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Information × Registration Number 0212U002475, 0109U000980 , R & D reports Title Investigation of influencing of hydrostatical pressure on on technological properties of arc and service characteristics of the welded connections of low-alloyed high-strength steels in the conditions of the wet deep-water welding (to 200 m) popup.stage_title Head Maksymov Sergii, Registration Date 01-03-2012 Organization E.O. Paton Electric Welding Institute popup.description2 The research object is influence of environment and welding conditions on technological properties of arc and service characteristics of the welded joints of low-alloyed increased strength steels at arc underwater welding on depths up to 200 m. The aim of work is research of features of technological properties of electric arc and weld bead formation at increased hydrostatical pressure and establishment of basic factors of providing of quality of the welded joints of low-alloyed increased strength steels in the conditions of the wet underwater welding on depths up to 200 m. Research methods are metallography researches, chemical and gas analyses, determinations of mechanical properties and technological strength of samples with the use of standard methodologies, radiography and fractografical researches, microdefraction analysis, electronic microscopy, mathematical methods of processing of research data and design of welding process with the use of the personal computing facilities. With the increase of depth the amount of breaking and short circuits of arc increases, thus last observed considerably anymore. Prevailing of short circuits results in the increase of mean value of current as compared to the current of arc burning. The increase of hydrostatical pressure is accompanied by the increase of frequency and duration of short circuits. It testifies to diminishing of length of arc and growth of drops sizes of electrode metal, because arc constriction with depth increase result in strengthening of her pressure on a drop, hindering to tearing away and extending life time With the increase of hydrostatical pressure the width of weld and depth of penetration diminish. On depths more than 100 m melting ability approaches a zero, the wettableness of metal gets worse. Taking into account circumstance that speed of wire feeding remained unchanging, it is possible to suppose that over the increase of hydrostatical pressure brings to the increase of losses of electrode metal and redistribution of balance of energy in anode and cathode areas. It has been established that with the increase of welding depth content of alloying elements reduced and stabilized on depths a more than 40.50 m. Thus transition coefficients diminish: Mn - from 0,21 to 0,06; Sі - from 0,05 to 0,03; C - from 0,25 to 0,08. Such result can be explained by high oxidizing potential of vapor-gas bubble. In addition in investigation of arc constriction her temperature increases and is 9000...12000 K. It results in the increase of intensity of evaporation of alloying elements and intensification of processes on the stage of drop. The concentration of oxygen in the weld metal increases almost in 5 time. The use of the external electromagnetic field allows to control the geometrical parameters of weld metal. At the value of induction the 8 mTl depth of penetration increases on 20.30%, and at 18 mTl - almost in 1,5 time, thus in the range of depths an over 50 m, that very importantly taking into account the set problem. It has been established that application of external electromagnetic influence allows effectively to decrease the amount of hydrogen in the weld metal. With the increase of depth the use of the external electromagnetic field slows the rate of increase of hydrogen amount in the weld metal more than in two times. Such result resulted in diminishing of porosity - total volume of pores (to 8 times), their size (to 6 times). It was establish possibility to control chemical composition of the welded joint. At imposition of the external electromagnetic field there is an increase of concentrations of basic alloying elements as in the metal of weld (on 30…50%) so HAZ (40%). Partly it takes place from the increase of transition from electrode material, and partly - due to diffusion from a parent metal. At welding with electromagnetic influence with the increase of the field induction exponentially a heat transfer increases from an arc to the electrode and, accordingly, intensity of it rises. External electromagnetic field homogenizes the structure of metal of welded joints, promotes her dispersion. Variation of values of microhardness within the limits of one area diminishes and at 15 mTl almost is absent. The size of microhardness goes down, both in the weld metal and in the HAZ metal. X-ray structure phase analysis showed that the parameter of crystalline grate diminished. His increase on a depth a 50 m makes all 1% by comparison to 4 % at welding without external electromagnetic field. It testifies that the use of external electromagnetic field diminishes the degree of degradation of structure of weld metal and HAZ under the action of water environment and hydrostatical pressure. At welding with modulation of current the width of HAZ diminishes approximately on 30%, the size of grain in it diminishes on 35%. Resistance against formation of cold cracks increases. As base at development of electrode materials the system CaF2- LіF - K2ZrF6 was chosen, that provides the satisfactory bead appiarence and separability of slag on depths up to 200 m. On her basis a flux-cored wire is developed, at welding of that resistance against formation of cold cracks in HAZ are got in this range of depth. The flux-cored wire and technological recommendations on the use of external electromagnetic influence provide the enhanceable level of plasticity of weld metal as it applies to renewal of underwater metal structures, jurisdiction Derzgnagliydohoronpratsi. Analogues abroad are not had. The got results entered the project of department building norms of "Technology of repair of underwater transitions of main oil pipelines". Technological instruction is worked out on manufacturing of the flux-cored wire for welding of low alloyed increased strength steels on depths up to 200 m. By contract her production will be put right in China. Used in Russia for repair of port building. Application of the flux-cored wire instead of the imported electrodes of firm Broco EasyTouch UW/CS2, the cost of that at the Ukrainian market makes 960 hrn., and coefficient of the efficiency below in 1,4 time, will allow to economize a not less than 600 hrn. on 1 kg. Product Description popup.authors Бут Віктор Степанович Грецький Юрій Якович popup.nrat_date 2020-04-02 Close