鋼筋冷拉是在常溫條件下，以超過原來鋼筋屈服點強度的拉應力，強行拉伸鋼筋，使鋼筋產生一塑性變形達到提高鋼筋屈服點強度和節約鋼材的目的。 此處常溫為平均室外溫度大于5℃。
鋼筋冷拔時，鋼筋同時經受張拉和擠壓而發生塑性變形，拔出的鋼筋截面積減小，產生冷作強化，抗拉強度可提高40—90％。冷拉和冷拔是金屬冷加工的兩種不同的方法，兩者并非一個概念。冷拉指在金屬材料的兩端施加拉力，使材料產生拉伸變形的方法。
冷拔是指在材料的一端施加拔力，使材料通過一個模具孔而拔出的方法，模具的孔徑要較材料的直徑小些。冷拔加工使材料除了有拉伸變形外還有擠壓變形，冷拔加工一般要在專門的冷拔機上進行。經冷拔加工的材料要比經冷拉加工的材料性能更好些。
冷拔鋼筋是將鋼筋用強力拔過比它本身直徑還小的硬質合金拔絲模，這是鋼筋同時受到縱向拉力和橫向壓力的作用，截面變小，長度變長，鋼絲的強度大大提高，但塑性降低很多。冷拉只能提高鋼筋的抗拉強度，而冷拔不但能提高其抗拉強度，而且還能提高其抗壓強度。
這兩種冷加工都是以犧牲鋼材的變形能力為代價，達到了提高強度和硬度的效果，但是經過處理后的鋼材屈強比增大，安全儲備降低，延性降低，破壞前不再有明顯的變形發生。對于可能承受動力荷載的部位或重要部位是禁止使用此類鋼筋的。
中譯英：
Cold drawing steel is at ambient conditions, to surpass the original steel yield strength tensile stress of tensile steel, forcibly, result in steel plastic deformation to enhance the yield strength and the purpose of saving steel. Here at room temperature for the average outdoor temperature more than 5 DEG c.
Cold drawn steel reinforced, simultaneously tensioning and extruded and deformed plastically, pull out the steel area decrease, produce cold hardening, tensile strength can be increased by 40 - 90%. Cold drawing and cold drawn metal cold processing by two different methods, the two are not a concept. Cold drawn refers to the metal material at both ends of a tensile force is applied, so as to cause the material tensile deformation method.
Drawing refers to the material is applied pulling force, so that the material through a die hole and pull out method, mold aperture diameter smaller than material. Cold drawing processing materials in addition to tensile deformation and extrusion, drawing processing in general to the special drawing machine for. Through cold drawing materials than the processing of cold-drawn material properties.
Cold-drawing steel reinforced by strong pull off is smaller in diameter than its hard alloy wire drawing die, which is reinforced by longitudinal force and lateral pressure, section becomes smaller, the length of variable length, steel strength greatly enhanced, but the plastic to reduce many. Cold drawn steel can improve the tensile strength, and drawing can not only improve its tensile strength, but also can improve the compressive strength.
These two kinds of cold working steel is at the expense of deformation capacity for the price, can increase the strength and hardness of the effect, but the processed steel bend strong ratio increasing, safety stock reduced ductility, failure, there is no significant deformation. In may under dynamic load position or the main part is the prohibition of the use of this kind of steel.
(圖/文m.ncwanke.cn) |
