Effect Of Thermal Refining On Microstructure And Mechanical Properties Of CM690 Anchor Chain

With the development of the country,the shipping industry is developing rapidly.Anchor chain is an important part of the ships,which requirements are constantly improving.The reason why CM690 widely used in anchor chain industry is that CM690 has a lot of advantage,such as high fatigue strength and smaller quenching deformation,as well as high strength,toughness and good wear resistance after thermal refining.However,CM690 has a widespread problem of poor properties and high energy consumption in production.Therefore,the study on the anchor chain with good properties and low energy consumption is of great significant for the development of anchor chain industry.This topic mainly focuses on CM690 anchor chain without heat treatment that produced Laiwu Iron and Steel Group Zibo Anchor Chain Co.,Ltd.Firstly,the microstructure and mechanical properties of CM690 anchor chain without heat treatment and its raw materials are analyed.Then the effect of quenching temperature,tempering temperature and tempering holding time on the microstructure and properties of the CM690 anchor chain's back,bending region and welded joints are researched,finding the best machining process of improving the properties and reducing the energy consumption.Then the topic carry out a Reformation feasibility analysis of tempering furnace for Zibo Anchor Chain Co.,Ltd.The analysis of the CM690 anchor chain without heat treatment shows that the Rm of anchor Chain's back and welded joints are slightly lower than the properties requirement.As the presence of a large amount of widmanstatten structure of welded joints,which impact energy at 0? is poor and far below the target requirements.Therefore,reasonable heat treatment process is need to improve its performance.By analyzing the inclusions of anchor Chain's back and welded joints,we can find that the types and sizes of inclusions are same.However,there are more inclusions at welded joints,which make the impact energy of the welded joints fluctuate greatly.Reaearch has shown that the quenching temperature had little effect on the microstructure and properties of each part.The properties under the quenching temperature of 830 ?,860 ? and 890 ? all meet the requirements.As the increase of quenching temperature,strength,reduction of region and wear resistance of anchor chain's back increase first and then decrease.Meanwhile,hardness,elongation and impact energy at 0? change little;hardness of the bending region does not change much;Rm,weld hardness and impact energy at 0? of welded joints are increased.The wear mechanism under different quenching temperatures is a comprehensive wear mechanism of abrasive wear and adhesive wear.And wear resistance increases first and then decreases with the increase of quenching temperature.The best wear resistance is at 860 ?.The tempering temperature has a significant effect on the microstructure and properties.With the increase of tempering temperature,the content of acicular a-ferrite phase decreases,and the cementite changes from flaky or thin rod to granular.Strength and hardness of the anchor chain's back decreased sharply.Meanwhile,elongation,reduction of region and impact energy at 0? increase;hardness of the bending region decreases;Rm and weld hardness of welded joints decline,as well as elongation and impact energy at 0? rise.The wear mechanism of different tempering temperature is a comprehensive wear mechanism of abrasive wear and adhesive wear,and wear resistance decreases with tempering temperature increasing.When the tempering holding time is less than 30min,the effect of tempering holding time on the microstructure and properties of the CM690 anchor chain is obvious.When the holding time is more than 30min,the effect is inconspicuous..With the increase of holding time,the content of acicular a-ferrite phase gradually declines,and the cementite changes from flaky or short rod to granular.Strength and hardness of the anchor chain's back decreases as well as elongation,reduction of region and impact energy at 0? increasing;hardness of bending region decreases;Rm and weld hardness of welded joints increase first and then decrease,and reach the summit at 30min.Meanwhile,elongation and impact energy at 0? increasing.The wear mechanism of different tempering holding time is a comprehensive wear mechanism of abrasive wear and adhesive wear,and the wear resistance increases first and then decreases with the increase of tempering holding time.When the tempering holding time is up to 30min,the wear resistance is the best.