CN115029634A - 一种高强高韧性桥梁结构钢Q690qE及其生产方法 - Google Patents
一种高强高韧性桥梁结构钢Q690qE及其生产方法 Download PDFInfo
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Abstract
一种高强高韧性桥梁结构钢Q690qE及其生产方法,钢的化学成分以重量百分数计为:C=0.11~0.13,Si=0.30~0.40,Mn=1.45~1.55,P≤0.015,S≤0.003,Nb=0.020~0.030,V=0.075~0.085,Ti=0.010~0.015,Cr=0.30~0.35,Alt=0.02~0.05,N=0.015~0.017,CEV=0.42~0.45,余量为Fe和不可避免的杂质元素。本发明利用VN微合金化,取消Ni、Mo等贵重金属加入,可节约大量成本;生产的钢板以回火马氏体及贝氏体为主,屈服强度达810~850Mpa,抗拉强度达850~890Mpa,‑40℃冲击功达250J以上,A/B/C/D夹杂物≤0.5级。
Description
技术领域
本发明属于低合金钢技术领域,涉及一种高强高韧性桥梁结构钢Q690qE及其生产方法。
背景技术
伴随着经济的发展,桥梁建设越来越多,桥梁用钢大幅度增长。
桥梁用钢的发展从20世纪60年代开始到现在已成功开发及应用了五代桥梁钢,前面大致经历“碳钢-低合金钢-低碳微合金钢-低碳贝氏体钢”的四个发展阶段,从最开始武汉长江大桥的A3q,然后到南京长江大桥的16Mnq,再到芜湖长江大桥的14MnVNq,后来到沪通长江大桥的Q500qE。桥梁的主跨从100多米到1000多米甚至更长,结构形式由铆接向栓焊、全焊发展。新时代的桥梁工程正向着大跨度、多车道等方向发展,对钢材的要求也在不断地提高,高强、高韧是桥梁结构钢发展的必然趋势,第五代高强桥梁用钢Q690qE的研发成为必然。
Q690qE是一种超高强低合金桥梁用钢,常规采用DQ+T或者QT工艺生产,通过添加淬透性元素Mo、Cr等来提高强度,再利用低碳+Ni、Cu等元素来改善韧性,从而达到高强、高韧的效果,所以Q690qE的生产成本都普遍较高。如中国专利CN109136747A,Q690q成分体系采用Cr+Mo系,生产方法采用调质工艺,合金及工序成本较高;中国专利CN104264064A,利用高Mo+高Ni+在线淬火+回火生产出特厚Q690C,成本高且冲击韧性偏低,不符合桥梁钢的技术要求;中国专利CN110699601A,采用Cr+Mo+V体系,并添加B增加钢板淬透性,通过调质工艺得到一种综合性能较好的Q690D,但是成本太高。
发明内容
本发明旨在提供一种高强高韧性桥梁结构钢Q690qE及其生产方法,采用低价合金替代,炼钢过程进行增氮处理,钢板经轧制、正火水冷及回火处理,得到高强高韧10~50mm厚度规格桥梁结构钢Q690qE,钢板以回火马氏体及贝氏体为主,屈服强度达810~850Mpa,抗拉强度达850~890Mpa,-40℃冲击功达220J以上。
本发明的技术方案:
一种高强高韧性桥梁结构钢Q690qE,采用的生产工艺路线为:转炉冶炼→LF精炼→VD真空精炼→连铸→板坯加热→控制轧制→正火打水→回火处理,钢的化学成分以重量百分数计为:C=0.11~0.13,Si=0.30~0.40,Mn=1.45~1.55,P≤0.015,S≤0.003,Nb=0.020~0.030,V=0.075~0.085,Ti=0.010~0.015,Cr=0.30~0.35,Alt=0.02~0.05,N=0.015~0.017,CEV=0.42~0.45,余量为Fe和不可避免的杂质元素。
