SOME ASPECTS OF JOIN FORMATION DURING EXPLOSIVE WELDING Pervukhina O.L., Rihter D.V., Pervukhin L.B., Denisov I.V., Bondarenko S.Yu. Institute of structural Macrokinetics and Materials Sciences Russia

Scheme of explosion welding with formation of cumulative jet To obtain a join at explosion welding it is necessary to follow to next conditions: D < C o where: С о sound velocity in welded materials D is detonation velocity P ≥ P кр where: Р кр is a critical pressure in join Р is a pressure in join γ < γ кр where: γ is an angle of collision γ кр is a critical angle of collision Welded join after sudden stop of explosion welding where: U 0, δ 1 is velocity and thickness of general jet U c, δ с is velocity and thickness of cumulative jet moving to the right (reverse) U n, δ n is velocity and thickness of jet moving to the left

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

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

Method of “traps” where: 1 – welded plates, 2 – trap, 3 – explosive charge, 4 – detonator, 5 – sand Surfaces of “traps” after explosion welding of titanium with steel in argon Coating is absent, traces of mechanical treatment are visible. 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. Состав: Fe, Fe 3 N Material and sizesMedium of standoff Presence of particles on the surface of “trap” Base sheet (carbon steel) Clad sheet 09Г2С 30х1400х5900 Тр321ASTM 4х1500х6000 Airno 09Г2С 35х2800х2400 Титан Вт1-0 8х2900х3000 Argonno 09Г2С 35х500х2000 Титан Вт1-0 5х500х2000 AirНапылённый слой 50-70мкм

Schemes of explosion welding where: V 0 – plate velocity, γ – angle of collision, δL – next concerned element, а – zone of chemical reaction. Suggested scheme of explosion welding.Accepted scheme of explosion welding. 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. 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.

Dependence of middle thickness of cast impurities in join  2 and thickness of layer  1, extracting from welding surfaces on detonation velocity D (а); parameter r (  ) and standoff h св (b) (  k  calculation thickness of cumulative jet).

Zones singled out during join formation at explosion welding 1- zone of contact point, 2- zone of ahead of contact point and 3- zone of join formation. D – detonation velocity, V в - velocity of shock-compressed gas, V k – velocity of contact point. 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: Calculation of temperature into standoff Boltzmann’s equation

Experimental data testified to formation of plasma into standoff. 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 brightness gas temperature on detonation velocity Curve 1 – dependence of brightness temperature of gas clot on detonation velocity. Curve 2 – shock Hugoniot of air D, km/sТ к, КδМγL 50, cmL 100, cm 3,550008,92,551, ,265009,442,631, , ,352,81,211,42,2 Dependence of distance of melting beginning on parameters of gas flow where: L 50 и L 100 – 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. – №6. – С * - 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

Plasma 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. – №6. – С General view of surface after plasma-arc cleaning Method Energy density, Watt/m 2 Time of plasma influence, sec Thickness of moving off layer, μm Plasma-arc cleaning Shock plasma10 0,023-5

Formation of welded join.  h= 8 mm, D= 2500 m/s, V 0 = 400 m/s.  Time of plate flight to collision is 20х10 -6 sec,  Time of beginning of intense glowing of gas clot is 30-40х10 -6 sec. Overall is 50-60х10 -6 sec.  During all this time detonation passed mm that conformed to stabilization site sizes observed in practice at manufacture of bimetal. At pressure At explosion welding welding according to Lysak Our supposition and others 1. Formation of physical 1.Formation of physical 1. Activation and cleaning of contact. contact. surface. 2. Activation of surface. 2. Activation of surface. 2. Formation of physical contact. 3. Volume interaction Calculation of stabilization length at explosion welding

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.