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The application of PVD coating for tools used at tube straightening

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Straightening is a technology that is used to remove undesirable distortions. Curvature of the product axis arises as a result of the production technology [1]. Straightening leads to the elimination or reduction of curvature in the metal products using external forces. In practice, the tube runs between the straightening rolls that are rotated to the direction of straightening at an angle (Fig. 1). The roll’s profile is not the tube’s radius. The profile is hyperbolic; the contact roll touches the tube at just three points (Fig. 2). The tube rotates as it passes through the straightening machine. While passing through the machine, the tube is subjected to two specific straightening forces: 1. Pressure straightening. Each pair of rolls can be adjusted so that the gap between them is slightly smaller than the outside diameter of the tube. As the tube passes through this restricted gap, it is subjected to pressure which, if sufficient, will cause the tube walls to be strained past their elastic limit, thereby causing some straightening of the tube. If this ability to squeeze the tube is used correctly, the tube will be "rounded up," removing some or all of its ovality (Fig. 3) [2]; 2. Bend, or offset, straightening. One or more pairs of rolls can be adjusted to cause the tube to follow a curved path through the machine (F[...]

The application of CVD coatings for cold forming tools

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The cold forming tools of axis symmetrical faces are subject to abrasion, and the high demands of cohesive strength of operating surface are required. The paper deals with the possibilities of usage of CVD coatings on chosen tooling materials with the view of lifetime and reliability increase. After the tooling material was chosen the conditions of two-layers coating (TiC +TiN) were optimized[...]

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