1: What is a weld screw?
1.1 Definitions and overview
Weld screws (also known as weld bolts) are a type of fastener that securely connects a screw to a workpiece through resistance welding technology. This type of connection utilizes the heat generated by an electric current to melt and fuse the metal material between the screw and the workpiece, creating a high-strength fixed point. Welded screws are widely used in modern industry, especially in automotive manufacturing, electronic equipment, construction and machinery, and are particularly suited for application scenarios that require high strength connections and stability requirements.
With welded screws, productivity can be increased and the installation of conventional bolts and nuts can be simplified while maintaining high joint strength, greatly reducing labor costs and installation complexity. The advantage of welded screws is that they provide a stronger connection and maintain consistent quality in high-speed, high-volume production.
1.2 Principles of operation
The working principle of welded screws is based on resistance welding technology. This technique melts the metal material between the screw and the workpiece by heating and pressurizing it, and combines it by means of an electric current to form a strong connection. The welding process not only depends on the strength of the current and the welding time, but is also influenced by a number of factors such as the resistance of the material itself, the surface finish and the pressure of the welding electrode.
This method of welding ensures high precision in joining different materials and thicknesses with virtually no damage, which is important where high strength connections with high demands on surface quality are required. The different types of weld screws can be subdivided into various types depending on the connection method and the requirements of the working environment.
1.3 Strengths
Welded screws offer a range of significant advantages over traditional bolt and nut connections:
- High Strength Connection: Through resistance welding, the strength of the connection between the screw and the workpiece far exceeds that of the traditional bolted connection, and is able to withstand greater mechanical loads.
- Strong durability: welded screws have better resistance to vibration, especially suitable for long-term use in harsh environments.
- Easy Installation: Since welded screws are installed using professional welding equipment, the traditional tightening process is eliminated. This not only simplifies the installation process but also enhances production efficiency, making it especially suitable for mass production.
- Strong adaptability: welding screws adapt to a wide range of applications, from electronic products to building structures can be used, and to meet the welding needs of different materials.
Thanks to these advantages, weld screws have become indispensable fasteners in several industries, especially in areas where reliable connections are required.
2: Types of welding screws and application scenarios
2.1 Types of welding screws
Welding screws can be divided into the following main types according to different application requirements and welding techniques:
- Capacitor Discharge Welding Studs (PT type) iso13918
- The energy storage type welding stud is suitable for welding thin sheet metal and is able to heat up quickly and complete the welding task efficiently. With short welding times and low surface heat damage, it is ideally suited for applications that require high precision and less surface damage, such as the production of electronics and precision equipment.
- Arc welding studs iso13918 or din 32501
- This type of welding stud has a faster welding speed and is suitable for scenarios where high strength connections are required. Although it may produce large surface marks during the welding process, it is still highly efficient in many industrial applications, and is especially used in the automotive and construction industries.
- Under Head Weld Screw DIN 34817 or BS 7670
- This type of weld screw is suitable for most standardized production lines, especially in the automotive and household appliance industries, providing a stable and strong connection. The advantages are ease of production and consistency.
- Over Head Weld Screw IFI 148
- Over Head weld studs serve a similar function to Under Head weld studs, with the main difference being the installation method. The topbody weld stud eliminates the need for drilling holes in the sheet metal, as the stud is directly welded to the surface. This method simplifies the production process, saves time, and reduces machining costs.
2.2 Application scenarios
Weld screws are widely used in several industries, mainly including the following areas:
- Automotive Manufacturing
In the automotive industry, weld screws are widely used for the fixing of car bodies and interior structures. They ensure the stability and safety of the vehicle body and play a key role especially in terms of high strength and durability. - Electronics
Weld screws also have an integral role in the production of electronic products, such as TVs and home appliances. They provide a tight and solid connection during the assembly process, helping to improve the quality and stability of the product. - Construction
In the field of construction and steelwork, weld screws are commonly used to fix steel structures and building parts. Their high-strength connections are able to withstand enormous pressure and external stresses, ensuring the safety and long-term stability of buildings.
