CN102095654B - Method for measuring distribution of microhardness of welded pipe - Google Patents
Method for measuring distribution of microhardness of welded pipe Download PDFInfo
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Abstract
The invention discloses a method for measuring the distribution of microhardness of a welded tube, which is used for obtaining the distribution of hardness in various areas by performing a hardness test on a tube-blank local cross section sample comprising a welding seam, a heat affected zone and a part of base materials. The tube-blank local cross section sample of the base materials comprises the welding seam, the heat affected zone and a part of base materials so as to form a mixed sample for testing the microhardness, and the sample is prepared and subjected to microhardness measurement so as to finally determine the distribution of the microhardness. When the microhardness is measured, different feeding spaces are adopted for measurement respectively in a base material zone, the heat affected zone area and a welding seam zone. The measured hardness distribution reflects the characteristics of the microhardness of the entire welding seam zone and heat affected zone so that the distribution condition of average microhardness in the welding seam zone and the heat affected zone can be accurately measured, and the obtained result lays a foundation for the determination of the widths and the areas of the welding seam zone, the heat affected zone and the base material zone, as well as the obtainment of the mechanical property parameters of the materials in the welding seam zone, the heat affected zone and the base material zone by further combination with a tensile test.
Description
Technical field
The invention belongs to the forming tubular product studying technological domain, be specifically related to a kind of method of measuring the welded tube microhardness distribution.
Background technology
Different welding methods and technology cause the range size of weld metal zone and heat-affected zone and properties of materials different, and have significant difference with the performance of mother metal.And the responsive difference of material on chemical constitution, institutional framework that reflects weld seam, heat-affected zone and mother metal zone of the result of hardness test ability.Therefore, hardness is the most frequently used performance index in the reflection welded tube mechanical property, and the Hardness Distribution in welded tube weld metal zone, heat-affected zone and mother metal district is still accurately confirmed the basis of each regional width and this structure of welded tube.
And at present domestic and international common method is after with sand paper welded tube surface finish to be measured being polished, and circumferentially pastes a slice coordinate paper on edge, pipe surface.Clip pipe fitting with anchor clamps, be put on the testing table, begin to measure hardness from weld seam center line center; Unclamp anchor clamps then, pipe is rotated 1mm (the 1mm mesh lines through alignment coordinate paper is realized), clamp pipe once more, measure once more.So repeat, till a week.There is following limitation in this method:
(1) because the face of weld oxide layer of pipe and the existence of impurity, possibly make experimental measurement to hardness number comprised the hardness number of face of weld oxide layer and impurity, the surface heat processing also can influence the measurement of hardness number in addition.Direct like this outer surface of tube blank is carried out the microhardness characteristic that micro-hardness measurement just can't really reflect whole welding line district and heat-affected zone; And the microhardness of the xsect of weld seam and internal surface of bloom all can't measure, so the hardness that this method is measured is not very accurate.
(2) this method is not suitable for the hardness measurement of diameter greater than the pipe of 60mm.Because when tube blank size is excessive, overall height may surpass the flexible scope of maximum perpendicular of microhardness testers worktable behind the clamping, thereby causes and can't carry out micro-hardness measurement to pipe.
(3) because the pipe surface is an arc surface, when pressure head is pressed into convex surface, to being pressed into power lateral support seldom will be arranged, like this, pressure head will be darker than what be pressed on the metal flat with same rigidity.Therefore, for the convex surface sample, will obtain lower reading.
(4) because the pipe surface is an arc surface, microscope is not easy to focus on, and blur the visual field that causes measuring, and makes it precision and reduces.
(5) sample clamping position out of true or clamp not strongly admittedly, the impression that makes the pressure head of instrument get easily is not the square of rule, makes precise decreasing, even causes instrument to measure.
Therefore (6) minimum scale of coordinate paper is 1mm, for the bead weld pipe of weld width less than 1mm, adopts measurement point that this method can welded seam area very few even do not have, thereby causes the gained result inaccurate.
