CN112548104A - 一种降低模具钢激光增材修复过程中热裂敏感性的方法 - Google Patents
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Abstract
本发明公开了一种降低模具钢激光增材修复过程中热裂敏感性的方法。首先对基材预热处理,预热至280℃;采用热成像仪对激光增材制造过程中熔池进行监测,获得熔池表面温度信息,计算出熔池边界的平均温度梯度G与冷却速率ξ;根据5.5×103℃/m≤G≤1.5×105℃/m,且5.5×103℃/s≤ξ≤1.5×105℃/s原则对工艺参数进行优化,获得的优化工艺窗口:激光功率为1400‑1600W,扫描速度为14~16mm/s,光斑直径为3.5~4.5mm,送粉量为25‑32g/min,搭接量50%,高度方向增量Z为0.25~0.35毫米/层;获得高质量的增材修复零件。本发明能有效提高激光增材修复的内部质量。
Description
技术领域
本发明涉及激光金属材料加工领域,尤其涉及一种降低模具钢激光增材修复过程中热裂敏感性的方法。
背景技术
模具服役过程中易出现多种形式的失效,如磨损、裂纹、疲劳、断裂等。模具因损伤、失效而导致报废,将造成严重的经济损失。激光增材修复技术具有基材热损伤程度低、变形小及柔性高等特点,在模具修复再制造领域具有广阔的应用前景。然而,由于激光增材修复是一个移动式热源瞬时加热熔化并快速冷却的过程,修复过程中局域熔池具有温度梯度高、冷却速率快及多重热循环影响等特点。目前,激光增材修复内部质量难以保障,尤其是易产生热裂纹等缺陷,导致修复零件性能急剧下降。本发明提供一种降低模具钢激光增材修复过程中热裂敏感性的方法,可有效防止修复过程中热裂纹的产生,提高修复零件的内部质量及性能。
发明内容
本发明的目的是提供一种降低模具钢激光增材修复过程中热裂敏感性的方法。
一种降低模具钢激光增材修复过程中热裂敏感性的方法,包括以下步骤:
步骤一:首先,对待修复区进行打磨、超声清洗及烘干,采用电磁感应加热设备将基材预热至280℃;
步骤二:采用热成像仪对激光增材制造过程中熔池进行监测,获得熔池表面温度信息,计算出熔池边界的平均温度梯度G与冷却速率ξ;
步骤三:根据5.5×103℃/m≤G≤1.5×105℃/m,且5.5×103℃/s≤ξ≤1.5×105℃/s原则对工艺参数进行优化;
步骤四:获得的优化工艺窗口如下:激光功率为1400-1600W,扫描速度为14~16mm/s,光斑直径为3.5~4.5mm,送粉量为25-32g/min,搭接量50%,高度方向增量Z为0.25~0.35毫米/层;
步骤五:最后,按上述工艺参数及方法进行激光增材修复,获得高质量的模具钢修复零件。
在步骤二中,热成像仪发射率设置为1.05,单个数据采集时间为2ms。
在步骤五中,合金粉末为模具钢、纯锆粉及纯铝粉的混合粉末,其中包括质量分数为97%的模具钢粉末,2%的纯铬粉与1%的纯铝粉,扫描路径为交叉扫描路径或双向扫描路径。
本发明通过大量实验验证,根据5.5×103℃/m≤G≤1.5×105℃/m,且5.5×103℃/s≤ξ≤1.5×105℃/s原则对工艺参数进行选取,获得优化工艺参数:激光功率为1400-1600W,扫描速度为14~16mm/s,光斑直径为3.5~4.5mm,送粉量为25-32g/min,搭接量50%,高度方向增量Z为0.25~0.35毫米/层;按优化工艺参数及方法进行激光增材修复,一方面对温度梯度G进行控制,减小热应力;另一方面对熔池冷却速率进行控制,有效细化枝晶组织,减少链状共晶相的形成。此外,通过在模具钢合金粉末中加入纯锆粉及纯铝粉,在增材制造过程中纯锆粉与纯铝粉通过与熔池中的氧气发生原位反应生成高熔点的氧化锆与氧化铝陶瓷颗粒,为晶粒或枝晶的形核提供异质形核点,进而细化显微结构,并促进大量等轴枝晶的形成,进而避免热裂纹产生,提高修复过程中零件的热裂敏感性。
附图说明
图1为现有方法得到的激光增材修复试样金相图;
图2为本发明得到的激光增材修复试样金相图。
具体实施方式
实施例1
以Cr12MoV钢为例。
