The wire surface has different shapes of rupture called cracks, divided into longitudinal cracks and transverse cracks. General longitudinal cracks in the wire surface is continuous or intermittent distribution; and transverse cracks are discontinuous distribution. Some cracks have inclusions and decarburisation on both sides.
Causes of forming crack
1 Billet used in the existence of uneliminated cracks, subcutaneous bubbles and non-metallic inclusions will cause crack defects; if the casting billet has pinholes not be cleared away, by rolling is extended, oxidation, fusion will cause the linear streak in the finished product.
2 Billet is over-burnt when reheating; for high-carbon steel coil or high alloy content of the billet, preheating speed is too fast, the heating temperature is too high;
3 There is a serious temperature uneven or uneven deformation (also likely to appear transverse cracks);
4 Rolled parts are cooled too quickly or local quench. improper control of cooling after rolling the formation of cracks without decarburisation phenomenon accompanied by cracks in the general absence of iron oxide.
Prevention methods
1 Inspect billet quality;
2 Correct controlling heating temperature to avoid billet overburnt;
3 Provide reasonable rolling temperature or cooling temperature.
