What is the manufacturing process of tungsten plate

The manufacturing process of tungsten plate is a fascinating and highly specialized field of metallurgy. Unlike common metals like steel or aluminum which can be melted and cast, tungsten's extremely high melting point (3422°C or 6192°F) makes traditional melt-processing impractical.

Therefore, the entire process is based on Powder Metallurgy.

Tungsten Plate Manufacturing Process

Here is a detailed, step-by-step breakdown of the manufacturing process for tungsten plate:

Process Overview: From Ore to Plate

The journey can be broadly divided into three major stages:

Powder Production: Creating high-purity tungsten metal powder from raw ore.

Consolidation & Sintering: Turning the loose powder into a solid, dense metal ingot.

Mechanical Working: Shaping the ingot into a plate through rolling and heat treatment.

Step 1: Raw Material Preparation & Powder Production

This is the chemical phase of the process, focused on refining the ore into pure metal powder.

Mining and Refining: Tungsten ore (typically Wolframite or Scheelite) is mined. It then undergoes a series of chemical processes to produce an intermediate compound called Ammonium Paratungstate (APT). This step purifies the tungsten and removes other elements from the ore.

Calcination to Oxide: The APT is heated in a process called calcination to produce high-purity Tungsten Trioxide (WO₃), a fine yellow powder.

(NH₄)₁₀(H₂W₁₂O₄₂)·4H₂O (APT) → 12WO₃ + 10NH₃ + 10H₂O

Hydrogen Reduction: The tungsten trioxide is then placed in a multi-zone furnace under a controlled atmosphere of flowing hydrogen gas. It is heated in stages to temperatures up to 1200°C. The hydrogen "reduces" the oxide, stripping away the oxygen atoms and leaving behind pure tungsten metal powder.

WO₃ + 3H₂ → W + 3H₂O

The final properties of the tungsten plate depend heavily on the characteristics of this initial powder, especially its particle size and purity.

Step 2: Consolidation and Sintering (Creating a Solid Ingot)

This is where the loose powder is transformed into a solid block of metal without melting it.

Pressing (Consolidation): The pure tungsten powder is loaded into a mold and subjected to extremely high pressure. The most common method is Cold Isostatic Pressing (CIP):

The powder is placed in a flexible, sealed mold (like a rubber bag).

This mold is submerged in a liquid-filled pressure vessel.

The liquid is pressurized to thousands of PSI, applying uniform pressure from all directions onto the powder.

This compacts the powder into a dense, but still fragile, block called a "green compact" or "green bar". It has enough strength to be handled carefully.

Sintering: This is the most critical step. The green compact is heated to an extremely high temperature, typically 2000°C to 3000°C, which is about 90% of its melting point.

Atmosphere: The heating is done in a protective atmosphere, usually pure, dry hydrogen, to prevent any oxidation.

Mechanism: At this high temperature, the individual tungsten particles don't melt, but they bond and fuse together through solid-state diffusion. The atoms migrate across the boundaries of the particles, causing the pores between them to shrink and close up.

Result: The bar shrinks significantly in size, its density increases dramatically (to about 92-96% of tungsten's theoretical density), and it transforms into a solid, strong, but brittle tungsten ingot or sinter bar.

Step 3: Mechanical Working (Forming the Plate)

The sintered ingot is hard and brittle at room temperature. To shape it into a plate and improve its mechanical properties, it must be worked at very high temperatures.

Hot Rolling:

Heating: The tungsten ingot is heated in a furnace to a working temperature between 1200°C and 1600°C. At this temperature, tungsten becomes more ductile and can be shaped without cracking.

Rolling: The glowing-hot ingot is passed repeatedly through a set of powerful rollers. Each pass reduces the thickness of the ingot and elongates it. This is a gradual process requiring many passes.

Microstructure Refinement: This hot working process is crucial. It breaks down the coarse, crystalline grain structure of the sintered ingot and realigns it into a finer, elongated ("wrought") structure. This significantly increases the plate's ductility and strength.

Annealing (Stress Relief):

Between rolling stages, the plate undergoes work hardening, becoming harder and more brittle.

To counteract this, it is periodically annealed—reheated to a specific temperature in a controlled atmosphere (hydrogen or vacuum).

Annealing relieves internal stresses and recrystallizes the grain structure, restoring some ductility so that it can be rolled further without fracturing.

Finishing Processes:

Warm/Cold Rolling: For thinner plates or specific surface finishes, some final rolling passes may be done at lower temperatures ("warm rolling").

Leveling/Straightening: The rolled plate is passed through leveling rollers to ensure it is perfectly flat.

Surface Conditioning: The surface may be ground, sandblasted, or chemically cleaned to remove any oxide layer and achieve the desired surface finish.

Cutting and Shearing: The large rolled sheets are cut to the final required dimensions of the tungsten plate.

Step 4: Quality Control

Throughout the process, rigorous quality control is essential. Final inspections include:

Dimensional Checks: Verifying thickness, width, length, and flatness against specifications.

Surface Inspection: Checking for cracks, scratches, or other defects.

Internal Integrity: Using ultrasonic testing to detect any internal voids or flaws.

Property Testing: Measuring density, hardness, and sometimes tensile strength to ensure the plate meets performance requirements.

Summary Flowchart

Tungsten Ore → Chemical Processing → Ammonium Paratungstate (APT) → Calcination → Tungsten Oxide (WO₃) → Hydrogen Reduction → Pure Tungsten Powder → Cold Isostatic Pressing → Green Compact → High-Temperature Sintering → Solid Tungsten Ingot → Hot Rolling → Tungsten Plate → Annealing & Finishing → Final Product