Forging Part

About forgings

Forge parts application :

1. Civilian industry – general industrial forgings

Refers to machine tool manufacturing, agricultural machinery, farm tool manufacturing, bearing industry, etc.

2. For heavy industry – forgings of various shapes

① Forgings for locomotives, such as locomotive axles, wheels, leaf springs, crankshafts, etc. According to statistics, forgings account for 60% of the locomotive mass.
② Forgings for hydroelectric generators, such as main shafts, intermediate shafts, etc.
③ Forgings for thermal power stations, such as rotors, impellers, retaining rings, spindles, etc.
④ Metallurgical machinery, such as cold rolls, hot rolls and herringbone gear shafts, etc.
⑤ Forgings for pressure vessels, such as cylinders, kettle ring flanges, heads, etc.
⑥Marine forgings, such as crankshaft, stern shaft, rudder stock, thrust shaft and intermediate shaft, etc.
⑦ Forging machinery and equipment, such as hammer head, hammer shaft, column, cylinder block of hydraulic press, pillar and cylinder block of wheel axle press, etc.
⑧ Die forgings, mainly forging dies of hot die forging hammers.
⑨Forgings for the automobile industry, such as left and right steering knuckles, front beams, couplers, etc. According to statistics, forgings account for 80% of the mass of a car.

3. Military industry – military forgings

Such as barrel, door body, bore bracket and traction ring, etc. According to statistics, in a tank, forgings account for 65% of its mass.

Forging Process:

At YOGO METAL CO., LTD, we specialize in the precision forging of large components. Our skilled technicians and engineers employ advanced forging techniques such as open-die forging and closed-die forging. Through careful shaping and deformation of the metal, we create forged parts with superior strength, durability, and dimensional accuracy.Large forgings are usually produced by free forging, die forging, rolling forging and other processes to ensure the compactness and mechanical properties of forgings.

Types of Forgings:

Large forgings usually include shaft forgings, disc forgings, ring forgings, plate forgings, etc. These forgings are commonly used in marine, petrochemical, energy, nuclear power, automotive and other industries. We can mainly produce various types of large forgings for offshore equipment, including anchor chain plates, ship shafts, large gears, forged hubs, connecting rods, etc. We can do custom design and production according to customers’ requirements.

Commonly Used Materials:

We work with a diverse range of materials suitable for large forgings. This includes various alloy steels, stainless steels, carbon steels, and other high-performance alloys, such as Titanium alloy. Our material selection is based on the desired mechanical properties, corrosion resistance, and suitability for the intended application.

Forging size:

YOGO METAL CO., LTD can produce large shaft forgings with a diameter ranging from tens of millimeters to several meters, disc forgings with a diameter of several meters, ring forgings with an inner diameter of several meters, and lengths and widths up to several meters plate forgings.

Characteristics of forged workpieces：

1) The weight range that can be processed is large. Forgings range from a few grams to hundreds of tons
2) Higher quality than castings. The mechanical properties of forgings are better than castings, and they can withstand large impact forces and other heavy loads. Therefore, forgings are used for some important and stressed parts.
For high carbide steels, forgings are of better quality than rolled products. For example, high-speed steel rolled products can only meet the requirements of use after forging. In particular, high-speed steel milling cutters must be forged.
3) The lightest. Under the premise of ensuring the design strength, forgings are lighter than castings, which reduces the weight of the machine itself, which is of great significance for vehicles, aircraft, vehicles and aerospace equipment.
4) Save raw materials. For example, for a crankshaft with a static weight of 17kg used in automobiles, when the rolled material is cut and forged, the chips account for 189% of the weight of the crankshaft, but when die forging is used, the chips only account for 30%, and the machining time is shortened by 1/6. Precision forged forgings can not only save more raw materials, but also save more machining hours.
5) High productivity. For example, using two hot forging presses to forge radial thrust bearings can replace 30 automatic cutting machine tools. When the upsetting automatic machine is used to produce M24 nuts, the productivity of the six-axis automatic lathe is 17.5 times.
6) Free forging has great flexibility, so forging is widely used in some repair factories to produce various accessories.

