US3066408A

US3066408A - Method of producing steel forging and articles produced thereby

Info

Publication number: US3066408A
Application number: US706377A
Authority: US
Inventors: William L Fader
Original assignee: United States Steel Corp
Current assignee: United States Steel Corp
Priority date: 1957-12-31
Filing date: 1957-12-31
Publication date: 1962-12-04
Anticipated expiration: 1979-12-04

Description

Dec. 4, 1962 w. FADER 3,066,408

METHOD OF PRODUCING STEEL FORGING AND ARTICLES PRODUCED THEREBY 4 Sheets-Sheet 1 Filed Dec. 51, 1957 IN VE R WILL/AM L. FAD

By Attorney.

Dec. 4, 1962 w. 1.. FADER 3,066,408

METHOD OF PRODUCING STEEL FORGING AND ARTICLES PRODUCED THEREBY Filed Dec. 31, 195'? 4 Sheets-Sheet 2 Dec. 4, 1962 w. FADER 3,066,408

METHOD OF PRODUCING STEEL FORGING AND ARTICLES PRODUCED THEREBY 4 Sheets-Sheet 5 Filed Dec. 51, 1957 FILE-.- 1

I/VVENTOR WILLIAM L. FADE/P,

Attorney.

Dec. 4, 1962 w. L. FADER 3,066,403

ME D OF PRODUCING STEEL FORGING ARTICLES PRODUCED THEREBY Filed Dec. 31, 195'? 4 Sheets-Sheet 4 lNVE/VTOR W/LL/AM L. FADE/i,

'QOMw OW Attorney.

United States Fatent Office 3,006,403 Patented Dec. 4, 1962 3,066,408 METHOD OF PRODUCING STEEL FQRGIN G AND ARTICLES PRODUCED THEREBY William I... Fader, Lorain, Ohio, assignor to United States Steel Qorporation, a corporation of New Jersey Fiied Dec. 31, 1957, Ser. No. 706,377 2 Claims. ((31. 29-5523) This invention relates to an improved method of producing steel forgings and more particularly to the production of shell forgings.

In the conventional treatment of billets or slugs to produce shell forgings, the billets are heated to austenitizing temperatures, i.e. well above the upper critical temperature and pierced to form a closed-end cylindrical body. Immediately thereafter they are hot drawn through dies while on a mandrel to reduce the wall thickness to the desired size. After rough machining of outside surface of forging and before heat treatment, the cylindrical body is tapered by a nosing operation to impart the desired ogive shape thereto. The force required for nosing tends, however, to gather the preheat-treated material of the shell walls in bulges, due to the low column strength, which, after being machined off, reduces the wall thickness below permissible limits leading to an undesirable percentage of forgings which must be scrapped.

It is accordingly an object of the present invention to providea method of producing shell forgings which overcomes the foregoing difficulties.

It is a further object of this invention to produce shell forgings having improved microstructural characteristics.

The foregoing and further objects will be apparent from the following specification when read in conjunction with the attached drawings wherein:

FIGURE 1 is a suitable billet for converting into a shell forging by the process of my invention;

FIGURES 2 through 4 are schematic views showing the essential piercing, drawing and nosing steps in the production of shell forgings by my invention;

FIGURE 5 is a cross-sectional view of the forging after the piercing operation of FIGURE 2;

FIGURE 6 is a similar view of the forging after the drawing operation of FIGURE 3;

FIGURE 7 is a cross-material view of the drawn forging of FIGURE 6 after finish machining; and

FIGURE 8 is a similar view of the forging after the nosing operation of FIGURE 4.

Shell forgings are conventionally produced from plain carbon steel to specified minimum values of 65,000 p.s.i. yield strength, 15% elongation and 30% reduction in area. Steel of the desired composition is cast into ingots which are rolled by conventional processes into roundcornered square billets of the desired diameter and these are cut or broken into lengths or slugs S of suitable size for the production of a single shell forging. Thereafter these slugs are heated to about 2200 F. and pierced by inserting a mandrel 2 therein, while held in a suitable die or container 4. Production of finished forging requires the following additional operations.

CONVENTIONAL PROCESS Shells made in this manner of 0.50% carbon steel have a yield strength of 67,000 to 78,000 pounds per square inch, an ultimate strength of 112,000 to 121,000, an elongation of 19% and a reduction of area of 50%. When made of 0.40% carbon steel, they average 72,515 pounds per square inch yield strength, 119,000 tensile strength, 20% elongation, and 48.7% reduction of area.

In the process of my invention, I use steel containing between .35 and 65% carbon, .40 to 1.00% manganese, .05 to 30% silicon with normal amounts of phosphorus and sulfur and residual amounts of other elements. Other elements commonly present in low-alloy steels may be used if desired. The individual slugs S are heated to a temperature slightly above the AC3 temperature to insure complete austenitization without exceeding the grain coarsening temperatures and then pierced, as shown in FIGURE 2, at a temperature between the Ar and Ar For the steels of this invention, this is a temperature between 1350 and 1600 F. Following this the forging is drawn through dies 6 as shown in FIGURE 3, to reduce the wall thickness. If necessary the forging may be reheated between piercing and drawing to insure the proper temperature. The wall of the forging, while within the temperature range of 1350 to 1600 F., should be reduced or deformed an amount sufiicient to produce a change in cross-sectional area of between 20 and Following the piercing and drawing operations, the shell is cooled in still air at least until transformation is completed and may thereafter be cooled by any accelerated method desired. It is then shot blasted, finished machined and nosed in a cold forming operation as shown in FIGURE 4.