3: Capacitor Discharge vs. Arc Welding Screws
3.1 Welding methods
- Capacitor Discharge Welding Studs
Capacitor Discharge Welding Studs provide efficient welding by means of a short energy storage. The technology relies on the stored energy of an electric current to quickly heat up the weld joint and complete the weld in a very short time. The shorter welding time makes it particularly effective for welding thin plates with a smaller surface heat affected zone. Energy storage welding effectively reduces thermal expansion and material distortion while providing a high-quality joint, making it suitable for applications that require a fine weld and low surface impact. - Arc Welding Studs
Arc-welded studs are heated by an electric arc. This method creates high temperatures between the screw and the base material through an electric arc, which melts the metal and completes the joint. Typically used for thicker metal parts, it provides a stronger weld, but due to the higher temperatures and longer welding time, the welding process leaves more visible marks on the surface of the workpiece and can create a larger heat affected area.
3.2 Contrast
- Welding Quality
Dissipative weld screws provide a finer weld result and are suitable for applications where high surface quality is required. Due to their short heating time and low surface impact, the welded surface is relatively flat with almost no significant marks. In contrast, drawn-arc weld screws produce a noticeable heat-affected zone due to long heating times at high temperatures, and the surface may be burnt and deformed, which has a greater impact on surface quality despite the higher welding strength. - Cost and Time
Capacitorized welding screws are more efficient in welding thin sheet metal, with shorter welding times, which usually results in lower costs. This type of welding improves productivity and reduces production costs when doing mass production. Draw-arc welding, on the other hand, is more costly due to longer welding times and the need for high-temperature heating. For thick metal parts requiring high-strength connections, the advantages of weld results and strength make it still a suitable choice, despite the higher cost.
3.3 Application recommendations
- Capacitor Discharge Screws:
If your application requires a high level of surface quality and the welding object is a thin plate, it is recommended to use capacitor discharge type welding screws. Especially in the electronics and automotive industries, capacitor discharge welding screws provide a fine, fast and efficient welding solution. - Drawn Arc Welding Screws:
For industries that require more strength, such as aerospace and military, drawn-arc weld screws are more suitable. Despite their higher cost, they provide the necessary strength and reliability metal parts and applications requiring extremely high welding strength.
4: welding Requirements for sheet metal
4.1 Sheet metal material and thickness requirements
Material and thickness are the most important considerations when part. Common choosing a welded sheet metal sheet metal materials include stainless steel, aluminum alloy, carbon steel, etc. Different materials and thicknesses require different welding conditions.
- Material:
Different materials have different electrical conductivity, thermal conductivity and coefficients of expansion, so parameters such as welding current and welding time need to be adjusted according to the specific material when welding. For example, stainless steel has a lower thermal conductivity and therefore requires a longer welding time and higher current to ensure full melting. - Thickness:
to be welded The thickness of directly affects the amount of energy required for welding. Thinner the sheet metal parts require lower temperatures and shorter welding times to avoid distortion caused by overheating, while thicker parts require higher welding temperatures and longer welding times to ensure that the metal is fully melted and firmly bonded.
Depending on different thread sizes and material thickness requirements, it is necessary to ensure that when welding in the sheet metal thickness meets the standard order to achieve ideal welding results.
| Thread Specification | Material thickness requirements (δ) |
| M5 | ≤ 1.4 mm |
| M6 | ≤ 1.4 mm |
| M8 | ≤ 2.0 mm |
| M10 | ≤ 2.5 mm |
| ≥M12 | Adjustment to specific needs |
4.2 Welding surface requirements
The surface quality of parts has a direct impact on the quality of the weld. In order to ensure the strength and stability of the welded joint, welded sheet metal the surface of the must meet the following requirements:sheet metal
- Smooth surface:
The surface should be flat and smooth, with no visible bumps or damage, to ensure that the current can be conducted evenly to the contact points and avoid localized overheating. - Free of oxidized layers and oil:
The surface of must be clean and free of oil, rust or oxidized layers, impurities that can affect the welding results and lead to reduced strength of the welded joints.the sheet - No interferences:
The welding position should be free from any interferences to avoid obstruction of electrodes or other equipment during the welding process, which may affect the welding accuracy and efficiency.
4.3 Design and process considerations
The design of parts should take full account of factors such as thermal expansion and contraction during the welding process. During the welding process, the metal will expand due to high temperature and contract after cooling, which may lead to sheet metal deformation or cracks in the parts. Therefore, the design should ensure the following points:sheet metal
- Thermal Expansion Considerations:
The design should allow some room for thermal expansion to avoid structural problems due to excessive expansion or contraction. - Shrinkage control:
Reasonable arrangement of welding sequence and location of welding points to reduce unnecessary stress concentration in order to prevent warping or cracking. - Strengthening of welded joints:
Ensure that welded joints are not prone to fracture or failure when subjected to external forces through rational design and process planning.
