Knowledge point 1: Influencing factors and countermeasures of welding process quality
Process quality refers to the degree of guarantee of product quality in the process of production. In other words, the quality of the product is based on the quality of the process, and it must have excellent process processing quality to produce excellent products.
The quality of the product is not only after the completion of all processing and assembly work, through the full-time inspection personnel to determine a number of technical parameters, and obtain user approval even if the requirements are met, but in the beginning of the processing process exists and runs through the whole process of production.
Whether the final product is qualified or not depends on the cumulative result of all process errors. Therefore, the process is the basic link of the production process, but also the basic link of the inspection.
The production of welded structure includes many processes, such as decontamination and rust removal of metal materials, straightening, marking, blanking, groove edge processing, forming, fitting of welded structure, welding, heat treatment, etc. Each process has certain quality requirements, and there are factors that affect its quality.
Since the quality of the process will ultimately determine the quality of the product, it is necessary to analyze the various factors affecting the quality of the process and take effective control measures to ensure the quality of the welding products.
The factors that affect the quality of the process are summarized as follows: personnel, equipment, materials, process methods and five aspects of the production environment, referred to as “people, machines, materials, methods, and rings” five factors. The degree of influence of each factor on the quality of different processes is very different, and it should be analyzed in detail.
Welding is an important process in the production of welded structures, and the factors that affect its quality are also the above five aspects.
1.Welding operator factors
The various welding methods depend on the operator to different degrees.
For manual arc welding, the welder’s operating skills and careful working attitude are crucial to ensure the quality of welding.
For submerged arc automatic welding, the adjustment of welding process parameters and welding can not be separated from human operation.
For all kinds of semi-automatic welding, the movement of the arc along the welded joint is also controlled by the welder. If the welder welding quality awareness is poor, careless operation, do not comply with the welding process procedures, or low operating skills, unskilled technology will affect the quality of direct welding.
The control measures for welding personnel are as follows:
(1) Strengthen the quality awareness education of welders “quality first, user first, the next process is the user”, improve their sense of responsibility and meticulous work style, and establish a quality responsibility system.
(2) Regular job training for welders, master the process rules theoretically, and improve the level of operational skills in practice.
(3) In the production, welders are required to strictly implement the welding process regulations, and strengthen the self-inspection of the welding process and the inspection of full-time inspectors.
(4) Conscientiously implement the welder examination system, adhere to the welder certificate, establish the welder technical files.
For the production of important or significant welded structures, more detailed consideration of the welder is also required. For example, the length of welder training time, production experience, current technical status, age, length of service, physical strength, vision, attention, etc., should all be included in the scope of assessment.
2.Welding machine equipment factors
The performance, stability and reliability of various welding equipment directly affect the welding quality. The more complex the structure of the equipment, the higher the degree of mechanization and automation, the higher the dependence of welding quality on it.
Therefore, this type of equipment is required to have better performance and stability. Welding equipment must be inspected and tested before use, and a regular inspection system should be implemented for all kinds of in-service welding equipment.
In the welding quality assurance system, starting from ensuring the quality of the welding process, the welding machine and equipment should do the following:
(1) Regular maintenance, maintenance and overhaul of welding equipment, and important welding structures should be tested before production.
(2) Regularly check the ammeter, voltmeter, gas flow meter and other instruments on the welding equipment to ensure accurate measurement during production.
(3) Establish technical files of welding equipment status to provide ideas for analyzing and solving problems.
(4) Establish the responsibility system of welding equipment users to ensure the timeliness and continuity of equipment maintenance.
In addition, the use conditions of welding equipment, such as the requirements of water, electricity, environment, etc., the adjustability of welding equipment, the space required for operation, and the adjustment of errors also need to be fully paid attention to, so as to ensure the normal use of welding equipment.
3.Welding material factor
The raw materials used in welding production include base metal, welding materials (electrode, wire, flux, protective gas), etc. The quality of these materials is the basis and premise to ensure the quality of welding products.