Common metal processing technology:

Casting:

Advantages: The casting process can be used to manufacture complex shapes and large pieces, and is suitable for a variety of metals. The casting process provides good material properties such as high strength and wear resistance.

Disadvantages: The casting process may cause defects such as internal pores, inclusions and shrinkage cavities, which affect the strength and mechanical properties of the material. At the same time, the casting process may have certain limitations for parts with complex shapes.

Forging:

Advantages: The forging process can provide the excellent mechanical properties of the material, such as high strength, excellent toughness and fatigue life. Forging can be used to produce high-quality metal parts, suitable for small and medium-sized parts manufacturing.

Disadvantages: The forging process requires high equipment and energy input, and requires greater equipment and process support for the processing of large parts. In addition, the forging process may produce cracks in the processing of some brittle materials.

Cold Heading:

Advantages: The cold heading process is used to produce small fasteners such as bolts and nuts. This process provides high strength and good shape accuracy of the material.

Disadvantages: The cold heading process is mainly used for the production of small fasteners, and it is not suitable for the processing of large parts. In addition, the cold heading process requires the use of special equipment, which is costly.

Pressure processing (Forming):

Advantages: Including rolling, stretching, die-casting and other processes, it can be used to produce metal plates, wire rods and profiles. These processes provide excellent surface quality, dimensional accuracy and mechanical properties.

Disadvantages: During press working, metallic materials may undergo plastic deformation, resulting in changes in size and shape. In addition, press working can create scratches and blemishes on the surface of the material.

Classification of forgings:

1) Classification according to processing temperature:

Divided into cold forging, warm forging and hot forging. Cold forging is generally processed at room temperature, and hot forging is processed at a temperature higher than the recrystallization temperature of the metal blank.

2) Classification by structure

The difference in the complexity of the geometric structure of forgings determines the obvious difference between the die forging process and the die design. Defining the structure type of forgings is a necessary prerequisite for process design. In the industry, general forgings are divided into 3 categories, and each category is subdivided into 3 groups, a total of 9 groups.

Category I – Forgings whose main body axis is vertically placed in the die cavity and have similar two-dimensional dimensions in the horizontal direction (mostly circular/revolving bodies, square or similar shapes). Upsetting steps are usually used in die forging of such forgings. It is subdivided into 3 groups according to the difference of forming difficulty.

Group Ⅰ-1: Forgings formed by upsetting and slightly press-in, such as gears with little change in height between the hub and the rim.
Group Ⅰ-2: Forgings formed by extrusion with slight upsetting or combined extrusion, press-in and upsetting, such as universal joint forks, cross shafts, etc.
Group Ⅰ-3: forgings formed by composite extrusion, such as hub shafts, etc.

Category Ⅱ – the main body axis is placed horizontally in the die cavity to form, and the straight long axis forgings have a long one-dimensional dimension in the horizontal direction. It is subdivided into 3 groups according to the degree of difference of the cross-sectional area of the vertical main axis.

Group Ⅱ-1 Forgings with little difference in sectional area of the vertical main axis (ratio of the largest sectional area to the smallest sectional area <1.6, can be made without other equipment).
Group Ⅱ-2 Forgings with large differences in cross-sectional area of the vertical main axis (the ratio of the largest cross-sectional area to the smallest cross-sectional area>1.6, other equipment is required to make blanks in the front), such as connecting rods.
Group Ⅱ-3 Forgings whose ends (one or both ends) are fork-shaped/branch-shaped, in addition to determining whether blank making is required according to the above two groups, the pre-forging process must be reasonably designed, such as casing forks.
Class I and II forgings are generally plane parting or symmetrical surface parting, and asymmetrical surface parting increases the complexity of forgings.

Category III – forgings with curved main axis and lying in the die cavity. It is subdivided into 3 groups according to the axis direction of the main body.

