Exploring the Versatile Applications of Explosion Welding

Exploring the Versatile Applications of Explosion Welding

Explosion Welding Process of Titanium-Steel Composite Plate

Titanium-steel composite plates are increasingly used in petrochemicals and pressure vessels. Equipment made of titanium-steel composite plates has a corrosion-resistant titanium inner layer and a high-strength steel outer layer.

The composite structure also has good thermal conductivity, overcoming shortcomings such as thermal stress, heat fatigue resistance, and pressure difference resistance, allowing it to work under more stringent conditions, while also significantly reducing equipment costs.

Therefore, titanium-steel composite plates have become indispensable structural materials in modern chemical industry and pressure vessel industry.

1. Installation of Titanium-Steel Composite Plate Explosion Welding

When explosion welding large-area titanium-steel composite plates, the parallel method is often used for installation, and the central detonation method is often used for detonation.

In a few cases, detonation is initiated in the middle of the long edge. Schematic diagrams of various installation processes are shown in Figure 8-8.

There are two projection views in the figure, representing the length and width directions of the plate respectively. Figures 8-8 a and 8-8 b represent different positions of the detonator placement; Figures 8-8 c to 8-8 e represent the detonator placement positions when there is high-speed detonation mixed explosives.

Figure 8-8 Schematic Diagram of Thick Titanium-Steel Composite Plate Installation

1- Detonator
2- Explosives
3- Cover Plate
4- Base Plate
A- High-Speed Mixed Explosives

2. Selection of Explosion Welding Parameters for Titanium-Steel Composite Plates

The welding parameters for typical large-size titanium-steel composite plates are shown in Tables 8-5 and 8-6. From an exhaust angle, the thicker and larger the cover plate, the lower the detonation speed of the explosive should be, and the central detonation method should be used.

To reduce and eliminate the influence of the detonator area, a certain amount of high-speed explosives are usually added under the detonator. When explosion welding large-area composite plates, to ensure gap support, a certain shape and number of metal spacers can be placed between the two plates.

In the case of explosion welding of large thick plate blanks, the gap column should be supported outside the base plate. To improve efficiency and better ensure welding quality, symmetric collision explosion welding process can be used to manufacture this composite plate blank, as shown in Figure 8-9.

Table 8-5 Welding Parameters for Explosive Welding of Large-Sized Titanium-Steel Composite Plates

Titanium Plate Size/mmSteel Plate Size/mmExplosivesWg/(g/cm²)h/mmBuffer LayerDetonation Method
TA1, 3 ×1100 ×2600Q390,18×1100×2600TNT1.75~37Asphalt + Steel PlateTriangle Lead from Short Side
TA5,2×1080×213013SiMnV,8×1100×2100TNT1.45Asphalt + Steel PlateExtend Short Side by 300mm
TA1,5×1800×1800Q235,25×1800×1800TNT1.53 ~ 203mm AsphaltDetonate at Center of Short Side
TA2,3×2000 ×2030Q235,20×2000×2030TNT1.53 ~253.6mm AsphaltDetonate at Center of Short Side
TA1,5×2050×205018MnMoNb,35×2050×20502 #2.8203.5mm AsphaltDetonate at Center of Short Side
TA2,1×1000×1500Q235,20×1500×200025 #1.53Lubricating GreaseCentral Detonation
TA2,3×1500×300020G,25×1500×300025 #2.26Water GlassCentral Detonation
TA2,4×1500×3000Q345,30×1500×300025#2.48Water GlassCentral Detonation
TA2,5×1500×3000Q345,35×1500×300025 #2.610Water GlassCentral Detonation

Table 8-6 Welding Parameters for Explosive Welding of Thick Titanium-Steel Composite Slabs

Titanium Material Model and Size/mmSteel Material Model and Size/mmType of Explosiveh2/mmh1/mmBuffer LayerDetonation Method
TA1,10×700 ×1080Q235,75×670×105025 #4412Lubricating GreaseAuxiliary Charge, Central Detonation
TA2,10×690×1040Q235,70×650×100042 #3512Water Glass
TA2,10×730×1130Q235,83x660x105042 #4012Lubricating Grease
TA2,12 ×690 ×1040Q235,70×650×100025 #5112Water Glass
TA2,12×620×1085Q235,60×570×105025 #5513Lubricating Grease
TA2, 8×1500 ×3000Q345,80×1500×300025 #4014Water Glass
TA2,10×1500×3000Q345,100×1500×300025 #5014Water Glass

Note: h1 and h2 respectively represent the small and large gaps between the cladding and the base plate during explosive welding using the angular method.

3. Microstructure of the Titanium-Steel Composite Plate Bonding Zone

Typically, the bonding zone of the titanium-steel composite plate presents a wavy structure, with the shape of the waves varying based on the welding parameters.

Different strengths and characteristics of explosive loads, different strengths and characteristics of metallic materials, and their interactions, result in bonding zone waves with different shapes and parameters (wavelength, amplitude, and frequency). Within a wave, different structural changes occur on the metal on both sides of the interface.

