The forging processing methods for the blank of the ball valve body are diverse. They can be classified according to temperature, force, and process characteristics. The details are as follows:
I. Classification by Forging Temperature
1. Hot forging
Definition: The workpiece is heated to a high temperature (usually above the recrystallization temperature) and then forged.
Feature:
The metal has high plasticity and low deformation resistance, making it easy to shape into complex forms.
It can refine the crystal grains and improve the mechanical properties of the material.
The heating temperature needs to be controlled to avoid overheating or over-burning.
Application: Suitable for the forging of most ball valve ball bodies, especially for large-sized or high-strength products.
2. Cold forging
Definition: The process of forging the billet at normal temperature.
Feature:
The forgings have high precision and excellent surface finish, and no further processing is required.
The deformation resistance is high, requiring large-tonnage equipment, and the molds wear out quickly.
There may be a phenomenon of work hardening, and intermediate annealing treatment is required.
Application: Suitable for small-sized and high-precision ball valve balls, such as those made of stainless steel or alloy steel.
3. Warm forging
Definition: The material is heated to a temperature lower than the hot forging temperature (usually 30% to 50% of the recrystallization temperature) before being forged.
Feature:
Combining the advantages of hot forging and cold forging, it reduces the deformation resistance and decreases the equipment tonnage.
The precision and surface quality of the forgings are better than those of hot forging, but lower than those of cold forging.
Application: Suitable for medium-sized ball valve balls, especially for products with certain requirements for strength and precision.
II. Classification by Force Application Method
1. Hand forging
Definition: The process of forging the raw material using manual tools (such as hammers and anvil) and human labor.
Feature:
The equipment is simple and the operation is flexible. It is suitable for single-piece or small-batch production.
The labor intensity is high, the production efficiency is low, and the accuracy and consistency of the forgings are poor.
Application: Suitable for the repair of special materials or customized ball valve balls, or for small-scale production.
2. Machine Forging
① Definition: Forging billets using forging equipment (such as air hammers, friction presses, and hydraulic presses).
② Classification:
Free forging: The billet freely deforms between the upper and lower anvil, and the shape is controlled by the operator.
- Feature: High flexibility, but low precision. Suitable for single-piece or small-batch production.
- Application: Preliminary forming of large ball valve ball blanks.
Model forging (mold forging): The billet undergoes deformation within the fixed mold cavity, resulting in a shape that matches the mold.
-Features: high precision, good surface quality, high production efficiency, but high mold cost.
- Application: Mass production of standardized ball valve balls.
Tubular die forging: It lies between free forging and die forging, using a tubular die for shaping. The die is not fixed to any equipment.
- Feature: Combines the advantages of both, suitable for medium-scale mass production.
- Application: Forging of the ball bodies of small and medium-sized ball valves.
Special forging: This includes precision forging, roll forging, ring rolling, etc.
- Features: High precision and high efficiency, suitable for special-shaped or high-performance ball valves.
- Application: Manufacturing of high-end valves or balls under special working conditions.
III. Other Special Processes
1. Spinning forming
Definition: By applying pressure to the rotating billet through the rotating wheel, the billet gradually shrinks in diameter and narrows at the opening to form a sphere.
Feature:
The material utilization rate is high (up to 80% - 90%), saving processing time.
Suitable for the manufacture of hollow spheres, such as those made of stainless steel or alloy steel.
Application: For high-end valves or the production of spherical components with strict weight requirements.
2. Composite Forging
Definition: Combining multiple forging processes (such as hot forging + die forging) or integrating with other processes (such as welding).
Feature:
Optimize material properties and enhance production efficiency.
Ball valves with ball bodies suitable for complex structures or high-performance requirements.
Application: Valve manufacturing under special conditions, such as high pressure, high temperature or corrosive medium environments.
