Single pass welding and multi pass welding
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This post was last written by megaherz_Edited by IGGE on 2023-2-25 09:29 1) Dear teachers, may I ask about the definition of multi-pass welding?: “The number of weld passes in each groove is considered as multi-pass welding. "The number of weld passes ≥ 2" refers to the total number of weld passes in each groove, or is it calculated according to whether the number of weld passes in each welding method is ≥ 2 (a welding method with ≥ 2 passes is considered multi-pass, otherwise it is single pass, and each welding method is counted separately)? For example, Figure 1: Are the four methods of GTAW, PAW, SMAW, and SAW considered multi-pass welding, or is only GTAW considered multi-pass welding, and the other PAW, SMAW, and SAW are considered single-pass welding? 2) Personal understanding, single channel and multiple channels, generally from the channel: The mechanical influence of the thermal effects of front-pass preheating + subsequent inter-pass annealing, as well as the differences in welding process and welding evaluation coverage due to defects such as slag inclusions between multi-pass welding passes and lack of fusion between passes. ； Based on this premise, as shown in Figure 2, can the first GTAW pass be regarded as a single pass welding? If we look at the total number of grooves on each side, as shown in Figure 2, GTAW+SMAW, the total number is 3 passes, which should be multi-pass welding. However, when the bottom weld pass GTAW is used alone, there is no thermal effect of the subsequent weld pass, and there is no preheating of the front weld pass, and there is no influence of inter-pass slag inclusion and lack of fusion of the subsequent weld pass. Can GTAW be regarded as a single pass welding application at this time? 3) Based on the expansion of question 2, for the plasma P+T project as shown in Figure 3, if the welder code is PAW-1G-06/08/19 and GTAW-1G(K)-05/06/09/19, is it reasonable to write 08 for PAW and 09 for GTAW?
Single-pass welding refers to welding along a weld bead (usually a weld seam) on the surface of a metal material. It can be used to join components of complex shapes. Since there is only one working principle, it requires higher precision, better welding speed and greater welding efficiency in terms of quality, and the operation is relatively more cumbersome. Multi-pass welding refers to multiple passes of welding on the metal surface, which can be divided into horizontal welding, vertical welding, corner welding, etc., and is used to connect large-sized objects. The advantage of multi-pass welding is that it is easier to operate and has higher welding accuracy. It can weld multiple parts, which can reduce the number of welds and improve the efficiency of the welding process. However, due to the principle of fluid mechanics, vertical welding requires more welding materials, so in terms of welding quality, more attention needs to be paid to the process control during the welding process. -
Answer 1: Multi-pass welding means that the total number of welding passes in each groove is greater than 2. Regardless of the welding method, as long as the total number of welding passes in each groove is greater than 2, it can be called multi-pass welding. Therefore, in Figure 1, the four methods of GTAW, PAW, SMAW, and SAW are all considered multi-pass welding. Answer 2: According to the above definition, as long as the total number of weld passes in each groove is greater than 2, it can be called multi-pass welding, so GTAW+SMAW in Figure 2 should be multi-pass welding. When GTAW is used alone, since the number of welding passes is less than 2, it should be regarded as single-pass welding. Answer 3: If it is a plasma P+T project, if the welder code is PAW1G06/08/19 and GTAW1G(K)05/06/09/19, it is reasonable to write 08 for PAW and 09 for GTAW, because according to the existing definition, writing 08 for PAW means there are 2 welds in each groove, and writing 09 for GTAW means there are 3 welds in each groove. This is a multi-pass welding, so it is reasonable. -
Today I compared the old and new versions of the "Welding Examination Regulations". The old version 08/09 only said "Weld bead inside each side groove". The current TSG Z6002-2010 says "Weld bead inside each side groove by various welding methods". With the addition of the words "Various welding methods", the meaning has changed. According to TSG Z6002-2010, this sentence should mean:: The number of passes is calculated separately for each welding method on each side to determine whether it is single pass welding or multi-pass welding.
Single-pass welding and multi-pass welding are two different welding methods commonly used in metal processing. Single-pass welding is a simple and direct welding method, which refers to only one continuous single-pass welding of the metal workpiece. This welding method is suitable for thin-walled, low-carbon and high-beauty welds. It can reduce production costs and improve production efficiency to a certain extent. Multi-pass welding requires multiple welding processes, and the entire welding process is completed through multiple superimposed heating and cooling. This welding method can solve difficult-to-handle workpieces such as thick plates and large pipe diameters that are difficult to weld with single-pass welding, but it requires more time and human resources, and the weld quality control is relatively difficult. Two different welding methods, single pass welding or multi-pass welding, need to be selected based on specific project requirements. .
The reason why Chinese is not accurate is that this should be every, not each. All welding methods are counted, and the number of weld passes in each breach is