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 < Cowhere: Со sound velocity in welded materials D is detonation velocity

P ≥ Pкрwhere: Ркр is a critical pressure in join Р is a pressure in join

γ < γкрwhere: γ is an angle of collision

γкр is a critical angle of collision Welded join after sudden stop of explosion welding

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

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 argonCoating 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, Fe3NMaterial and sizes Medium of

standoffPresence of particles on the surface of “trap”

Base sheet(carbon steel)

Clad sheet

09Г2С30х1400х5900

Тр321ASTM4х1500х6000

Air no

09Г2С35х2800х2400

Титан Вт1-08х2900х3000

Argon no

09Г2С35х500х2000

Титан Вт1-05х500х2000

Air Напылённый слой

50-70мкм

Schemes of explosion welding

where: V0 – 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 hсв (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, Vв- velocity of shock-compressed gas, Vk – velocity of contact point.

R

VT

3

2

КT

727031,83

029,025002

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:

RT

V3

Calculation of temperature into standoffBoltzmann’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 velocityCurve 1 – dependence of brightness temperature of gas clot on detonation velocity . Curve 2 – shock Hugoniot of air

D, km/s Тк, К δ М γ L50, cm L100, cm

3,5 5000 8,9 2,55 1,24 30 46

4,2 6500 9,44 2,63 1,23 16 22

4,5 8300 10,35 2,8 1,21 1,4 2,2

Dependence of distance of melting beginning on parameters of gas flow

where: L50 и 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.

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. – 1980. - №6. – С.69-73

General view of surface after plasma-arc cleaning

MethodEnergy density,Watt/m2

Time of plasma

influence, sec

Thickness of moving off layer,

μm

Plasma-arc cleaning 103 5-10 200-300

Shock plasma 1010 0,02 3-5

Formation of welded join.

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 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 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.