当事人就迟延履行约定违约金的，违约方支付违约金后，还应当履行债务。
Where the parties prescribed liquidated damages for delayed performance, the breaching party shall, in addition to payment of the liquidated damages, render performance.
若供应商未履行交付义务，伍尔特有权主张违约金，金额以每次迟延交付中每件货物人民币500元为单位计算。
In the event the supplier defaults on a delivery, wurth may claim a contractual penalty in the amount of RMB 500 per delayed customer delivery and delayed article.
第二部分从最基础的定性问题入手，论述了现有观点的不足，并最终将超期使用费定性为迟延履行违约金；
The second part is about the nature of container demurrage. The author analyzes the shortage of current views, and finally defines container demurrage as kind of penalty for delayed performance.
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