จุดหลอมเหลวของไทเทเนียมคืออะไร?

1. การแนะนำ

The equilibrium melting point of pure ไทเทเนียม (ของ) ที่ 1 บรรยากาศคือ 1668.0 องศาเซลเซียส (≈ 1941.15 เค, 3034.4 °F).

That single number is a crucial reference, but for engineering and production it is only the starting point: titanium exhibits an α→β allotropic transformation at ≈ 882 องศาเซลเซียส;
alloys and impurities produce solidus/liquidus ranges rather than a single point; and titanium’s extreme chemical reactivity at elevated temperatures forces manufacturers to melt and handle it in vacuum or inert environments.

This article explains the melting point in thermodynamic terms, shows how alloying and contamination alter melting/solidification behaviour, provides practical melting energy estimates and describes industrial melting technologies and process controls needed to produce clean, high-performance titanium and titanium-alloy products.

2. The physical melting point of pure titanium

3. Thermodynamics and kinetics of melting

• Thermodynamic definition: melting is the first-order phase transition at which Gibbs free energies of solid and liquid phases are equal.
  For a pure element at fixed pressure this is a sharply defined temperature (จุดหลอมเหลว).
• Latent heat: energy is absorbed as latent heat of fusion to break crystalline order; temperature does not rise during the phase change until melting is complete.
• Kinetics and undercooling: during solidification the liquid can remain below the equilibrium melting (ของเหลว) temperature — การระบายความร้อนต่ำเกินไป — which changes nucleation rates and microstructure (grain size, morphology).
  ในทางปฏิบัติ, the cooling rate, nucleation sites and alloy composition determine the solidification path and final microstructure.
• Heterogeneous vs homogeneous nucleation: real systems solidify by heterogeneous nucleation (on impurities, mold walls, or inoculants), so process cleanliness and mold design influence the effective solidification behavior.

4. Allotropy and phase behavior relevant to melting

• อัน ↔ β transformation: titanium has two crystal structures in the solid state: hexagonal close-packed (α-Ti) stable at low temperature and body-centred cubic (β-Ti) stable above the β-transus (~882 °C for pure Ti).
  This allotropic change is far below the melting point but affects mechanical behavior and microstructural evolution during heating and cooling.
• Implications: the existence of α and β phases means many titanium alloys are designed to exploit α, α+β, or β phase fields for required strength, toughness and processing response.
  The β transus controls forging/heat-treatment windows and influences how an alloy will behave as it approaches melting during processes such as welding or remelting.

5. How alloying, impurities and pressure affect melting/solidification

• โลหะผสม: most engineering titanium parts are alloys (Ti-6Al-4V, Ti-6Al-2Sn-4Zr-2Mo, ฯลฯ). These alloys show ของแข็ง→ของเหลว temperature intervals; some alloying additions raise or lower the liquidus and broaden the freezing range.
  Broader freezing ranges increase susceptibility to shrinkage defects and make feeding more difficult during solidification. Always use alloy-specific solidus/liquidus data for process setpoints.
• Interstitials & tramp elements: ออกซิเจน, nitrogen and hydrogen are not simple “melting point changers” but they strongly affect mechanical properties (oxygen and nitrogen raise strength but embrittle).
  Trace contaminants (เฟ, อัล, วี, ค, ฯลฯ) affect phase formation and melting behaviour. Small amounts of low-melting contaminants can create local melting anomalies.
• ความดัน: elevated pressure slightly raises the melting point (ความสัมพันธ์แบบคลาเปรอง). Industrial melting of titanium is done near atmospheric or under vacuum/inert gas;
  applied pressures in solidification (เช่น, in pressure casting) do not significantly change the fundamental melting temperature but can influence defect formation.

6. Melting Ranges of Common Titanium Alloys

Below is a clean, engineering-focused table showing การละลายทั่วไป (ของแข็ง→ของเหลว) ranges for commonly used titanium alloys.
Values are approximate typical ranges used for process planning and alloy comparison — always verify with the alloy supplier’s certificate of analysis or with thermal analysis (ดีเอสซี / cooling-curve) for the exact melt/processing setpoints of a particular batch.

7. Industrial melting and remelting methods for titanium

Because titanium is chemically reactive at elevated temperatures, its melting and remelting require special technologies and atmospheres to avoid contamination and embrittlement.

Common industrial methods

• ส่วนโค้งสูญญากาศ remelting (ของเรา): consumable electrode remelting under vacuum; widely used to refine chemistry and remove inclusions in high-quality ingots.
• ลำแสงอิเล็กตรอน (อีบี) ละลาย: performed under high vacuum; offers extremely clean melts and is used for high-purity ingots and additive-manufacturing feedstock production.
• Plasma Arc Melting / Plasma Hearth: vacuum or controlled atmosphere plasma systems are used for alloy production and reclamation.
• Induction skull melting (ISM, skull melting): uses an induced current to melt the metal inside a water-cooled copper coil; a thin solid “skull” of metal forms and protects the melt from crucible contamination—useful for reactive metals including titanium.
• Cold hearth melting / consumable electrode EB or VAR for titanium sponge and scrap: allows removal of high-density inclusions and control of tramp elements.
• Powder production (gas-atomization) for AM: for powder metallurgy and additive manufacturing, remelting and gas atomization are performed in inert atmospheres to produce spherical, low-oxygen powders.
• การหล่อการลงทุน: Requires ceramic molds (resistant to 2000℃+) and molten titanium at 1700–1750℃. The high melting point increases mold cost and cycle time, limiting casting to small, ส่วนประกอบที่ซับซ้อน.

Why vacuum/inert atmospheres?