Depending on the specifications of the weld screw, the welded the size of the opening and the required part torque value of sheet metal will also affect the welding effect. Therefore, standardized opening sizes and required torque values should be considered during design to ensure a strong and stable connection.
| Thread Specification | Maximum hole size (mm) | Required torque (N.m) |
| M5 | 5.5 | ≥30 |
| M6 | 6.5 | ≥30 |
| M8 | 8.5 | ≥40 |
| M10 | 10.5 | ≥50 |
| M12 | 12.5 | ≥60 |
5: Inspection of welding quality
5.1 Visual inspection
Visual inspection is the first and most basic step in welding quality control. Upon completion of the weld, the weld surface must be thoroughly inspected for any visible defects. Common defects include cracks, porosity, spatter, overheating, inadequate welding, and other problems that can affect the quality of the weld and the robustness of the connection.
- Cracks: Cracks in the weld area will greatly reduce the strength of the weld and affect the reliability of the product. Cracks usually appear in the weld zone and may be caused by temperature changes, stress concentrations or uneven heating during the welding process.
- Porosity: Porosity usually occurs when gases are not expelled in time during the welding process or when the weld material is not completely melted. These pores can cause a reduction in the strength of the weld and affect the stability of the overall structure.
- Spattering: Spattering is the phenomenon of molten metal spattering from the weld joint to the surrounding area during the welding process. Spatter not only affects the appearance, but can also lead to uneven surfaces and increase the complexity of subsequent cleanup.
Through visual inspection, welding operators can detect these defects and repair them in time to ensure that the welded parts meet quality standards. For some hidden defects, auxiliary tools (e.g. X-ray or ultrasonic testing) can also be used for further confirmation.
5.2 Strength testing
After welding is completed, in addition to visual inspection, strength testing is an important part of ensuring the quality of the welded joint. Strength testing with a torque wrench verifies the robustness and reliability of the welded joint.
- Torque Wrench Inspection: Torque testing is mainly used to check whether the connection of welded bolts or screws meets the process requirements by applying a predetermined torque moment. If the strength of the welded joint is not up to standard, it may lead to loose connection or even breakage during use. The testing process should ensure that the applied torque value meets the design requirements and that the connection does not experience any loosening or cracking under the specified torque.
- Unqualified correction: If the strength of the welded joints found through the strength test fails to meet the requirements, it is necessary to timely adjust the welding parameters, such as current strength, welding time, welding speed, etc., to ensure that the joints meet the specified strength standards.
5.3 General quality testing of fasteners
Quality control of fasteners is a core aspect of ensuring product safety and reliability. Common fastener quality testing methods include hardness testing, tensile testing, corrosion resistance testing, etc. These tests help to evaluate the performance of fasteners under different operating conditions.
To learn more about general quality inspection methods for fasteners, you can read the article “Screw quality inspection whole process guide” for an in-depth look at scenarios where each inspection technique can be applied and its impact on product quality. These methods are not only applicable to welded screws, but can be used in a wide range of applications for all types of fastener inspections to help ensure compliance with standards and customer needs.
6: Summary
In the production and application of weld screws, the selection of appropriate welding technology and quality weld screws is the key to ensuring product quality. By reasonably selecting the type of weld screws, materials and welding parameters, the strength, stability and long-term reliability of the connection can be ensured. In this article, we discuss in depth the types of weld screws, working principles, application scenarios and welding quality testing methods to help purchasing decision makers in various industries better understand the characteristics and applications of weld screws.
As a leading fastener manufacturer in the industry, WanHong Fastener has more than 10 years of manufacturing experience and is committed to providing high quality weld screws and customized fastener solutions to customers worldwide. We have become a long-term partner of many well-known companies in the manufacture and supply of welded screws, including Xiaomi, Hisense, Haier Air Conditioning and so on. Our weld screws are widely used in many fields such as electronic products, home appliance manufacturing, automotive industry and construction engineering, etc. They are highly recognized by our customers for their advantages of high strength, durability and easy installation.
Our company is not only committed to the improvement of product quality, but also strictly adheres to international standards to ensure that the quality of each batch of products can meet the needs of customers. Whether it is a standard product or a customized solution, we can provide our customers with professional technical support and perfect after-sales service.
By choosing WanHong Fastener, you will get welded screw products with excellent performance, stable quality and high cost performance. We look forward to working with you to provide more efficient and reliable connection solutions for your projects and to promote the technological progress of the industry.
