How to distinguish titanium materials? What is the difference between TA1 and TA2?
What is the difference between TC4 and these?
(1) In air and oxidizing, neutral aqueous medium, the surface of titanium is prone to produce a dense passivation film of titanium oxide, which makes the electrode potential of titanium significantly shift positively, which greatly improves the thermodynamic stability. The passivation coefficient is used to indicate the degree of chemical stability improvement after metal passivation. Iron is 0.18, nickel is 0.37, molybdenum is 0.49, chromium is 0.74, aluminum is 0.82, and titanium is 2.44. Titanium has much better corrosion resistance than stainless steel, aluminum, etc. in many media. (The mobile container also utilizes the characteristics of light weight and high specific strength of titanium)
(2) Titanium does not have the problem of low temperature brittleness like ferritic steel. Titanium can be used as a low temperature container with a temperature as low as -269 degrees, but because austenitic stainless steel, aluminum, copper, etc. can also be used as a low temperature container, And it is cheaper than titanium, so titanium is actually rarely used in low-temperature fixed containers. In aviation and aerospace, titanium is used as a mobile low-temperature container. It is important to take advantage of its high specific strength, light weight and light weight.
(3) In the chlorine-containing medium such as sea water and brine, carbon steel, low alloy steel, general stainless steel, aluminum have poor corrosion resistance, while titanium has unique excellent corrosion resistance, about 50% of titanium containers It is used to resist the corrosion of chlorine-containing medium.
(4) Since the corrosion resistance of titanium is due to the surface oxide film, general industrial pure titanium and titanium alloys are not resistant to strong reducing media such as high temperature hydrochloric acid. Ti-32Mo is resistant to hydrochloric acid corrosion, but its plasticity and process performance are poor. It has not been included in the pressure processing titanium standard, nor is it included in this standard as container titanium.
(5) Titanium fumed nitric acid, dry chlorine, methanol, trichloroethylene, liquid nitrous oxide, molten metal salts, carbon tetrachloride and other media may produce combustion, explosion or stress corrosion under certain conditions, which makes the titanium container If a vicious accident occurs, the titanium container should avoid or use these media with caution.
(6) In pure oxygen with a temperature exceeding 500 degrees or air with a temperature exceeding 1200 degrees, titanium will burn. Therefore, the titanium container must not be exposed to open flames in contact with air and oxygen to avoid the burning of the titanium container.
(7) Titanium and titanium containers generally do not require assessment of impact toughness.
(8) There are two main uses of titanium. One is used for supersonic aircraft in aviation. Mainly use its high specific strength. The main grade is Ti-6Al-4V, and the other is for civil industry, mainly for its excellent corrosion resistance, and the main grade is industrial pure titanium. More than 90% of my country's titanium is used in civil industry. About 3/4 of titanium used in civil industry is used in containers (including heat exchangers). Therefore, my country's container titanium occupies an important position in the titanium industry.
Determination of titanium for containers
1. The titanium used for the container is the same as steel, which must meet the basic requirements for the manufacture and use of the container, that is, it is easy to be strip and welded during manufacture, and can be safely carried when used. Therefore, titanium for containers is required to have appropriate strength, good plasticity and welding performance.
The bearing capacity of the container is not only related to the strength of the titanium material, but also to the size of the component calculated according to the material strength in the design, so the strength of the material only affects the size of the component. Generally does not affect whether the material can be used.
2. Titanium is much more expensive than steel, and more expensive than aluminum, copper, etc. The use of expensive titanium to make containers is because titanium has the following irreplaceable characteristics of other metals.
(1) Titanium has a high specific strength, and aerospace containers often use this feature, but aerospace containers are not within the scope of this standard. Ground-mounted containers do not particularly pursue light-weight containers.
(2) Titanium has good low-temperature plastic and its toughness, so it is suitable for low-temperature containers, but since aluminum, copper, austenitic stainless steel, etc. can also be used in low-temperature containers, in fact expensive titanium is rarely used in low-temperature containers.
