Zhuojin Pipe Fitting Co., LtdGTAW Welding of Blast Furnace Copper Spiral Tuyeres
Literature Overview
This paper by Yang Daxue, published in 1990 in the journal "Welding," describes the gas tungsten arc welding (GTAW) process development for blast furnace purple copper (electrolytic copper) spiral tuyeres. Produced at the Southern Machinery Factory of Ansteel Mechanical Manufacturing Company, this work addresses a critical component in iron and steelmaking operations where the tuyere is the nozzle through which air is injected into the blast furnace to support combustion of coke.
Technical Content and Process Analysis
The spiral tuyere is a complex component that combines a copper body with a spiral channel design to optimize air distribution and wear resistance. The selection of GTAW for this application is well-founded, as this process provides:
- Excellent weld quality with minimal spatter, which is critical for copper components where spatter can contaminate the weld and reduce electrical and thermal conductivity.
- Precise heat input control, essential for preventing excessive grain growth and softening in copper, which has a relatively low melting point compared to steel.
- Good weld penetration with minimal dilution, maintaining the purity and properties of the copper base metal.
Key process considerations for copper GTAW include:
| Parameter | Typical Range | Notes |
|---|---|---|
| Shielding gas | Pure argon or Ar-He mixture | High argon content for stability |
| Welding current | 150-300 A DCEN | Depends on thickness |
| Travel speed | 150-400 mm/min | Slower for thicker sections |
| Preheat | 150-300 C | To reduce thermal stress |
| Interpass temperature | Below 200 C | To control grain growth |
| Wire diameter | 1.6-3.2 mm | Matched to current level |
The spiral geometry of the tuyere presents unique welding challenges. The varying wall thickness along the spiral channel requires careful adjustment of welding parameters to maintain consistent penetration and avoid burn-through in thin areas while ensuring full fusion in thicker sections. The geometry also limits access for welding torches and filler wire feeding, requiring specialized fixture design and possibly robotic or semi-automated welding setups.
Engineering Practice and Quality Control
Blast furnace tuyeres operate under extreme conditions: high temperatures (exceeding 1500 C at the throat), abrasive gas flow, and significant thermal cycling. The weld quality directly affects tuyere service life and furnace operational reliability. Therefore, rigorous quality control measures are essential:
- Visual inspection of all welds for proper bead geometry, no undercut, and no porosity.
- Non-destructive testing using radiographic testing (RT) or ultrasonic testing (UT) to detect internal defects.
- Penetrant testing (PT) for surface-breaking defects, particularly at the spiral channel transitions.
- Hardness testing to verify that the weld and HAZ have not been excessively softened.
- Hydrostatic testing to verify leak-tightness of the assembled tuyere.
Study Insights and Reflections
This paper, though brief, addresses a practically important welding application in the iron and steel industry. Copper spiral tuyeres are critical components whose failure can lead to unplanned furnace shutdowns, resulting in significant production losses. The selection and optimization of GTAW for this application demonstrates sound engineering judgment.
The challenges of welding copper, including its high thermal conductivity, low melting point, and susceptibility to oxidation, require careful process control. The use of GTAW with appropriate shielding gas and controlled heat input is the industry standard for copper welding, and this paper confirms its applicability to the complex spiral tuyere geometry.
For engineers working on similar copper component fabrication, the key lessons from this paper are the importance of process optimization for geometrically complex parts, the need for rigorous quality control, and the value of systematic welding procedure development. The experience gained in welding blast furnace tuyeres can be transferred to other high-performance copper component applications in the metallurgical industry.