The first stage is called primary rolling, or cogging.

这个阶段叫作初轧或开坯。

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The problems existed at primary rolling plants in china are comprehensively analysed, and the necessary measures to increase the billet yield are proposed accordingly.

综合分析了我国初轧厂目前存在的一些问题。提出了进一步提高成坯率应做的工作；

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Today, rolling suitcases have replaced bamboo poles as the primary means of hauling loads, and the walk across Suzhou station's platforms is a leisurely stroll.

今天，拉杆箱早已取代了扁担，在苏州火车站，通往站台的一段路途也变成了闲庭信步。

youdao

Indeed, when the ball gets rolling the fear of principal loss may become a primary reason for foreign central banks the world over to bail on U.S. government debt.

FORBES: America, poised for a hyperinflationary event? ...the Roadmap

But if you're not quite in the top 1% and since you haven't yet paid off your primary mortgage yet, I'm guessing you aren't then I'm rolling my eyes, too.

WSJ: Breaking the Home-Buying Habit -- WSJ House Talk