离心铸造双金属环件热辗扩实验研究

Experimental Research on Hot Ring Rolling of Centrifugally Cast Bimetallic Rings

与单金属环件相比,双金属环件可以同时满足复杂环境对环件内外层金属的不同使用要求,具有很大的优势。针对目前双金属环件的制造方法费时费力、结合效果差的现状,笔者提出并研究一种双金属复合环件短流程制造技术,利用离心铸造的双金属环坯直接热辗扩成形双金属环件,生产效率高,节约能源,结合层为冶金结合,结合效果好。本工作以离心铸造的双金属环坯(内层Q345,外层40Cr)为研究对象,采用不同的初始辗扩温度(1200℃、1150℃、1050℃)和辗扩比(2.3、2.0、1.5)进行了辗扩实验,对不同辗扩工艺参数下的环件进行金相实验和拉伸实验。结果表明,随着辗扩比增大,环件整体晶粒先变小后变大,抗拉强度先提高后降低;随着初始辗扩温度降低,晶粒变小,40Cr抗拉强度和塑性提高,Q345抗拉强度先升高后降低,塑性提高。结合层是一个过渡区,没有明显的界线,从一种金属逐渐向另一种金属过渡,它的晶粒比内外层大。辗扩后环件椭圆度均小于0.02,超声波检测无裂纹缺陷。初始辗扩温度为1050℃、辗扩比为2.3时成形的环件综合性能最好。离心铸造的双金属环坯在辗扩后,环件外形好,探伤合格,组织和力学性能得到改善,成功实现了双金属环件的铸辗复合成形。

Compared with the single metal ring,the bimetal ring has great advantages.It has two different metal with different properties to meet the different requirements for the inner and outer layers of the ring at the same time.Aiming at the problems of time-consuming,labor-intensive and poor bonding effect in the current manufacture of bimetallic rings,the authors proposes and studies a short-process manufacturing technology for bimetallic composite rings.In this process,two metals are joined together by centrifugal casting to form an annular billet,which is then hot rolled into a bimetallic ring.The method has the advantages of high production efficiency,energy saving,and good bonding layer.Based on the centrifugal casting bimetallic ring billets(inner layer Q345,outer layer 40Cr),ring rolling experiments were carried out at different initial rolling temperatures(1200℃,1150℃,1050℃)and different rolling ratios(2.3,2.0,1.5).Metallographic and tensile experiments were performed on these rings.With the increase of rolling ratio,the grain size of the ring first became smaller and then larger,and the tensile strength first increased and then decreased.With the increase of rolling ratio,the grain size of the ring first became smaller and then larger,and the tensile strength first increased and then decreased.The bonding layer is a transition region with no obvious boundaries and its grains are larger than those of inner and outer layers.With the decrease of initial rolling temperature,the tensile strength increases first and then decreases,and the plasticity increases.All the ovality of rolled rings are less than 0.02,and no crack is detected by ultrasonic.When the initial rolling temperature is 1050℃and the rolling ratio is 2.3,the comprehensive performance of the ring is the best.The bimetallic ring of centrifugal casting has good shape,no crack defect,and its microstructure and mechanical properties have been improved after rolling.The casting and rolling compound forming of bimetallic ring is realized successfully.