How to distinguish T1, T2 and T3 copper - Knowledge

What Is the Difference in Copper Content Between T1 Copper, T2 Copper, and T3 Copper?

The most fundamental difference between T1 copper, T2 copper, and T3 copper is their copper (Cu + Ag) content:

Grade	Minimum Copper + Silver Content	Maximum Impurities
T1 copper	99.95%	0.05%
T2 copper	99.90%	0.10%
T3 copper	99.70%	0.30%

T1 copper has the highest purity and is the purest grade. T2 copper is a copper-silver alloy with no phosphorus requirement. T3 copper has the lowest purity and highest impurity content.

T1 copper tubing

How Do T1 Copper, T2 Copper, and T3 Copper Compare in Tensile Strength?

The mechanical properties differ significantly among the three grades:

Grade	Tensile Strength (MPa)	Elongation After Fracture	Hardness (HBS)
T1 copper	≥295	45-50%	35-40
T2 copper	≥195	45-50%	35-40
T3 copper	≥210	45-50%	35-40

T1 copper offers the highest tensile strength (≥295 MPa), making it suitable for applications requiring mechanical strength. T2 copper has the lowest tensile strength among the three. T3 copper falls in between.

What Are the Conductivity and Resistivity Differences Between T1 Copper, T2 Copper, and T3 Copper?

T1 copper has the best electrical and thermal conductivity because it contains the fewest impurity elements that reduce conductivity. A small amount of oxygen in T1 copper has little effect on its conductivity or processing performance. T1 copper can be used for light welding and fiber welding.

T2 copper also has good electrical and thermal conductivity, with low impurity content. However, T2 copper is susceptible to "hydrogen disease" (hydrogen embrittlement) when processed in high-temperature reducing atmospheres.

T3 copper has the lowest conductivity among the three grades. It contains more impurities that reduce conductivity and has higher gas content than T2 copper. T3 copper is more prone to hydrogen disease and cannot be processed (annealed, welded, etc.) in high-temperature reducing atmospheres.

Resistivity ranking (lowest to highest): T1 copper (lowest) → T2 copper → T3 copper (highest)

What Is Hydrogen Disease (Hydrogen Embrittlement) in T2 Copper and T3 Copper?

Hydrogen disease, also known as hydrogen embrittlement, occurs when copper containing oxygen is heated in a reducing atmosphere containing hydrogen. The hydrogen reacts with copper oxide to form water vapor, which creates internal pressure and causes cracking.

T2 copper: Susceptible to hydrogen disease. Use caution when annealing or welding T2 copper in reducing atmospheres.

T3 copper: More susceptible to hydrogen disease than T2 copper due to higher oxygen content. Do not anneal, weld, or use T3 copper in high-temperature reducing atmospheres above 370°C.

T1 copper: Less susceptible due to higher purity and lower oxygen content.

For applications involving welding or high-temperature processing in reducing atmospheres, specify T1 copper or oxygen-free copper (TU1/TU2) instead of T2 or T3 copper.

What Are the Best Applications for T1 Copper, T2 Copper, and T3 Copper?

Grade	Best Applications	Limitations
T1 copper	High-conductivity electrical components, light welding, fiber welding, conductive parts requiring maximum purity	Higher cost
T2 copper	General electrical and thermal applications, brazing, soldering, conductive components	Avoid high-temperature reducing atmospheres
T3 copper	Structural materials (gaskets, rivets, nozzles, conduits), electrical lighting parts, less important conductive components	Not suitable for welding or annealing in reducing atmospheres; lower conductivity

T3 copper is primarily used as a structural material rather than for high-conductivity applications. Common T3 copper products include electrical lighting parts, gaskets, rivets, nozzles, and various conduits.

What Is the Difference Between Ordinary Red Copper, Oxygen-Free Copper, and Deoxidized Copper?