Group III-1 isThe axis of the main body is bent in the vertical plane (the parting surface is a gently undulating curved surface or with a drop), but the plan view is straight and long-axis (similar to Type II), and generally no special bending steps are required. Formed forgings.
Group Ⅲ-2 is a forging whose main body axis is bent in the horizontal plane (the parting surface is generally a plane), and bending steps must be arranged to form the forging.
Group Ⅲ-3 Forgings whose main axis is space bending (asymmetric surface parting).

There are also forgings with two or three types of structural features and more complex forgings, such as most automobile steering knuckle forgings.

Summary and Analysis of Common Defects in Forging Process

1. Large grain

Large grains are usually caused by too high initial forging temperature and insufficient deformation degree, or too high final forging temperature, or the deformation degree falls into the critical deformation zone. If the aluminum alloy is deformed too much, it will form a texture; if the deformation temperature of the superalloy is too low, it may also cause coarse grains when forming a mixed deformation structure. The coarse grains will reduce the plasticity and toughness of the forging, and the fatigue performance will decrease significantly.

2. Uneven grain

Uneven grains mean that the grains in some parts of the forging are particularly coarse, while some parts are smaller. The main reason for the uneven grain is that the uneven deformation of the billet makes the grain breakage different, or the deformation degree of the local area falls into the critical deformation area, or the local work hardening of the superalloy, or the local grain size during quenching and heating. thick.

Heat-resistant steels and high-temperature alloys are particularly sensitive to grain inhomogeneity. Uneven grains will significantly reduce the durability and fatigue performance of forgings.

3. Cold and hard phenomenon

During deformation, due to low temperature or too fast deformation speed, and too fast cooling after forging, the softening caused by recrystallization may not keep up with the strengthening (hardening) caused by deformation, so that after hot forging, the inside of the forging still partially retains cold deformation organize.

The existence of this organization increases the strength and hardness of the forging, but reduces the plasticity and toughness. Severe chilling and hardening may cause forging cracks.

4. Cracks

Cracks are usually caused by large tensile stress, shear stress or additional tensile stress during forging. The part where the crack occurs is usually the part with the highest stress and the thinnest thickness of the billet.

If there are microcracks on the surface and inside of the blank, or there are structural defects in the blank, or the plasticity of the material is reduced due to improper thermal processing temperature, or the deformation speed is too fast, the degree of deformation is too large, and the plastic index allowed by the material is exceeded, etc., in upsetting, Cracks may occur in processes such as drawing, punching, reaming, bending and extrusion.

5. Fracture

Fracture are shallow tortoise-like cracks on the surface of forgings. Surfaces subjected to tensile stress during forging forming (for example, underfilled protrusions or portions subject to bending) are most prone to this defect.

There may be many internal causes of Fracture: ① The raw material contains too much fusible elements such as Cu and Sn. ②When heated at high temperature for a long time, there will be copper precipitation on the surface of the steel material, coarse grains on the surface, decarburization, or the surface that has been heated many times. ③The sulfur content of the fuel is too high, and sulfur penetrates into the surface of the steel material.

6. Flash crack

Flash cracks are cracks generated at the parting surface during die forging and trimming.

The causes of flash cracks may be: ① During the die forging operation, the metal flows strongly due to the heavy blow, resulting in the phenomenon of rib penetration. ②The trimming temperature of magnesium alloy die forgings is too low; the trimming temperature of copper alloy die forgings is too high.

7. Cracks on parting surface

Parting surface cracks refer to cracks generated along the parting surface of forgings. There are many non-metallic inclusions in the raw materials, and the flow and concentration to the parting surface during die forging or the shrinkage pipe residue often form parting surface cracks after being squeezed into the flash during die forging.

8. Folding

Folding is formed when the oxidized surface metal joins together during metal deformation. It can be formed by the convection of two (or more) metals; it can also be formed by the rapid and large flow of a metal that brings the surface metal of the adjacent part to flow, and the two merge; it can also be due to deformation. The metal is bent and reflowed; it can also be formed by partial deformation of a part of the metal and being pressed into another part of the metal.

