the use of materials such as tool or alloy steel scrap or the like which frequently contain one or more of them, as by thus preventing their initial introductioninto the charge the necessity for subsequently endeavoring to reduce them in amount or remove them entirely is avoided.

It is believed the good weldability of this steel may be due in large measure to its low heat conductivity which is appreciably less than or- .dinary carbon steels, and which probably tends to prevent rapid dissemination of the heat from the weld into adjacent parts of the work and resultant too rapid cooling of the welded seam and metal in its vicinity with consequent minimization of internal stress necessitating, in other steels, the stress relieving heat treatments to which reference has been made.

When rolled into sheets, plates or other shapes, or forged or otherwise converted into finished or semi-finished articles of commerce the alloy can be readily welded by usual methods without the necessity of preheating in the vicinity of the weld and/or subjecting the welded article to subsequent stress relieving treatment as it exhibits no material tendency to crack either in the weld or in its vicinity while the weld is being made or after its completion, a characteristic or quality which I believe to be distinctly novel and unique in copper-mckel steel.

I am aware that certain steels have heretofore been suggested having good weldability but these steels do not possess other properties found in my alloy steel and thus are not, for example, comparable thereto in their strength and resistance to corrosion. On the other hand, as far as is known to me, the other low alloy steels containing chromium and metals of that group which 'possess great strength and high resistance to corrosion are subject to cracking when an eifort is made to weld them without preheating and subjection to a stress relieving treatment after the making of theweld. My alloy steel thus not only possesses desirable qualities of both of these two types of steels but is devoid of certain undesirable qualities inherent in each of them.

It is thus characterized particularly by its good weldability in conjunction with relatively great strength and resistance to corrosion, while through avoidance of the use of large quantities of the more expensive alloying elements, its cost is maintained sufliciently low to permitits satisfactory commercial production and employment for many purposes.

Having thus described my invention, I claim and desire to protect by Letters Patent of the United States:

1. An alloy steel comprising carbon not exceeding 0.20%, manganese 0.35% .to 0.70%, copper 0.90% to 1.10%, nickel 1.80% to 2.20%, silicon 0.10% to 0.25%, sulphur not exceeding 0.10%, and substantially iron to make the ratio between the copper and nickel being as near asremainder substantially iron to make 100%, the

ratio between the copper and nickel being as near as may be to 1:2.

GUSTAV A. REINHARDT.