Analysis of causes of wire drawing machine defects

Analysis of causes of Wire Drawing Machine defects
In wire drawing production, various steel wire defects can occur due to factors such as raw materials, equipment, process conditions, and operations, resulting in substandard product quality.
The common defects and their causes in wire drawing include the following aspects:
(1) Unqualified size of finished steel wire
1. The diameter of the finished steel wire exceeds the tolerance
(1) The newly replaced wire drawing die, after jogging and driving, measures the wire diameter. If it exceeds the tolerance, it belongs to the mold manufacturing error or the mold "wrong number", and the wire drawing should be replaced
Membrane.
(2) During the production process, the diameter of the finished steel wire exceeds the positive tolerance, mainly due to the operator's failure to perform frequent inspections. If the diameter exceeds the negative tolerance,
Usually referred to as "shrinkage", the main reason is poor lubrication. This phenomenon often occurs during high-speed pulling, especially during wet pulling
See you. Either because the lubricant cannot adapt to high-speed drawing, or due to poor coating, the lubricant cannot be effectively loaded into the mold hole or blocked with lubricant
Poor lubrication is caused by the plug mold hole (often due to the small angle of the inlet cone of the wire drawing mold or the excessively long sizing belt). Partial compression rate is too high, and it is also possible to "shrink"
Silk. Sometimes the drawing conditions improve, and the phenomenon of "shrinkage" disappears, causing the diameter of the two ends of the entire steel wire to be qualified and the middle to be unqualified, making it difficult to detect during inspection,
Affects the overall performance of steel wires.
2. The ovality of the steel wire is out of tolerance, which is caused by: on the one hand, the manufacturing error of the wire drawing die itself, which can be found during inspection before driving;
On the other hand, it is due to poor pre-treatment before wire drawing (poor acid cleaning, poor coating) or poor material of the wire drawing die, which leads to uneven wear of the mold and steel wire
Uneven deformation.
(2) Surface defects of finished steel wire
1. Surface scratches, also known as "fuzzing", are caused by poor machining of the wire drawing die and poor smoothness; Insufficient rust removal or poor lubrication of raw materials,
Causing mold cracking and forming linear scratches on the surface of the steel wire, resulting in a decrease in the mechanical properties, especially toughness, embrittlement, and even wire breakage of the steel wire.
In such situations, it is necessary to replace the mold in a timely manner and improve lubrication.
2. There are rust scales, spots, and rust on the surface of the steel wire, which are caused by severe rusting of the raw materials, poor pre-treatment before drawing, and still some oxygen after drawing
The residual iron sheet on the surface of the steel wire; Alternatively, the steel wire may rust due to being placed in a humid or corrosive atmosphere (such as acid mist).
3. Scars on the surface of the steel wire, such as oxidation scars and right gray scars. It is due to the adsorption of unwashed iron oxide scales or hard particles in the coating on the surface of the steel wire,
Caused by being pressed on the surface of the steel wire during drawing; There is also a type of rooting scar that is in the shape of a "tongue" or "nail" and connected to the steel substrate, which is due to
Caused by scarring or peeling of raw materials.
4. Cracks (cracks), there are two situations:
(1) Longitudinal cracks occur along the longitudinal direction of the steel wire, with shapes ranging from straight to "r" shaped, varying in length. There are many reasons for this, mostly
It is caused by cracks, bubbles or inclusions, and residual shrinkage in the raw material.
(2) Transverse cracks, transverse cracks on the surface of steel wires, distributed locally. Cause: Segregation of wire composition, surface carburization, greatly reducing plasticity
Sexual, metal delamination and cracking after drawing; Steel wire overheats or cools too quickly during heat treatment; Excessive total or partial compression during drawing
Excessive tension; Poor lubrication can cause metal adhesion and scratches, etc.
5. The surface of the steel wire is in the shape of bamboo knots, which means that the steel wire undergoes periodic bamboo undulations along its length direction after coming out of the finished mold, also known as waves. Cause of occurrence
There are mainly the following aspects:
(1) The working cone angle of the wire drawing die is not straight and forms an oblique hole, or the cross section of the sizing strip is not straight and forms an ellipse;
