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high-speed wire rolling mill
High-speed wire rolling mill
steel wire
The assembly and use process of steel wire screw sleeve

The quality of wire rod

The steel types of wire are very wide, including carbon structural steel, high quality carbon structural steel, spring steel, carbon tool steel, alloy structural steel, bearing steel, alloy tool steel, stainless steel, electric heating alloy steel, etc., and the steel types that need to be processed into wire are mostly produced into wire rod and then drawn into wire by wire mill. Wire is divided into the following categories normally:

The quality of wire rod
  1. Soft wire, refers to the ordinary low carbon steel hot rolled disc, the current grade is mainly Q195, Q215, Q235 stipulated in the carbon structural steel standard and the high quality carbon structural steel stipulated in the 10, 15, 21 steel;
  2. hard wire, refers to the high quality carbon structural steel wire rod, such as rope wire rod, knitting wire rod, tire steel wire, piano steel wire and other special wire rod, hard wire generally high carbon content, generally refers to the high quality carbon structural steel above 45, 40MN-70MN, T8MnA, T9A, T10, etc.;
  3. welding wire refers to the wire rod used for welding rod, including carbon electrode steel and alloy electrode steel wire rod;
  4. Jingang wire, it refers to all kinds of alloy steel and special steel wire rod with high alloy content. Such as bearing steel rod, alloy structural steel, stainless steel, alloy tool steel rod and so on. Low alloy steel wire is generally classified as hard wire, and can also be classified as alloy steel if it has special properties.

Wire is divided into two kinds by use, one kind is used directly, used as building reinforcement more; One is used after deep processing, used to wire into metal products or cold pier into screws, nuts and so on.

  1. General wire delivery technical conditions are: shape and dimensional accuracy; Surface quality and oxide scale; Section quality and metallographic structure; Section refers to the section perpendicular to the center line of the wire; Chemical composition and mechanical properties (including process properties of deep processing); Heavy plate; Warranty and marking.
  2. The use of wire has different quality requirements, such as cold pier material in addition to the mechanical properties of strict requirements, the most important is to require cold pier cracking, and in order to ensure that no cracking should be strictly controlled inclusions and surface cracks, folding, scratching and other defects caused by cracking. The quality requirements of electrode steel wire rod are mainly strict control of chemical composition and segregation.
The quality of wire rod

The quality of wire rod

1, precision

The use of high-precision wire as reinforcement can reduce the discrete difference of allowable force of reinforcement and thus save steel. The high precision wire used in drawing process can improve the drawing performance of metal, reduce the uneven deformation in drawing and the difference in mold pressure caused by the uneven deformation, so as to reduce the broken wire and improve the surface quality of steel wire.

It is not difficult for the product diameter deviation of high speed wire mill to reach ±0.1mm, even to reach ±0.05mm, but it is uneconomical to require very high precision of hot rolled products. A very small number of high-precision products can only be produced in good condition of the rolling mill. But the requirement of high precision does not always have obvious effect in use. For example, for flexible wire and welding wire, the raw materials with diameter deviation of ±0.15mm and ±0.25mm were compared, and it was found that there was almost no difference in the quality, production efficiency and processing cost of cold-drawn products. Since the product that asks cold to draw performance very high, the requirement to wire precision is not very tall also. When the cost of hot rolling to produce high-precision products is higher than the cost of adding a heat treatment in cold drawing process, it is no longer required to improve the accuracy of hot rolling to meet the needs of drawing.

2, the surface

The surface requirement of wire is smooth and clean and must not have the blemish that hinder use, must not have ear child, crack, fold, scar, interlayer namely wait for blemish, allow to have local indentation, convex piece, pit, scratch and not serious hemp face. No matter wire is used at building directly or deep processing becomes all kinds of goods, the blemish such as its ear child, crack, fold, scar, interlayer affects use performance directly is absolutely do not allow some. As to the a few blemishes that affect surface smooth and clean degree can give control according to use requirement, the wire that uses as reinforcing bar surface smooth and clean degree affects directly is not big. The wire used for cold pier is sensitive to scratch, and the bump affects the drawing.

The less the iron oxide on the surface of the wire, the better, which can not only improve the metal yield and can shorten pickling time, reduce acid consumption, and even replace pickling with mechanical descaling, eradicate environmental pollution. Based on the requirement of easy removal and good corrosion resistance, it is hoped that the composition of oxide sheet is mainly FeO. The total amount of oxide sheet is required to be less than 10kg/t, and generally up to 8kg/t abroad. To control the generation of high-priced oxide sheet (Fe O, Fe O), the final rolling temperature, the spinning temperature and the time of the wire staying above 350℃ should be strictly controlled.

The quality of wire rod

3, section quality and metallographic organization

Usually mass is not called section mass. However, it is not very scientific to completely attribute shrinkage cavity, center porosity, inclusion and other defects to surface defects, and it is sometimes difficult to find such defects without cross section inspection. Some defects such as decarbonization, overheating and so on without the help of metallographic microscope can not be quantitatively determined correctly. And this kind of blemish occupies important position in evaluating wire quality.

When the carbon content is above 0.3% of the wire, the depth of its surface decarbonization layer should be strictly controlled. Decarbonization is the formation of canine ferrite embedded in the matrix on the surface, which will seriously affect the tensile strength of the wire, especially its fatigue strength. The wire used for cold drawing will increase deformation resistance due to internal and external organization difference. Therefore, it is necessary to strictly control the depth of decarbonization layer for the important wire directly used as cold drawn material, high strength bolt and cold pier. The following table shows the actual depth of decarbonization layer controlled by some manufacturers.