一种高强高韧性桥梁结构钢Q690qE的生产方法,关键工艺步骤包括:
(1)转炉炼钢:出钢C=0.06~0.08%,P=0.008~0.010%;
(2)LF精炼:钢水在LF炉总在站时间=50~55min,化渣后加入合金;
(3)VD精炼:VD炉增氮处理,在站总吹氮气时间=30~35min,氮气流量120~130m3/h,真空度在0.5tor以下,保持时间=15~25min,VD炉破空后喂入氮线300~350m,喂入氮线速度为150~180m/min;
(4)连铸:断面选用260mm,连铸实行全程保护浇铸,拉速=0.85~0.90m/min,钢水过热度15±5℃控制;
(5)板坯加热:板坯在步进炉中进行加热,炉膛加热温度=1230~1250℃,在炉时间=240~260min,出炉温度1190~1210℃;
(6)控制轧制:一阶段开轧温度1100~1150℃,终轧温度=1020~1050℃,保证后三道次压下率在17%,以上中间坯厚度≥2倍成品板厚;二阶段开轧温度在860~960℃,终轧温度780-820℃;
(7)正火打水:正火温度890±10℃,在炉时间2.0×钢板厚度×mm-1min,正火出炉后加速冷却,冷却速率=10~15℃/s,终冷温度250~350℃;
(8)回火处理:回火温度600±10℃,在炉时间2.5×钢板厚度×mm-1 min。
发明原理:
本发明钢的化学组成设计原理:
C:碳元素能显著提高钢的强度,但会降低钢的塑性、韧性,同时过高的碳含量还有恶化钢的基体组织,影响钢的焊接稳定性。碳含量对高强钢必须提供强度支撑,但又不能过多影响塑性、韧性,还不能影响钢的焊接性,因此综合考虑性能要求,本发明钢的C含量控制在0.11%~0.13%。
Si:硅在钢中溶于铁素体内,可明显提高钢的强度、硬度,但塑性、韧性降低。硅通常以脱氧剂而加入钢中,与 FeO能结成密度较小的硅酸盐炉渣而被除去,因此硅能显著提高钢水纯净度素。但是硅含量≥0.50%后对钢的塑韧性和焊接性不利。本发明确定硅含量的范围为0.30%~0.40%。
Mn:锰是重要的强韧性元素,能降低钢中γ→α的相变Ar3温度,从而促进贝氏体转变。Mn通过溶入铁素体而引起固溶强化,提高钢的强度。对晶粒细化有促进作用,因此Mn在提高强度的同时也可适当提高钢的韧性。但锰也容易发生偏析,与S结合生成MnS影响厚度方向性能。本发明确定锰含量的范围为1.45%~1.55%。
P:冷脆性元素,在冷加工时容易产生“冷脆”,且是易偏析元素,增加回火脆性,对钢的低温韧性及焊接性能非常不利。因此应该严格控制钢中磷的含量,本发明钢中的P控制在0.015%以下。
S:钢中的有害杂质,降低钢的延展性、韧性及焊接性,容易产生热脆现象。另外,S还可以与Mn形成MnS偏析,严重影响钢的综合性能。因此,本发明采用低硫设计,限制硫含量不大于0.003%。
Nb:和C、N结合能生成高熔点、高度分散的Nb(C、N),这种碳化物强烈抑制奥氏体再结晶,从而得到细小的原始奥氏体晶粒,也为后续贝氏体转变起到较好的细化作用。本发明Nb含量0.20~0.30%。
V:有较强的析出强化和细晶强化效果,可提高钢的强度和韧性,减小过热敏感性,提高热稳定性。本发明钢将V控制在0.075~0.085%。
N:氮通过与钒元素微合金化,优化钒的析出从而细化铁素体晶粒,充分发挥了细晶强化和沉淀强化两种强化方式的作用,大大改善了钢的强韧性配合。本发明钢将N控制在0.015~0.017%。
Ti:钛能细化钢的晶粒组织,从而提高钢的强度和韧性,降低时效敏感性和冷脆性,改善焊接性能。微钛处理形成的TiN,能有效钉扎奥氏体晶界,有利于控制奥氏体晶粒的长大,但钛含量较高时,易生成大尺寸的液析TiN,影响钢的机械性能。本发明确定钛含量的范围为0.010%~0.015%。
