| 摘要 |
Process for manufacturing seamless precision steel tubes with improved isotropic toughness at low temperature for hydraulic cylinders comprising the following steps;—(i) providing a steel having a composition comprising 0.06-0.15% by weight of carbon, 0.30-2.5% by weight of Mn, and 0.10-0.60% by weight of Si,—(ii) hot-rolling the said steel at a temperature higher than Ac3 such as to obtain a seamless steel tube,—(iii) heating the said seamless steel tube at a temperature in the range between Ac1 and Ac3,—(iv) quenching the said heated seamless steel tube, such as to establish a dual (or multi-) phase microstructure in the steel employed, composed of ferrite and martensite and optionally bainite and/or retained austenite,—(v) cold drawing the quenched seamless steel tube such as to provide a seamless precision steel tube of the desired dimensions,—(vi) subjecting the so-obtained seamless precision steel tube to stress relieving treatment to improve its isotropic toughness, and optionally—(vii) straightening the so-obtained seamless precision steel tube with improved toughness. |