Chinese red copper (pure copper) processing materials are divided into four categories:

Category	Grades	Key Characteristics
Ordinary red copper	T1, T2, T3	Standard pure copper with varying purity levels
Oxygen-free copper	TU1, TU2, high-purity vacuum OFC	No hydrogen embrittlement, highest conductivity
Deoxidized copper	TUP, TUMn	Phosphorus or manganese added for deoxidation
Special copper	Arsenic copper, tellurium copper, silver copper	Small alloying additions for specific properties

For highest purity applications (audio equipment, vacuum electronic devices, cables), specify oxygen-free copper with 99.995% purity or higher, such as:

LC-OFC (Linear Crystalline Oxygen-Free Copper): purity ≥99.995%

OCC (Single Crystal Oxygen-Free Copper): purity ≥99.996%

UP-OCC (Ultra-Pure Copper by Ohno Continuous Casting): no directionality, extremely low electrical impedance, ideal for high-speed signal transmission

FAQ

Q1: What is the exact copper content difference between T1 copper and T2 copper?
T1 copper has minimum 99.95% copper + silver content. T2 copper has minimum 99.90% copper + silver content. The 0.05% difference affects conductivity, price, and susceptibility to hydrogen embrittlement.

Q2: What is the tensile strength of T1 copper compared to T3 copper?
T1 copper has tensile strength ≥295 MPa. T3 copper has tensile strength ≥210 MPa. T1 copper is stronger by approximately 85 MPa.

Q3: What ASTM grade is equivalent to T1 copper?
T1 copper is approximately equivalent to ASTM C10200 (oxygen-free copper). However, confirm specific requirements with your supplier, as exact equivalence varies by application.

Q4: What is the ASTM equivalent of T2 copper?
T2 copper is equivalent to ASTM C11000 (electrolytic tough pitch copper). This is the most common pure copper grade for electrical applications worldwide.

Q5: What is the ASTM equivalent of T3 copper?
T3 copper does not have a direct ASTM equivalent due to its lower purity. For applications specifying T3 copper, ASTM C12500 (fire-refined copper) may be considered.

Q6: Can T2 copper be welded without hydrogen embrittlement risk?
T2 copper can be welded, but it is susceptible to hydrogen embrittlement when welded in reducing atmospheres. Use proper shielding gas and avoid high-temperature hydrogen-containing environments. For critical welded joints, specify T1 copper or oxygen-free copper (TU1/TU2).

Q7: What is hydrogen disease in T3 copper, and how can it be prevented?
Hydrogen disease is cracking caused by hydrogen reacting with oxygen in the copper. T3 copper has higher oxygen content and is more susceptible. Prevent by: (1) avoiding welding or annealing T3 copper in reducing atmospheres, (2) using T1 or oxygen-free copper for welded components, and (3) keeping processing temperatures below 370°C in hydrogen-containing environments.

Q8: Is T3 copper suitable for electrical wiring applications?
Not recommended. T3 copper has lower conductivity due to 0.30% maximum impurities. For electrical wiring, specify T1 copper (99.95%) or T2 copper (99.90%) instead.

Q9: What is the recrystallization temperature of T3 copper?
The recrystallization temperature of T3 copper is 200-280°C. This is important for annealing processes. Exceeding this temperature range during annealing can cause unwanted grain growth.

Q10: What is the difference between ordinary T3 copper and oxygen-free copper (TU1/TU2)?
Ordinary T3 copper has 99.70% minimum copper content and is susceptible to hydrogen embrittlement. Oxygen-free copper (TU1/TU2) has 99.95-99.97% minimum copper content, no hydrogen embrittlement, higher conductivity, and better weldability. Oxygen-free copper is used for high-end electronics and vacuum devices.

Q11: Can T3 copper be used for cryogenic (low temperature) applications?
Yes. T3 copper actually increases in strength at temperatures below -250°C. However, verify the specific low-temperature requirements with your engineer, as impact properties may also change.

Q12: What are OCC and UP-OCC copper, and how do they compare to T1 copper?
OCC (Single Crystal Oxygen-Free Copper) and UP-OCC (Ultra-Pure Copper by Ohno Continuous Casting) are ultra-high-purity coppers with 99.996% minimum purity. They have no grain directionality, extremely low electrical impedance, and superior signal transmission. T1 copper (99.95%) is lower purity and does not have single-crystal structure. For high-end audio or high-speed data cables, specify OCC or UP-OCC instead of T1 copper.