CN111288907B - A metallographic detection method for measuring the diameter of a resistance spot welding nugget - Google Patents

A metallographic detection method for measuring the diameter of a resistance spot welding nugget Download PDF

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CN111288907B
CN111288907B CN202010188641.XA CN202010188641A CN111288907B CN 111288907 B CN111288907 B CN 111288907B CN 202010188641 A CN202010188641 A CN 202010188641A CN 111288907 B CN111288907 B CN 111288907B
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nugget
length
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CN111288907A (en
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苏崇涛
郭晓静
左海霞
海超
于健
孙健
何群才
赵广东
田玉伟
王亚芬
王亚东
王立刚
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Bengang Steel Plates Co Ltd
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01BMEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00Measuring arrangements characterised by the use of optical techniques
    • G01B11/08Measuring arrangements characterised by the use of optical techniques for measuring diameters
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    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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Abstract

本发明的一种电阻点焊接熔核直径测量的金相检测方法,包括如下步骤:步骤1:选取电阻点焊接零件,选择焊点的一个表面,计算焊点的压痕区直径的平均值L1;步骤2:选取经过焊点中心且长度为L1的切割线,用切割机沿切割线对焊点进行切割;步骤3:对焊点切割面进行磨平、粗磨、细磨、抛光及腐蚀处理;步骤4:在显微镜下对焊点切割面进行测量,获得压痕区直径的测量长度L2和熔核直径的测量长度d2;步骤5:判断L1和L2之间的误差是否小于误差阈值,如果是则d2即为熔核区长度,否则执行步骤6;步骤6:根据设计的公式计算熔核直径长度d1。

Figure 202010188641

A metallographic detection method for measuring the diameter of a resistance spot welding nugget of the present invention includes the following steps: Step 1: Select a resistance spot welding part, select a surface of the welding spot, and calculate the average value L1 of the diameter of the indentation area of the welding spot ; Step 2: Select a cutting line that passes through the center of the solder joint and has a length of L1, and use a cutting machine to cut the solder joint along the cutting line; Step 3: Smooth, coarsely grind, finely grind, polish and corrode the cutting surface of the solder joint Processing; Step 4: Measure the cutting surface of the solder joint under a microscope to obtain the measured length L2 of the diameter of the indentation area and the measured length d2 of the nugget diameter; Step 5: Determine whether the error between L1 and L2 is less than the error threshold, If so, d2 is the length of the nugget area, otherwise, step 6 is performed; step 6: Calculate the nugget diameter length d1 according to the designed formula.

Figure 202010188641

Description

一种电阻点焊接熔核直径测量的金相检测方法A metallographic detection method for measuring the diameter of a resistance spot welding nugget

技术领域technical field

本发明属于电阻点焊接技术领域,涉及一种电阻点焊接熔核直径测量的金相检测方法。The invention belongs to the technical field of resistance spot welding, and relates to a metallographic detection method for measuring the diameter of a nugget of resistance spot welding.

背景技术Background technique

电阻点焊接在汽车领域或其他需要采用点焊接进行连接的工艺中应用非常广泛,在对焊接工艺下的焊点质量进行检测中,有一个检测内容为熔核直径的测量,需要对焊点切割,然后对焊点剖面进行研磨抛光腐蚀,最后在光学显微镜下对焊接熔核直径进行测量。电阻点焊接的测量为破坏性实验,因此对焊点的切割就非常重要,但是在切割过程中,很容易偏离所需要切割的部位,这样造成所检测部位不能完全和所需要的部位匹配,造成检测部位的错位,而一旦切割部位偏离所需要检测的部位就会导致整个测量失败。当发生偏离测量线问题时,当前没有相关方法对检测结果进行修正。Resistance spot welding is widely used in the automotive field or other processes that require spot welding to connect. In the inspection of the solder joint quality under the welding process, one of the inspection content is the measurement of the diameter of the nugget, which requires cutting the solder joint. , and then grind, polish and corrode the solder joint profile, and finally measure the diameter of the welding nugget under an optical microscope. The measurement of resistance spot welding is a destructive experiment, so the cutting of the solder joint is very important, but during the cutting process, it is easy to deviate from the part to be cut, so that the detected part cannot be completely matched with the required part, resulting in The misalignment of the detection part, and once the cutting part deviates from the part to be detected will cause the entire measurement to fail. When the deviation from the measurement line occurs, there is currently no relevant method to correct the detection results.

