What does welding quality control rely on?

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Overview: With the rapid development of modern welding technologies, the continuous improvement in welding production standards, and the growing expansion of international trade in welded products, quality management for such products has gradually moved toward standardization and regulation in order to ensure their quality, make effective use of resources, and protect the interests of consumers. In March 1987, the International Organization for Standardization (ISO) officially released the ISO 9000–9004 series of standards on quality management and quality assurance. In 1994 and 2000, the International Organization for Standardization revised the ISO 9000 family of standards on two occasions, making them simpler, more focused, more scientific, and more universal, and raising quality assurance systems to the level of quality management systems. In response, our country issued the GB/T19000:2000 \"Quality Management Systems\" standard series in 2000, which equivalently adopts this international standard series. Modern quality management holds that in order for products to meet all required quality criteria, efforts must be made at every stage of production; this is ensured by controlling and adjusting the factors that affect process quality. Process quality, in turn, must be achieved through work quality by employing various management methods. Therefore, in quality management, work quality must be used to ensure process quality, and process quality must be used to ensure product quality. It is evident that to achieve quality goals, it is necessary to establish an effective and easy-to-operate quality management system within the management structure. And apply this system to the entire manufacturing process of the product. Knowledge Point 1: Factors Affecting the Quality of Welding Processes and Corresponding Countermeasures Table of Contents 1. Personnel – Factors related to the welders themselves 2. Machinery – Factors related to welding equipment 3. Materials – Factors related to welding raw materials 4. Methods – Factors related to welding processes 5. Environment – Environmental factors. Process quality refers to the extent to which the processing steps during production ensure the quality of the product. In other words, product quality is based on the quality of the manufacturing processes; excellent product quality can only be achieved by ensuring high standards in these processes. The quality of a product is not determined merely by having specialized inspectors measure various technical parameters after all processing and assembly tasks are completed, and by obtaining customer approval; rather, it exists from the very beginning of the manufacturing process and remains consistent throughout the entire production cycle. Whether the final product is qualified or not depends on the cumulative effect of errors in all processing steps. Therefore, the process is a fundamental element of the production process as well as a basic aspect of inspection. The production of welded structures involves many processes, such as degreasing and derusting of metal materials, straightening during material preparation, marking, cutting, edge preparation for grooves, forming, as well as assembly, welding, and heat treatment of the welded structures. Each process has certain quality requirements, and there are factors that affect its quality. Since the quality of the manufacturing processes ultimately determines the quality of the product, it is necessary to analyze various factors that affect process quality and implement effective control measures in order to ensure the quality of welded products.    The factors that affect process quality can be summarized into five aspects: personnel, equipment, materials, processing methods, and the production environment – commonly referred to as the five elements of \"people, machines, materials, methods, and environment\". The degree of impact of various factors on the quality of different processes varies greatly, and a case-by-case analysis is required. Welding is an important process in the production of welded structures, and the factors affecting its quality are also the same five aspects mentioned above. 1. Personnel-----Welding operator factors: Different welding methods require varying degrees of reliance on the operator. For manual arc welding, the welder’s operational skills and careful work attitude are crucial to ensuring welding quality. For submerged arc automatic welding, the adjustment of welding process parameters and the actual welding process also require human operation. For various types of semi-automatic welding, the movement of the arc along the weld joint is also controlled by the welder. If a welder lacks a sense of quality while welding, is careless in their operations, fails to follow the welding procedures, or has poor skill levels and inadequate expertise, all of these factors can affect the quality of the weld. The control measures for welders are as follows: (1) Strengthen quality awareness education among welders, emphasizing that \"quality comes first, the customer comes first, and the next processing step represents the customer,\" in order to enhance their sense of responsibility and their meticulous work style, and establish a quality responsibility system. (2) Provide regular on-the-job training for welders to help them understand the technical procedures theoretically and improve their operational skills practically. (3) In production, welders are required to strictly follow the welding procedure specifications, and enhanced self-inspection during the welding process as well as inspection by dedicated quality control personnel are necessary.   (4) Strictly implement the welder examination system, ensure that welders work only with valid certificates, and establish technical records for welders. For the production of important or major welded structures, more detailed consideration must also be given to the welders. For example, the duration of welder training, production experience, current technical proficiency, age, years of work experience, physical strength, eyesight, concentration, etc., should all be included in the assessment criteria. 2. Machine-----Welding machine equipment: The performance, as well as the stability and reliability of various welding devices, have a direct impact on the quality of welding. The more complex the equipment structure is, and the higher the degree of mechanization and automation, the greater the reliance on welding quality. Therefore, it is required that such devices have better performance and stability. Welding equipment must be inspected and tested before use; a regular inspection system should be implemented for all welding equipment in service. In the welding quality assurance system, with the aim of ensuring the quality of the welding process, the following measures should be taken regarding welding machinery and equipment: (1) Regularly maintain, service, and inspect the welding equipment, and conduct trials before producing important welded structures. (2) Regularly calibrate various instruments on the welding equipment, such as ammeters, voltmeters, and gas flow meters, to ensure accurate measurement during production. (3) Establish a technical record of the condition of welding equipment to provide guidance for analyzing and resolving emerging problems. (4) Establish a responsibility system for personnel using welding equipment to ensure timely and continuous equipment maintenance. Furthermore, the operating conditions of welding equipment, such as requirements regarding water, electricity, and the environment, as well as the adjustability of the equipment, the space required for its operation, and error adjustment, all need to be given due attention in order to ensure its proper use.   3. Materials ----- Factors related to raw materials for welding. The raw materials used in welding production include base metals, welding materials (welding electrodes, wires, fluxes, shielding gases), etc. The quality of these materials themselves is the foundation and prerequisite for ensuring the quality of welded products. To ensure welding quality, it is important to inspect the quality of raw materials. At the beginning of production, that is, before materials are introduced, it is essential to ensure their quality in order to maintain stable production and consistent quality of the welded products. In the welding quality management system, the quality control of welding raw materials mainly includes the following measures: (1) Strengthening the inspection and verification of welding raw materials upon arrival at the factory, and conducting retests on their physical and chemical properties as well as mechanical properties when necessary. (2) Establish a strict management system for welding raw materials to prevent contamination of such materials during storage. (3) Implement a marking system for welding raw materials during production in order to achieve traceability and control over the quality of these materials. (4) Select welding raw material suppliers and partner factories with high reputations and good product quality for ordering and processing, in order to fundamentally prevent welding quality accidents. In short, the quality control of welding raw materials should be based on welding specifications and **standards**, with their quality monitored in a timely manner; it is not sufficient to merely conduct inspections upon arrival at the factory, ignoring the marking and testing processes during production. 4. Method – Welding process factors: Welding quality is highly dependent on the process methods, and these factors play a very significant role among all those that affect the quality of welding operations. The impact of the welding process on weld quality arises mainly from two aspects: one is the rationality of the process design ； On the other hand is the strictness of the manufacturing process. First, it is necessary to conduct a process evaluation for the welding process of a particular product or material. Based on the results of this evaluation and the technical requirements specified in the drawings, a welding procedure specification is developed, along with a welding procedure card. These written documents, which outline various process parameters, serve as guidelines for carrying out welding operations. They are formulated based on tests conducted under conditions similar to those of actual production, on accumulated experience over time, and on the specific technical requirements of the product. They constitute an important foundation for ensuring welding quality, and are characterized by their specificity, rigor, caution, and consistency. It is usually prepared by experienced welding technicians to ensure its accuracy and rationality. On this basis, it is necessary to ensure the strict implementation of the process methods; process parameters must not be changed arbitrarily without sufficient justification. Even when changes are indeed necessary, certain procedures and formalities must be followed. An unreasonable welding process cannot guarantee the formation of qualified welds; however, even with a properly established and verified welding procedure, failure to follow it strictly will also result in Unqualified welds. The two complement each other and are interdependent; neither aspect can be ignored or neglected. In a welding quality management system, an effective approach to controlling the factors that affect welding processes is: (1) The welding process must be evaluated in accordance with relevant regulations or **standards. (2) Select experienced welding technicians to prepare the required process documents, which must be complete and consistent. (3) In accordance with the provisions of the welding procedure specification, strengthen on-site management and supervision during the welding process.    (4) Before production, welding product test plates and welding process inspection test plates shall be prepared in accordance with the welding procedure specifications to verify the correctness and rationality of the process methods. Additionally, the formulation of welding procedure specifications must be thorough and meticulous. For important welded structures, there should be contingency plans for quality-related incidents, so as to minimize any losses. For information on the important factors and additional factors related to various welding processes, refer to Table 1-1; for information on the secondary factors of various welding methods, refer to Table 1-2. Table 1-1 Relationship between Important Factors and Supplementary Factors of Welding Processes and Welding Defects
Process conditions, slag, lack of fusion, incomplete penetration, undercutting, distortion, warping, porosity, crack formation, weld defects. Welders, welding methods: ○○○○○○○◎; Welding materials: △△△○◎◎◎; Welding position: ◎◎◎○○△○◎; Weld joints: ◎◎◎◎◎◎◎○; Welded structures: ○◎○◎; Fit-up welding: ○○○◎○○○◎.
① Explanation: ◎ indicates a strong relationship, ○ indicates a moderate relationship, △ indicates an average relationship.