(3) Titanium is mainly used in containers to have excellent corrosion resistance superior to other metals mentioned above
(4) The thermal conductivity of titanium is about 1/5 of that of carbon steel, which is close to that of austenitic stainless steel. Due to the high strength of titanium, the wall thickness of the heat exchange tube of the shell and tube heat exchanger can be thin.
(5) The titanium materials for containers specified in this standard are limited to the grade, status and size range that can guarantee the mechanical properties in the current national standard for titanium materials in my country.
For example, in China's titanium plate standard GB/T3621, the thickness of the mechanical properties is only 10mm (TA2 is 25mm), while in the foreign titanium plate standards, the titanium grades that are equivalent to the titanium grades of China's containers are used to ensure that the mechanical properties are thicker. It is 25mm, Japan is 15mm, Germany is 35mm, Russia is 150mm. In fact, the thickness of the titanium plate that can be supplied in China's titanium plate standard can reach 60mm. As long as the mechanical properties can be guaranteed when supplied, it can also be applied to the container. Mechanics The qualified index of performance can be negotiated and determined. If the guaranteed strength is slightly lower than the guaranteed strength value of the thickness below 10mm in the standard, the allowable stress value can be calculated separately. It is understood that our Baoji non-ferrous metal processing plant does not exceed 25mm thick The titanium plate can guarantee the mechanical properties of the titanium plate with a thickness not exceeding 10mm in GB/T3621.
(6) The chemical composition and mechanical properties of titanium materials in China and the corresponding foreign brands are not completely the same, but there is a good correspondence. It is allowable and convenient to use foreign titanium materials to replace the corresponding titanium brands in China. In addition to complying with the requirements of Article 22 of the "Technical Supervision Regulations for Pressure Vessel Safety", when the strength of foreign titanium materials and domestic titanium materials is slightly different, the allowable stress value should also be adjusted accordingly.
When it is necessary to use titanium materials other than the titanium grade and status of the container specified in this standard and newly developed titanium materials to manufacture the container due to the needs of special circumstances, it shall be in accordance with Article 23 of the <<Pressure Vessel Safety Technical Supervision Regulations>> In addition to the regulations, at least the following conditions should also be met:
1 The chemical composition meets the requirements of corresponding titanium standards
2 The lower limit values of room temperature tensile strength, specified residual elongation stress and elongation are guaranteed values
3 Generally, the elongation of deformed titanium material at room temperature is not less than 18%.It can be applied only when it is known that titanium material is only used for container components without deformation or a small amount of deformation, and it can be smoothly formed after being approved by the manufacturing department. For titanium materials with low elongation, the elongation should not be less than 15%.
4 The titanium material has the guaranteed value data of the tensile strength and the specified residual elongation stress at the design temperature of the container.
(7) The 6 grades of deformed titanium listed in this standard have a certain application basis in China.
Before 1993, there were only three grades of TA1, TA2, and TA3 in the titanium standard for containers, and TA2 was basically used as the basic grade. TA1 was used when the plasticity and corrosion resistance were required to be higher. TA3. Although TA0, TA9 and TA10 were officially included in the standard after 1993, the US grade Gradel equivalent to TA0 has been adopted domestically, and TA9 and TA10 have also been based on Ti-0.2Pd and Ti-0.3Mo-0.8Ni Informal grades are mostly used in containers. The two grades of cast titanium have been included in national standards since 1986 and have been widely used.
Therefore, the titanium for containers determined by this standard has accumulated more experience in titanium production and supply, container manufacturing and application, and has a solid foundation.
(8) In addition to the six grades in GB/T3620, the titanium plate TA1-A for plate heat exchangers is listed according to GB/T14845-1993, which has good deep drawing performance
Technical requirements for ordering titanium for containers
(1) Titanium for containers is based on the current titanium material standard, so the order should first meet the technical requirements in the titanium material standard.
Because these titanium material standards are not special material standards for pressure vessels, but general material standards, only the technical requirements in the titanium material standards cannot yet meet the technical requirements for titanium for containers, and supplementary technical requirements must be proposed. The general supplementary technical requirements are proposed in this standard; the special supplementary technical requirements for the titanium materials used in specific containers are proposed in the container design drawings and technical documents. The technical requirements for ordering titanium for containers should be the sum of these three parts
(2) Deformed titanium for containers requires annealed supply.
