Process For Forming A Flared End Tubular Metal Part

Abstract

A two-step cold forming process for forming a flared end tubular metal part in a press having a lower fixed support and a downwardly movable upper press ram, comprising the step of extruding the lower portion of a short tubular blank, whose diameter is approximately equal to the diameter of the flared end of the part, into approximate finished length and diameter by means of pressing downwardly an elongated, cylindrical punch, mounted upon the press ram, against and through the blank positioned in a flared diameter, vertically axised, die opening in a die mounted upon the press support, and thereafter, the step of expanding the upper portion of the blank to the exterior and internal diameters of the flared portion of the part in a second die opening in a press support mounted die, with a second ram mounted, flared diameter punch pressed downwardly through the extruded part.

Description

BACKGROUND OF INVENTION

The invention herein relates to the cold forming of elongated, flared end tubular parts, such as a spindle housing used for journalling the axle of a truck wheel. Parts of this type, are generally cylindrically tubular in shape with one end of an enlarged or flared diameter and are usually made of steel.

In the past, such parts have been cold formed by an upwards forging technique, wherein a blank is inserted into a die located upon the bed or table or support of a forging press and then a ram mounted spindle or pin is pressed into the part for cold flow of the metal upwardly around the spindle. The enlarged flared portion has typically been forged at the lower end of the part during the forging process. In this prior process, the part has been formed, step by step, through a series of three, four or five steps, into a finished forged part.

In this prior type process, the finished part is not dimensionally accurate and requires some considerable machining for accurate sizing, after the forging process. In addition, the formation of the part is relatively expensive because of the number of press steps required, particularly since it is customary to heat treat or anneal between each press step and to re-lubricate the part and the press dies during this sort of process.

Hence, the invention herein relates to a simplified process for forming flared and tubular parts by a cold forging process which is so modified and improved as to reduce the number of steps in the press, thereby considerably reducing the cost of production, and in addition produce a part which is of considerably greater accuracy than that produced prior to the invention herein.

SUMMARY OF INVENTION

The invention herein contemplates cold forming a flared and tubular part, such as a truck spindle housing or the like, by means of first forming a short, centrally bored blank of approximately the diameter of the flared end of the part. Thereafter, the blank is inserted into a die opening formed in a die fastened upon the fixed table or support of a forging press, with the die opening preferably vertically axised. Next, a punch presses down against the top of the blank to extrude its lower end around a punch extension spindle which functions like a central mandrel, so that the part main body portion is extruded downwardly into the die opening into the approximate length and outside diameter required, but with a uniform central bore.

Following the extrusion step, the part is placed into a second die opening, similar to the first, and with a second punch, also having a spindle or pin extension arranged within the bore of the body of the part. The punch expands the flared end of the part to desired O.D. and I.D. Hence, the process essentially involves an extrusion step using a downwardly moving punch for extruding the body portion of the part downwardly into the die opening, and thereafter, an expansion step, using a similar punch and die opening for expanding the flared end of the part to correct size.

By heating the part before each step, to a temperature below the transition temperature of the metal, as for example, to a temperature of roughly 1,200.degree.F, the extrusion and expansion steps may be accomplished with relatively low pressures, without changing the metallurgical structure. Thus, although the process is referred to herein as cold forming, it may better be referred to as "warm" forming, that is, not at room temperature and also not at a temperature where the metallurgical structure of the metal may change.

The part may require heat treatment, such as stress relieving between the two press steps. Also, it is desirable to suitably coat the part and the die and punch with conventional lubricants, such as the conventional phosphates, etc., these treatments being conventional in cold forming processes.

These and other objects and advantages of this invention will become apparent upon reading the following description, of which the attached drawings form a part.

DESCRIPTION OF DRAWINGS

FIG. 1 is an elevational view of a flared end spindle housing.

FIG. 2 is a view similar to FIG. 1, but showing the part in cross-section.

FIG. 3 is a cross-sectional, perspective view of a blank from which the part is made.

FIG. 4 schematically shows the positioning of the blank within a die opening.

FIG. 5 shows the extrusion step, and

FIG. 6 shows the expansion step.

FIG. 7 is an enlarged view of the upper end of the part, in cross-section, showing in dotted lines the part after the extrusion step, and in solid lines, the finished part.

DETAILED DESCRIPTION

FIGS. 1 and 2 illustrate a flared end tubular metal part 10, as for example, a steel spindle housing within which a truck wheel axle may be journalled. The process herein is particularly adaptable for the production of such type parts having an elongated tubular body portion and a flared or enlarged end integral therewith.

The part 10 includes the elongated, cylindrically shaped body portion 11, having a central bore 12, and a flared or enlarged diameter end 13 with an enlarged internal or flared bore 14. For illustration purposes, the exterior of the part is further widened or enlarged at a mid portion 15 between the flared end and the body.

In order to manufacture the part 10, a suitable blank 18 is formed. Preferably, the blank is formed of seamless tubing of an appropriate steel and is formed with a central bore 19. The blank may be formed by cutting lengths of seamless tubing into the blanks lengths and machining where necessary to appropriate size.

The blank is processed within a die 20, schematically shown, mounted upon the fixed table or fixed support 21 of a forging press. The press and the method of securing the die are conventional and thus shown only schematically. The die has a vertically axised die opening 22 having an upper flared end 23, a narrowed mid portion 24 forming a shoulder 25 with the upper flare end portion, and a straight, cylindrically shaped lower end 26. Thus, the die opening is formed in several steps.

The blank is dropped into the flared upper end 23 of the die opening so that it is coaxial therewith and fits fairly closely within the die opening.

