SOME ASPECTS OF JOIN FORMATION DURING EXPLOSIVE WELDING

1. Institute of structural Macrokinetics and Materials Sciences Russia SOME ASPECTS OF JOIN FORMATION DURING EXPLOSIVE WELDING PervukhinaO.L., RihterD.V., PervukhinL.B., DenisovI.V.,Bondarenko S.Yu.

2. Scheme of explosion welding with formation of cumulative jet where: U0, δ1 is velocity and thickness of general jet Uc, δс is velocity and thickness of cumulative jet moving to the right (reverse) Un, δn is velocity and thickness of jet moving to the left To obtain a join at explosion welding it is necessary to follow to next conditions: D<Co where: Соsound velocity in welded materials Disdetonation velocity P≥Pкр where: Ркрis a critical pressure in join Р is a pressure in join γ<γкр where: γisan angle of collision γкрis acritical angle of collision Welded join after sudden stop of explosion welding

3. Change of join parameters along the full length. σ, ∆, λ ε where: σ – strength of join (MPа); ∆ - quantity of cast impuritie; λ – size of waves; ε – stabilization site of explosion welding;

4. Method of marks Sites: А – 400 mminterval – 25 mm; B – 1500 mminterval – 50 mm; С – 2500 mminterval – 500 mm; D – 1500 mminterval 50 mm

5. Method of “traps” Explosion welding with applying of method of “traps”. Surfaces of “traps” after explosion welding of titanium with steel in air Coating of titanium oxides is visible. where:1 – welded plates, 2 – trap, 3 – explosive charge, 4 – detonator, 5 – sand Состав: Fe, Fe3N Surfaces of “traps”after explosion welding of titanium with steel in argon Coating is absent, traces of mechanical treatment are visible.

6. According to the results of experiments about method of marks it is necessary to emphasize two points: • Distance between the marks on the clad sheet doesn’t change along the full surface. • Marks on the clad sheet coincide with their projections on the base sheet. Schemes of explosion welding Accepted scheme of explosion welding. Suggested scheme of explosion welding. where: V0 – plate velocity, γ – angle of collision, δL – next concerned element, а – zone of chemical reaction. The absence of oblique collision at explosion welding doesn’t allow considering a process of join formation as a collision of straight and reverse liquid jet.

7. Dependence of middle thickness of cast impurities in join 2andthickness of layer 1,extracting fromwelding surfacesondetonation velocity D (а); parameter r () andstandoff hсв (b) (k calculation thickness of cumulative jet).

8. Zones singled out during join formation at explosion welding 1- zone of contact point, 2- zone of ahead of contact pointand 3- zone of join formation. D – detonation velocity, Vв- velocity of shock-compressed gas, Vk – velocity of contact point. Calculation of temperature into standoff Boltzmann’s equation where R=8,31 (universal gas constant), μ=0,029 (molar mass of air), V– velocity of collision. For the used conditions V = 2500 m/s(detonation velocity of mixture of porous ammonium nitrate with diesel oil 96:4) we obtain:

9. Experimental datatestified toformation of plasma into standoff. Dependence of brightness gas temperature on detonation velocity Curve 1 –dependence of brightness temperature of gas clot on detonation velocity . Curve 2 – shockHugoniot of air Experimental setup for measuring of gas temperature: 1-explosive charge, 2-clad plate, 3-light filter, 4- chink, 5-immovable plate, 6-condensed air Dependence of distance of melting beginning on parameters of gas flow where: L50и L100 – distances on which melt of plates surface appears at roughness of 50 and 100 μm accordingly. * - Ишуткин С.Н., Кирко В.И., Симонов В.А. Исследование теплового воздействия ударно-сжатого газа на поверхность соударяющихся пластин // Физика горения и взрыва. – 1980. - №6. – С. 69-73 * - Козлов П.В., Лосев С.А., Романенко Ю.В. Поступательная неравновесность во фронте ударной волны в аргоне // Вестник Московского Университета. Серия 3. Физика. Астрономия. 1998, №5, стр.46-51.

11. Plasma cleaning General viewof surface after plasma-arc cleaning • * Сенокосов Е.С., Сенокосов А.Е., Плазменная электродуговая очистка поверхности металлических изделий, "Металлург", №4, 2005 г. • * * Ишуткин С.Н., Кирко В.И., Симонов В.А. Исследование теплового воздействия ударно-сжатого газа на поверхность соударяющихся пластин // Физика горения и взрыва. – 1980. - №6. – С.69-73

12. Formation of welded join. At pressure At explosion welding welding according to Lysak Oursupposition and others 1. Formation of physical 1.Formation of physical1. Activation and cleaning of contact. contact. surface. 2. Activation of surface. 2. Activation of surface. 2. Formation of physical contact. 3. Volume interaction3. Volume interaction • h= 8 mm, D= 2500 m/s, V0= 400 m/s. • Time of plate flight to collision is 20х10-6sec, • Time of beginning of intense glowing of gas clot is 30-40х10-6sec. Overall is 50-60х10-6sec. • During all this time detonation passed 125-150 mmthat conformed to stabilization site sizes observed in practice at manufacture of bimetal. Calculation of stabilization length at explosion welding

13. Conclusions • 1. By the method of marks and the method of traps on the articles and large-sized sheets it was established that at explosion welding collision of clad sheet with base sheet on-the-miter is absent and the cumulative effect is not observed. • 2. Cleaning of welded surfaces ahead of the contact point from oxides and contaminations occur due to impact of plasma flow that leads to the dissociation of oxides and organic contaminations. Positive metal ions formed due to the dissociation of oxides and their ionization come back into the refined surface. Atoms of oxygen form elemental gaseous compounds (carbonic gas and water) which take away from standoff. • 3. Three-staging of formation of strong bonds between the atoms of welded metals is established: activation of contact surfaces; formation of physical contact; volume impact and plastic deformation behind the contact point.