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Why should the length of sizing zone and compression angle of drawing die be strictly controlled

Do you encounter the following situations in the production of wire rod?

1.Wire diameter fluctuates greatly during wire drawing.
2.It didn't take long for the drawing die to crack.
3.The service life of drawing die is too short.
4.The surface of wire is cracked and rough.

Let's have a look. Why?
Wire drawing die is a very important consumable die in the drawing production of various metal wires.The cost of wire drawing die accounts for a large proportion of the drawing cost.As a wire production enterprise,how to reduce the cost,obtain stable long-time drawing,accurate size and better surface quality is very important.

But how?Of course,it is difficult to achieve without high quality drawing die.Under certain die material conditions,the pass structure is the key factor to determine the quality of the drawing die,because different drawing conditions need different pass structure to adapt to it.Only in this way can the life of the drawing die be prolonged and great economic benefits be created.Therefore,the pass structure of wire drawing die is very important for wire drawing enterprises.

Today,we are going to focus on the two most important areas of the drawing die compression area and sizing area.

1.Compression zone
The compression zone is the area of wire drawing deformation,and the angle of compression zone (compression angle) is the main parameter of the compression zone of the drawing die.The compression angle plays a decisive role in the size and distribution of the pressure acting on the inner hole of the drawing die,the size of the drawing stress and the mechanical properties of the drawn wire.

If the angle of the compression zone is too large,the deformation rate of the metal material will increase and the deformation zone will become smaller during the control process,resulting in a large amount of heat generated by the wire drawing die,scorch the lubricating powder and make it invalid, thus seriously affecting the wire drawing effect.At this time, if the compression zone is not cooled,it will directly affect the drawing quality of metal filaments;if the angle of compression zone is larger or the compression ratio is smaller,the metal material will be closer to the sizing zone and the deformation will be greater,so it is difficult to reach the specified area of the sizing zone and form concave convex phenomenon on the surface.If the material texture is soft,it will occur in the drawing process Ellipse phenomenon.

At this time, the increase of the lubrication area can provide better lubrication effect,but it is not the case in fact.On the contrary,due to the increase of the surface relief area,the lubricating powder will produce eddy current effect and flow out from the die hole in the reverse direction,which reduces the lubrication effect and eventually leads to the formation of cracks or scratch marks on the surface of the metal wire.Therefore,the angle of the compression zone should not be too large,too large will easily make the lubricating powder lose the lubricating effect,and then affect the wire drawing quality. What happens if the compression angle is too small?When the angle of the compression zone becomes smaller,a lot of heat will be produced in the drawing die,and then the lubricating powder will fail.Because when the angle is too small,the contact point of the metal material is close to the top of the compression zone,which makes the deformation zone increase,and then leads to the increase of the useless power of the drawing die and a lot of heat.In addition, when the lubrication area is reduced,the lubrication function is reduced because the amount of lubrication is also reduced.And then affect the drawing quality of wire.When the tensile stress increases,the diameter of the sizing strip will become larger,which makes the ellipse phenomenon easy to appear,and then leads to the fracture and contraction of the wire.

2.Sizing area
The sizing area is the control part of the mold aperture size,through which the metal wire can get the final size.Reasonable length of sizing zone can improve flatness,dimensional accuracy,surface roughness quality and die life.

The longer the sizing area is,the larger the contact area between the wire and the die hole will be,and the friction will also be greatly increased.Therefore,the long sizing area will especially increase the tensile force.However,the tensile stress must be greater than the tensile strength limit of the wire,so that the tensile process can be carried out,otherwise the wire breakage will be caused,and the tensile can not be carried out.Therefore,it is very important to find a suitable sizing zone length for drawing different grades of metal wires.

The sizing area must be straight and of reasonable length.If the sizing area is too long,the friction of stay wire increases, and the wire is easy to shrink or break when it is pulled out of the die hole.If the sizing area is too short,it is difficult to obtain the wire with stable shape,accurate size and good surface quality.At the same time,the die hole will soon wear out of tolerance.

To sum up,as a wire production enterprise,in order to obtain stable long-time drawing,accurate size,better surface quality,reduce costs and create great economic benefits,it is essential to detect the pass structure of wire drawing die.

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