US2254629A - Method of manufacturing turbine blades - Google Patents

Description

Sept 2, 1941.

s. s. S TINE METHOD OF MANUFACTURING TURBINE BLADES Filed Sept. 26, 1939 2 Sheets-Sheet 2 INVENTOR Sam/E1. S. STINE.

ATTORNEY Patented Sept. 2, 1941 UNlTED STATES PATENT OFFICE iun'rnon or magggt'gunme TURBINE I 2 Samuel S. Stine. Lansdowne, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application September 26, 1939, Serial No. 296,567

2 Claims.

My invention relates to turbine blade manufacture and it has for an object to provide an improved method of rolling so that bladesof decidedly unsymmetrical section may be satisfactorily rolled. r

More particularly, my invention is concerned with rolling of strip material which may be divided to provide vane or blade elements for turbines and the like and having 'a section such as disclosed and claimed in Reissue Patent No. 18,485, vMay 31, 1932. It will be apparent that theblade sectionshown in this patent diflfer'sfrom the ordinary reaction and impulse sections in the relatively greater lack of symmetry. The standard impulse section is symmetrical, or nearly so, and the usual reaction section, while unsym-- I metrical, is not so much so as the new section and it has sharp edges at both sides. These prior shapes or sections have been rolled; however, it was found with the section of said patent, due-to the rounded blunt edge at one side and the thin tapered edge at the other side, that rolling was not satisfactory because of excessive side thrust and the tendency to waviness at the thin edge. In this connection, when rolling a single unsymmetrical section, tremendous pressures have to be applied to .roll down the thin edge, and the utilization of such pressures for this purpose involves the imposition of end thrusts on the rolls.

In accordance with the present invention, the

aforementioned difficulties are avoided by roll- 9 ing a double strip and then slitting the latter.

When rolling double, the problem of end thrust on the rolls is not encountered, irregularity or waviness of the thin edge is avoided, and a more convenient and better relation of the passes with respect to the rolls may. be secured. Stock of elongated cross-section is rolled in a suitable number of passes to form the double strip, the latter being severed or slit to form strips to be divided into blade sections. While either hot or cold rolling may be employed, it is preferred to use a combination of hot and cold passes. The work is annealed and pickled in suitable relation tothe passes, annealing serving the usual purpose of stress relieving and pickling that of scale or oxide removal. If cold rolling is depended upon, then it is necessary to anneal and pickle the double strip alternately with rolling passes or with two or more such passes. If the combination of hot and cold rolling is used, the blank may be treated and passed through all hot passes without the necessity of reheating, or it maybe reheated if required: and, after going through the final hot pass, the shape is pickled, annealed,

and again pickled, after which it may be passed through one or more cold passes to bumish and polish the surface. Preferably, suitable stock of circular cross section is used, the stock being heated and rolled to form a transversely elongated shape having curved edges and the shape is edge-rolled to secure uniformity in width and then rolled in a suitable number of passes toform a double strip, which, after annealing and picklin is cold rolled and slit at the junction region of the thin edges. After severing of the double strip, the parts thereof are passed through straightening rolls to straighten the strip and to roll down any burring at the thin edge. Accord- 111813. a further object of my invention is to roll unsymmetrical blading by rolling a double blade strip and then slitting the latter. I

A further object of my invention is to roll vane orblade strip of unsymmetrical section by providinga shape of elongated section, edge rolling the shape to secure width uniformity, then rollingthe shape to form .a double blade or vane strip, and slitting the double strip to provide blade or vane strips of the desired unsymmetrical section.

These and other objects are effected by my in-' vention as will be apparent from the following description and c1aims,-taken in connection with the accompanying drawings, forming a part of this application, in which: Fig. 1

Fig. 2 showsdiagrammatically a break-down pass for exfoliating scale; I

Fig. 3 is a diagrammatic view showing further flattening to provide a shape which is transversely elongated and curved at the edges;

Fig. 4 shows edge-rolling of the elongated shape to eflect uniformityin width;

Figs. 5, 6, and 7 show passes for forming the transversely elongated shape into a double I line x1-xr of Fig. 10, showing the effect of the straightening rolls in rolling down the thin edge of a strip;

Fig. '12 shows a strip sectioned for turbine blades; and,

is a fragmentary isometric view of .stock;

Fig, 13 shows a turbine blade employing one of the sections.

Referring to the drawings more in detail, as already pointed out, the invention may be carried out by either cold or hot rolling, preferably by a suitable number of hot and cold passes, to form a double strip. I f cold rolling is depended upon,

then the work must be pickled and annealed in suitable relation'to the passes to obtain satisfactorily rolled blade material. Also, following the hot passes, the double strip should be pickled, annealed, and pickled before being subjected to cold rolling to give a burnished and polished surface.

