Bài giảng Nhập môn điểu khiển quá trình công nghiệp

Chapter 14

Rèn kim loại

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Quá tình rèn

Rèn là phương pháp làm

thay đổi hình dạng bởi tác

động một lực vượt quá giới

hạn đàn hồi lên vật liệu. Là

phương pháp cổ điển nhất

đã được áp dụng.

Figure 14.1 (a) Schematic illustration of the steps involved in forging a knife. (b) Landing-

gear components for the C5A and C5B transport aircraft, made by forging. (c) General view

of a 445 MN (50,000 ton) hydraulic press. Source: (a) Courtesy of the Mundial LLC. (b and

c) Courtesy of Wyman-Gordon Company.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Cấu trúc kim loại ở các phương pháp gia công

Đúc

Gia công cơ

Rèn

Figure 14.2 Schematic illustration of a part made by three different processes showing grain

flow. (a) Casting by the processes described in Chapter 11. (b) Machining form a blank,

described in Part IV of this book, and (c) forging. Each process has its own advantages and

limitations regarding external and internal characteristics, material properties, dimensional

accuracy, surface finish, and the economics of production. Source: Courtesy of Forging

Industry Association.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Đặc điểm của phương pháp rèn

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Upsetting with Barreling











2r

3h

Forging force, F  Y r²1



f

Figure 14.3 (a) Solid cylindrical billet upset between two flat dies. (b) Uniform

deformation of the billet without friction. (c) Deformation with friction. Note the

barreling of the billet caused by friction forces at the billet-die interfaces.

Yf : ứng suất chảy của vật liệu

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Rèn tự do trên một thanh vuông

Figure 14.4 (a) Schematic illustration of a cogging operation on a rectangular bar.

Blacksmiths use this process to reduce the thickness of bars by hammering the part on an

anvil. Reduction in thickness is accompanied by barreling, as in Fig. 14.3c. (b) Reducing the

diameter of a bar by open-die forging; note the movements of the dies and the workpiece. (c)

The thickness of a ring being reduced by open-die forging.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Rèn khuôn

Figure 14.5 (a) through (c) Stages in impression-die forging of a solid round billet. Note

the formation of flash, which is excess metal that is subsequently trimmed off (see Fig.

14.7). (d) Standard terminology for various features of a forging die.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Rèn khuôn kín

Figure 14.6 Die inserts used in

forging an automotive axle housing.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Forging a Rod, Fullering, and Edging

Figure 14.7 (a) Stages in forging a connecting rod for an internal combustion engine. Note

the amount of flash required to ensure proper filling of the die cavities. (b) Fullering and (c)

edging operations to properly distribute the material when preshaping the blank for forging.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Lực khi rèn khuôn

F  kY_fA

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Cắt bavia sau khi rèn

Figure 14.8 Trimming flash from a forged part. Note that

the thin material at the center is removed by punching.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Rèn khuôn kín

Figure 14.9 Comparison of closed-die forging with flash (left side of each illustration) and

precision or flashless forging (right side) of a round billet. Source After H. Takemasu, V.

Vazquez, B. Painter, and T. Altan.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

The Coining

Process

(b)

Figure 14.10 (a) Schematic illustration of the coining process. The earliest coins were

made by open-die forging and lacked precision and sharp details. (b) An example of a

modern coining operation, showing the workpiece and tooling. Note the detail and superior

finish that can be achieve in this process. Source: Courtesy of C & W Steel Stamp Co., Inc.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Chồn một đầu bulong

Figure 14.11 (a) Heading operation to form heads on fasteners, such as nails and rivets.

(b) Sequence of operations to produce a typical bolt head by heading.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Sự di chuyển của cấu trúc vật liệu khi rèn

Figure 14.12 A pierced round

billet showing grain-flow

pattern (see also Fig 14.12c).

Source: Courtesy of Ladish

Co., Inc.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Các bước của quá tình rèn

Figure 14.13 (a) The stepped pin used in Case Study 14.1. (b) Illustration of the

manufacturing steps used to produce the stepped pin. Source: Courtesy of National

Machinery, LLC.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Rèn liên tục

Figure 14.14 (a) Schematic illustration of the rotary-swaging process. (b) Forming internal

profiles on a tubular workpiece by swaging. (c) A die-closing swaging machine showing

forming of a stepped shaft. (d) Typical parts made by swaging. Source: Courtesy of J.

Richard Industries.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Swaging with and without a Mandrel

(tóp)

Figure 14.15 (a) Swaging of tubes without a mandrel; note the increase in wall

thickness in the die gap. (b) Swaging with a mandrel; note that the final wall

thickness of the tube depends on the mandrel diameter. (c) Examples of cross-

sections of tubes produced by swaging on shaped mandrels. Rifling (internal

spiral grooves) in small gun barrels can be made by this process.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Nhiệt độ khi rèn nóng

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Khiếm khuyết khi rèn

Figure 14.16 Examples of defects in forged parts. (a) Laps formed by web buckling during

forging; web thickness should be increased to avoid this problem. (b) Internal defects

caused by an oversized billet. Die cavities are filled prematurely, and the material at the

center flows past the filled regions as the die closes.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

Bài giảng Nhập môn điểu khiển quá trình công nghiệp - Chương 14: Rèn kim loại