The Measures To Improve The Quality Of SWRCH22A Wire Rod

Publish Time: 06/19 2021 Author: Site Editor Visit: 16996

SWRCH22A is a kind of hot-rolled non-twist and controlled cooling wire rod. Mainly used to manufacture standard fasteners such as bolts, screws, studs, nuts, rivets and self-tapping screws. The quality problems that are prone to occur during the manufacturing process are: breakage during the drawing process, cold heading cracking, substandard torque of self-tapping nails, and nail tip cracking.
Analysis shows that inclusions and Widmanstatten structure are the main factors that affect the wire rod drawing performance. The surface quality defects of the wire rod cause cold heading cracking, and the loose center and shrinkage cavity of the continuous casting billet will lead to insufficient torque and nail tip cracking. .

To this end, the following control measures are taken:

1. Increase the ratio of acid-soluble aluminum by controlling the Al content in the molten steel treatment stage.

Specific:

(1) The C content of the converter tapping is controlled above 0.10%, the alloy adding sequence is standardized, the tapping process is strictly prohibited from slagging, the tapping is equipped with aluminum, and the incoming Al is controlled at about 0.020%.
(2) In the early stage of LF furnace, calcium carbide and aluminum pellets are used to quickly form white slag. After the white slag, aluminum wire is used to adjust the Al content to ensure the wire feeding speed. When feeding the wire, the bottom blowing is appropriately increased, and the Al is adjusted to 0.050%. ~0.060%, and subsequent aluminum supplementation is strictly prohibited. The Si content is controlled within 0.06%.
(3) In the later stage of refining, feed the iron-calcium line 400m to ensure the line speed. After feeding the thread, perform soft blowing, and the soft blowing time is controlled 12 to 15 minutes. The proportion of acid-soluble aluminum stabilized at more than 80% after process adjustment.

2. Through the use of terminal electric agitation, the looseness of the heart and the segregation of ingredients can be improved.

The casting process of the casting machine is fully protected and prevents secondary oxidation. The electric stirring parameters are adjusted to: the first end electric stirrer 3Hz, 200A (the original process 3.5Hz, 350A); the end electric stirrer 8Hz, 350A (two-way alternating, the original process does not Turn on the end electric stirrer).

3. The central shrinkage defect is due to the volume shrinkage caused by the solidification of the cast slab and the volume shrinkage caused by the cooling has not been completely supplemented, and the hole is produced in the final solidification place. In the smelting and continuous casting process, low superheat, low drawing speed, suitable secondary cooling strength, combined with electromagnetic stirring, strong end cooling and other technologies, through the relative stability of the entire continuous casting process and the coordination of each link , It is helpful to eliminate or reduce the center shrinkage defect of continuous casting slab.

4. Control the surface quality of the wire rod by strengthening the inspection of steel rolling process parts, increasing the frequency of on-line pickling of the wire rod surface, and stopping the inspection and processing when problems are found.

5. Strengthen the implementation of the heating system, strictly control the steel temperature, and further optimize the air-cooled line controlled cooling process. For example, the spinning temperature should not be too high, and the air-cooled roller table speed should not be too fast to extend the decomposition of austenite at a moderate temperature The lower transition time ensures uniform structure and avoids mixed crystal and Widmanstatten structure.

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