Cold heading and hot forging are very different: a complete analysis of the manufacturing process of high-strength bolts

In modern manufacturing, high-strength bolts are important components for structural connections, and their production process directly affects the performance and safety of the product. Cold heading and hot forging are two main manufacturing processes, each with unique advantages and disadvantages and applicable scenarios. This article will analyze these two processes in depth to help readers understand their differences and their respective applications in the manufacture of high-strength bolts.

1. Cold heading process

Cold heading refers to a method of stamping metal through a die at room temperature. It is mainly suitable for the production of small bolts with small diameters and complex shapes. The process flow of cold heading includes the following steps:

1. Metal strip preparation: Metal materials are sheared into strips of a certain length, usually using materials that are easy to form, such as low-carbon steel.
2. Stamping: In the cold heading machine, high pressure is used to stamp the strips in the die to form a preliminary shape.
3. Heat treatment: Heat treatment is performed on the formed bolts to improve their strength and hardness.
4. Machining: Follow-up processing such as grinding and coating is performed as needed.

Advantages and Disadvantages

Advantages: Cold heading products have high dimensional accuracy, good surface finish, and high material utilization.

Disadvantages: For some high-strength, thick-walled materials, cold heading is difficult to form.

2. Hot Forging Process

Hot forging is a manufacturing process that performs plastic deformation above the recrystallization temperature of metal materials, and is usually used to produce large-diameter, high-strength bolts. Its main processes include:

1. Material heating: Heat the metal material to an appropriate temperature to give it good plasticity.
2. Forging: Deform the heated metal through a forging machine or hammering machine to shape it into the desired shape.
3. Heat treatment: After forging, quenching and tempering are usually performed to improve mechanical properties.
4. Surface treatment: Finally, the finished product is surface treated, such as decontamination, coating, etc., to improve corrosion resistance.

Advantages and Disadvantages

Advantages: Hot forging is suitable for the production of high-strength, large-sized bolts with excellent mechanical properties; at the same time, the internal grains of the material are refined, which enhances the toughness of the bolts.

Disadvantages: The production efficiency of hot forging is low and the cost is high.

3. Choice between cold heading and hot forging

When choosing a production process, it is necessary to make a comprehensive consideration based on the specific application, size specifications and material properties of the bolts. For example, for structural parts that need to withstand high loads and impacts, hot forged bolts are more preferred; while for applications with high precision requirements and small sizes, cold heading has more advantages.

4. Summary

Cold heading and hot forging have their own characteristics and are suitable for the manufacture of high-strength bolts in different scenarios. Understanding the characteristics and applicable conditions of these two processes can help the manufacturing industry choose the most appropriate production plan and improve product quality and competitiveness.