调质低碳贝氏体钢的组织和性能.pdf

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1、第34卷第2期北京科技大学学报Vo1．34No．22012年2月JournalofUniversityofScienceandTechnologyBe

2、jingFeb．2012调质低碳贝氏体钢的组织和性能徐立善余伟圜张烨铭卢小节北京科技大学高效轧制国家工程研究中心，北京100083函通信作者，E-mail：yuwei@nercar．ustb．edu．cn摘要研究了C—Mn—Mo—Cu—Nb—Ti—B系低碳微合金钢915oC淬火和490～640℃回火的调质工艺对钢的组织及力学性能的影响．用扫描电镜和透射电镜对实验钢的组织、析出

3、物形态和分布以及断口形貌进行观察，采用x射线衍射仪分析钢中残余奥氏体的体积分数．结果表明：调质后，实验钢获得贝氏体、少量马氏体及残余奥氏体复相组织，贝氏体板条宽度只有250nm，残余奥氏体的体积分数随着回火温度的升高而降低，经淬火与520℃回火后残余奥氏体的体积分数为2．1％．调质后析出物的数量激增，6一-15am的析出物占70％以上．实验钢经过915℃淬火与520℃回火后，其屈服强度达到915MPa，抗拉强度990MPa，一40qC冲击功为95J．细小的析出物及窄的板条提高了钢的强度．板条间有残余奥氏体存在，改善了实验钢的

4、韧性．关键词高强钢；热处理；残余奥氏体；析出物；微观组织；力学性能分类号TG142．1MicrostructureandmechanicalpropertiesoflowcarbonbainitesteeltreatedbyquenchingandtemperingXULi—shan，YUWei，ZHANGYe．ming，LUXiao-fieNationalEngineeringResearchCenterforAdvancedRollingTechnology，UniversityofScienceandTechnolog

5、yBeijing，Beijing100083，China圜Correspondingauthor，E-mail：yuwei@nercar．ustb．edu．enABSTRACTTheeffectsofquenchingat915℃andtemperingat490～640℃onthemicrostructureandmechanicalpropertiesofC—Mn—Mo-Cu-Nb—Ti—Bbasedlow—carbonmicroalloyedsteelwereinvestigated．Themierostructure

6、．theshapeanddistributionofprecipi—tates，andthefractographofthesteelwereobservedbyscanningelectronmicroscopy(SEM)andtransmissionelectronmicroscopy(TEM)．ThevolumefractionofretainedaustenitewasmeasuredbyX-raydiffractometry(XRD)．Theresultsshowthatamuhiphasemicrostructu

7、rewithbainite，martensiteandretainedausteniteisachievedafterquenchingandtempering．Thebainitelathis250nminwidth．Thevolumefractionofretainedaustenitedecreaseswiththetemperingtemperaturerising．anditis2．1％aftertemperingat520℃．Thequantityofprecipitatesincreasessharplyaft

8、erheattreatment．andtheproportionofprecipitatesinasizerangeof6to15nmisabove70％．Afterquenchingat915oCandtemperingat520oC，theteststeelhasayieldstrengthof915MPa，atensilestrengthof990MPaanda一40oCimpactenergyof95J．Fineprecipitatesandnarrowlathbainitecanenhancethestrength

9、．buttheretainedausteniteexistingbetweenbainitelathscansignificantlyimprovethetoughness．KEYWORDShigbstrengthsteel；heattreatment；retainedaustenite；