Ferro Titanium for Chemical Processing Equipment Grades
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Chemical processing equipment is bought against a service description rather than a grade name: the medium, its concentration, the operating temperature, the presence of chlorides or fluorides, and the way the vessel is cleaned between campaigns all decide which alloy survives. Ferro titanium enters the picture at the very start of that decision chain, because it is the master alloy that puts controlled titanium into the steels and alloys from which reactors, columns, tube bundles, liners, valves and storage tanks are built.
Why Ferro Titanium Sits Behind Chemical Plant Materials
Ferro titanium is an iron-titanium master alloy produced by aluminothermic reduction and supplied in grades carrying roughly 25% to 75% titanium. Its function in the melting shop is to introduce titanium into a heat at a level and recovery that cannot be achieved reliably with pure metal, and to do so without loading the bath with unwanted residual elements. That function matters to chemical processing equipment because titanium is used in two separate ways in a process plant.
The first use is as a stabilizer in austenitic stainless steel. Titanium-stabilized grades keep titanium in the finished steel so that it combines with carbon and prevents chromium depletion at grain boundaries, which is what allows reactors, columns, piping and tube bundles to be welded and then operated at elevated temperature without falling victim to intergranular corrosion. The second use is as a structural metal: commercially pure titanium and its alloys form the shells, liners, coils, tube sheets, piping and internals of equipment handling chlorides, hypochlorites, oxidizing acids and seawater-based process streams. A titanium-stabilized stainless vessel and a titanium-lined reactor may look very different in the fabricator's shop, but both depend on the chemistry of the titanium unit that was charged to the melt.
Process Media and the Corrosion Map for Titanium Equipment
Grade selection for chemical equipment should be driven by the medium, not by habit. The table below summarises the usual direction of travel for titanium-bearing equipment; each entry assumes that the final choice is confirmed by the design conditions and, where the service is marginal, by corrosion testing under representative conditions.
| Process medium | Usual titanium grade direction | What drives the decision |
|---|---|---|
| Seawater, neutral chloride solutions, cooling water | Grade 2 (UNS R50400) | Stable passive film in oxygenated neutral chloride; wall thickness governed by design rather than corrosion allowance |
| Oxidizing acids such as nitric acid | Grade 2 (UNS R50400) | Oxidizing conditions reinforce the passive film, so the unalloyed grades perform well |
| Dilute reducing acids such as sulphuric or hydrochloric acid | Grade 7 (UNS R52400) | The small palladium addition of about 0.12-0.25% stabilizes the film where reducing conditions would otherwise cause rapid attack |
| Hot brine, salt solutions, crevice-prone geometries | Grade 12 (UNS R53400) | Molybdenum and nickel additions improve crevice corrosion resistance where deposits or gasketed joints create local chemistry |
| Caustic and alkaline process streams | Grade 2 with temperature review | Titanium resists alkaline media but hydrogen pickup risk rises with temperature, so the service envelope must be qualified |
| Fluoride-bearing streams and hydrofluoric acid | Not titanium | Fluoride complexes the passive film and attacks titanium rapidly in any grade; an alternative material family is required |
| Wet chlorine and chlorine dioxide | Grade 2 with ignition review | Titanium handles wet chlorine well but dry chlorine or oxygen-enriched dry atmospheres present an ignition hazard that must be engineered out |
| Hydrogen-containing streams at elevated temperature | Avoid titanium | Hydride formation and embrittlement are a general concern above roughly 70 degrees Celsius |
Ferro Titanium Grades and Residual Control for Equipment Steels
The equipment steelmaker chooses a ferrotitanium grade on the basis of the titanium level required in the finished heat and the residual elements the finished analysis can tolerate. GB/T 3282 defines the ferrotitanium grades and their composition limits, with sampling to GB/T 4010 or ISO 3713, particle size verification to GB/T 13247 and packing to GB/T 3650.
| Ferro titanium grade | Titanium level | Typical place in the melting sequence | Residual control priority |
|---|---|---|---|
| FeTi30 | About 25-35% Ti | Economical titanium addition and deoxidation in carbon and low-alloy equipment steels | Aluminium and silicon, since both alter deoxidation and inclusion characteristics |
| FeTi40 | About 35-45% Ti | Titanium-bearing steels where a moderate titanium residual is specified for grain control | Carbon and nitrogen interaction, which determines how much titanium remains available |
| FeTi70 | About 65-75% Ti | Stabilizing additions to austenitic stainless heats used for vessel shells, internals and tubing | Carbon, phosphorus and sulphur, all of which affect weldability and corrosion performance |
Aluminium and silicon are not merely filler elements in this context. Both act as deoxidizers, so a high aluminium ferrotitanium will change the oxygen balance and the inclusion population of the heat, and inclusions that survive into a finished vessel wall become initiation sites for pitting and, in cyclic service, for fatigue cracking. A certificate that reports titanium alone is therefore an incomplete document for equipment-grade steel.