Arranged above the die opening, is a vertically axised punch 27, appropriately mounted upon the movable ram 28 of the press for downward movement under press pressure. The punch includes an enlarged body portion 29 and a central, downwardly extending narrower spindle or pin or punch shaft 30 of a diameter to fit within the bore 19 of the blank 18. A pushing shoulder 31 is formed on the lower end of the body portion 29 of the punch.

Referring to FIG. 5, after the blank has been positioned within the die opening (FIG. 4), the ram of the press is actuated to push the punch downwardly so that its pushing shoulder 31 engages and pushes downwardly upon the upper edge of the blank. The punch spindle or pin 30, arranged within the blank, acts like a mandrel, and the lower portion of the blank is thus extruded downwardly, in the direction of ram movement. By appropriately sizing the blank at the outset, the extruded part 32 is of the proper length and its body portion is of the predetermined O.D. and I.D.

Thereafter, the extruded part 32 is placed into a second die 33 having a second die opening 34, which die is mounted upon the press bed or table 21. A second punch 35 is mounted upon the ram 28 for downward movement through the part.

This second punch is formed with a widened upper end portion 36 of a diameter corresponding to the part O.D., a mid portion 37 corresponding to the part flared I.D., and a tapered part 38 integral with a lower straight pin or spindle portion 39, corresponding to the diameter of the bore of the body of the part.

The downward movement of the second punch 35, expands the upper flared portion of the part to its predetermined O.D. and simultaneously expands the upper ends of the bore into the predetermined flared portion I.D. FIG. 7 illustrates, in dotted lines, the upper portion of the part following the extrusion step of FIG. 5 and in solid lines indicates the part following the expansion step of FIG. 6.

As is conventional, the blank and the extruded part 32 and also the punches and die openings may be suitably covered with conventional lubricants used in forging or cold forming. In addition, depending upon the type of metal involved, it may be necessary to heat treat the part between the extrusion and expansion steps for stress relief, etc., all in the conventional manner.

With the process as described above, the amount of press pressure, meaning size of the press, is considerably reduced, compared to the prior method for forming such parts. For example, in the prior method, press pressure of up to approximately 2,500 tons was required during the several steps. Here, press pressure can run up to roughly 800 tons for the extrusion step and up to 900 tons for the expansion step. Preferably, the part is warmed to a point well below its transition temperature for ease in press forming. For example, where the metal may have a transition temperature of roughly 1,700.degree.F, it would be desired to warm the metal to somewhere up to the range of about 1,200.degree.F.

The press pressures and warming temperatures given above are all illustrative, and of course, may vary depending upon the specific type of metal involved. However, it can be seen that the net result of this process is a considerable reduction in pressure and a substantial increase in accuracy of the finished part, as compared with the prior art method of forming such parts.

Claims

Having fully described an operative process, we now claim:

1. A process for cold forming an extruded, tubular metal part having an end portion whose O.D. and I.D. are flared relative to the body of the part, in a press having a fixed lower support and a downwardly movable pressure ram, comprising:

positioning a short tubular, vertically axised blank, whose O.D. is approximately equal to the O.D. of the finished part, into the upper end portion of a vertically axised die opening formed in a die mounted upon the press support, which opening upper end portion is of a diameter to closely receive the blank, with the lower portion of said opening corresponding to the O.D. of the body of the part;

extruding the lower part of the blank downwardly into the said die opening by means of moving downwardly a press ram mounted punch having an upper end portion closely fitted into the die opening upper end above and pressing downwardly against the upper end of the blank, and a punch lower end elongated cylindrical shape portion extending through the blank and a considerable distance downwardly through the die opening lower portion for thereby extruding the part into a flared upper end portion O.D. and a substantially uniform lower end portion O.D. of smaller diameter and a uniform I.D. throughout its length;

thereafter positioning the extruded part in a vertical axis, with its flared end up, in a second vertically axised die opening within a die mounted upon the press support, which second opening is formed to correspond to the finished O.D. of the part;

then expanding the flared upper end portion of the part outwardly to form its finished flared portion O.D. and I.D. by means of pressing downwardly through the part central opening a second punch mounted upon the press ram, which second punch is formed with an upper end portion of a diameter corresponding to the finished I.D. of the flared upper end portion of the part, and an elongated lower end portion of a diameter corresponding to the I.D. of the body of the part and of a length to extend a considerable distance through the body of the part, with the two punch portions integrally joined by a tapered central portion, for thereby expanding the part to finished I.D. and O.D. flared dimensions.

2. A process as defined in claim 1, and including warming the metal to a temperature well below the structural transition temperatures prior to each of the press extrusion and expansion steps.

3. A process for forming an elongated tubular metal part having an end portion flared into a larger O.D. and I.D. than the body of the part, comprising:

forming a short, cylindrical, centrally bored metal blank having an O.D. corresponding roughly to the O.D. of the part flared end;

inserting said blank into a fixed die opening having its entry end portion diameter formed approximately equal to the blank O.D. and the remainder of the opening being of a diameter approximately equal to the O.D. of the body of the part;

extruding the inner end portion of the blank into the opening by moving a punch into the die opening with a portion of the punch pushing against the exposed end of the blank and a second portion of the punch extending through the blank into the die opening smaller diameter portion, for thereby extruding the blank into approximate body O.D. and I.D. and approximate flared portion O.D.;

thereafter inserting the extruded part into a second fixed die opening of a size corresponding to the finished part size, with the flared diameter of the part at the open end of the die opening;

and expanding the part flared end portion into finished O.D. and I.D. by pressing a second punch through the central bore of the part, the central punch being of stepped diameters to correspond to the part body I.D. and the part flared end portion I.D. for expanding the end portion of the part into finished dimensions between the corresponding punch and die opening surfaces.