What type of steel is used in the skew rolling mill for steel balls?
Steel Ball Skew Rolling Process – Steel Ball Rolling – Steel balls are mainly divided into bearing steel balls and ball mill steel balls. In the past, steel balls were primarily manufactured using forging, cold heading, and casting methods, resulting in low production efficiency, poor working conditions, and high costs.
Currently, the spiral skew rolling process is widely used. This process can employ single-pass or multi-pass rolling. Single-pass spiral rolling refers to the rolls performing only one spiral roll, while multi-pass spiral rolling refers to the rolls performing two or more spiral rolls. In production, two-pass, three-pass, or four-pass spiral rolling is commonly used, allowing two, three, or four products to be produced per roll rotation, thus significantly improving production efficiency. Steel ball rolling typically uses hot rolling, while small-diameter steel balls can be cold rolled.
Steel Ball Skew Rolling Mill – In the hot rolling process of steel balls, a round steel billet with a diameter approximately 4% smaller than the diameter of the rolled ball is first heated to 850-1100℃ (the lower limit temperature for bearing steel) using an induction heating device. The heated steel billet is then fed into a skew rolling mill for rolling. The roll axis is inclined at a certain angle to the rolling line. The rolls are equipped with a spiral die. The rolled part advances in a spiral shape. Under the action of the spiral die, the round steel is gradually rolled into a spherical shape, the connecting neck between the spheres gradually narrows, and finally breaks to form a steel ball. After further processing, the rolled steel ball becomes a finished steel ball. The rolling die consists of two parts: a forming section and a finishing section.
In the forming section, the die engages the steel billet and rolls it into a spherical shape. In the finishing section, the rolled part is finished and separated from the steel billet. The total length of the die is between 1170 and 1350 mm. For bearing steel balls, the finishing section usually contains about one rotation, while the forming section contains one and a half to two rotations. An excessively long forming section increases the number of rotations of the bar in the die, which may cause loosening of the center of the steel ball and the cavity. The die design principle for ball milling steel balls is basically the same as that for bearing steel balls. However, the finishing ridge of the skew rolling die for ball milling is raised to (or slightly above) the axis of the rolled piece to cleanly remove the tail. The ridge of the finishing section of the die is straight, eliminating the need for a storage trough. The finishing section of the ball milling die is significantly longer than that of the bearing ball milling die, with a total die length typically ranging from 1260° to 1350°. For small tapered cylindrical rollers, single-cavity rolling is usually employed, with one roll having a helical die and the other a dieless smooth roll.
