1、 The Application Status and Prospects of Titanium Alloys in Ocean Engineering

Introduction

The ocean, which accounts for about 71% of the Earth's surface area, contains abundant resources. Developing and utilizing the ocean to make it a source of our enormous wealth has become one of the directions that people have been striving for for many years. However, due to the approximately 3.5% salt content in seawater, it is corrosive. In addition, certain biological pollutants in the ocean also accelerate the corrosion of seawater.

Titanium is a material with excellent physical properties and stable chemical properties. Titanium and its alloys have high strength, small specific gravity, resistance to seawater corrosion and marine atmosphere corrosion, and can well meet the requirements of people's applications in marine engineering. After years of efforts by professionals in the titanium industry and researchers in ocean engineering applications, titanium has been widely used in fields such as ocean oil and gas development, harbor construction, coastal power stations, seawater desalination, ships, marine fisheries, and ocean thermal energy conversion. Nowadays, titanium used in marine engineering has become one of the main fields of titanium civilian applications.

II. Application Status

2.1 Marine Oil and Gas Development

Oil is the economic lifeline of a country. It is estimated that the world's recoverable oil reserves are 300 billion tons, of which the seabed Oil reserves are about 130 billion tons. The development of underwater oil began in the early 20th century. Its development has gone through a process from nearshore to deep sea, and from shallow to deep sea. Due to limitations in technological conditions and material development, * can only initially extract oil and gas deposits that extend directly from the coast to shallow waters. Since the 1980s, stimulated by the Energy crisis and technological progress, offshore oil exploration and development has developed rapidly, and offshore oil development has moved rapidly towards the continental shelf, gradually forming a new offshore oil industry sector. Offshore drilling platforms are the work base for implementing seabed oil and gas exploration and extraction, marking the level of seabed oil and gas development technology. Offshore oil extraction equipment mainly includes oil production platforms and auxiliary equipment, including crude oil coolers, lift pipes, pumps, valves, joints, and fixtures. These devices come into contact with media such as sulfides, ammonia, and chlorine in seawater and crude oil. Because titanium has excellent corrosion resistance in these media, the United States used titanium made offshore Oil platform pillars in its oil fields in the early 1970s, and made tubular heat exchangers and plate heat exchangers with titanium. The titanium tube heat exchanger uses seawater as the cooling medium to cool the high-temperature steam/oil mixture extracted from the oil well. The titanium plate heat exchanger also uses seawater as the cooling medium to cool the fresh water that cools the crude oil inside the carbon steel heat exchanger. The United States has used about 100 titanium heat exchangers on drilling platforms in North Sea oil. The titanium components ordered by Hunting Oilfield Services in Aberdeen, Scotland, UK are said to be * titanium high pressure riser shafts in the world, which are used in the Heidrum project of Conoco, Norway.

The service life of petroleum titanium alloy titanium drilling pipes is longer, with a weight of only half that of stainless steel, and the flexibility of use is twice that of stainless steel, with a service life of 10 times that of steel. These excellent properties make titanium a material for drilling difficult, nearly circular, and deep oil wells. The combination drilling tool containing titanium drilling pipes can greatly reduce drilling time and total drilling cost. GrantPrideco, RTI Energy Systems, and Torch Drilling Services in the United States first used titanium drilling pipes for industrial applications in 2000. The titanium drilling pipes jointly produced and supplied by GrantPrideco and RTI Energy Systems are also equipped with steel tool joints provided by GrantPrideco Anti Fatigue. This type of joint is lightweight, has good flexibility in use, and can make titanium drilling pipes sturdy and sturdy.

The seawater pipeline system is an indispensable part of underwater oil extraction. Due to the high corrosion resistance of titanium to seawater, its service life is 10 times that of steel. Therefore, the cost of titanium pipeline system is cost-effective compared to Cu Ni system. Active Metal Company of the United States and Precision Tube Technology Company jointly established a titanium tube technology company to produce a large-diameter titanium alloy tube. The alloy used for this type of pipe is Ti-3Al-2.5V alloy, with a diameter of 650mm, a wall thickness of 22-25mm, and a length of 350m. One pipe weighs 80-90t and is planned for use in underwater oil exploration. Another American company used seamless titanium alloy pipes with a length of 15m, an outer diameter of 600mm, and a wall thickness of 25mm to produce a nearly 500m long vertical shaft pipe through extrusion, which has been used on an offshore drilling platform. It is said that the weight of the shaft tube can be reduced by half, thus greatly reducing the ballast cost. In addition, it also has high Fracture toughness and long fatigue life.

According to data reports, in the development project of the North Sea oil in the United States, the titanium consumption of floating body devices and seafloor fixed devices on ships has increased compared with that before. The demand for titanium materials for 24 floating structures on board and 64 seafloor fixed structures is 50-100t for safety protection devices, 50-100t for connecting devices, 400-100t for general lifting equipment, and 1400-4200t for drill pipes. The corrosion of structural components caused by biological pollution on offshore oil extraction platforms is quite severe. A company in the United States used long sleeves made of titanium pipes on the extraction platform to protect the parts on the platform.