On the steel plate side, the closer to the interface, the more severe the grain stretching and fibrous plastic deformation. A structure of tiny sub-grains similar to recrystallization or fragmentation appears close to the interface.

On the titanium plate side, there isn’t the same type of plastic deformation shape and pattern as on the steel plate side. However, there are more or less special plastic deformation lines and plastic deformation structures of varying lengths and densities.

4. Mechanical Properties of the Titanium-Steel Composite Plate

The mechanical properties of the titanium-steel explosive composite plate mainly include shear strength and bending performance, as shown in Table 8-7. The shear strength of the TA2 cladding (hot-rolled state) is 490~539MPa, with an elongation rate of 20%~25%. The shear strength of the Q235 steel base plate (delivery state) is 445~470MPa, with an elongation rate of 22%~24%.

Figure 8-9 Schematic of Symmetrical Collision Explosion Welding Installation
a) Welding of equal-thickness plates
b) Welding of unequal-thickness plates

1- Detonator
2- Explosives
3- Double Plate
4- Base Plate
5- Ground (Base)
B- Spacing
α- Angle between two plates

Table 8-7 Mechanical Properties of Titanium-Steel Composite Plates

ConditionComposite Plate and Dimensions
/mm
Shear Strength
/MPa
Cold Bending
d=2t, 180°
HV
Inner BendOuter BendLean Layer
/Bonding Layer
/Base Layer
Explosive StateTA2-Q235,
(3+10)×110×1100
397GoodFracture347/945/279
Annealed StateTA2-20G,
(5+37)×900×1800
191GoodGood215/986/160

Explosion Welding of Zirconium Alloy-Stainless Steel Pipe Joint

To conserve scarce and valuable metal materials in nuclear engineering construction, and to reduce project costs, zirconium alloy pipes can be used within the reactor, while relatively cost-effective stainless steel pipes can be used outside the reactor.

Explosion welding effectively solves the welding problem of these two types of pipes with significantly different physical and chemical properties.

1. Explosion Welding Process of Composite Pipe

When welding a stainless steel pipe (base pipe) with dimensions of Φ50mm x 3.4mm and a zirconium alloy pipe (cladding pipe) with dimensions of Φ42mm x 1.5mm, the following explosion welding process can be adopted. Before welding, clean the welding surface of the stainless steel pipe and zirconium alloy pipe.

The stainless steel pipe’s inner surface requires a high roughness, and it is necessary to remove oil and impurities with acetone or alcohol, then rinse with water and air dry. The zirconium alloy pipe can be cleaned with a solution of 45% HNO3 + 5% HF + 50% H2O to remove surface oxide films, oil stains, and impurities.

The schematic installation of the zirconium alloy and stainless steel composite pipe is shown in Figure 8-10. During assembly, it should be assembled on a fixed fixture, the spacing should be well controlled, and the usual spacing is 0.7~0.8mm.

Then load the explosives, the amount of which also depends on the wall thickness of the zirconium alloy pipe, such as 65~70g for a wall thickness of 1mm, 75 ~85g for a wall thickness of 1.5~2.0mm, and 80~100g for a wall thickness of 2.0~3.0mm.

During explosion welding, the entire joint should be placed in a well-fixed mold. This mold plays a good role in shaping and should have sufficient strength. The welding parameters and joint mechanical properties of the explosion welding of stainless steel pipes and zirconium alloy pipes are shown in Table 8-8.

Figure 8-10 Schematic Diagram of the Installation of Zirconium Alloy and Stainless Steel Tube by Explosive Welding

1- Detonator
2- Explosive
3- Casing tube
4- Base tube
5- Mold
6- Retaining ring
7- Wooden plug
8- Base
9- Ground (Foundation)

After the explosion welding is completed, the welded joint should be cleaned or processed according to the process requirements.

Table 8-8 Welding Parameters and Joint Mechanical Properties of Explosion Welding of Stainless Steel Pipes and Zirconium Alloy Pipes

Zirconium Cladding Pipe Dimensions/mmStainless Steel Base Pipe Dimensions/mmAmount of TNT per Unit Area (g/cm)Spacing/mmHeat Treatment or Test ConditionRm/MPaBending Angle/ (°)
T/℃t/minInternal BendExternal Bend
Φ42.0×1.5×125Φ50.0×3.4×1200.50.63001440372
Φ42.0×1.5×125Φ50.0×3.4×1200.50.64001440404
Φ42.0×1.5×125Φ50.0×3.4×1200.50.655030149
Φ42.0×1.5×125Φ50.0×3.4×1200.50.660030149>100>100

2. Joint Structure and Mechanical Properties

In the case of zirconium alloy and stainless steel composite tubes, the joint area created by explosive welding exhibits a regular waveform. The metals on both sides of the interface undergo tensile and fibrous plastic deformation, with the severity of the deformation increasing closer to the interface.

The vortex zone at the wavefront gathers most of the molten metal formed during the explosive welding process, with a small amount remaining on the wave crest, measuring in micrometers. The product images of the composite tubes are shown in Figures 8-11.

Figure 8-11: Actual Photo of the Zirconium Alloy and Stainless Steel Composite Pipe

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