1、Definition

1.1 prestressed steel strands istwisted steel wire rope made of 2 wire、3wire、7wire、19wire,and the stress has been eliminated(stabilization) ,suitable to be used forprestressed concrete structure and similar usage

2、manufacture method

  The main characteristic of PC steel strands is with high strength andbest relaxation,and very straight after expanding.the usual tensile strengthgrades such as 1860 Mpa,and 1470、1570、1670、1720、1770、1820、1960、2000、2100Mpaetc.

2.1 productionprocess

Pickling-phosphating-colddrawing-spooling-entwisting-stabilizingtreatment(tensile strength-medium frequence-air cool-water cool-air drying-tensilstrength)-low relaxation steel strands finished-stock

2.2 Steel Strands Structure Form

Figure 1、  Prestressed Steel Strands Structure

2.3  the purpose of stabilization treatment

 Becauseof stress relaxation of the prestressed steel,the prestess value in theprestressed concrete structure declines gradually ,which make the structure cannot arrive the designed life and destroyed easily in advance.so to use entwistand stabilization treatment united machineryand get the low relaxation prestressed steel

Strands in orderdecline the stress relaxation.

     To get the tension is relied on the speed differenceof the two group of traction wheels.the tension must be controlled at more than40% steel strands destroyed loading.and cool-water shouldbe after tempering 350~400℃,and blow-dry theresidual moisture with compressed air and keep the steel strands from rust.

2.4  Stress Relaxation

After the metal material stressed,under the condition ofunchanging of the general deformation,because of the effection of the part ofthe inner metal material move disorderly and atomic diffusion.which make partof elastic deformation into plastic deformation and lead the stress of metalmaterial decline gradually with the time of passing.

2.5 Entwist Direction:

Entwist Direction is refer to the spiral direction of the steelwire in the steel strands.the judgment method of the entwist is watching alongthe vertical direction,it should be right entwist if the precessional directionof the wire is from the left to the right,which is stead of letter “Z”, and it should bethe left entwist if the precessional direction of the wire is from the right tothe left.,which is stead of letter “S”,as shown in thefigure below.

                                                                                               Right twisting     Left twisting

                                     Figure2、Entwist Direction