Thick Plate Rolling Method for Titanium Steel Composite Plate
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Titanium steel composite plate combines a corrosion resistant titanium surface with a structural steel base, so the finished component behaves like titanium where it faces the medium and like steel where it carries the load. The thick plate rolling route builds that combination by roll bonding rather than by casting, and each stage of the sequence has a clear purpose: keep the interface clean, bring the two surfaces into intimate contact under heat and pressure, and then reduce the pack to the ordered thickness.
Building the Layered Assembly
The process starts by assembling the titanium plate, which becomes the cladding or composite material, with the steel plate, which becomes the base material, into one embedded slab. A suitable intermediate insert is placed between the titanium plate and the steel. Its role is to keep titanium and iron apart during heating, because a direct titanium to iron interface readily forms brittle intermetallic phases that destroy toughness and shear strength. The assembled pack is then sealed by electron beam welding under high vacuum, so that the gap between the two plates is evacuated and the joint line cannot pick up oxygen, nitrogen or moisture during the heating that follows.
Heating and Roll Bonding on a Thick Plate Mill
Once sealed, the pack is charged into a heating furnace and brought to rolling temperature. The pack is then rolled on the thick plate rolling mill, where force rolling reduces the section and presses the titanium and steel surfaces together hard enough to create a continuous metallurgical bond across the whole interface. Rolling continues until the pack reaches the required thickness. Because the bond is produced by deformation in the roll bite, the process depends on adequate reduction in the first passes, uniform heating and a correctly sized pack for the mill stand.
Cutting the Periphery and Separating the Plates
After rolling, the periphery of the pack is cut away, which removes the sealed edge region where the weld and the insert can affect bond quality. The pack is then separated into two boards. Each rolling pack therefore yields two clad plates, one from each face, which is one reason the route is efficient for volume production. The composite plate can continue to be hot rolled until the plate thickness reaches about 4 mm, so the same bonded slab can serve both heavy plate and thinner gauges.
Roll Bonding Compared with Explosive Welding
The sequence above is a hot roll bonding process. It is sometimes described as an explosive composite method, but that description is not accurate: the bond here is created by vacuum sealing, heating and rolling, with no detonation involved. Explosive welding is a separate route in which an angled high velocity impact forms the bond at ambient temperature and produces a characteristically wavy interface. In practice the two routes are complementary, because many plants use explosive welding to produce an initial clad slab that is subsequently hot rolled to final thickness.
| Item | Hot roll bonding | Explosive welding |
|---|---|---|
| Bond formation | Sealed pack heated and rolled | Angled high velocity impact at ambient temperature |
| Interface shape | Flat to slightly wavy | Distinctly wavy |
| Cladding thickness | Suits a wide range when reduction is adequate | Suits relatively thicker cladding layers |
| Plate size | Limited by furnace and mill capacity | Large single plates can be produced |
| Further rolling | Composite can be hot rolled down to about 4 mm | Usually supplied as welded, or rolled afterwards |
Inspection and Acceptance of the Bond
Bond quality is verified before the plate is released. Ultrasonic examination of the clad plate is carried out in line with ASTM A578/A578M, which defines the scanning method and the acceptance levels for laminations and unbonded areas, while ASTM B898 covers the specification of reactive and refractory metal clad plate and therefore the titanium clad product itself. Alongside the ultrasonic survey, producers check shear or tensile strength across the interface, cladding thickness and its tolerance, overall dimensions and flatness, and surface condition of the titanium face. Edge regions and the area close to the seal weld receive particular attention, because that is where incomplete bonding is most likely to appear.
Frequently Asked Questions
Q: What is titanium steel composite plate?
It is a clad plate in which a titanium layer is bonded to a steel base plate, so the part gains titanium corrosion resistance on the working face while the steel carries the structural load.
Q: Why is the pack welded by electron beam under high vacuum?
The vacuum seal removes air and moisture from the gap between the plates and prevents oxygen, nitrogen and hydrogen from contaminating the interface during heating.
Q: What is the intermediate insert for?
It separates titanium from steel at the bond line and limits the formation of brittle intermetallic phases that would reduce toughness and shear strength.
Q: How does one rolling pack produce two plates?
The pack is trimmed around the periphery and then separated into two boards, giving one clad plate from each face of the assembly.
Q: Is this the same as explosive welding?
No. The rolling method bonds the plates by heating and rolling a sealed pack, whereas explosive welding uses an angled high velocity impact. The two methods are often combined.
Q: Which standards apply to the clad plate?
ASTM B898 covers reactive and refractory metal clad plate, including titanium clad product, and ASTM A578/A578M defines ultrasonic examination and acceptance levels for the bond.