Summary of the invention
For overcome exist in the prior art or measuring accuracy low, be not suitable for the deficiency of caliber greater than the pipe micro-hardness measurement of 60mm, the present invention proposes a kind of method of measuring the welded tube microhardness distribution
The present invention obtains the method for each regional Hardness Distribution through comprising the method for carrying out hardness test on the pipe partial cross-section sample of weld seam, heat-affected zone and part mother metal, and its detailed process is following:
The first step, the cutting sample;
Adopt wire cutting method, with the weld seam be the center at pipe surface intercepting arc sample, make to cut in the sample down to include weld seam, heat-affected zone and part mother metal, formed the recombined sample of testing microhardness.
Second step, the preparation sample;
Adopt mounting press edge appearance, make seam cross-section, at last through obtaining the microhardness sample after the grinding and buffing operation perpendicular to scleroscopic pressure head.
In the 3rd step, measure microhardness;
When measuring,, control the microhardness appearance respectively in the vertical direction of sample weld seam and the displacement of pipe thickness direction through being positioned at the spiral dial gauge of directions X and Y direction on the microhardness appearance work top.Adopt different pitch of feedes to measure respectively in mother metal district, heat-affected zone and weld metal zone.In the mother metal district, directions X is every to carry out one-shot measurement at a distance from 1mm, on the Y direction, on average gets n according to formula (1) simultaneously
1Individual point is measured.In the weld metal zone, directions X is every to carry out one-shot measurement at a distance from 0.1mm, on the Y direction, on average gets n according to formula (2)
2Individual point is measured.In the heat-affected zone, directions X is every to carry out one-shot measurement at a distance from 0.25mm, on the Y direction, on average gets n according to formula (3) simultaneously
3Individual point is measured.
n
1＝int(t/0.8)+1 (1)
n
2＝int(t/0.4)+1 (2)
n
3＝int(t/0.5)+1 (3)
In formula (1), (2), (3), t is a tube wall thickness, and its unit is mm, n
1Be the measure dot number on the Y direction of upper edge, mother metal district, n
2For in the weld metal zone along the measure dot number of Y direction; n
3For in the heat-affected zone along the measure dot number of Y direction.
In the 4th step, confirm microhardness distribution;
Get the mean value of each measuring position of directions X, obtain the microhardness distribution in weld metal zone, heat-affected zone and mother metal district.
The present invention proposes and adopt the pipe partial cross-section sample that comprises weld seam, heat-affected zone and part mother metal, and prepare the microhardness sample, the method that also adopts different spacing to measure at weld seam, heat-affected zone and mother metal through operations such as polishing, polishings.Measured Hardness Distribution can really reflect the microhardness characteristic of whole welding line district and heat-affected zone; Comprise the xsect inside of weld seam and the microhardness distribution of internal surface of bloom, thereby measure the average microhardness distribution situation of weld metal zone and heat-affected zone exactly.It is low to have solved existing method measuring accuracy, is difficult to measure the difficulty of large diameter welded pipe and each regional microhardness distribution of bead weld welded tube.And the gained result is for confirming weld seam, heat-affected zone and mother metal each regional width and area, and then combines tension test to obtain each regional material mechanical parameters of weld seam, heat-affected zone and mother metal to lay a good foundation.