Preferably, a blank Iii-of circular cross-section, as indicated in Fig. 1, is used. .With the blank heated to a suitable temperature, it is given a break-down pass between roll elements I4 and i5 largely for the purpose of exfoliating scale, the broken-down blank being shown at Illa in Fig. 2. Next, the blank is passed between roll elements Ila and i5a, as shown in Fig. 3, to provide the shape lilb of elongated section having convexlycurved edges i8. h

To overcome the effect of minor variations in diameter of the rod ID as well as the extent of flat rolling, as shown in Figs. 2 and 3,.- and to assure of uniform sectional dimensions of the blade strip, the elongated shape iOb is edgerolled to secure uniformity in width, Fig. 4 showing the edge-roiled shape llic in relation to rolls b and IE1). Procurement in this way of width uniformity, any sectional area variations resulting in thickening, particularly toward the edges,

assures of adequate material for the passes hereinafter described with the material positioned widthwise for minimum deformation or flow, any variations in thickness secured by edge-rolling being rolled out with elongation in subsequent passes. As the double strip to be rolled has thick outer edges and joined thin edges, any bulging or thickness variation of the edge-rolled shape near verging to provide the sharp edge 25, the face 21 being convex and the face 22 being concave.

slitting or severing of the double strip may resuit in bending of the blade strips and the thin edge may be burred to some extent on account of shearing. Therefore, as shown in Figs. '11 and 12, each strip 2 is passed between straightening rolls, not only to effect straightening thereof, but cooperating rolls 2! and 2| assure of rolling out any burring at the thin edge.

- As shown in Fig. 12, each strip 24 is out into turbine blade sections 3] and such sections, when suitably joined to packing pieces or root elements 22, provide finished turbine blades, as shown in Fig. 13. While the blade strip material is preferably used in the manufacture of turbine blades, it will be obvious that such material may be employed in the manufacture of any suitable blade or vane element arranged in a path of fluid flow.

From the drawings, it will be noted that the junction region of the double strip I00 (Figure 8) is constituted by distinct angular portion 32 formed by the angular rib 34 on the roll ii! cooperating with the angular groove 25 on the roll Hf, this rib-and-groove relation being preserved throughout the forming passage, as shown in Figures 5 to 8, inclusive,

What I claim is:

,1. The method of rolling strip for sectioning into turbine blades, said strip being of an unsymmetrical section having rounded blunt inlet and thin sharp outlet edges and curved faces merging into the rounded blunt edge and converging to provide the sharp edge, one of said faces being convex and the opposed face being concave, said method comprising providing stock of circular cross section; heating said stock, and while heated, rolling it'to form a shape which is elonthe edges thereof is therefore positioned for deformation to the best advantage.

Preferably, hot rolling of the work,'without reheating, is continued, the edge-rolled elongated shape liic of Fig. 4 being rolled ina suitable number of passes to form the double strip. For

example, in Figs. 5, 6, and '1, there are diagrammatically shown pairs of opposed roll elements He and I50, lid and lid, and He and lie, forrolling the shape into the forms llid, Hie, and I01, respectively. The double strip iflf from the final hot pass is pickled, annealed, and again pickled before being rolled cold between the roll elements MI and i5} shown in Fig. 8, for burnishing and polishing the surfaces to provide the finished double strip ing.

The double strips iiig are passed between a pair of holding rolls 20 and 2! and cooperating rotary shear elements 22 and 23, the rolls gripping one of the strip parts 24 and. shear elements 22 and 23 slitting or severing the other part 24 therefrom along the common thin edge 25. Each strip part 24 has a rounded or blunt edge 26, curved faces 21 and 28 merging into the convex surface defining the rounded blunt inlet edge and con- ,gated transversely and has curved edges, rolling the shape by the application of rolling pressure to the curved edges to secure uniformity of width, and then rolling the shape to form a double strip wherein a pair of strips are joined at their thin edges; and, when cold, cold-roiling the hot-rolled double strip .to provide burnished and smooth blade surfaces and then severing the cold-roiled double strip to provide separate strips.

2. The method of rolling strip for sectioning into turbine blades; said strip being of an unsymmetrical section having rounded blunt inlet and thin sharp outlet edges and curved faces merging into the rounded blunt edge and converging to provide the sharp edge, one of said faces being convex and the opposed face being concave; said method comprising providing stock of circular cross section; heating said stock, and, while heated, rolling it to form a shape which is transversely elongated and has curved edgespand while heated, rolling said shape in a suitable I section thereof and to provide burnished and smooth blade surfaces; and slitting the coldrolled strip to provide separate strips.

SAMUEL s. S'IINE.

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