• Titanium reacts rapidly with oxygen, nitrogen and hydrogen at elevated temperatures; those reactions produce oxygen/nitrogen-stabilized phases (เปราะ), การเปราะ, and gross contamination.
  Melting in vacuum or high-purity argon prevents these reactions and preserves mechanical properties.

8. Processing challenges and mitigation

Reactivity and contamination

• Oxidation and nitridation: at melting temperatures titanium forms thick, adherent oxides and nitrides; these compounds reduce ductility and increase inclusion count.
  การบรรเทาผลกระทบ: melt under vacuum/inert gas; use skull melting or protective fluxes in specialized processes.
• Hydrogen uptake: causes porosity and embrittlement (hydride formation). การบรรเทาผลกระทบ: dry charge materials, การละลายสูญญากาศ, and controlling furnace atmosphere.
• Tramp elements (เฟ, ลูกบาศ์ก, อัล, ฯลฯ): uncontrolled scrap can introduce elements that form brittle intermetallics or change melting range — use strict scrap control and analytical checks (สศส).

Safety issues

• Molten titanium fires: molten titanium reacts violently with oxygen and can burn; water contact can produce explosive steam reactions.
  Special training and strict procedures are required for handling, pouring and emergency response.
• Dust explosions: titanium powder is pyrophoric; handling metal powders requires explosion-proof equipment, grounding, and specific PPE.
• Fume hazards: high-temperature processing can evolve hazardous fumes (oxide and alloy element vapors); use fume extraction and gas monitoring.

9. Measurement and quality-control of melting and solidification

• Thermal analysis (DSC/DTA): differential scanning calorimetry and thermal arrest analysis measure solidus and liquidus of alloys precisely and support control of melt and casting setpoints.
• Pyrometry & เทอร์โมคัปเปิล: use appropriate sensors; correct for emissivity and surface oxides when using pyrometers. Thermocouples must be protected (refractory sleeves) and calibrated.
• การวิเคราะห์ทางเคมี: สศส (optical emission spectrometry) and LECO/O/N/H analyzers are essential to track oxygen, nitrogen and hydrogen content and overall chemistry.
• การทดสอบแบบไม่ทำลาย: เอ็กซ์เรย์, ultrasonic and metallography to check for inclusions, porosity and segregation.
  สำหรับส่วนประกอบที่สำคัญ, microstructure and mechanical testing follow standards (มาตรฐาน ASTM, เอเอ็มเอส, ไอเอสโอ).
• การบันทึกกระบวนการ: record furnace vacuum levels, melt temperature profiles, power input and argon purity to maintain traceability and repeatability.

10. การวิเคราะห์เปรียบเทียบกับโลหะและโลหะผสมอื่นๆ

The data are representative industrial values suitable for technical comparison and process selection.

11. Practical implications for design, processing and recycling

• ออกแบบ: melting point places titanium in high-temperature structural applications, but design must account for costs and joining limitations (welding vs mechanical fastening).
• กำลังประมวลผล: การละลาย, การคัดเลือกนักแสดง, welding and additive manufacture all require controlled atmospheres and careful material control.
  For cast parts, vacuum investment casting or centrifugal casting in inert atmosphere is used when needed.
• การรีไซเคิล: titanium scrap recycling is practical but requires segregation and reprocessing (ของเรา, อีบี) to remove tramp elements and control oxygen/nitrogen levels.

12. บทสรุป

The melting point of titanium (1668.0 องศาเซลเซียส (≈ 1941.15 เค, 3034.4 °F) for pure titanium) is a fundamental property rooted in its atomic structure and strong metallic bonding, shaping its role as a high-performance engineering material.

ความบริสุทธิ์, องค์ประกอบการผสม, and pressure modify its melting behavior, enabling the design of titanium alloys tailored to diverse applications—from biocompatible medical implants to high-temperature aerospace components.

While titanium’s high melting point poses processing challenges (requiring specialized melting and welding technologies), it also enables service in environments where lightweight metals (อลูมิเนียม, แมกนีเซียม) fail.

Accurate melting point measurement (via DSC, laser flash, or electrical resistance methods) and a clear understanding of influencing factors are critical for optimizing titanium processing, ensuring material integrity, and maximizing performance.

 

คำถามที่พบบ่อย

Does alloying change titanium’s melting point significantly?

ใช่. Titanium alloys show solidus/liquidus ranges rather than a single melting point.

Some alloys melt slightly below or above the element depending on composition. Use alloy-specific data for processing.

Is titanium magnetic?

เลขที่. Pure titanium and the common titanium alloys are not ferromagnetic; they are weakly paramagnetic (very low positive magnetic susceptibility), so they are only negligibly attracted to a magnetic field.

Does titanium rust?

No — titanium does not “rust” in the iron-oxide sense. Titanium resists corrosion because it rapidly forms a thin, สานุศิษย์, self-healing titanium-oxide (TiO₂) passive film that protects the metal from further oxidation.

Why must titanium be melted in vacuum or inert gas?

Because molten titanium reacts vigorously with oxygen, nitrogen and hydrogen. Those reactions form brittle compounds and inclusions that degrade mechanical properties.

What melting methods are preferred for aerospace-grade titanium?

High-purity aerospace titanium is typically produced by ของเรา (vacuum arc remelting) หรือ อีบี (ลำแสงอิเล็กตรอน) การละลาย to control chemistry and inclusions.

For additive manufacturing feedstock, EB melting and gas atomization in controlled atmospheres are common.

How much energy does it take to melt titanium?

A rough theoretical estimate (ideal, no losses) เป็น ≈1.15 MJ per kg to heat 1 kg from 25 °C to liquid at 1668 องศาเซลเซียส (using cp ≈ 520 J·kg⁻¹·K⁻¹ and latent heat ≈ 297 กิโลเจ·กก.⁻¹).

Real energy consumption is higher because of losses and equipment inefficiencies.