步骤一:首先,对待Cr12MoV模具修复区进行打磨、超声清洗及烘干,采用电磁感应加热设备将基材预热至280℃;
步骤二:采用热成像仪对激光增材制造过程中熔池进行监测,获得熔池表面温度信息,计算出熔池边界的平均温度梯度G与冷却速率ξ;
步骤三:根据5.5×103℃/m≤G≤1.5×105℃/m,且5.5×103℃/s≤ξ≤1.5×105℃/s原则对工艺参数进行优化;
步骤四:获得的优化工艺窗口如下:激光功率为1550W,扫描速度为16mm/s,光斑直径为4.0mm,送粉量为27.5g/min,搭接量50%,高度方向增量Z为0.30毫米/层;修复粉末材料为Cr12MoV模具钢、纯锆粉及纯铝粉的混合粉末,其中包括质量分数为97%的Cr12MoV模具钢粉末,2%的纯铬粉与1%的纯铝粉;扫描路径为交叉扫描路径。
步骤五:最后,按上述工艺参数及方法进行激光增材修复,获得高致密、无冶金缺陷的高质量模具钢修复零件。
图1为采用已有方法所获得的增材修复试样金相图。试样层与层之间界面处存在明显的未融合缺陷,如图1所示。此类未融合缺陷的产生主要由于熔池没有足够的能量与时间对已沉积层进行有效稀释造成。上述结果表明,在本专利方法外,很难消除层间未熔合缺陷。
图2为采用本发明实施例1所获得的增材修复试样金相图。图2为试样宏观整体形貌。从图中可以看出,层与层之间为冶金结合,并没有发现未熔合及气孔等缺陷。采用本专利提出方法可以保证熔池具有足够的能量输入,以及熔池与已沉积层有足够的时间进行反应,从而消除层间界面缺陷。上述结果表明,采用本专利方法可以有效地提高增材修复试样的层间冶金结合能力。
实施例2
以H13钢为例。
步骤一:首先,对待H13钢模具修复区进行打磨、超声清洗及烘干,采用电磁感应加热设备将基材预热至280℃;
步骤二:采用热成像仪对激光增材制造过程中熔池进行监测,获得熔池表面温度信息,计算出熔池边界的平均温度梯度G与冷却速率ξ;
步骤三:根据5.5×103℃/m≤G≤1.5×105℃/m,且5.5×103℃/s≤ξ≤1.5×105℃/s原则对工艺参数进行优化;
步骤四:获得的优化工艺窗口如下:激光功率为1500W,扫描速度为15mm/s,光斑直径为4.0mm,送粉量为30g/min,搭接量50%,高度方向增量Z为0.30毫米/层;修复粉末材料为H13模具钢、纯锆粉及纯铝粉的混合粉末,其中包括质量分数为97%的H13模具钢粉末,2%的纯铬粉与1%的纯铝粉;扫描路径为双向扫描路径。
步骤五:最后,按上述工艺参数及方法进行激光增材修复,获得高致密、无冶金缺陷的高质量模具钢修复零件。
Claims (4)
1.一种降低模具钢激光增材修复过程中热裂敏感性的方法,其特征在于包括以下步骤:
步骤一:首先,对待修复区进行打磨、超声清洗及烘干,采用电磁感应加热设备将基材预热至280℃;
步骤二:采用热成像仪对激光增材制造过程中熔池进行监测,获得熔池表面温度信息,计算出熔池边界的平均温度梯度G与冷却速率ξ;
步骤三:根据5.5×103℃/m≤G≤1.5×105℃/m,且5.5×103℃/s≤ξ≤1.5×105℃/s原则对工艺参数进行优化;
步骤四:获得的优化工艺窗口如下:激光功率为1400-1600W,扫描速度为14~16mm/s,光斑直径为3.5~4.5mm,送粉量为25-32g/min,搭接量50%,高度方向增量Z为0.25~0.35毫米/层;
步骤五:最后,按上述工艺参数及方法进行激光增材修复,获得高质量的模具钢修复零件。
2.根据权利要求1所述的一种降低模具钢激光增材修复过程中热裂敏感性的方法,其特征在于:在步骤二中,热成像仪发射率设置为1.05,单个数据采集时间为2ms。
3.根据权利要求1所述的一种降低模具钢激光增材修复过程中热裂敏感性的方法,其特征在于:在步骤五中,合金粉末为模具钢、纯锆粉及纯铝粉的混合粉末,其中包括质量分数为97%的模具钢粉末,2%的纯铬粉与1%的纯铝粉。
4.根据权利要求1所述的一种降低模具钢激光增材修复过程中热裂敏感性的方法,其特征在于:在步骤五中,扫描路径为交叉扫描路径或双向扫描路径。
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