发明内容SUMMARY OF THE INVENTION

为解决上述技术问题,本发明的目的是提供一种电阻点焊接熔核直径测量的金相检测方法,可对测量数据进行修正,使计算结果更接近实际值,对无法测量的焊核起到评价和估算的作用。In order to solve the above-mentioned technical problems, the purpose of the present invention is to provide a metallographic detection method for measuring the nugget diameter of resistance spot welding, which can correct the measurement data, make the calculation result closer to the actual value, and play a role in the unmeasured nugget. The role of evaluation and estimation.

本发明提供一种电阻点焊接熔核直径测量的金相检测方法,包括如下步骤:The invention provides a metallographic detection method for measuring the diameter of a resistance spot welding nugget, comprising the following steps:

步骤1:选取电阻点焊接零件,选择焊点的一表面,计算焊点的压痕区直径的平均值L1;Step 1: Select resistance point welding parts, select one surface of the welding point, and calculate the average value L1 of the diameter of the indentation area of the welding point;

步骤2:选取经过焊点中心且长度为L1的切割线,用切割机沿切割线对焊点进行切割;Step 2: Select the cutting line that passes through the center of the solder joint and has a length of L1, and use a cutting machine to cut the solder joint along the cutting line;

步骤3:对焊点切割面进行磨平、粗磨、细磨、抛光及腐蚀处理;Step 3: Polish, rough, finely grind, polish and corrode the cutting surface of the solder joint;

步骤4:在显微镜下对焊点切割面进行测量,获得压痕区直径的测量长度L2和熔核直径的测量长度d2;Step 4: Measure the cutting surface of the solder joint under a microscope to obtain the measured length L2 of the diameter of the indentation zone and the measured length d2 of the diameter of the nugget;

步骤5:判断L1和L2之间的误差是否小于误差阈值,如果是则d2即为熔核区长度,否则执行步骤6;Step 5: Determine whether the error between L1 and L2 is less than the error threshold, if so, d2 is the length of the nugget zone, otherwise go to Step 6;

步骤6:根据下式计算熔核直径长度d1:

Figure BDA0002415078820000021
Step 6: Calculate the nugget diameter length d1 according to the following formula:
Figure BDA0002415078820000021

在本发明的电阻点焊接熔核直径测量的金相检测方法中,步骤1具体为:In the metallographic detection method of the resistance spot welding nugget diameter measurement of the present invention, step 1 is specifically:

分别测量压痕区的长轴长度和短轴长度,计算长轴长度和短轴长度的平均值,作为压痕区直径的平均值L1。Measure the length of the major axis and the length of the minor axis of the indentation area respectively, and calculate the average value of the length of the major axis and the length of the minor axis as the mean value L1 of the diameter of the indentation area.

在本发明的电阻点焊接熔核直径测量的金相检测方法中,步骤5中的误差阈值具体取值为压痕区直径的平均值L1的5%。In the metallographic detection method for measuring the nugget diameter of resistance spot welding of the present invention, the error threshold in step 5 is specifically 5% of the average value L1 of the diameter of the indentation area.

由于金相检测为破坏性实验,试样一旦切割错误,就会造成实验失败,采用本发明的一种电阻点焊接熔核直径测量的金相检测方法,当试样制备发生错误时,可以通过公式对测量数据进行适当的修正,使计算结果更加接近实际值,对无法测量的熔核直径起到评价和估算的作用。Since metallographic detection is a destructive experiment, once the sample is cut incorrectly, the experiment will fail. By using the metallographic detection method for measuring the diameter of the nugget of resistance spot welding of the present invention, when an error occurs in the preparation of the sample, the The formula corrects the measured data appropriately to make the calculation result closer to the actual value, and plays a role in evaluating and estimating the unmeasurable nugget diameter.

附图说明Description of drawings

图1为点焊接工作示意图;Figure 1 is a schematic diagram of spot welding work;

图2为本发明的一种电阻点焊接熔核直径测量的金相检测方法中焊点外形等效图;2 is an equivalent diagram of the shape of a solder joint in a metallographic detection method for measuring the diameter of a resistance spot welding nugget of the present invention;

图3为本发明的一种电阻点焊接熔核直径测量的金相检测方法中焊点切割面的示意图。3 is a schematic diagram of a cut surface of a welding spot in a metallographic detection method for measuring the diameter of a resistance spot welding nugget of the present invention.