Table 1-2 Relationship between Secondary Factors of Welding Processes and Welding Defects
Welding process conditions, slag, lack of fusion, incomplete penetration, undercutting, distortion, warping, porosity, cold cracks, hot cracks. Weld groove shape: ◎◎◎○○○○; Groove cleaning status: ◎◎; Shape of intermediate passes: ◎◎; Slag removal from the weld: ◎; Preheating before welding: △△△○◎; Welding current level: ○◎◎○○; Length of the welding arc: ○◎△; Angle at which the welding rod is moved: ○○○◎; Welding rod movement pattern: △; Weld deposition pattern: △△△△; Welding position: ○○○○; Wind conditions in the surrounding environment: ○○.
① Explanation: ◎ indicates a strong relationship, ○ indicates a moderate relationship, △ indicates an average relationship.

5. Environment – In specific environments, the quality of welding is also highly dependent on the surrounding conditions. Welding operations are often carried out outdoors, and are inevitably affected by external natural conditions such as temperature, humidity, wind strength, and weather conditions like rain and snow. Even when other factors remain constant, welding quality issues can arise solely due to environmental factors. Therefore, it should also draw some attention. In the welding quality management system, the control measures for environmental factors are relatively simple. When the environmental conditions do not meet the specified requirements – such as strong winds with a wind speed exceeding level 4, or weather conditions of rain, snow, and a relative humidity of over 90% – welding work can be temporarily halted, or welding can proceed only after taking measures to protect against wind, rain, and snow ； When welding at low temperatures, low-carbon steel should not be below –20°C, and ordinary alloy steel should not be below –10°C; if these temperature limits are exceeded, the workpiece can be preheated appropriately. Through the analysis of the five factors affecting the quality of welding processes, along with their control measures and principles, it can be seen that these five factors are interrelated and overlap with one another; therefore, a systematic and continuous approach is necessary when considering them.