Folding is related to the shape of raw materials and blanks, the design of the mold, the arrangement of the forming process, the lubrication situation and the actual operation of forging. Folding not only reduces the load-bearing area of parts, but also often becomes a source of fatigue due to the stress concentration here during work.

9. Through flow

Crossflow is a form of improper distribution of streamlines. In the through-flow zone, the streamlines originally distributed at a certain angle merge together to form a through-flow, which may cause a large difference in the size of the grains inside and outside the through-flow zone.

The reason for the through-flow is similar to that of the fold. It is formed by two strands of metal or one metal with another metal, but the metal in the through-flow part is still a whole, and the through-flow reduces the mechanical properties of the forging, especially When the difference between the grains on both sides of the through-flow zone is relatively large, the performance degradation is more obvious.

10. The streamline distribution of forgings is not smooth

Unsmooth distribution of streamlines in forgings refers to the occurrence of streamline disturbances such as streamline cutting, backflow, and eddy current at the low magnification of forgings.

If the mold design is improper or the forging method is unreasonable, the streamline of the prefabricated blank will be disordered; the improper operation of the workers and the wear of the mold will cause the metal to flow unevenly, which can make the streamline distribution of the forgings not smooth. Unsmooth streamlines will reduce various mechanical properties, so for important forgings, there are requirements for streamline distribution.

11. Casting tissue residue

Casting structure residues mainly appear in forgings that use ingots as blanks. The as-cast structure mainly remains in the difficult deformation zone of the forging.

Insufficient forging ratio and improper forging method are the main reasons for the residual casting structure. Residual casting structure will reduce the performance of forgings, especially impact toughness and fatigue performance.

12. The level of carbide segregation does not meet the requirements

The grade of carbide segregation that does not meet the requirements mainly occurs in ledeburite tool and die steel. The main reason is that the carbides in the forgings are unevenly distributed, concentrated in large blocks or distributed in a network.

The main reason for this defect is that the carbide segregation level of the raw material is poor, and the forging ratio is not enough or the forging method is improper during forging. Forgings with such defects are prone to local overheating and quenching cracking during heat treatment and quenching. The cutting tools and molds made It is easy to chip when using.

13. Ribbon tissue

The banded structure is a structure in which ferrite and pearlite, ferrite and austenite, ferrite and bainite, ferrite and martensite are distributed in bands in forgings, and they mostly appear in In subeutectic steels, austenitic steels and semi-martensitic steels.

This kind of structure is a banded structure produced during forging deformation under the coexistence of two phases, which can reduce the transverse plasticity index of the material, especially the impact toughness. During forging or part work, it is often easy to crack along the ferrite band or the junction of the two phases.

14. Partial filling is insufficient

Partial insufficient filling mainly occurs in ribs, convex corners, corners, and rounded corners, and the size does not meet the requirements of the drawing.

The reasons may be: ① low forging temperature, poor metal fluidity; ② insufficient tonnage of equipment or insufficient hammering force; ③ unreasonable design of billet mold, unqualified billet volume or cross-sectional size; ④ accumulation of scale or welding in the die cavity Alloy deformed metal.

15. Undervoltage

Underpressure refers to the general increase of the dimension perpendicular to the parting surface, which may be caused by: ① low forging temperature. ②Insufficient equipment tonnage, insufficient hammering force or insufficient hammering times.

16. Misalignment

Misalignment is the displacement of the forging along the upper half of the parting surface relative to the lower half. The reasons may be: ①The gap between the slider (hammer head) and the guide rail is too large; ②The design of the forging die is unreasonable, and there is no lock or guide post to eliminate the misalignment force; ③Poor installation of the mold.

17. Axis bending

The axis of the forging is bent, and there is an error with the geometric position of the plane. The reasons may be: not paying attention when the forging is out of the mold; uneven force when cutting the edge; different cooling speeds of each part when the forging is cooling; improper cleaning and heat treatment.