When Zhang Jianxin, an expert in Baogang, just finished speaking, Shen Huan saw that Chen Jinyi was the first to stand up, but thinking about this senior technician, he does have a lot to say, after all, he is an expert in welding.
I saw Chen Jinyi stand up and say loudly: "Leaders, let me say a few words, if there is anything wrong, please correct the leaders."
As we all know, the new special steel is specially developed for our new submarine, and the same is true for the supporting welding materials, but what makes us headache is that this high-strength steel is the first time we have encountered it, and it seems to have a kind of rigidity that would rather bend than bend, which is the reason why it is difficult to weld and the pass rate is very low.
Tensile and bending tests have been done, and chemical analysis has also been done, but why can't welding?
I think it is better to start with the welding materials and adjust the formula through trial and error to solve the current problem.
Thank you!
” At this time, a craftsman in the craft room stood up, Shen Huan saw that this was not Wang Guanghai, the backbone of the group, he had always been relatively silent, why did he take the initiative to stand up and speak this time.
Wang Guanghai said loudly: "I think what Chen Gong said makes sense, but how do we adjust the formula of welding materials?"
This is what the manufacturer has already finalized.
I think that at present, our current elastoplastic fracture toughness test method to determine the J integral of new special steel and welded parts can no longer obtain effective test data.
Why?
Because we know that the new special steel is high-strength steel, and when the standard was formulated, there was no such high-strength steel, and the strength of our marine steel was much lower than that of the 607A high-strength steel we use now, and the change in welding materials is also relatively large. ” Many participants whispered that this is a negation of the current standard, how easy it is to establish a new standard, which needs to be supported by a large amount of data, and how can there be time to do this now.
Wang Guanghai didn't care about everyone's discussions, but continued: "In the process of testing the weld samples of 607A steel welded joints in the Baogang laboratory, I heard that there was a local instability fracture for two reasons, one is a large non-metallic composite inclusion, and the other is alloy cementite.
Therefore, I think we should re-establish the test standard and use our finite element software to verify and analyze the J-integral conservation of welded joints, so as to test the J-integral value of the weld metal and study the influence of strength matching on the strength and toughness of 607A steel welded joints!
That's all my opinion, and if it's wrong, please criticize and correct the leaders!
” It's finite element again!
At this moment, everyone turned their attention to Shen Huan, because in the process design and process documentation of the new submarine construction, it was Shen Huan who proposed the introduction of finite element analysis software and successfully applied it!
Liu Guohua threw a trusting glance at Shen Huan, and Shen Huan understood that he had to say something.
After thinking about it, Shen Huan slowly stood up, and said without humility or arrogance: "Leaders, I think it is a feasible way for Comrade Wang Guanghai to use finite element software to analyze and verify the conservation of J integral of welded joints.
Of course, there are other factors that we need to take into account.
We all know that welding work accounts for about 40 percent of the shipbuilding workload, and if we do not solve the problem of welding quality pass rate in time, the construction period of our new submarine will be seriously delayed, and this is unacceptable to our national defense construction and to our Jiangnan Changxing. ” Shen Huan spoke very methodically, which made Liu Guohua and others very satisfied, and Sun Chengming, the military representative, also stared at Shen Huan with burning eyes, he knew that Shen Huan must have amazing words again.
Shen Huan paused for half a second, and then continued: "This time for the construction of new submarines, the welding process we use is a relatively new FCB submerged arc welding method, but the FCB method does still have some inherent welding defects, such as when the heat is input, the structure of the weld and the heat-affected zone is easy to coarse, easy to produce tiny cracks, etc., I think these defects are more prominent in high-strength steel welding, so there will be a serious problem of less than 20% of the qualified rate."
I believe that we need to solve the problem of adaptability of new special steel and supporting welding materials in shipyards, and overcome the inherent defects of the welding process, and these two problems can be achieved at the same time. ” Shen Huan analyzed so thoroughly, which shocked the experts present, they originally thought that Shen Huan, a young man, was a role model launched by the leaders of Jiangnan Changxing, maybe he was talented in some aspects, but what he didn't expect was that in terms of welding technology, he also had such a unique insight.
Shen Huan didn't have the time to look at the expressions of the experts, he thought and said: "If I want to overcome the inherent defects of the welding process, I still have to make good use of finite element analysis software."
We can use finite element analysis software to simulate various changes in the welding process, such as temperature field, stress field, etc., and then optimize the process parameters, according to the theory of welding heat transfer and finite element analysis, we can establish a finite element model of FCB welding temperature field.
By observing the changes in the temperature field, we can grasp the changes and characteristics of the welding start, quasi-steady state and welding end stage, and also calculate the temperature changes of each node on the weld section during the quasi-steady state, and with these basic data, the welding parameters can be optimized and adjusted to the best.
That's what I suggest, please leaders and experts to correct!
” The reason why Shen Huan put forward this suggestion is also because in his previous life, he participated in the design and research of the welding process of FCB submerged arc welding applied to 170,000-ton bulk carriers, but the bulk carriers use ordinary civil high-strength steel, the kind of E36 steel, the yield strength is not less than 355N/mm^2, but it is very similar to the yield strength of the current new submarine special steel, and the chemical composition should not be large, and the carbon content is relatively low.
At that time, the process design research team, through a large number of tests and finite element analysis, came to the conclusion that the weld and the heat-affected zone generated a certain amount of high-carbon martensite, and even the mixed structure of several substances, the embrittlement of the structure caused the toughness of the welding slider to decrease, and E36 steel added certain alloying elements in the smelting process, under the action of large heat input of the FCB method, the compounds of many alloying elements were dissolved in large quantities, and there was no time to precipitate during the cooling process, resulting in the embrittlement of the joint.
The process parameters are optimized, and the problems of welding efficiency and welding quality are solved.
Yu Tao couldn't help but say, "Shen Huan, you spoke very well!"
I think this is the only way to use it at present, and the finite element analysis software, introduced into our company, will come in handy again!
” Shen Huan smiled slightly: "I am only making a preliminary suggestion, and the specific work needs to be formulated by the leaders and experts here to formulate a detailed plan, I hope this problem can be solved in the fastest time!"
”