When so treated, the workpiece has a grain size of ASTM #5 or finer with a peculiar microstructure characterized by a substantial dispersion of iron manganese carbide and typical fine pearlite, resulting from simultaneous working and transformation. 0.50% carbon steel worked into shells in the manner of my invention had a yield strength of 71,000 to 72,500 pounds per square inch, ultimate strength of 111,200 to 111,500, an elongation of 21.5 to 22%, and reduction of area of 51 to 51.4%, when worked at 1600 F; when forging temperature of 1400 F. was used, tensile testing of shells showed. average 79,660 yield strength, 112,900 tensile strength, 23% elongation and 53.7% reduction of area, while working at 1350 F. resulted in 74,697 pounds per square inch yield strength, 112,073 tensile strength, 18.7% elongation, and 39.4% reduction of area. A 0.40% carbon steel forged at 1450" F. yielded 79,000 to 86,000 pounds per square inch yield strength, 100,000 to 102,000 tensile strength, 20 to 21% elongation and 55 to 59% reduction of area.

The resulting mechanical properties are such that there is no need for the conventional quenching and tempering. In addition, as a result of the microstructure, the impact properties and reduction in area are equivalent to or better than those obtained by quenching and tempering.

If desired, workpieces forged in this .manner may be given one or more cold forging passes to obtain surface smoothness and an increase in hardness. The cold working may be performed without the presoftening treatment frequently required.

According to data obtained the temperature of forging should vary somewhat with the carbon content as follows:

F. 60% carbon 1350 to 1600 50% carbon 1350 to 1600 .40% carbon 1400 to 1500 To obtain maximum benefit of the treatment, it is necessary to stay within these limits. Working at a temperature above the maximums given, results in lowered yield and tensile properties due to recrystallization of the grains at such temperature. On the other hand, it is necessary 3 to stay above the minimum because of lowered ductility. A further point of considerable interest, namely the transition temperature of shells made by the proposed and conventional methods can be illustrated by reference to the following table:

Lower transition temperatures are understood as leading to less brittle steel at subzero temperatures.

A major advantage of the proposed process-lies in reduced bulging occurring during the nosing process. EX- tensive measurements have shown that my process reduces the bulging observed in forgings produced by conventional operations by about fifteen times and to the extent rendering scrapping from this cause negligible.

From the foregoing, it is seen that forging produced in accordance with the teachings of my invention readily meet the requirement having a yield strength of at least 65,000 pounds per square inch, an elongation not less than 15%, a reduction of area of 30%, minimum. Moreover, it is apparent that my process produces such forgings more economically due to the elimination of a number of steps from the conventional process and the virtual elimination of scrapping of forgings due to bulging.

While I have shown and described several specific examples of my invention, it will be understood that these examples are merely for the purpose of illustration and description and that various other forms may be devised within the'scope of my invention, as defined in the appended claims.

I claim:

1. A method of producing shell forgings without quenching and tempering said forgings having a minimum yield strength of 65,000 p.s.i. together with a minimum elongation of 15% and reduction in area of 30%, characterized by a transition temperature below about +30 F. comprising forming billets of steel containing .35 to .65 carbon, .40 to 1.00% manganese, .05 to 30% silicon and other elements in amounts which do not adversely affect the properties, heating said billets to a temperature between the Ar and Ar temperature of the steel, piercing and drawing said billets while at said temperature to form open-end cylindrical forgings, cooling said pierced and drawn forgings to room temperature, finish machining them and cold forming the open end to the desired ogive shape.

2. A method of producing shell forgings without quenching and tempering, said forgings having a minimum yield strength of 65,000 p.s.i. together with a minimum elongation of 15% and reduction in area of 30%, characterized by a transition temperature below about +30 F., comprising forming billets of steel containing .35 to .65% carbon, .40 to 1.00% manganese, .05 to .30% silicon and other elements in amounts which do not adversely affect the properties, heating said billets to a. temperature between 1350 and 1600 F. for steels having about .50 to .60% carbon and between 1400 and 1500 F. for steels having about .40% carbon, piercing said billets while at said temperature to form open-end cylindrical forgings, drawing said forgings while in said temperature range to reduce the cross-sectional area between 20 and cooling said pierced and drawn forgings to room temperature, finish machining them and cold forming the open end to the desired ogive shape.

References Cited in the file of this patent UNITED STATES PATENTS 1,437,690 Sylvester Dec. 5, 1922 1,598,240 Carlson Aug. 31, 1926 1,925,823 Singer Sept. 5, 1933 1,941,101 Meyer Dec. 26, 1933 1,946,117 Sparks Feb. 6, 1934 2,183,637 Biginelli Dec. 19, 1939 2,569,248 Miller Sept. 25, 1951 FOREIGN PATENTS 120,799 Great Britain Nov. 28, 1918

Claims

1. A METHOD OF PRODUCING SHELL FORGINGS WITHOUT QUENCHING AND TEMPERING SAID FORGINGS HAVING A MINIMUM YIELD STRENGTH OF 65,000 P.S.I. TOGETHER WITH A MINIMUM ELONGATION OF 15% AND REDUCTION IN AREA OF 30%, CHARACTERIZED BY A TRANSITION TEMPERATURE BELOW ABOUT -30*F.