| This paper analyzed the working principle and applications in petroleum drilling of Expandable Tubular Technology from its all sides. And it put forward the design rules of expandable tubulars materials, i.e. the materials should have high plasticity, high strength and high work-hardening rate. According to the design rules, this paper researched and developed two types of expandable alloys successfully- stainless steel alloys and dual phase steel alloys with low carbon.The first kind of stainless steel expandable tubular materials has good comprehensive properties by the strengthening-plasticity mechanism of Transformation-Induced Plasticity(TRIP) based on the design theory of stainless steel. We researched the expandable properties from microstructure, mechanical properties and hot processing. The testing showed that this kind of materials has reasonable microstructure and good comprehensive properties. This kind of materials can be used as expandable tubulars materials.Ms(ε) is a symbol parameter of the degree of difficulty for transformation induced plasticity of stainless steels. And the calculation of Ms(ε) need to be solved when designing stainless expandable alloys. In order to convenience the design , this paper deduced the Ms(ε) formula of stainless steel Fe-based alloys , as follows:The first kind of expandable alloy can be used as expandable tubulars materials,but the price of Ni and Cr are high. Another kind of expandable alloy-dual phase steel was designed to lower the cost of expandable tubular. The second kind of dual expandable alloys got the mixture structure of ferrite, austenite and martensite used the method of dual phase heating and uniform temperature quenching heating treatment .Ferrite can improve plasticity and the mixture of austenite and martensite structure can improve the strength of matetials. The mechanical properties testing showed that its strength is 640MPa, plasticity 33%. We researched a kind of expandable alloy with low price which...
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