Titanium
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| Corrosion Resistant Applications Titanium has excellent resistance to corrosion in a broad range of environments including acids, alkalis, oxidative agents, water, salt water, and many industrial chemicals. A natural oxidative films forms on titanium, which enhances its corrosive resistance in many environments. Click here for corrosion tables of titanium alloys. Titanium is especially resistant to metallic salts, chlorides, hydroxides, nitric, and chromic acids. Titanium also exhibits excellent erosion resistance, making it excellent for applications that have low impurity tolerance. Commercially Pure Titanium Commercially pure titanium has a density of about 0.163 lbs./in.3 and a tensile strength ranging from 35,000 to 80,000 psi. It is used extensively in corrosion resistant applications. Commercially pure titanium is a great choice for process equipment in corrosive environments. Besides its corrosion resistance, titanium has a high strength-to-weight ratio. This allows for thinner walls, facilitating better heat transfer. Physical property information is available here. Alpha-Beta Alloy Alloyed titanium is used extensively in applications where a high strength, low density metal is required. It is used for its excellent strength-to-weight ratio. Physical property information is available here. Machining Titanium A copy of this document is available here. Titanium and stainless steel are generally compared in terms of machinability, except when there is a higher alloy content, the machinability decreases. There should not be any problems in the machining of titanium and its alloys, if the characteristics of titanium are taken into account. Titanium can be cut very easily, but only if the tools you use are kept sharp. It is always easier to sharpen a tool than to have a wearland develop. Proper tool angles, adequate coolants and the use of slow speeds and heavy feeds are also advised. Due to the fact that titanium has low thermal conductivity, when cutting, the chips have a tendency to gall and weld to the cutting edges on the tool. This always speeds up the wear on the tool itself. Rather than lose production, it is best advised to work the tool to its maximum capacity and then replace it when productivity decreases. To lengthen tool life, proper use of the coolant is necessary to reduce cutting temperature and inhibit galling. Any cutting fluids containing chlorine, fluorine, bromine and iodine should not be used in order to avoid corrosion problems. Turning Titanium, whether commercially pure or alloyed, can be turned easily. Carbide tools are highly recommended for turning. Best results are acquired from metal carbides such as C-91 and similar types. Of the high speed steels, cobalt-types seem to be the best. If carbide is not available, Stellite, Tantung, Rexalloy, or other types of Castalloy tools may be used. Drilling Drilling may be accomplished successfully with ordinary high speed steel drills. When drilling titanium, the most important factor is the length of the unsupported section of the drill. This section of the drill should not be any longer than is required to drill the depth of the hole and allow the chips to flow through the flutes and out the hole. Following this process permits maximum cutting pressure and quick removal to clear chips without breaking the drill. Using a "Spiro-Point" drill for grinding is recommended. Tapping Tapping titanium is one of the more difficult machining operations, due to the problem of chip removal. The use of a gun-type tap where the chips are pushed ahead of the tap can make this process less difficult. When titanium smears on the land of the tap, it may cause another problem, tap freezing or binding in the hole. Sulfurized and chlorinated oil is recommended for this. Best performance in tapping titanium is when using a 65% thread. Grinding For grinding titanium, the ideal combination of grinding fluid, abrasive wheel and wheel speeds can quicken this form of shaping titanium. Alundum and silicon carbide wheels are used. The ideal way to perform this procedure is to use lower wheel speeds than in general grinding of steels. An excellent coolant is a water-sodium nitrite mixture, although, unless proper precautions are taken, this mixture may be very corrosive to equipment. Sawing Sawing titanium requires slow speeds - in the 50 fpm range - and heavy, constant pressure from the blade. Parts that have been machined and will be exposed to higher temperatures should have all cutting oils thoroughly removed. The solvent basically used for this is methyl-ethyl-ketone. Low flash point cutting oils are not recommended, due to the fact that during machining, high heat is generated, which may cause the oil to ignite. High flash point cutting fluids or water-soluble oils are recommended. Welding Titanium A copy of this document is available here. The most often used method of joining metals is welding. Welded assemblies with high tensile and compressive loads with fatigue causing stresses have a great advantage if they are made of titanium. Titanium, whether commercially pure or in one of the many titanium alloys, may be welded. Inert-gas shield arc welding, spot, seam and flash welding are methods used for welding titanium. Protection for shielding the molten weld metal and adjoining heated zones from active gases that could contaminate the metal are included in these methods. Nitrogen, oxygen and hydrogen are greatly reactive with molten titanium, which dissolves large quantities of these gases. Titanium tends to become brittle from these contaminating gases, therefore, ductile welds cannot be produced by oxyacetylene welding or other forms of welding using active gases, electrode coatings, or fluxes. Arc Welding A welding torch designed to allow inert gas to flow through it, giving the molten metal pool and electrode a protective environment, is used for inert-gas shield arc welding. While solidifying, the weldment is protected by a trailing shield with inert gas, the underside has a grooved back-up bar filled with inert gas for its protection. For protecting the atmosphere, helium, argon or a mixture of the two can be used. Manual or automatic welding of titanium can use either inert-gas tungsten-arc or inert-gas metal arc processes. Spot and Seam Welding Procedures for spot and seam welding on titanium are comparable to those used on other metals. Inert-gas shielding required in arc-fusion welding is not needed in this process. Satisfactory welds may be achieved a number of ways