钢筋冷拉是在常温条件下，以超过原来钢筋屈服点强度的拉应力，强行拉伸钢筋，使钢筋产生一塑性变形达到提高钢筋屈服点强度和节约钢材的目的。 此处常温为平均室外温度大于5℃。
钢筋冷拔时，钢筋同时经受张拉和挤压而发生塑性变形，拔出的钢筋截面积减小，产生冷作强化，抗拉强度可提高40—90％。冷拉和冷拔是金属冷加工的两种不同的方法，两者并非一个概念。冷拉指在金属材料的两端施加拉力，使材料产生拉伸变形的方法。
冷拔是指在材料的一端施加拔力，使材料通过一个模具孔而拔出的方法，模具的孔径要较材料的直径小些。冷拔加工使材料除了有拉伸变形外还有挤压变形，冷拔加工一般要在专门的冷拔机上进行。经冷拔加工的材料要比经冷拉加工的材料性能更好些。
冷拔钢筋是将钢筋用强力拔过比它本身直径还小的硬质合金拔丝模，这是钢筋同时受到纵向拉力和横向压力的作用，截面变小，长度变长，钢丝的强度大大提高，但塑性降低很多。冷拉只能提高钢筋的抗拉强度，而冷拔不但能提高其抗拉强度，而且还能提高其抗压强度。
这两种冷加工都是以牺牲钢材的变形能力为代价，达到了提高强度和硬度的效果，但是经过处理后的钢材屈强比增大，安全储备降低，延性降低，破坏前不再有明显的变形发生。对于可能承受动力荷载的部位或重要部位是禁止使用此类钢筋的。
中译英：
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.
(图/文www.wxlgjx.cn) |