In the current titanium product standards, only the tube and heat exchange tube standards stipulate that the supply is in an annealed state, and the supply state in the standard of plates, rods, and forgings is selected by the purchaser. In the state of supply, the supplier generally supplies hot or cold.
Both the bar and forging standards stipulate that the mechanical properties are tested on the sample blank after heat treatment, that is, the mechanical properties of the sample are qualified, which does not mean that the titanium material supplied is also annealed, nor that the titanium material supplied has reached Qualified mechanical properties listed in the warranty book. It is required that the supplied titanium material and the mechanical property sample are in the same annealing state, that is, the sample blank should be taken from the annealed titanium material or its extension.
(3) Titanium for containers shall ensure the tensile strength at room temperature σb and the specified residual elongation stress σ.r02 as mandatory technical requirements.
In some titanium standards, σ.r02 is not clearly required, some are only additional requirements, and some are only tested when required by the purchaser (only to provide measured data, there is no guarantee), these can not meet the requirements of the container The requirements of titanium should be clearly defined as mandatory requirements in the purchase contract. If the qualification index is not listed in the titanium standard, the qualification indications listed in Tables 4-1 to 4-5 of this standard may be used, or the qualification index may be separately determined through negotiation, but the maximum allowable tensile stress value at this time is also To be determined separately.
(4) Among the titanium product standards, only heat exchange tubes and forgings have listed non-destructive testing as a mandatory technical requirement. If users have no special requirements, they can follow the requirements of their nondestructive testing. The titanium plate standard does not mention the requirements for non-destructive testing. CD1308-87 proposes five situations that require titanium plates for ultrasonic testing.
1. The design temperature is below -60
2. The design pressure exceeds 6
3. Used as inner cylinder of multi-layer pressure equipment;
4. Used as a lining for Sana's pressure vessels and heat exchangers;
5. The thickness of the titanium plate is greater than 20mm
(5) Considering the determination of non-destructive testing of the steel plate by GB150, it is mainly distinguished by the thickness of the steel plate. Thick plate thickness is easy to cause defects. The thick plate is also mainly used for large load-bearing occasions. Sometimes the fashion of ordering cannot be fully understood. What kind of application conditions a titanium plate is used for, so this standard only stipulates that titanium plates with a thickness of more than 20mm should be subjected to ultrasonic testing, and there is no unified provision for non-destructive testing under what application conditions. If necessary, design drawings and technical documents can be used Added in.
In addition, the GB/T5193 ultrasonic inspection method standard is only applicable to workpieces with a thickness of more than 13mm, and is not suitable for thin plate inspection. The Lamb wave ultrasonic inspection method can be applied to titanium plates with a thickness of 0.5mm-13mm, but the Lamb wave ultrasonic inspection method It has not been listed as a formal standard, so there is no suitable test method for thin titanium plates for lining. It is not appropriate to provide universal testing. The standard of titanium tubes that are generally used does not list non-destructive testing requirements. Ultrasonic or eddy current testing is carried out. In the titanium rod standard, only ultrasonic non-destructive testing is taken as an additional technical requirement. This standard does not make a unified provision, and is determined by the design according to the specific situation.
(6) The standards for titanium tubes and titanium heat pipes stipulate that the manufacturing methods of tubes are divided into rolling (pulling), welding and welding-rolling. When ordering, you should indicate which one is in the contract, because these tubes Different inspection technical requirements and application performance (such as allowable stress) are also different.
These five situations. The first four are the application conditions of titanium. Only the latter parameter belongs to the titanium plate itself.
Baoji Hongyada Nonferrous Metal Material Co., Ltd.
Address: Xuguang Industrial Park, Baotai New District, High-tech Zone, Baoji City
Contact: Zhang Hongbin
Mobile phone: 13809171560 (same number on WeChat)
Electricity: 0917-3854158
E-mail: hongyadajinshu@163.com
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