摘要
钢铁的生产已经步入连铸连轧时代,其中连铸工艺的关键部件—结晶器的性能好坏对连铸坯质量、连铸生产效率起着决定性的作用。结晶器铜板又被称作连铸结晶器的心脏,其工况条件除了受到钢水的冲刷及结晶器自身的震动带来的损伤之外,还受到温度极高的钢水和冷却水共同的热应力作用。
本文研究内容为选取目前国内连铸结晶器中主要用到的两种铜合金即Ag-Cu、Cr-Zr-Cu合金及电镀有1mmNi-Co镀层的两种合金,通过室温、高温拉伸实验,300℃、400℃、500℃的高温疲劳试验和热疲劳试验,结合显微组织的变化对两种合金的性能变化进行了分析,得出以下主要结论:
(1)在室温及350℃下,合金元素的加入产生的固溶强化效应使两种合金都有着较好的室温及高温强度。由于Cr和Zr的复合加入除了起到固溶强化的效应外,还起到沉淀强化的作用,所以Cr-Zr-Cu合金的屈服及抗拉强度都要高于Ag-Cu合金。带有镀层的合金在室温和350℃的力学性能要优于不带镀层的基材。
(2)通过对两种铜合金的高温疲劳实验得出,在300℃、400℃、500℃下,Cr-Zr-Cu合金的高温疲劳性能都要优于Ag-Cu合金,两种铜合金的高温疲劳性能都随着温度的升高而逐渐下降。Cr-Zr-Cu合金中第二相随着温度的升高而长大使沉淀强化效应下降导致了高温疲劳性能的下降。
(3)在上限温度为450℃,下限温度为室温条件下对两种铜合金及带有1mmNi-Co镀层的两种合金进行了热疲劳试验。结果表明,随着冷热循环次数的增加,两种合金加工硬化效应减弱而导致硬度逐渐下降。晶界处的Zr元素在热疲劳过程中被消耗掉可能导致了Cr-Zr-Cu合金硬度的下降。Cr-Zr-Cu合金的硬度始终高于Ag-Cu合金。镀层对提高铜板的硬度效果十分明显。Cr-Zr-Cu合金与镀层的热膨胀系数相差较大导致了镀层与基体的剥落。
Steel production has entered the era of continuous casting and rolling, The quality of crystallizer play a decisive role in billet quality and continuous casting production efficiency. Copper also known as the heart of the Continuous casting crystallizer. Besides being damdged by the liquid steel Scouring and the vibration of the crystallizer, the copper is also subjected to the thermal stress caused by the high temperature steel and cooling water.
The research in this paper mainly include: Ag-Cu、Cr-Zr-Cu、Ag-Cu and Cr-Zr-Cu with 1mm Ni-Co coating were chosen. By tensile test at room temperature and high temperature, high temperature fatigue tests at 300℃,400℃,500℃and the thermal fatigue test , the main conclusions drawed from study just as following:
(1) Solid solution strengthening effect produced by adding alloying elements make the two alloys have a good room and high temperature strength. As the compound by adding Cr and Zr in addition to play solid solution strengthening effect,but also play a role in precipitation strengthening. So the yield strength and the tensile strength of Cr-Zr-Cu alloy are higher than the Ag-Cu alloy,s at the room temperature and 350℃.The mechanical properties of alloys with coating are better than the alloys without coating.
(2) By the high temperature fatigue tests, it can be concluded that the high temperature fatigue properties of Cr-Zr-Cu alloy are better than the Ag-Cu alloy,s at 300℃,400℃,500℃. Two types of copper alloys, high temperature fatigue properties are decline with the temperature increases. The second-phase particle of Cr-Zr-Cu alloy are growing up with the temperature increases, that makes the precipitation strengthening effect decreased lead to the high temperature fatigue properties gradually decreased.
(3) At the upper limit temperature of 450℃, minimum temperature at room temperature for two types of copper alloys and alloys with 1mm Ni-Co coating had thermal fatigue test. It can be concluded that all alloys, hardness are decline increased as the hardening effect of eliminating with the number of thermal cycling. The Zr element on the Grain boundaries are consumed might result in the hardness decreased of the Cr-Zr-Cu alloy. The hardness of Cr-Zr-Cu alloy is always higher than the hardness of Ag-Cu alloy. The hardness have been significantly improved after plating the coating.The thermal expansion coefficient between Cr-Zr-Cu alloy and the coating is large difference lead to the coating flaked.
引文
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