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Mathematical model of gas-coverage formed by ideal welding nozzle

Szefner Z.

Advances in Manufacturing Science and Technology

2008

Vol. 32, nr 1

81-97

This article shows the model of body of gas-coverage that is formed by the shielding gas flowing out from so called standard welding nozzle. The meaning "standard nozzle" shall be understood as the welding nozzle of any shape ended with a straight, smooth, long section of a pipeline. The paper presents a short description of properties of the gas coverage in the generalised coordinates in which the key significance is attributed to the newly introduced value - "the number of mass current density". A construction of the abductive model of the gas coverage of protective gas jet is described in this work on the basis of series of the experimental research. Then, the discovered model is verified empirically for the standard nozzle. The solution presented in this paper replaces the hitherto existing in the old theory of gas-shielded arc welding model of "shielding gas outflow" with the model of body of gas-coverage.

Opracowano model osłony łuku spawalniczego, kształtowanej przez wypływający gaz ochronny. W modelu przyjęto wzorcową dyszę spawalniczą - dowolną dyszę spawalniczą zakończoną prostoliniowym gładkim, długim jej odcinkiem. Przedstawiono właściwości obszaru chronionego we współrzędnych uogólnionych z uwzględnieniem nowego parametru "liczby ilości ruchu strumienia". Na podstawie wyników doświadczalnych przedstawiono budowę abdukcyjnego modelu obszaru chronionego osłony łuku spawalniczego. Następnie, model tzw. gazoosłony idealnej poddano weryfikacji doświadczalnej dla dyszy wzorcowej. Przedstawione rozwiązanie zastępuje dotychczasowy model "wypływu gazu osłonowego" modelem gazoosłony wzorcowej.

Kształtowanie osłony gazowej łuku spawalniczego

Szefner Z.

Prace Naukowe Politechniki Szczecińskiej. Instytut Inżynierii Materiałowej

2007

Nr 588 (20)

5-216

W rozprawie przedstawiono problem kształtowania gazowej osłony łuku spawalniczego. Istotą problematyki jest identyfikacja i proces modelowania strumienia ochronnego oraz osłony właściwej jako obiektu badań.

The monograph presents the problem of modelling of gas coverage in the gas-shielded -are welding. The essence of the problem lies in the examination of the hydrodynamic properties, the identification and the modelling process of the shielding gas jet and the gas shielding of the arc as a technical object. The study is the result of a research programme of the International Institute of Welding IIW/IIS entitled "study on the efficiency of shielding gas and influence of welding gun on the efficiency of the gas shielding". The fundamental part of the monograph describes the technological characteristics of the shielding gas stream, which forms after escaping from the welding nozzle according to the conditions of the variable technological welding process. Based on the results of the examination of the concentration profile of the shielding gas components, the transformation in comparison with the mathematical model of a free gas jet as well as according to abductive logics, the study presents the modelling process of the shielding gas body as the (infinite) quantity of the gas coverages of the shielding gas stream. The result of the shap modelling process of the shielding gas jet is a mathematical model of the shielding gas body, essential and adequate with regard to the supposed population of simple welding nozzles. This model can be used directly for the calculation of the technological variables of the welding arc gas shielding and be integrated in the control systems for the output of shielding gas in modern welding installations. The developed method makes it possible to directly measure the value (diameter) of the gas coverage, with the empirical indication of two characteristic quantities of the shielding gas body, that is the extent of the shielding and its upper and lower bounds, i.e. the gas coverage with the biggest dimensions in the entire quantity. The model of the shielding gas body makes it possible to choose and control technological variables such as the flow rate of shielding gas, the diameter of the welding nozzle and the distance between the nozzle and the parent metal and it offers in addition the possibility to optimize these variables. The study presents a method for the evaluation of the welding nozzles and guns on the efficiency of gas shielding, developed in connection with the modelling process. This is followed by an evaluation based on defined indicators of the quality of the gas shielding and a comparison of the shielding effect of simple welding nozzles chosen from a catalogue. Two annexes complete the monograph. The first annex offers an extensive description of the shielding gas jet escaping from the welding nozzle on the basis of an examination method typical for the jet theory (examination of the mean and fluctuating component of velocity profile). The second annex contains a catalogue of simple welding nozzles developed in connection with the research methodology for the modelling of gas coverage and the verification of the mathematical model of the research object.