Titanium is a very active metal with a very low equilibrium potential and a high thermodynamic corrosion tendency in the medium. But in fact titanium is very stable in many media, such as titanium is corrosion resistant in oxidizing, neutral and weakly reducing media. This is because titanium and oxygen have a great affinity, in the air or oxygen-containing media, titanium surface to generate a layer of dense, strong adhesion, inert oxide film, protecting the titanium substrate from corrosion, even due to mechanical wear will soon self-heal or regenerate. This shows that titanium is a metal with a strong tendency to passivate.
(1) Titanium has excellent corrosion resistance in many chemical media, and the use of titanium equipment operates stably, has a long life and enhances production, which compensates for its poor thermal conductivity;
(2) Titanium yield strength ratio is higher than copper and steel, in the design can be titanium, titanium tube thinning use, which is conducive to heat transfer, therefore, to obtain a better heat transfer effect than steel, copper equipment;
(3) Titanium equipment used at higher temperatures, due to the poor thermal conductivity of titanium, in the shell wall is easy to form a high temperature gradient, resulting in greater thermal stress or thermal fatigue stress of the equipment, but the coefficient of linear expansion of titanium is only 2/3 of low carbon steel, less than 50% of stainless steel, such a low coefficient of linear expansion of the above shortcomings are compensated;;
(4) Titanium in the chemical medium is resistant to pollution, its surface is not easy to scale or scale layer is thin, which makes it difficult to form an insulating heat transfer film layer on the surface of titanium, to obtain a better heat transfer effect;
(5) Steam condensation simulation tests have proved that condensation on the titanium surface is still within the range of film condensation, but compared with steel and copper, the titanium surface has a tendency to promote drop condensation, which is beneficial to heat transfer;
(6) Media in the tube bundle flow rate test proved that the titanium tube bundle allows a higher flow rate, while copper alloys (such as B10, B30) tube bundle in more than 2m / s will occur in the "horseshoe" impact abrasion. Titanium allows the medium flow rate is large, can strengthen the heat transfer efficiency.
(1) In 400 ℃ above a large number of hydrogen absorption, will cause hydrogen embrittlement. It is generally believed that the titanium matrix hydrogen content of more than 0.009% ~ 0.015%, will precipitate along the grain boundaries or grain boundaries in the direction of intracrystalline hydrogen precipitation phase, such as needle, flake or block, similar to the titanium matrix in the microcrack, under the stress of expansion until rupture. When there are hydrides in the titanium surface film, the oxide film is easy to fall off under the washout of the flowing medium.
(2) Titanium equipment in the actual application, because of the chemical reaction in the environment to increase the hydrogen content, titanium surface oxide film is destroyed and can not be self-healing, the presence of iron particles on the surface of titanium, etc., has also occurred in the titanium equipment excessive hydrogen absorption caused by hydrogen embrittlement and scrap accidents. In order to prevent titanium from absorbing hydrogen, the following working conditions should be avoided in general: non-oxidizing acid with temperature > 315℃ and pH < 3; organic acid with pH = 3; alkali solution with pH > 12; neutral solution containing H2S; salt solution containing fluorine ion and iodine ion, etc. The presence of iron accelerates the process of hydrogen absorption by titanium, so when titanium processing and molding and equipment welding, iron contamination should be strictly prevented.
(3) Titanium in pure oxygen, when the temperature reaches 500 ~ 550 ℃ will be a fierce reaction and combustion or explosion. In the oxygen content of more than 47% of the environment, titanium by impact and friction is also easy to catch fire. In the gas-liquid two-phase pure oxygen, titanium ignition occurs in the gas phase.
(4) Titanium can spontaneously combust in bromine.
(5) Titanium in dry chlorine gas, due to the lack of a source of nascent oxygen, so that titanium and chlorine undergo a violent exothermic reaction, which is a collapse reaction for titanium, until the consumption of titanium or dry nitrogen, in the course of the reaction can cause titanium fire or even explosion. It is generally believed that: the environment has more than 1.5% moisture can ensure the passivation of titanium to prevent fire and explosion.
(6) Titanium in the fuming nitric acid application. When the moisture is greater than 2% can prevent titanium's tendency to spontaneous combustion; when the moisture is less than 1%, NO2 greater than 6%, due to the intense reaction between titanium and NO2 to make titanium on fire. In the actual application there have been accidents of titanium valve explosion due to friction.
Material Grade: TA1,TA2, TA4, TA9, TA10, Gr 2, Gr 3, Gr 5 ,Gr 6, Gr 7, Gr 12 etc.
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