(2) The cone and fillet radii of the drum are not suitable, or there are too many or heavy accumulated lines, which makes it difficult for the steel wires to smoothly move upwards and press each other's lines mechanically
Delayed injury;
(3) The drum assembly is not tight, and the swing is loose during wire drawing, causing the centerline of the wire drawing die to be not tangent to the drum and not in a straight line. The steel wire is aligned with the direction of the drawing force
Deviation will result in "bamboo knots" along the length direction of the steel wire;
(4) Insufficient lubrication caused by poor lubricant introduction leads to uneven deformation of the steel wire and the formation of "bamboo knots". The defects caused by this reason are caused by the "bamboo knot"
The wavy curvature is very small and almost unrecognizable with the naked eye, so it needs to be identified by hand feeling. In addition, some compression ratios that are too small may also cause "bamboo knots",
So the compression rate of the last pass is generally greater than 10%.
6. The "∞" line and "Yuanbao" line are more prone to this defect when drawing medium and high carbon steel wires on a continuous wire drawing machine, which is initially not easy to occur
It has been found that once discovered, a lot of wire has been pulled out, and sometimes the entire coil of wire is twisted and cannot be pulled back, resulting in waste. The main reasons for this are as follows:
(1) The axis of the mold hole is not perpendicular to the end face of the mold sleeve, or there is an uneven cushion between the end faces of the mold sleeve (such as lubricant squeezing in the middle), or the position of the mold box is not correct
Correct, causing the mold axis to not be tangent to the drum direction, and excessive deviation angle causing uneven deformation of the steel wire;
(2) The assembly of the wire drawing machine equipment is poor, causing the drum to sway left and right, or the mold box to move, causing the relative position of the mold box and the drum to be either high or low, left or right,
Uneven deformation of steel wires;
(3) If the diameter of the roll is too large and the diameter of the steel wire is small, the two are not proportional and are prone to additional torsional stress;
(4) A car in front of the finished drum of the continuous wire drawing machine has too much wire accumulation. It stops to lay out the wire, and every time it is laid out, the steel wire is twisted by 3600, resulting in
Additional torsional stress;
(5) When the finished drum is equipped with a straightener, repeated bending to eliminate insufficient or excessive stress can also easily cause such defects.
(3) Wire breakage during drawing process
1. Wire breakage caused by raw material defects, such as residual shrinkage cavity, local carburization, folding, inclusion, Martensite structure, widmanstatten structure, etc., may occur
Causing wire breakage during drawing. When the wire rod has a local brittle Martensite structure, the fracture surface of the drawn broken wire is straight. When there is a Weinsteinite structure and crystal in the wire
When the particles are coarse and there is a large amount of network ferrite precipitation, the wire has low strength, poor toughness, and is prone to wire breakage during drawing.
2. Uneven strength or poor organization of the steel wire after heat treatment can cause wire breakage.
3. "Hydrogen embrittlement" causes wire breakage. The pickling time of steel wire is too long, the concentration is too high, and the hydrogen generated during the pickling reaction enters the steel matrix along the grain boundaries.
Fracture analysis shows traces of acid infiltration. Place the "hydrogen embrittlement" wire blank for a period of time or heat it in the drying furnace for a period of time, and the "hydrogen embrittlement" is generally
Can be eliminated.
4. Poor electrical connection causes wire breakage, and traces of polishing after butt welding can be found near the fracture surface.
5. If the working cone angle of the wire drawing die is too large or too small, and the length of the sizing belt is too long, the friction force increases, which can also easily cause wire breakage.
6. Poor lubricant quality and poor lubrication state, resulting in adhesion and wire breakage.
7. The drawing process is unreasonable, and the total or partial compression rate is too high, resulting in wire breakage.
8. Due to the aforementioned "shrinkage" causing wire breakage.
Studying the different shapes of fracture surfaces can roughly estimate the cause of wire fracture. The fracture surface of brittle fracture exhibits various abnormal shapes, such as cup cone and flat
Cut, stepped, canine, split, etc; The fracture surface of plastic fracture generally has necking or slight necking.

There are often multiple reasons for each type of wire drawing defect. In on-site work, it is necessary to analyze all factors

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