with combinations of current, time and electrode force. Adjusting the current, time or force to previously established welding constitions for similar thicknesses of stainless steels is a good procedure to follow. Any type of welding cycles including slope control, preheat, post weld heat treatment and forging cycles are basically not needed. Flash Welding Flash welds have the same advantages in titanium as other metals. The need for gaseous shielding is eliminated, due to the fact that the molten metal present at the farying surfaces is expelled at the time the weld is consummated. Forged cross sections, complex or hollow shapes may need shielding to avoid possible contamination. Pressure Welding There are two main differences between titanium pressure welding and flash welding. First of all, an oxyacetylene flame or induction coil provides the heat instead of an arc. Heat is applied to the metal until it reaches a highly plastic state, because the weld doesn't require actual melting of the metal. The pieces are then welded together by externally applied pressure. Normally, gas shielding is not necessary. However, if the part to be welded is hollow, the inside may require shielding to prevent contamination. Careful material preparation is very important to a successful pressure weld. The joining faces must be machined properly to assure perfect alignment. The degree of pressure maintained during the welding cycle depends on time, temperature and alloy. Electron Beam Welding For joining titanium where exceptionally high standards of weld quality and purity are required, electron beam welding has particular advantages. Because this type of welding is performed in a high vacuum, atmospheric contamination of the weld is prevented. Heat is provided by a high density stream of electrons. Cutting grooves in the metal is rarely needed, because electron beam welds are deeper and narrower than those encountered in other welding methods. Electron beam welds are less apt to warp the assembly because of the high depth-to-width ratio. Forming Titanium A copy of this document is available here. Hot forming is generally preferred with titanium sheet, though cold forming is also manageable. Four methods are basically used for forming with a bit more application of pressure than with steel. They are: - Hydropress - Stretch - Power Brake - Drop Hammer Titanium material, if received in the annealed condition, is then in its most easily formed and workable condition. Hydraulic Press Forming To fabricate parts that are basically flat with straight or contoured edges, rubber pad hydraulic press forming is used. Cold work is best when done in stages, with annealing between stages. When planned as a two-phase operation, hydropress forming is most successful: 1. Cold hydropress forming to semi-finished conductor. 2. Mechanical hot-sizing to blueprint finish, or final creep forming with furnace-type fixtures. With this additional hot forming stage, hydropress dies can be designed with a controlled contoured bulge or shrink flange, eliminating possible cracks or bends. For the hot sizing equipment or creep forming in a furnace, dies are machined to blueprint requirements. Time and temperature to hot size rely on the individual titanium alloy. Usually 10- 20 minutes at 1000°F is acceptable. Power Brake Forming To form angles, Z-sections, hat sections, and channels, brake forming is used. A round-nosed male punch and trough-like female die is used in this type of forming. When using this method, the sheet metal blank is laid over the trough die and angle formed by forming the sheet into the trough using the male die. Stretch Forming Stretch forming has been used on titanium mainly to contour angles, hat sections, Z-sections and channels, and also to form skins to specification-contours. This kind of forming is attained by gripping the section to be formed in knurled jaws, loading until plastic deformation begins and then wrapping the part around a male die. Loading of the part or sheet until plastic deformation begins and wrapping around the die should be done at a slow rate. Springback of most titanium alloys is equivalent to that of 1/4 to 1/2-hard 18-8 stainless steel. Drop Hammer Forming Drop hammer forming has been very successful, and has been accomplished at both room and elevated temperatures. Kirksite is satisfactory for male and female dies where only a few parts are needed. If it is a long run, usually steel inserts are necessary. In drop hammer forming, the greatest success has been obtained by warming the female die to 200 - 300°F to remove the chill, and heating the blank to 800 - 1000°F for 10-15 minutes. The part is then struck and set in the die. In most cases, a finished part, which requires no handwork, is obtained. Cold vs. Hot Forming The advantages of hot forming of titanium are reduced springback, lower forming pressures and increased ductility. As in drop hammer forming, the use of preheated dies to avoid chilling the work is recommended. When titanium blanks are heated so that actual deformation takes place (at temperatures of 400 - 600°F for the commercially pure grades, or 800 - 1300°F for the alloy grades) the titanium will behave much like annealed to 1/8-hard stainless steel. When commercially pure titanium is cold formed, it will behave much like 1/8 to 1/4-hard stainless steel, and most titanium alloys like 1/2-hard stainless steel. Stress Relief As an aid to cold forming, normally it is necessary to stress relieve when more than one stage of fabrication is involved. For example, a part should be stress relieved after brake forming prior to stretching and also between room temperature hydropress forming stages. Heat treatment is necessary to relieve residual stresses imposed during forming after cold forming operations are complete. Available Raw Materials Titanium is available in nearly all forms in raw materials including sheet, plate, round bar & billet, square bar, rectangular bar, seamless & welded pipe, and tubing. Click the above links to see available sizes and weight per foot/square foot on pieces. Also, feel free to contact the Rasmussen Company with any inquiry of a dimension that is not listed in the above tables. Custom Fabrication We can fabricate almost any item out of titanium if we are provided with a drawing and/or specifications. Contact us for any custom fabrication you would like made from titanium. |
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Please contact us with any inquiry! Rasmussen Company, Inc. Phone: 800-558-0575 (in the U.S.) or 262-695-3320 |