具体实施方式Detailed ways

图1为点焊接工作示意图,电源10向电极20供电,通过上下电极20下压将两块待焊接件40焊接到一起。如图2所示,从点焊接的焊点分布特征上看,可以近似为三个同心圆组成,最外层为黑色的表面氧化层区1;中间为电阻焊点在电极头压力下减薄过渡的区域,即压痕区2;钢板之间产生高温,使钢板心部熔化,冷却后形成近似圆形的熔核3。在电极20的极头压力下,待焊接件40外表面形成氧化层区1和压痕区2,熔核3位于两个待焊接件40之间。根据点焊接的原理,在受力均匀的情况下,焊点内部熔核的形态决定了焊点外形上产生的减薄区域形态,因此从外形形貌上,熔核3与压痕区2为同心分布。本发明方法在对熔核直径进行测量的过程中,将中间圆的直径测量值,即压痕区直径引入作为一个特征参数。FIG. 1 is a schematic diagram of spot welding work. The power source 10 supplies power to the electrodes 20 , and the two pieces to be welded 40 are welded together by pressing down the upper and lower electrodes 20 . As shown in Figure 2, from the distribution characteristics of spot welding, it can be approximately composed of three concentric circles, the outermost layer is the black surface oxide layer area 1; the middle is the resistance welding spot thinning under the pressure of the electrode tip The transition area is the indentation area 2; a high temperature is generated between the steel plates, which melts the core of the steel plate, and forms a nearly circular nugget 3 after cooling. Under the tip pressure of the electrode 20 , an oxide layer area 1 and an indentation area 2 are formed on the outer surface of the parts to be welded 40 , and the nugget 3 is located between the two parts to be welded 40 . According to the principle of spot welding, when the force is uniform, the shape of the nugget inside the solder joint determines the shape of the thinned area generated on the shape of the solder joint. Therefore, from the shape of the shape, the nugget 3 and the indentation area 2 are Concentric distribution. In the process of measuring the diameter of the nugget in the method of the present invention, the measured value of the diameter of the middle circle, that is, the diameter of the indentation zone, is introduced as a characteristic parameter.

本发明的一种电阻点焊接熔核直径测量的金相检测方法,具体包括如下步骤:A metallographic detection method for measuring the diameter of a resistance spot welding nugget of the present invention specifically includes the following steps:

步骤1:选取电阻点焊接零件,选择焊点的一表面,计算焊点的压痕区直径的平均值L1;Step 1: Select resistance point welding parts, select one surface of the welding point, and calculate the average value L1 of the diameter of the indentation area of the welding point;

具体实施时,分别测量压痕区的长轴长度和短轴长度,再计算长轴长度和短轴长度的平均值,作为压痕区直径的平均值L1。In specific implementation, the long axis length and the short axis length of the indentation area are measured respectively, and the average value of the long axis length and the short axis length is calculated as the average value L1 of the diameter of the indentation area.

步骤2:选取经过焊点中心且长度为L1的切割线,用切割机沿切割线对焊点进行切割;Step 2: Select the cutting line that passes through the center of the solder joint and has a length of L1, and use a cutting machine to cut the solder joint along the cutting line;

具体实施时,此步骤选取的焊点中心存在一定误差,保证尽量靠近焊点中心即可。During specific implementation, there is a certain error in the center of the solder joint selected in this step, and it is sufficient to ensure that it is as close as possible to the center of the solder joint.

步骤3:对焊点切割面进行磨平、粗磨、细磨、抛光及腐蚀处理;Step 3: Polish, rough, finely grind, polish and corrode the cutting surface of the solder joint;

步骤4:在显微镜下对焊点切割面进行测量,获得压痕区直径的测量长度L2和熔核直径的测量长度d2;具体参照图3的焊点切割面示意图;Step 4: Measure the cutting surface of the solder joint under a microscope to obtain the measured length L2 of the diameter of the indentation zone and the measured length d2 of the diameter of the nugget; specifically refer to the schematic diagram of the cutting surface of the solder joint in FIG. 3 ;

步骤5:判断L1和L2之间的误差是否小于误差阈值,如果是则d2即为熔核区长度,否则执行步骤6;Step 5: Determine whether the error between L1 and L2 is less than the error threshold, if so, d2 is the length of the nugget zone, otherwise go to Step 6;

具体实施时,误差阈值具体取值为压痕区直径的平均值L1的5%。In specific implementation, the error threshold is specifically 5% of the average value L1 of the diameter of the indentation area.

