Technical knowledge
Welding titanium: shielding, contamination and why colour matters
Why titanium welds need primary, trailing and backing gas shielding, what weld colour tells you about contamination, how to control iron and interstitial pickup, and the examination steps that verify a clean weld.
What the colour of a titanium weld tells you
| Colour | Interpretation | Action |
|---|---|---|
| Bright silver | Effective shielding | Acceptable |
| Light straw | Minimal contamination | Often acceptable, confirm against the specification |
| Dark straw or bronze | Increasing contamination | Usually remove and reweld |
| Blue or purple | Significant contamination | Cut out and reweld |
| Grey or white powdery | Severe contamination, brittle layer | Cut out and reweld |
The three shielding zones
- Primary shielding from the torch, covering the weld pool.
- Trailing shielding following the torch, protecting the hot solidified metal as it cools below the reactive range.
- Backing shielding on the root side, usually argon purge with a verified oxygen level.
Tip Most titanium weld defects are shielding defects. If a weld is discoloured, check the gas coverage, the purge dam integrity and the hose condition before changing any welding parameter.
Contamination sources that are easy to miss
- Carbon steel swarf and tools. Embedded iron particles become corrosion initiation sites.
- Marking crayons and paints. Chloride and sulphur bearing markers are a known cracking risk.
- Handling with bare or contaminated gloves. Oils leave carbon residue.
- Grinding wheels shared with steel. Cross contamination is immediate and invisible.
- Moisture and grease in the joint. Introduces hydrogen and oxygen.
Verification and repair
Clean before welding with a chloride free solvent, use dedicated stainless or titanium tools, and examine the finished weld visually for colour and then by dye penetrant examination. Radiography is used where the design requires volumetric examination. Where discoloured welds are found, remove the affected metal completely before rewelding; grinding the surface smooth without removing the contaminated layer leaves a brittle zone behind.
Questions about this topic
Why can titanium not be welded in open air?
Above roughly 400 C it absorbs oxygen and nitrogen from the air, forming a hard brittle layer that cracks under service stress. Shielding is not optional; it is the fundamental requirement of the process.
Can I grind off a discoloured weld and accept it?
No. The contaminated layer extends into the metal and along the heat affected zone. The affected area must be cut out completely and rewelded with corrected shielding.
Does titanium need preheat?
No. Preheat is not required and increases the time in the reactive temperature range, which makes shielding more difficult. Cleanliness and shielding are the controls that matter.
Questions about our products
What products does Hangbo Alloy supply?
Four product families, all available in nickel-based alloys, titanium, duplex and special stainless steel: flanges, butt weld pipe fittings, elbows, and seamless tube and pipe. Flanges cover weld neck, long weld neck, slip-on, blind, socket weld, threaded and lap joint patterns. Fittings and elbows cover concentric and eccentric reducers, equal and reducing tees, caps, stub ends, and 45°, 90° and 180° returns in both long and short radius, plus 3D and 5D bends for piggable lines. Seamless tube and pipe is supplied cold drawn or hot finished from 6 mm to 630 mm outside diameter.
Which alloy grades are available for these products?
More than 90 grades are published in our grade library. The most requested are Inconel 625, 718, 600 and X-750, Hastelloy C-276, C-22 and B-2, Monel 400 and K-500, Incoloy 800H, 825 and 925, duplex 2205 and super duplex 2507, 316L, 904L and 254SMO stainless steel, and titanium Grade 2 and Grade 5. Nickel-based grades can also be supplied with VIM plus ESR double melting where cleanliness or fatigue life is critical.
What sizes, wall thicknesses and pressure classes can you supply?
Flanges run from NPS ½ to NPS 24 to ASME B16.5 and from NPS 26 to NPS 60 to ASME B16.47 Series A or B, in pressure classes 150 through 2500. Butt weld fittings and elbows run from NPS ½ to NPS 48 (DN 15 to DN 1200) in wall thickness Schedule 5S through XXS. Seamless tube and pipe covers 6 mm to 630 mm outside diameter, in random lengths of about 5 to 7 metres or fixed lengths up to 12 metres. Non-standard and intermediate sizes are quoted on request.
Which material and dimensional standards do you work to?
Forged flanges to ASTM B564, B381 and A182 with dimensions to ASME B16.5 and ASME B16.47. Butt weld fittings and elbows to ASTM B366 and A403 with dimensions to ASME B16.9 and MSS SP-43. Seamless tube and pipe to ASTM B444, B423, B622, B163, B167, B861, A312, A213 and A790. Marking follows MSS SP-25 and the applicable product standard. If your project is governed by EN, DIN, JIS or a company specification, send the document and we will confirm equivalence before quoting.
Is there a minimum order quantity?
There is no minimum for standard sizes and grades held in stock, and prototypes, spares and small trial batches are accepted. Made-to-order melts and special forgings carry a minimum weight that depends on the alloy and the route, typically from about 500 kg for special grades.
What inspection and certification is issued with the goods?
Every shipment carries an EN 10204 3.1 mill test certificate quoting the actual chemical and mechanical results for the specific heat lot, together with dimensional records and heat treatment data where applicable. Testing is carried out in house by optical emission spectrometry, tensile, impact and hardness testing, plus ultrasonic and eddy current examination, with hydrostatic pressure and intergranular corrosion testing to ASTM G28 or A262 Practice E where the specification requires it. Third party inspection by SGS or another recognised agency can be arranged, and their report is issued alongside the shipment.
What are typical lead times?
Standard stock items ship within days. Common production grades such as Inconel 625 or duplex 2205 are typically a few weeks. Special chemistries, larger forgings and items that require third party inspection take longer and are quoted individually against the requirement.
How are the products packed for export?
Flanges and fittings receive a rust preventive coating, are individually wrapped and are packed in plywood cases secured with steel banding. Tube ends are capped and bundles are strapped. Packing lists quote heat numbers so every case can be cross-checked against the mill certificate on arrival. We quote EXW, FOB, CFR, CIF and DAP, and mixed-alloy orders can be consolidated into one shipment with a single documentation package.
How do I request a quotation or a sample?
Send the grade or UNS number, the dimensions including schedule or wall thickness, the governing material and dimensional standards, quantity, any heat treatment or NDT scope and the certificate type you need; a drawing is ideal for special flanges and fittings. Email demi@nickel-alloy.com or message us on WhatsApp +86 15618279078 and we normally issue a formal quotation within 24 hours on working days. Samples and previous test reports can be arranged before the first order.
Talk to an engineer
Share your duty conditions and we will shortlist candidate alloys within one working day.