Common problems and solutions during the use of cold heading machines
Source：http://mmjiao.cn Author：冷鐓機 Time：2014/8/19 Click：
The reason for cold heading cracking!
The internal quality problems of the wire rod are mainly caused by inclusions, and generally slag inclusions are caused by rolling slag during continuous casting. The type and grade of non-metallic inclusions are also another reason that affects the internal quality of the wire rod. Experience in producing cold heading machines has shown that non-metallic inclusions rarely cause cold heading cracking. Compared to the internal quality issues of the wire rod, the proportion of surface quality issues of the wire rod accounts for the vast majority.
There are two manifestations of surface quality problems with wire rods: first, surface cracks on wire rods with oxidation characteristics; This is mainly inherited from surface cracks on the cast billet. Secondly, there are surface cracks on the wire rod without oxidation characteristics, including: ① a special type of wire rod surface crack without oxidation characteristics. ② The surface quality problems caused by steel rolling are mainly due to rolling folding defects!
The solution to cold heading cracking
The measures taken for cold heading cracking include steelmaking and continuous casting, steel rolling, and steelmaking and continuous casting. Due to the liquid level fluctuation being controlled within ± 20mm, the depth of subcutaneous slag inclusion will be less than 2mm, so the liquid level fluctuation is controlled within ± 15mm; If the depth of subcutaneous slag is less than 2mm, it can be eliminated during heating in the furnace. The liquid level fluctuation increased from ± 5mm to ± 20mm, and the longitudinal crack index on the surface of the casting billet increased from 0 to 2.0. Considering the actual situation of the steel plant, the liquid level fluctuation should be controlled within ± 15mm. Multi station cold heading machine
The overheating degree of molten steel increases by 10 ℃, and the flow of high-temperature molten steel in the crystallizer will eat up about 2mm of the solidified shell, causing stress concentration. Therefore, a stable and appropriate overheating degree can reduce longitudinal cracks on the surface of the casting billet. Strictly controlling the uniformity of cooling in the secondary cooling zone and using weak cooling to control the repeated temperature rise of the billet shell can reduce the occurrence of edge cracks in the cast billet.
The measures taken for steel rolling are: ① When rolling multi station automatic cold heading machines, check and replace the guide device, guide wheel, and sleeve roller frequently; ② For the rolling of cold heading machine wire rods, the coarse rolling pass system is adjusted reasonably, the settings of the finishing mill and reducing mill are optimized, the process parameters are improved, the temperature during rolling is strictly controlled, and the delayed cooling after rolling greatly improves the product quality.
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