Description of drawings
Fig. 1 is the process flow diagram of the method for the measurement welded tube microhardness distribution that proposes of the present invention;
Fig. 2 is a microhardness sample cutting position synoptic diagram of the present invention;
Fig. 3 is a hardness measurement synoptic diagram of the present invention;
Fig. 4 is the microhardness distribution of the Q215 welded tube that obtains of the present invention;
Fig. 5 is the microhardness distribution of the QSTE340 welded tube that obtains of the present invention.Wherein:
1. 5. mother metal districts, 4. heat-affected zones, pipe 2. recombined samples, 3. weld metal zones
Embodiment
Embodiment one
Present embodiment is the Q215 welded tube that certain iron company produces, and welding method is a high frequency resistance welding.The welded tube specification is Φ 60 * 3.3 (tube outer diameter is 60mm, and wall thickness is 3.3mm).The test apparatus that adopts is that the HXP-1000TM/LCD type microhardness testers that Instr Ltd. produces are learned by safe Mingguang City, Shanghai.Concrete operations are following:
The first step, the cutting sample;
As shown in Figure 2; With the weld seam is that the arc sample of wire cutting method at pipe 1 surperficial intercepting length of side 20mm adopted at the center; Make the xsect under cutting comprise weld seam, heat-affected zone and part mother metal; With this as the microhardness recombined sample, then at the onesize microhardness base metal test specimen that only contains mother metal of the plane of symmetry intercepting of weld seam.
Second step, the preparation sample;
Through mounting press edge appearance, make seam cross-section perpendicular to scleroscopic pressure head.With 160,240,600,1000 and 1500 waterproof abrasive paper sample is polished successively, and on buffing machine, polish, obtain present embodiment and inlay good arc recombined sample and arc base metal test specimen.
In the 3rd step, measure microhardness;
As shown in Figure 3, when measuring,, control the microhardness appearance respectively in the vertical direction of sample weld seam and the displacement of pipe thickness direction through being positioned at the spiral dial gauge of directions X and Y direction on the microhardness appearance work top.In the mother metal district, directions X is every to carry out one-shot measurement at a distance from 1mm, on the Y direction, on average gets 5 points according to formula (1) simultaneously and measures.In the weld metal zone, directions X is every to carry out one-shot measurement at a distance from 0.1mm, on the Y direction, on average gets 9 points according to formula (2) and measures.In the heat-affected zone, directions X is every to carry out one-shot measurement at a distance from 0.25mm, on the Y direction, on average gets 7 points according to formula (3) simultaneously and measures.
n
1＝int(t/0.8)+1 (1)
n
2＝int(t/0.4)+1 (2)
n
3＝int(t/0.5)+1 (3)
In formula (1), (2), (3), t is a tube wall thickness, and its unit is mm, n
1Be the measure dot number on the Y direction of upper edge, mother metal district, n
2For in the weld metal zone along the measure dot number of Y direction; n
3For in the heat-affected zone along the measure dot number of Y direction.
The 4th goes on foot, obtains microhardness distribution
Get the mean value of each measuring position of directions X, the average microhardness that obtains weld metal zone, heat-affected zone and the mother metal district of the Q215 welded tube of Φ 60 * 3.3 distributes, and is as shown in Figure 5.
Embodiment 2:
Present embodiment is the QSTE340 welded tube that certain iron company produces, and welding method is a high frequency resistance welding.The welded tube specification is Φ 78 * 2.7 (tube outer diameter is 78mm, and wall thickness is 2.7mm).The test apparatus that adopts is that the HXP-1000TM/LCD type microhardness testers that Instr Ltd. produces are learned by safe Mingguang City, Shanghai.Concrete operations are following:
The first step, cutting sample
As shown in Figure 2; With the weld seam is that the arc sample of wire cutting method at pipe 1 surperficial intercepting length of side 20mm adopted at the center; Make the xsect under cutting comprise weld seam, heat-affected zone and part mother metal; With this as the microhardness recombined sample, then at the onesize microhardness base metal test specimen that only contains mother metal of the right opposite intercepting of weld seam.
Second step, preparation sample
Through mounting press edge appearance, make seam cross-section perpendicular to scleroscopic pressure head.With 160,240,600,1000 and 1500 waterproof abrasive paper sample is polished successively, and on buffing machine, polish, obtain present embodiment and inlay good arc recombined sample and arc base metal test specimen.
