In view of the problem of bulge particle defect on the surface of hot-dip galvanized sheets, the causes were analyzed by investigating defect characteristics and surface cleanliness of cold-rolled steel sheets. The results show that the cause of bugle particle defect lies mainly in the residual iron on the surface of cold rolled steel sheets, which has not been cleaning off during degreasing and interfere the normal formation of coating. The bugle particle defect can be effectively prevented when the laser-textured work rollers of No.1 stand of HC tandem cold mills are replaced by smooth rollers, because the residual iron on the surface of cold rolled steel sheets can be reduced obviously.

Aiming at the question of improvement expansive soil in Nanyang area, the composite improvement method of lignin and cement was adopted. Based on the unconfined compressive strength test, the variation law of unconfined compressive strength of improved expansive soil with different lignin content, different compaction degree and different curing age was studied. The test results show that the composite of lignin and cement can effectively improve the unconfined compressive strength of expansive soil. The unconfined compressive strength of L-C (lignin and cement) improved expansive soil reaches the maximum when the cement content is fixed at 4% and the lignin content is 1%. The unconfined compressive strength of L-C improved soil increases with the increase of compaction degree and curing age, and the strength growth mainly concentrated in the first 7 days of curing age. From the point of improvement mechanism, the hydration and gelation reaction of cement occur in expansive soil, and gel material with higher strength is formed to enhance the strength of expansive soil. The appropriate amount of lignin can fill the pores between soil particles and make the connection between soil particles more closely, so as to improve the strength of expansive soil.

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