Another way to overcome deflection issues is by decreasing the load on the rolls, which can be done by applying a longitudinal force; this is essentially drawing. Other method of decreasing roll deflection include increasing the elastic modulus of the roll material and adding back-up supports to the rolls.[10]
The different classifications for flatness defects are:
• Symmetrical edge wave - the edges on both sides of the workpiece are "wavy" due to the material at the edges being longer than the material in the center.
• Asymmetrical edge wave - one edge is "wavy" due to the material at one side being longer than the other side.
• Center buckle - The center of the strip is "wavy" due to the strip in the center being longer than the strip at the edges.
• Quarter buckle - This is a rare defect where the fibers are elongated in the quarter regions (the portion of the strip between the center and the edge). This is normally attributed to using excessive roll bending force since the bending force may not compensate for the roll deflection across the entire length of the roll.
It is important to note that one could have a flatness defect even with the workpiece having the same thickness across the width. Also, one could have fairly high crown or wedge, but still produce material that is flat. In order to produce flat material, the material must be reduced by the same percentage across the width. This is important because mass flow of the material must be preserved, and the more a material is reduced, the more it is elongated. If a material is elongated in the same manner across the width, then the flatness coming into the mill will be preserved at the exit of the mill.
轧机的发明归功于莱昂纳多•达•芬奇。最早的轧机是1950相继出现在比利时和英国的分切机。通过轧辊形成的铁板又会被槽辊成铁条,这些铁条会被重新压辊镀锡做成镀锡板。在欧洲,早期的铁板生产是靠锻造,而不是轧制。
分切机适用于生产桶上的箍环和半圆或其他截面的铁,这个方法采用了c.1679两个专利中的主要思想。
最早的有关于轧机的文献资料可以追溯到1761年Christopher Polhem的《Patriotista Testamente》一书中,在书中他提到想将带一条手柄的锤子斜立的往事。
1795年,英国的托马斯•布洛克利,因为金属的抛光和轧制被授予专利。另一个专利被授予英国的理查德•福特,他发明了第一台串列式轧机。串列式轧机可对金属进行连续轧制,福特式串列式轧机是线材热轧。论文网
其他金属 铅的轧制于17世纪末就存在了。铜和黄铜的轧制则在18世纪末。
现代轧制
费勒姆附近的Funtley炼铁厂里,亨利•卡特首先为现代轧制做出了贡献。1783年,亨利•卡特因用槽辊轧制铁栅栏,被授予专利。这种新式轧机能使锤子的产量增加15倍。虽然卡特不是第一个使用槽辊的人,但他是第一个将当时已知的将最好的炼铁技术和成型工艺联系起来的人。所以现在人们称他为“现代轧制之父”。
1820年,约翰•伯肯肖建立里第一台导轨轧机,他在机床上生产了15到18英寸长的鱼腹式锻铁导轨。随着技术的进步,轧机的型号随着被扎产品的型号在快速增长。有这样一个例子,在1851年的万国工业展览会上,康赛特钢铁公司展出了一个20英尺长,3.5英尺宽,7/16英寸厚,重1125磅的轧机。1853年,三辊轧机的发明志轧机有了进一步的发展,三辊轧机可用于轧制重型部件。
热轧和冷轧毕业论文
热轧
热轧是在高于再结晶温度的环境中进行轧制的金属加工工艺。在变形过程中,晶体重结晶,保持等轴状组织,同时防止金属的加工硬化。原材料通常是大型金属件,像半成品铸件,如板材、锻铁、钢坯等。如果这些产品是通过连续铸造得来的,它们就将会在适当的温度直接被输送至轧机轧制。在小规模的轧制中,材料在室温下进行加热。可以在一个用于较大工件或较小工件感应加热的天然气或燃油均热炉中完成这一步。必须要强调的是,这时材料的温度必须控制以确保它高于再结晶温度。为了确保结束的温度高于再结晶温度,需文持一个安全系数;这个温度通常是在再结晶温度以上,50到100°C(90至180°F)的范围内。如果温度跌至这个温度范围一下,需在热轧前再加热。
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