What Is Spin Casting?

Rotary forging, also known as radial forging, is a forming process for long shaft rolling products. The workpiece is hit with a high-frequency radial reciprocating motion, and the workpiece rotates and moves axially. Under the impact of the hammer, the workpiece achieves radial compression and length extension deformation. It is widely used in the production of step shafts for various machines such as automobiles, tractors, machine tools, and locomotives. ^[1]

Rotary forging, also known as radial forging, is a forming process for long shaft rolling products. Its working principle is shown in Figure 1. The workpiece is radially symmetrically arranged with more than two hammer heads. It strikes the workpiece with high-frequency radial reciprocating motion. The workpiece rotates and moves axially. Deformation in compression and extension. Rotary forging is different from rolling continuous forming, but it is different from traditional forging. It has a large number of blows, and the surface of each blow is similar to rolling, so people still attribute it to rolling. Forming.

Rotary forging has both the characteristics of pulse loading and multi-directional forging, which is conducive to uniform deformation of the metal and improve plasticity. Therefore, this process is not only suitable for general steels, but also for high strength and low plasticity high alloys, especially refractory metals such as tungsten, molybdenum, niobium, etc. and their alloys. Rotary forging has the characteristics of high quality forgings, high dimensional accuracy, high production efficiency and high degree of automation. Rotary forging has a wide range of sizes, but its equipment structure is complicated and its speciality is strong.

Rotary forging is widely used in the production of step shafts for various machines such as automobiles, tractors, machine tools, and locomotives, including right-angle steps and shaft parts with taper; hollow shafts with steps and profiled inner wall materials; various gas cylinders and shells. Closing and so on.

Rotary forging has both pulse loading and multi-directional forging. The striking frequency is very high, which can reach 180 to 1700 times per minute, the friction is small, and the metal is deformed uniformly. Due to the use of multi-hammer head forging, the metal is deformed under three-dimensional compressive stress, which is conducive to the improvement of metal plasticity. Rotary forging is not only suitable for steel materials with good plasticity, but also for high-strength and low-plasticity materials, especially it is widely used for forging high-temperature refractory powder sintered materials with small plasticity and severe drawing of tungsten, molybdenum, and tantalum. , Niobium, zirconium, hafnium and other rare metals, as well as extremely low-intensity spray materials such as aluminum tube coated aluminum nickel powder.

In addition to the deformation degree and deformation temperature, the main technical parameters of rotary forging include the speed of the blank, the radial feed speed, the axial feed speed, and the radial reduction. The heating temperature of the billet during hot forging is 50 ~ 150 ° C lower than other die forging processes. During rotary forging, the blank rotates with the rotation of the chuck, so the speed of the blank during forging is actually the speed of the chuck. Hammer feed speed refers to the feed amount of the hammer head in the radial direction per unit time, also known as the radial feed speed. The axial feed speed refers to the distance the chuck moves per unit time. The greater the axial feed speed, the higher the productivity, but the surface quality of the workpiece decreases. Radial reduction refers to the reduction in the radial dimension of the blank in a single stroke of the hammer.

Rotary forging can be divided into cold forging, warm forging and hot forging according to its forging temperature. Forging of hollow parts can be divided into coreless forging and cored rod forging.

Rotary forging process can be divided into stepwise forging and continuous forging. The former can be carried out on a radial feeding non-adjustable forging machine, and the shape of the forging is guaranteed by a closed hammer head. Currently widely used is continuous forging. It is performed on a forging machine with adjustable radial feed. The shape of the forging is guaranteed by changing the stroke of the hammer forging and the axial feed of the blank. This method is suitable for forging multi-step forgings with large cross sections and long lengths. ^[2]

Rotary forging is divided into two types of pushing and pulling according to the movement direction of the chuck relative to the hammer. When the blank is deformed by pulling, the chuck gradually moves away from the hammer; when it is deformed by pushing, the chuck gradually approaches the hammer. Rotary forging tools include hammer head, collet and mandrel. There are also copying plates on the mechanical copying forging machine.

There are two types of rotary forging equipment: rotary forging machines (roller rotary forging machines) and radial precision forging (shaft) machines. Rotary forging machines are available in the form of fixed roller ring and main shaft rotation, and fixed main shaft and roller ring rotation, etc., but they are mostly the former. Radial precision forging (shaft) machines can be divided into vertical and horizontal. When forging by a vertical precision forging machine, the forgings are fed in the vertical direction, and the hammerhead hammers the workpiece in the horizontal direction. When the horizontal precision forging machine is forging, the forgings are fed in the horizontal direction, which is easy to automatically load and unload and is suitable for forging long shafts. At present, horizontal precision forging machines are mostly used.

One or two precision forging machines can be used with multi-stand continuous rolling mills for continuous forging and rolling processing lines for alloy steel forging and rolling, and 90 to 130 mm continuous casting billets are used to produce round steel with a diameter of 28 to 70 mm.

Rotary forging equipment can be basically divided into two types: forging die rotation type and forging die non-rotation type. From the temperature of the billet, the rotary forging machine can be divided into two types: hot rotary forging machine and cold rotary forging machine. Rotary forging die rotary forging machine is mainly used for forging bar material with diameter below 150 mm and pipe material with diameter below 320 mm. The forging die non-rotating rotary forging machine, because the forging die only reciprocates in the main shaft groove to forge the pressed part, therefore, it can not only forge products with symmetrical sections, but also products with asymmetric sections.

Radial precision forging machine is also a type of rotary forging machine that does not rotate the forging die. The hammer head is driven by the crank link mechanism. The size of the forging can be precisely controlled by adjusting the eccentric distance of the crank. On the radial precision forging machine, a solid shaft with a diameter of 400 mm and a hollow shaft with a diameter of 600 mm can be forged up to 6 m in length. Radial precision forging can be used to manufacture various solid step shafts, tapered shafts, hollow shafts, rifled barrels and gun barrels, deep L-nuts, and various necked and narrowed cylindrical parts. Divided into three types according to the type of movement of the rotary forging machine:

(1) Spindle type forging machine

The mandrel of this type of machine rotates, and the sliders and forging dies in the chute on the end face: as components, it periodically strikes the forging to cause plastic deformation.
(2) Rim type rotary forging machine

This type of machine relies on drums and collars, etc., which rotate around a stationary mandrel, as a part 1: it pushes the slider to strike the forging with a forging die.
(3) Rotary rotary forging machine

This type of machine uses the inner and outer mandrels that are driven from both ends and rotate in opposite directions to push the slider and the forging die to strike the forging through rollers and the like.