In order to ensure the quality of welding, the quality inspection of raw materials is very important. In the initial stage of production, that is, it is necessary to close the material before feeding, in order to stabilize the production and stabilize the quality of welding products.
In the welding quality management system, the quality control of welding raw materials mainly includes the following measures:
(1) Strengthen the acceptance and inspection of welding raw materials, and reinspect their physical and chemical indexes and mechanical properties if necessary.
(2) Establish a strict management system for welding raw materials to prevent the contamination of welding raw materials during storage.
(3) Implement the marking operation system of welding raw materials in production to achieve the tracking and control of the quality of welding raw materials.
(4) Select welding raw material supply factories and cooperative factories with high reputation and good product quality for ordering and processing, and fundamentally prevent the occurrence of welding quality accidents.
In short, the control of welding raw materials should be based on welding specifications and national standards, timely tracking and control of its quality, rather than just entering the factory acceptance, ignoring the marking and inspection in the production process.
4.Welding process method factors
The welding quality is very dependent on the process method, and occupies a very prominent position in the factors that affect the quality of the welding process.
The influence of process method on welding quality mainly comes from two aspects, one is the rationality of process formulation; The other is the rigor of the execution process.
First of all, the welding process of a product or a certain material must be evaluated, and then according to the technical requirements of the process assessment report and drawings, the development of welding process procedures, the preparation of welding process instructions or welding process cards, which are expressed in written form of various process parameters are the basis for guiding the welding. It is based on the simulation of similar production conditions made by the test and long-term accumulated experience and the specific technical requirements of the product and prepared, is to ensure the quality of welding an important basis, it has the characteristics of prescriptivity, seriousness, prudence and continuity. It is usually prepared by experienced welding technicians to ensure its correctness and rationality.
On this basis, to ensure the rigor of the implementation of the process method, it is not allowed to change the process parameters without sufficient basis, and even if it is necessary to change, it must perform certain procedures and procedures.
Unreasonable welding process can not guarantee a qualified weld, but with the correct and reasonable process procedures verified by the evaluation, if not strictly implemented, the same can not weld a qualified weld. The two complement each other and depend on each other, and neither aspect can be ignored or neglected.
In the welding quality management system, the effective control of the factors affecting the welding process method is:
(1) The welding process must be evaluated in accordance with relevant regulations or national standards.
(2) Select experienced welding technicians to prepare the required process documents, and the process documents should be complete and continuous.
(3) Strengthen the on-site management and supervision in the welding process according to the welding process regulations.
(4) Before production, the welding product test plate and the welding process inspection test plate should be made in accordance with the welding process regulations to verify the correctness and rationality of the process method.
In addition, the development of welding process regulations is no size, and there should be a remedy plan for quality accidents for important welding structures to minimize losses.
5.Environmental factor
In a specific environment, the dependence of welding quality on the environment is also large. The welding operation is often carried out in the outdoor air, which is bound to be affected by the external natural conditions (such as temperature, humidity, wind and rain and snow weather), and in the case of other factors, it is possible to cause welding quality problems simply due to environmental factors.
Therefore, some attention should be paid to it. In the welding quality management system, the control measures of environmental factors are relatively simple, when the environmental conditions do not meet the requirements of the regulations, such as large wind, wind speed greater than four, or rain and snow weather, relative humidity greater than 90%, can temporarily stop the welding work, or take wind, rain and snow measures before welding;
When welding at low temperatures, low carbon steel shall not be lower than -20 ° C, ordinary alloy steel shall not be lower than -10 ° C, such as exceeding this temperature limit, the workpiece can be properly preheated.
Through the above analysis of the factors affecting the quality of the five aspects of the welding process and its control measures and principles, it can be seen that the five aspects of the factors are related to each other and cross each other, and there should be systematic and continuous consideration.
Post time: Jul-05-2023