Titanium-Stabilized Stainless Steel in Reactors, Columns and Piping
Stabilized austenitic stainless steel remains the default material for reactors, distillation columns, mixing vessels and interconnecting piping in the moderate-temperature range, particularly where the process stream is organic or mildly corrosive and where welded fabrication is extensive. Titanium and niobium stabilized grades are specified so that carbon is tied up before it can form chromium carbides at grain boundaries during welding or service exposure, and the design rule widely used is to keep titanium at approximately five times the carbon content or more.
Acceptance of stabilized material should include a documented titanium value and a documented carbon value on the certificate, followed by intergranular corrosion testing in accordance with ASTM A262 where the purchase specification calls for it. Grain size, determined in accordance with ASTM E112, is a useful supplementary check because coarse grain structures are more prone to intergranular attack after sensitizing treatments. For tubing used in exchangers and coils, ASTM A213 and ASTM A269 provide commonly applied product specifications for seamless and welded austenitic tube.
Fabrication, Welding and Heat Treatment
Titanium equipment requires fabrication discipline that differs from stainless practice. The metal's affinity for oxygen and nitrogen at welding temperature means that molten and hot titanium must be shielded by inert gas until it has cooled below the temperature at which it absorbs these elements, otherwise the joint becomes hard, brittle and markedly less corrosion resistant. Fabricators therefore qualify welding procedures under a recognized code - ASME Boiler and Pressure Vessel Code Section IX for pressure-retaining work, or an equivalent national qualification - and control shielding gas purity, trailing shields and interpass temperature as essential variables.
Stabilized stainless steel imposes a different discipline: heat input and interpass temperature have to be controlled so that stabilizing elements do not redistribute badly, and any post-weld heat treatment has to be planned with the stabilization mechanism in mind. Mechanical testing of production welds is performed against the qualified procedure, with tensile testing to a method such as ASTM E8 and, for titanium and stainless tube and plate, the specified minimum values of the applicable product standard.
Pressure Retaining Design and Code Compliance
Equipment that contains a process fluid under pressure is designed to a pressure vessel code, with ASME Boiler and Pressure Vessel Code Section VIII Division 1 among the most widely applied frameworks, supported by material specifications that the Code recognizes. For titanium construction, ASTM B265 covers plate, sheet and strip, ASTM B338 covers seamless and welded tube for condensers and heat exchangers with ASME SB338 as the Code-recognized companion, ASTM B861 covers seamless pipe, and ASTM B363 covers titanium fittings. For stainless construction, the applicable plate, forging and tube specifications apply together with the code rules for design, fabrication and inspection.
The practical consequence for a buyer is that material certificates should name the Code-recognized specification rather than a generic statement of chemical composition, because the design calculations, allowable stresses and examination requirements all follow from that specification. Where a project is executed to a national framework instead, the corresponding GB product specifications and the applicable pressure vessel rules serve the same purpose.
Inspection, Testing and Non-Destructive Examination
An inspection plan for chemical processing equipment normally combines chemical verification of the delivered material, dimensional and wall thickness verification, mechanical testing, corrosion testing where the service is aggressive, and non-destructive examination of welds. Radiographic, ultrasonic, liquid penetrant and magnetic particle methods are applied according to the code and the joint type, with acceptance criteria written against the code in force for the project; ASME Boiler and Pressure Vessel Code Section V provides the standard examination methods for Code work. Surface cleanliness verification matters for titanium and stainless alike, because embedded iron from tooling becomes a pitting site in chloride service and is often the root cause of a field corrosion complaint rather than the alloy itself.
Corrosion testing should be specified for marginal services. The result to look for is a uniform, low corrosion rate with no evidence of localized attack at welds, heat-affected zones or crevices, because titanium and stabilized stainless steel usually fail in service through localized mechanisms rather than through general wastage.
