Whether the development of marine economy or the development of the modern navy, the need to develop a series of marine equipment. Practice shows that the advanced marine equipment, both deep-sea oil and gas production equipment, or nuclear submarines, submersibles and other equipment, are involved in titanium equipment, lightweight, corrosion resistance of titanium and titanium alloy materials can for the realization of marine equipment of high efficiency, long life and high reliability made a significant contribution.
And the current time of the development of titanium in marine engineering. China is a big country of the world titanium industry, which has a relatively complete titanium research and development, production and application system, with large-scale production capacity and many applications of technical reserves, to speed up the development of marine engineering titanium, not only is necessary, but also feasible.
Compared with steel, stainless steel, copper, aluminum and other materials, titanium is the most prominent feature is low density, high strength, corrosion resistance, but also has the ability of resistance to seawater erosion, non magnetic, no cold brittleness, high permeability, and so on, which is easy to form, casting, welding, so that it has a wide range of various marine engineering.
Titanium in ocean engineering can display one's skill to the full but there are some disadvantages, and problems worthy of attention. Marine engineering is faced with many challenges, mainly in five aspects:
First, in the production of titanium material.
Because of the high melting point (1668), the high temperature deformation resistance and narrow heat treatment temperature zone, it is difficult to produce titanium material, especially the large size and high performance titanium material. It needs not only the large vacuum smelting furnace (vacuum arc furnace, electron beam cold hearth furnace and the need for heavy pressure processing equipment (forging machine, rolling machine, extrusion, etc.). Titanium production unit products investment is huge, up to 30 ~40 million / ton. Titanium material production capacity of equipment than the same specifications of steel (1633, -16.00, -0.97%) is a considerable or more equipment, and its output and equipment utilization is only one of its dozens, leading to high production costs.
Second, in product design.
Titanium bending strength and high bit (0.9), high welding strength coefficient (above 0.9), while the elastic modulus, heat conduction coefficient and damping coefficient are low. Under certain conditions, titanium crevice corrosion, galvanic corrosion and hydrogen embrittlement contact problems. Due to the physical, chemical and mechanical characteristics of titanium, the design of titanium equipment should adopt new design codes and technical specifications (such as safety factor, corrosion allowance, fire prevention measures, structural form, weld form, etc.). Titanium material damping coefficient is small (except for TiNi shape memory alloy), in the use of vibration, the need to take measures to prevent vibration. Titanium into the industrial field only a few decades of history, design experience is less, many problems remain to be explored.
Third, in product manufacturing.
Because of the low elastic modulus of titanium and cold processing rebound, low thermal conductivity surface easy to abrasion, scratches, and other characteristics, all bring certain difficulty to the titanium parts forming, heat treatment, machining and other, mature technology need long time exploration.
Fourth, in the application.
Due to the high corrosion resistance of titanium, titanium equipment for the "permanent" or semi permanent equipment, equipment assessment cycle is very long, so that the use of units of one or two, the three generation of engineering and technical personnel are difficult to fully grasp the application of a device, can not make a comprehensive and objective evaluation of titanium equipment.
Fifth, in the selection of material concept.
Most people are still very difficult to break through the "price of titanium is too expensive," the inertia of thinking. Under the limited investment capabilities, it is difficult to use than the hull steel expensive 5 ~ 10 times of titanium material to replace steel or copper manufacturing marine equipment. Relatively speaking, the one-time investment of titanium equipment is really great, the technology and economic advantages of titanium equipment mainly rely on the full life cost to reflect, that is mainly rely on long-term benefits to reflect. Titanium material to expand the application in the ocean engineering, in the benefit assessment and the promotion of universal respect to do a lot of work.