步骤6:根据下式计算熔核区长度d1:

Figure BDA0002415078820000031
Step 6: Calculate the nugget length d1 according to the following formula:
Figure BDA0002415078820000031

具体实施时,测量原理及公式的推导如下:In specific implementation, the measurement principle and formula are deduced as follows:

如图2所示,根据焊点外形等效图建立几何模型,该几何模型是建立在熔核直径与压痕直径为几何相似的圆或者类圆形基础上的建立的,实际工作中不规则的焊点形态,可以转换成图2中同心圆的模型来进行计算。图2中外面大圆为压痕形态,内圆为熔核形态,假设按实际需要测量线条BC所在部位的熔核直径d1,但是在实际工作中切割或试样制备后实际切割测量部位为AD线条所在位置。测量所得该处的熔核直径为d2,压痕直径为L2:As shown in Figure 2, the geometric model is established according to the equivalent diagram of the shape of the solder joint. The geometric model is established on the basis of a circle or a quasi-circle whose nugget diameter and indentation diameter are geometrically similar, and are irregular in actual work. The shape of the solder joints can be converted into the model of concentric circles in Figure 2 for calculation. In Figure 2, the outer large circle is the indentation shape, and the inner circle is the nugget shape. It is assumed that the nugget diameter d1 at the position of the line BC is measured according to actual needs, but the actual cutting and measurement position is the AD line after cutting or sample preparation in actual work. location. The nugget diameter obtained from the measurement is d2, and the indentation diameter is L2:

设定AE=GF=x,三角形AOE与三角形GOF都为直角三角形,根据勾股定理可知:Set AE=GF=x, the triangle AOE and the triangle GOF are both right-angled triangles, according to the Pythagorean theorem:

AE2+OE2=AO2 (1)AE 2 +OE 2 =AO 2 (1)

GF2+OF2=GO2 (2)GF 2 +OF 2 =GO 2 (2)

其中,

Figure BDA0002415078820000041
带入式(1)可得:in,
Figure BDA0002415078820000041
Bringing into equation (1), we can get:

Figure BDA0002415078820000042
Figure BDA0002415078820000042

其中,

Figure BDA0002415078820000043
带入式(2)可得:in,
Figure BDA0002415078820000043
Bringing into equation (2), we can get:

d12=d22+4x2 (4)d1 2 =d2 2 +4x 2 (4)

联立公式(3)(4)可推导出:

Figure BDA0002415078820000044
Simultaneous formulas (3) and (4) can be deduced:
Figure BDA0002415078820000044

以上所述仅为本发明的较佳实施例,并不用以限制本发明的思想,凡在本发明的精神和原则之内,所作的任何修改、等同替换、改进等,均应包含在本发明的保护范围之内。The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the idea of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the present invention. within the scope of protection.

Claims (3)

1. A metallographic detection method for measuring the diameter of a resistance spot welding nugget is characterized by comprising the following steps:
step 1: selecting a resistance spot welding part, selecting one surface of a welding spot, and calculating the average value L1 of the diameters of the indentation areas of the welding spot;
step 2: selecting a cutting line which passes through the center of the welding point and has the length of L1, and cutting the welding point along the cutting line by using a cutting machine;
and step 3: grinding, coarse grinding, fine grinding, polishing and corrosion treatment are carried out on the cutting surface of the welding spot;
and 4, step 4: measuring the cutting surface of the welding point under a microscope to obtain a measured length L2 of the diameter of the indentation area and a measured length d2 of the diameter of the nugget;
and 5: judging whether the error between L1 and L2 is smaller than an error threshold value, if so, d2 is the length of the nugget area, otherwise, executing step 6;
step 6: the nugget diameter length d1 was calculated according to the following formula:
Figure FDA0002415078810000011
2. the metallographic detection method for measuring the diameter of a resistance spot welding nugget according to claim 1, wherein the step 1 specifically comprises:
the major axis length and the minor axis length of the indentation area were measured, respectively, and the average of the major axis length and the minor axis length was calculated as the average L1 of the diameter of the indentation area.
3. The metallographic detection method for the measurement of the diameter of a resistance spot weld nugget according to claim 1, wherein the error threshold in step 5 is specifically 5% of the average value L1 of the diameter of the indentation area.
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