The production process of bolts usually involves the following main steps:
1. Raw material preparation
- Material selection: The main materials of bolts are usually carbon steel, stainless steel, alloy steel, etc. Select appropriate raw materials according to the use environment and performance requirements of the bolts.
- Inspection: The raw materials must undergo chemical composition analysis, mechanical property testing and other inspections to ensure qualified quality.
2. Billet manufacturing (ingot or bar)
- Ingot or bar production: The selected metal raw materials are melted and cast into ingots or bars. Bars are usually long strips with a circular cross-section and are the basic materials for bolt manufacturing.
- Hot rolling or cold rolling: The ingots are hot rolled or cold rolled to further improve their mechanical properties and shape to achieve the required diameter and length of the bolts.
3. Forming processing
- Cold heading: After heating the steel bar to an appropriate temperature, use cold heading equipment (such as a cold heading machine) to press the steel bar into the basic shape of the bolt. This is one of the core processes of bolt production. Cold heading can enhance the fluidity of the metal and ensure the forming of the bolt head and thread.
- Heading: The head of a metal rod is pressed into a head shape by a cold heading machine. The head of a bolt is generally hexagonal, round or other specific shapes.
- Cutting: If necessary, the formed bolt can be cut into appropriate lengths according to design requirements.
4. Thread processing
- Thread rolling: The thread is processed on the rod of the bolt. Generally, a thread rolling machine is used to roll the thread to make the thread have better precision and strength. The thread rolling process is more efficient than cutting and can improve the durability of the thread.
- Cutting thread: In some cases, the bolt can also be processed by cutting thread, which is suitable for bolts with low strength requirements.
5. Heat treatment
- Annealing, quenching and tempering: Bolts are sometimes heat treated to improve their hardness and wear resistance, especially for high-strength bolts. The heat treatment process can change the internal structure of the bolt and improve its mechanical properties.
- Surface hardening: Bolts that require high strength may also need surface hardening treatment (such as nitriding or carburizing) to make the threaded portion more wear-resistant.
6. Surface treatment
- Galvanizing/electroplating: The surface of the bolt is often treated with anti-corrosion treatments such as galvanizing, electroplating or painting to improve corrosion resistance.
- Black oxide treatment: Some bolts are also black oxide treated to prevent rust and improve appearance.
- Anti-corrosion coating: For example, phosphating or spraying other anti-corrosion coatings to improve the corrosion resistance of bolts, especially for use in marine or chemical environments.
7. Quality inspection
- Dimension inspection: Including dimensional inspection of bolt length, outer diameter, thread shape, etc. to ensure compliance with standards.
- Mechanical property testing: Such as tensile testing, hardness testing, torque testing, etc., to ensure that the bolts have sufficient strength, hardness and stability.
- Appearance inspection: including whether there are surface defects (such as cracks, pores, rust, etc.), whether there are scratches, whether the coating is uniform, etc.
8. Packaging and shipment
- Packaging: After the bolts pass the quality inspection, they are packaged according to different specifications and quantities. Commonly used packaging forms include bag packaging and box packaging to ensure safety during transportation.
- Shipping: The bolts are handed over to the logistics department for shipment and transported to the customer’s designated location.
Strict quality control is required in each step to ensure that bolts that meet the requirements are produced. Different types of bolts (such as high-strength bolts, automotive bolts, etc.) will have different production processes and quality requirements.
Post time: Dec-20-2024