In the past few years, the application of titanium alloy components in oil drilling and coastal production operations has significantly increased. Titanium alloy components allow oil drilling to enter deeper water bodies and oil wells, including higher temperatures and highly corrosive (i.e., saline) production environments.

For such applications, considering the overall performance, TC4 titanium rod (Ti-6Al-4V) based alloy is * applicable and cost-effective. The seawater pipeline system is an indispensable part of underwater oil extraction. Due to the high corrosion resistance of titanium to seawater, its service life is 10 times that of steel. Therefore, the cost of titanium pipeline system is cost-effective compared to Cu Ni system. Active Metal Company of the United States and Precision Tube Technology Company jointly established a titanium tube technology company to produce a large-diameter titanium alloy tube. The alloy used for this type of pipe is TA18 (Ti-3Al-2.5V) alloy, with a diameter of 650mm, a wall thickness of 22-25mm, a length of 350m, and a pipe weighing 80-90t. It is planned to be used for underwater oil exploration. Another American company used seamless titanium alloy pipes with a length of 15m, an outer diameter of 600mm, and a wall thickness of 25mm to produce a nearly 500m long vertical shaft pipe through extrusion, which has been used on an offshore drilling platform. It is said that the weight of the shaft tube can be reduced by half, thus greatly reducing the ballast cost. In addition, it also has high Fracture toughness and long fatigue life.

Practice has proven that Ti-6Al-4V (Gr.5_TC4) alloy is a material for drilling pipes. As a drilling application, yield strength and fatigue strength are important. Therefore, two particularly low clearance elements of Gr.5 alloy are suitable for critical dynamic lifting devices. When the service temperature exceeds 75~80 ℃, Gr29 alloy containing ruthenium is used to prevent Crevice corrosion or stress corrosion.

*Common components include coastal drilling lifting devices, drilling pipes, conical stress joints (TSJ), and titanium/steel hybrid lifting devices.

Small titanium components such as titanium pumps, valves, joints, fasteners, fixtures, and spare parts have been widely used on petroleum exploration platforms. Titanium alloy is also widely used on the casing of offshore oil exploration and logging tools abroad.

2.2 Port Architecture

The surface of titanium material has an oxide film with a thickness not exceeding 10nm, which is very stable in corrosive environments and has excellent corrosion resistance to air, seawater, and marine environments. It is currently a raw material that can adapt to various marine environments. Japan vigorously carries out marine development, such as the bridge from Honshu to Shikoku, Tokyo Bay cross road, Kansai Airport, floating oil storage base, etc. The investigation reports on the exposure tests conducted by the Ministry of Construction and the Steel Club of Japan on the Ōi River Ocean surface and various anti-corrosion exposure tests conducted by the Ministry of Transport and the Steel Pipe Pile Association on the floating sand trestle in Bozaki also show that titanium is a suitable material. Titanium not only has excellent anti-corrosion performance, but also has the advantages of very few ions dissolved in seawater environment, non-toxic, and no need to worry about environmental pollution. Japan has also built a super large floating marine building that uses titanium steel composite materials at the point of seawater erosion; In the construction of Tokyo Bay cross highway, titanium materials are used as the splash proof body of piers, and the titanium consumption of each pier is 0.9t. Large floating marine buildings that have been used or are planned include airports, harbor logistics bases, sports facilities, etc.

2.3 Coastal Power Stations

The comprehensive utilization of seawater is one of the important projects in ocean engineering, and the condenser of coastal power plants is a device that utilizes a large amount of seawater. The main titanium used in coastal power stations is for condensers. Since the condenser uses seawater as cooling water, and seawater contains a large amount of silt, suspended substances, marine organisms and various Corrosive substance, the situation is more serious in the brackish water where seawater and river water alternate. Traditional condensers use copper alloy pipes, which are often severely damaged in seawater due to various types of corrosion. Titanium has good corrosion resistance in seawater, especially in polluted seawater, and its high-speed erosion and corrosion resistance in seawater is particularly outstanding.

2.4 Seawater Desalination Plant

Water is the source of life. At present, the lack of water resources has become a problem that troubles the world. About 25% of the world's population does not have sufficient drinking water resources. The land rivers and groundwater resources in the world are far from meeting the needs of industrial development. Therefore, in the future, seawater desalination will be an effective way for humans to solve freshwater resources.

From the development of seawater desalination at home and abroad, there are mainly two methods: distillation and Anti-Infiltration Act. The former is to heat seawater to vaporize it, and then condense the steam to obtain fresh water. The latter is to pressurize seawater, allowing the fresh water to pass through a special membrane and retain salt to obtain fresh water. Early seawater desalination devices used materials such as copper alloy and carbon steel, which were not resistant to seawater corrosion and had low production efficiency. They were quickly replaced by titanium with excellent seawater corrosion resistance. In seawater desalination, the main application of titanium is the heater heat transfer tube of the desalination device. The main producing countries for seawater desalination plants are the United States and Japan. By 2004, there were over 15000 seawater desalination plants under construction and construction worldwide, with a daily output of approximately 32 million tons of fresh water. A Japanese company has built 10 distillation units for Saudi Arabia with a daily output of 30000 tons of fresh water, using 3200 tons of titanium tubes. The average daily output of the unit is 10000 tons, requiring 107 tons of titanium.