Cr:铬在管线钢中的作用多元且重要,能形成较稳定、细小的铬碳化物,均匀度分布在钢体积中,起到组织细化,提高强度、耐磨性的作用。铬和镍形成稳定的化合物,能起到抗氧化和腐蚀的作用,对保护管线钢的表面质量有较好的作用。本发明确定铬含量的范围为0.30%~0.35%。
Al:铝是钢中的脱氧剂,适量Al、Ca的复合,有利于减少夹杂物的数量,改变夹杂物的形态,对管线钢的内部质量及塑、韧性都有利。Al有一定的细化晶粒的作用,提高冲击韧性及降低钢的韧脆转变温度。本发明确定铝含量的范围为0.02%~0.05%。
本发明工艺方法上的创新原理:采用“中低碳+NCC+回火VN析出强化”的制造方法,VD以氮代氩,氮气较空气轻,炼钢过程夹杂物更容易捕获上浮,成分均匀化效果更好,通过VD全程吹氮+破真空喂氮线两种方式有效控制钢水中N含量,控制V与N结合比例,可大大提高VN的析出强化作用;后续采用控轧+NCC+中高温回火,完全奥氏体后通过快冷加速细晶组织形成,高温回火促进VN的弥散析出,最后可得到高纯净度、高强、高韧的Q690qE钢板。
本发明的有益效果:利用VN微合金化,取消Ni、Mo等贵重金属加入,Q690qE吨钢可节约大量成本;本发明方法生产的钢,钢板以回火马氏体及贝氏体为主,屈服强度达810~850Mpa,抗拉强度达850~890Mpa,-40℃冲击功达250J以上,A/B/C/D夹杂物≤0.5级;该发明方法具有普适性,过程可控、易于实现,有效提升钢材的综合性能。
附图说明
图1为本发明实施例1钢板1/4厚度处的光学显微镜照片。
具体实施方式
以下以一组实施例进一步说明本发明的内容。实施例钢种的化学成分如表1。
实施例1:
厚度10mm Q690qE的生产,关键工艺步骤:
(1)转炉炼钢:出钢C=0.06%,P=0.008%;
(2)LF精炼:钢水在LF炉总在站时间50min,化渣后加入合金;
(3)VD精炼:VD炉增氮处理,在站总吹氮气时间30min,氮气流量120m3/h,真空度0.5tor保持时间15min,VD炉破空后喂入氮线300m,喂入氮线速度为150m/min;
(4)连铸:断面选用260mm,连铸实行全程保护浇铸,拉速0.90m/min,目标钢水过热度20℃控制;
(5)板坯加热:板坯在步进炉中进行加热,炉膛加热温度1250℃,在炉时间240min,出炉温度1190℃;
(6)控制轧制:一阶段开轧温度1100℃,终轧温度1020℃,后三道次压下率20%、23%、24%,中间坯厚度60mm;二阶段开轧温度在960℃,终轧温度820℃;
(7)正火打水:正火温度900℃,在炉时间20分钟,正火出炉后加速冷却,冷却速率10℃/S,终冷温度250℃;
(8)回火处理:回火温度610℃,在炉时间25分钟。
实施例2:
25mm厚度Q690qE的生产,关键工艺步骤:
(1)转炉炼钢:出钢C=0.07%,P=0.010%;
(2)LF精炼:钢水在LF炉总在站时间52min,化渣后加入合金;
(3)VD精炼:VD炉增氮处理,在站总吹氮(气)时间35min,氮气流量125m3/h,真空度0.45tor保持时间20min,VD炉破空后喂入氮线320m,喂入氮线速度为170m/min;
(4)连铸:断面选用260mm,连铸实行全程保护浇铸,拉速0.88m/min,钢水过热度15℃控制;
(5)板坯加热:板坯在步进炉中进行加热,炉膛加热温度1240℃,在炉时间250min,出炉温度1200℃;
(6)控制轧制:一阶段开轧温度1120℃,终轧温度1030℃,后三道次压下率20%、21%、22%,中间坯厚度75mm;二阶段开轧温度在900℃,终轧温度800℃;