Storage, Handling and Installation
Ferro titanium shipments should be held dry and segregated from carbonaceous or sulphurous material, with packing and marking agreed against GB/T 3650; moisture pickup and fines contamination both lead to erratic recovery and hydrogen pickup in the melt. Finished titanium and stainless components should be stored off the ground with protective covers, lifted with clean slings, and protected from carbon steel contact during transport and site storage. Gaskets, bolting and supports should be reviewed at the same time as the pressure parts, because a grade mismatch at a tube sheet joint or a support pad frequently creates the crevice that drives the first corrosion failure.
Procurement Checklist for Chemical Processing Projects
A workable purchase specification for titanium-bearing chemical equipment covers six items before price is discussed. Define the medium with concentration and temperature range, including cleaning and shutdown conditions. State the material grade system explicitly, whether by UNS designation with the applicable ASTM product specification or by the corresponding GB grade and specification. Require a lot-certified analysis for any ferrotitanium or titanium feedstock, reporting titanium with individual residual elements. Require the fabricator to state the welding code and procedure qualification standard, and to submit procedure qualification records. Specify the non-destructive examination methods and acceptance criteria. Finally, specify packaging, marking and documentation requirements so that material can be traced from heat number through to installed component.
Where a quotation is being compared, the meaningful comparison is against that specification rather than against a price per tonne. Wall thickness, material grade, examination extent, documentation and welding qualification all move cost substantially, and a lower figure normally reflects a different combination of those four variables rather than a more efficient supply chain.
Frequently Misunderstood Points
Three misunderstandings recur. Ferro titanium is not the material of construction for a chemical reactor; it is the master alloy used to make the steel or alloy that becomes the reactor. A higher titanium content in the master alloy does not mean better performance in the finished equipment, because the requirement is a narrow residual window, not a maximum. And titanium is not universally corrosion-proof: it is an excellent choice in oxidizing, neutral chloride and seawater service but is the wrong choice in fluoride-bearing and strongly reducing streams, and its use in hydrogen service at elevated temperature carries an embrittlement risk that must be designed around.
FAQ
Q: What is ferro titanium used for in chemical processing equipment?
It is a melting-shop master alloy used to introduce controlled titanium into steel and alloy heats. In chemical plant supply chains that means titanium-stabilized austenitic stainless steel for reactors, columns, vessels and piping, and titanium-bearing steels for other pressure and structural parts of the equipment.
Q: Which titanium grade should be used for a chemical reactor or vessel?
The medium decides. Grade 2 (UNS R50400) suits oxidizing acids, seawater and neutral chlorides, Grade 7 (UNS R52400) is used for dilute reducing acids, and Grade 12 (UNS R53400) for hot brine and crevice-prone geometries. Fluoride-bearing streams and hydrofluoric acid are not titanium services in any grade.
Q: How is ferrotitanium specified for equipment-grade steel?
Grades and composition limits are defined in GB/T 3282, sampling for chemical analysis follows GB/T 4010 or ISO 3713, particle size is verified against GB/T 13247, and packing and marking are agreed against GB/T 3650. The certificate should report titanium together with aluminium, silicon, carbon, phosphorus and sulphur individually.
Q: Why is a titanium-to-carbon ratio specified for stabilized stainless steel vessels?
Because titanium must be present in sufficient quantity, commonly about five times the carbon content or more, to combine with carbon and keep chromium in solution at grain boundaries. This is what preserves intergranular corrosion resistance after welding and during elevated-temperature service, and it is verified through ASTM A262 testing where the specification requires it.
Q: Which material specifications apply to titanium pressure equipment?
Plate, sheet and strip are ordered to ASTM B265, seamless and welded tube for exchangers to ASTM B338 with ASME SB338 as the Code companion, seamless pipe to ASTM B861, and fittings to ASTM B363. Stainless tube for exchanger and coil service is commonly ordered to ASTM A213 or ASTM A269. Design and fabrication follow the pressure vessel code in force for the project, such as ASME Section VIII Division 1, with welding qualified under Section IX.
Q: What are the main causes of early corrosion failure in titanium equipment?
Localized attack rather than general wastage. Typical causes are grade selection that ignores a reducing or fluoride-bearing stream, crevices at gasketed joints, tube sheet or support contacts, iron contamination of surfaces during fabrication or site work, and weld zones that were inadequately shielded from oxygen and nitrogen during welding.