Tianjin, Shandong and other places in China have or are currently constructing seawater desalination plants. The preliminary plan for seawater desalination in Tianjin is to produce 500000 tons of fresh water per day by 2007 and 700000 tons by 2010. The estimated amount of titanium used in seawater desalination projects in Tianjin and Shandong is approximately 250 tons.

2.5 Ships

Titanium and its alloys are corrosion-resistant in seawater and marine atmospheres, with light weight, high strength, impact resistance, no magnetism, sound transmission, and low expansion coefficient, making them considered good ship materials. In recent years, the application of titanium in ships has attracted people's attention. The navies and shipbuilding industries of various countries also attach great importance to the application research of titanium on ships, and have developed many grades of titanium alloys for ships. Titanium and its alloys are widely used in ships, such as hull structural components, deep-sea survey ships and submarine pressure resistant shells, pipelines, valves, rudders, shaft brackets, accessories, thrusters and propeller shafts in power drive devices, heat exchangers, coolers, hull sonar fairs, and so on.

Titanium was first applied to ship shells in the former Soviet Union α Class A submarine. Subsequently, titanium was used for artificial or unmanned deep-sea research and deep-sea assistance submarines. Industrial pure titanium is used for general structural components, and Ti-6Al-4V alloy is used for pressure vessels. According to data reports, titanium used in ship hull structure can not only reduce the weight of the ship itself, increase the effective loading weight, but also reduce maintenance and extend the service life of the ship. Hull structural materials such as aluminum alloy and soft steel generally require maintenance within 10 years, while titanium materials hardly require maintenance and repair, and their lifespan can be extended from about 20 years to 30-40 years.

Japan's research on titanium alloys for deep-sea survey ships has been fruitful, with almost all of the "Deep Sea 6500" pressure vessels that can accommodate three operators using titanium alloy materials. This is the result of the long-term efforts of Mitsubishi Heavy Industries Kobe Shipyard. Submarines use a large amount of titanium, such as a nuclear submarine with a depth of 900m, which uses up to 3500t of titanium.

2.6 Marine Fisheries

According to reports, Japan's fisheries have shifted from fishing to fish farming, with artificial farming of lionfish, flatfish, eels, and other fish. In artificial aquaculture technology, titanium metal mesh and titanium tube heat exchangers that maintain a certain seawater temperature are extensively used. The artificial cultivation of Grouper has been realized in the coastal areas of Fujian Province in China, and the titanium plate aquaculture basket has brought excellent benefits to the cultivation of Grouper.

2.7 Ocean thermal energy conversion

The ocean contains huge energy, such as Tidal power, Wave power, temperature difference energy, Marine current power and salt difference energy. With the increasing shortage of World energy resources, people will be more interested in the development and utilization of marine energy. We have researched and developed thermal and tidal power generation projects. The principle of thermoelectric power generation is to use seawater with higher surface temperatures to vaporize ammonia or Freon to drive the turbine to rotate and generate electricity. Then, the vaporized ammonia or Freon is cooled by deep low-temperature seawater in the ocean, forming a continuously circulating heat engine system.

The main equipment for thermoelectric power generation is evaporators, condensers, seawater suction pipes, loops, etc. The equipment is required to not only be corrosion resistant, but also to be resistant to ammonia and fluorine corrosion. Titanium and its alloys not only have good corrosion resistance to seawater, but also to ammonia and fluorine corrosion, so titanium is an ideal material.

Titanium tube evaporators and condensers have been used in thermal power plants in the United States and Japan, achieving good results.

III. Outlook

Ocean engineering, as an emerging civilian market for titanium, has developed rapidly in recent years. With the further aggravation of the World energy resources crisis, countries around the world will invest a lot of manpower and material resources to exploit the oil resources and other mineral resources on the seabed; In the trend of increasing global freshwater scarcity, various coastal countries will use seawater to produce freshwater; Moreover, the increasingly fierce competition for naval equipment among major military powers is inseparable from titanium and titanium alloy materials. Therefore, the application of titanium and its alloys in marine engineering will become increasingly widespread. It is expected that titanium for marine engineering is expected to become a major application market for titanium materials.

2、 Market situation of titanium alloy civilian health products

1. Current market situation

At present, iron, aluminum, and stainless steel are widely used materials for tableware and cooking utensils both domestically and internationally. During use, they may cause some unhealthy factors to the human body:

① Iron pot: The iron in the dish is trivalent iron, which cannot be absorbed by the human body. The human body can only absorb it