(7)正火打水:正火温度890℃,在炉时间50倍分钟,正火出炉后加速冷却,冷却速率12℃/S,终冷温度300℃;
(8)回火处理:回火温度600℃,在炉时间63分钟。
实施例3:
50mm厚度Q690qE的生产,关键工艺步骤为:
(1)转炉炼钢:出钢C=0.08%,P=0.008%;
(2)LF精炼:钢水在LF炉总在站时间55min,化渣后加入合金;
(3)VD精炼:VD炉增氮处理,在站总吹氮(气)时间40min,氮气流量130m3/h,真空度在0.4tor,保持时间25min,VD炉破空后喂入氮线350m,喂入氮线速度为180m/min;
(4)连铸:断面选用260mm,连铸实行全程保护浇铸,拉速0.85m/min,钢水过热度10℃控制;
(5)板坯加热:板坯在步进炉中进行加热,炉膛加热温度1230℃,在炉时间260min,出炉温度1210℃;
(6)控制轧制:一阶段开轧温度1150℃,终轧温度1050℃,后三道次压下率18%、19%、20%,中间坯厚度110mm;二阶段开轧温度在860℃,终轧温度780℃;
(7)正火打水:正火温度880℃,在炉时间100分钟,正火出炉后加速冷却,冷却速率15℃/S,终冷温度350℃;
(8)回火处理:回火温度590℃,在炉时间125分钟。
对以上三个实施例的钢板进行检测,具体性能如表2。
表1 实施例钢种的化学成分(%)
表2 实施例钢板的冲击性能检测结果
Claims (2)
1.一种高强高韧性桥梁结构钢Q690qE,采用的生产工艺路线为转炉冶炼→LF精炼→VD真空精炼→连铸→板坯加热→控制轧制→正火打水→回火处理,其特征在于:钢的化学成分以重量百分数计为C=0.11~0.13,Si=0.30~0.40,Mn=1.45~1.55,P≤0.015,S≤0.003,Nb=0.020~0.030,V=0.075~0.085,Ti=0.010~0.015,Cr=0.30~0.35,Alt=0.02~0.05,N=0.015~0.017,CEV=0.42~0.45,余量为Fe和不可避免的杂质元素。
2.根据权利要求1所述的一种高强高韧性桥梁结构钢Q690qE的生产方法,其特征在于关键工艺步骤包括:
(1)转炉炼钢:出钢C=0.06~0.08%,P=0.008~0.010%;
(2)LF精炼:钢水在LF炉总在站时间=50~55min,化渣后加入合金;
(3)VD精炼:VD炉增氮处理,在站总吹氮气时间=30~35min,氮气流量120~130m3/h,真空度在0.5tor以下,保持时间=15~25min,VD炉破空后喂入氮线300~350m,喂入氮线速度为150~180m/min;
(4)连铸:断面选用260mm,连铸实行全程保护浇铸,拉速=0.85~0.90m/min,钢水过热度15±5℃控制;
(5)板坯加热:板坯在步进炉中进行加热,炉膛加热温度=1230~1250℃,在炉时间=240~260min,出炉温度1190~1210℃;
(6)控制轧制:一阶段开轧温度1100~1150℃,终轧温度=1020~1050℃,保证后三道次压下率在17%,以上中间坯厚度≥2倍成品板厚;二阶段开轧温度在860~960℃,终轧温度780-820℃;
(7)正火打水:正火温度890±10℃,在炉时间2.0×钢板厚度×mm-1min,正火出炉后加速冷却,冷却速率=10~15℃/s,终冷温度250~350℃;
(8)回火处理:回火温度600±10℃,在炉时间2.5×钢板厚度×mm-1 min。
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