When the steel pipe is sized by the micro-tension reducer of the steel pipe plant, the steel pipe wall is unevenly thickened due to the lateral deformation of the metal (flowing in the radial direction), and the inner hole of the cross-section is "six square", commonly known as "inside" Six parties." The “inner hexagon” is the result of uneven lateral deformation of the metal, and is also a special manifestation of uneven wall thickness of the steel pipe.
Hot-rolled seamless steel pipe produced by steel pipe plant, the maximum reduction rate of single frame of mill is 3.5%, the average tension coefficient is less than 0.48, adopts micro-tension rolling, three-roller fourteen two-motor centralized differential drive micro-tension reducer Sizing, the diameter and wall thickness of the steel pipe can reach the final finished product size. However, when this equipment is used to roll small-diameter thick-walled steel pipes, it is prone to "inner hexagonal" defects, which seriously affect the wall thickness and inner diameter accuracy. This work is mainly formulated by adjusting the reduction ratio and modifying the hole type parameters of the reducer. The production process can effectively reduce the "inner hexagonal" defects.
1 Steel pipe plant production process and process points
The production process is as follows: blank sawing blank heating perforated rolling pipe micro-tension reducing cooling cooling straightening pipe packaging delivery.
2 Determination of process parameters and hole design of steel pipe plant
When the steel pipe plant uses the ¢120mm continuous casting billet to produce 114mm×22mm steel pipe, the wall thickness coefficient of the steel pipe is large, so that the transverse wall thickness of the steel pipe after sizing is uneven, resulting in the “inner hexagonal” degree of the inner surface of the steel pipe. serious.
When the micro-tension is reduced, the reduction rate is the most important factor for the “inner hexagonal”, and the total reduction rate and the single-frame reduction ratio have the same mechanism. If the reduction ratio is too large and the tension coefficient is increased, the axial flow is intensified when the metal is deformed, and the radial flow is weakened, and the radial wall thickness is uneven. That is, the large reduction ratio of the single frame means that the height non-uniformity at the top and the roll gap and the greater the difference in metal flow increase the inner polygon.
When the total reduction rate is constant, increasing the number of finished racks can reduce the reduction rate of the single frame. Five sizing machines were used before optimization, and six sizing machines were used after optimization. The formula can calculate the reduction ratio of the single frame of each frame. The first reduction rate depends on the size of the outer diameter before the sizing. In actual production, this number is a range value, so the first reduction rate is one. Uncertain value. The main parameters of the traditional hole type of the micro-tension reducer include: wide expansion coefficient, average diameter of the hole type, long semi-axis of the hole type, short half-axis of the hole type, and ellipticity coefficient.
3 actual production results
After reducing the total reduction rate and the single frame reduction rate and optimizing the hole type parameters, the 114mm×22mm finished spiral steel pipe was sampled in kind, and the actual measurement data showed that the “inner hexagonal” degree was significantly reduced and reached the national standard. And fully meet the needs of users. By comparing the data measured before and after the optimization, it can be known that the "inner hexagonal" metric value of the steel pipe produced by applying the optimized 114 mm hole type is significantly reduced.
The production practice proves that the three-roller four-motor two-motor differential drive micro-tension reducer of the 114mm unit of the steel tube plant can reduce the total reduction ratio and the single-frame reduction ratio and select a reasonable hole design. Until the "inner hexagonal" defect of the micro-tension reducing steel pipe is eliminated.
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