The 3rd step, measurement microhardness
As shown in Figure 3, when measuring,, control the microhardness appearance respectively in the vertical direction of sample weld seam and the displacement of pipe thickness direction through being positioned at the spiral dial gauge of directions X and Y direction on the microhardness appearance work top.In the mother metal district, directions X is every to carry out one-shot measurement at a distance from 1mm, on the Y direction, on average gets 4 points according to formula (1) simultaneously and measures.In the weld metal zone, directions X is every to carry out one-shot measurement at a distance from 0.1mm, on the Y direction, on average gets 8 points according to formula (2) and measures.In the heat-affected zone, directions X is every to carry out one-shot measurement at a distance from 0.25mm, on the Y direction, on average gets 6 points according to formula (3) simultaneously and measures.
n
1＝int(t/0.8)+1 (1)
n
2＝int(t/0.4)+1 (2)
n
3＝int(t/0.5)+1 (3)
In formula (1), (2), (3), t is a tube wall thickness, and its unit is mm, n
1Be the measure dot number on the Y direction of upper edge, mother metal district, n
2For in the weld metal zone along the measure dot number of Y direction; n
3For in the heat-affected zone along the measure dot number of Y direction.
The 4th goes on foot, obtains microhardness distribution
Get the mean value of each measuring position of directions X, the welded tube that obtains Φ 78 * 2.7 gets the average microhardness distribution in weld metal zone, heat-affected zone and mother metal district, and is as shown in Figure 5.
Claims (1)
1. a method of measuring the welded tube microhardness distribution is characterized in that, the detailed process of measuring the welded tube microhardness distribution is following:
The first step, the cutting sample; With the weld seam is that the center is at pipe surface intercepting arc sample; Include weld seam, heat-affected zone and part mother metal in the sample under cutting, formed the recombined sample of test microhardness;
Second step, the preparation sample; Adopt mounting press edge appearance, make seam cross-section perpendicular to scleroscopic pressure head; Through obtaining the microhardness sample after the grinding and buffing operation;
In the 3rd step, measure microhardness;
When measuring,, control the microhardness appearance respectively in the vertical direction of sample weld seam and the displacement of pipe thickness direction through being positioned at the spiral dial gauge of directions X and Y direction on the microhardness appearance work top; Adopt different pitch of feedes to measure respectively in mother metal district, heat-affected zone and weld metal zone; In the mother metal district, directions X is every to carry out one-shot measurement at a distance from 1mm, on the Y direction, on average gets n according to formula (1) simultaneously
1Individual point is measured; In the weld metal zone, directions X is every to carry out one-shot measurement at a distance from 0.1mm, on the Y direction, on average gets n according to formula (2)
2Individual point is measured; In the heat-affected zone, directions X is every to carry out one-shot measurement at a distance from 0.25mm, on the Y direction, on average gets n according to formula (3) simultaneously
3Individual point is measured,
n
1＝int(t/0.8)+1 (1)
n
2＝int(t/0.4)+1 (2)
n
3＝int(t/0.5)+1 (3)
In formula (1), (2), (3), t is a tube wall thickness, and its unit is mm, n
1Be the measure dot number on the Y direction of upper edge, mother metal district, n
2For in the weld metal zone along the measure dot number of Y direction; n
3For in the heat-affected zone along the measure dot number of Y direction;
In the 4th step, confirm microhardness distribution; Get the mean value of each measuring position of directions X, obtain the microhardness distribution in weld metal zone, heat-affected zone and mother metal district.
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| RU2066861C1 (en) * | 1992-12-24 | 1996-09-20 | Комбинат "Электрохимприбор" | Process of determination of microhardness on microsection |
| CN2406244Y (en) * | 1999-12-28 | 2000-11-15 | 时代集团公司 | Hardness-meter test table |
| JP4320018B2 (en) * | 2006-01-06 | 2009-08-26 | 株式会社レニアス | Micro hardness measurement method and micro hardness tester |
| CN201444136U (en) * | 2008-12-15 | 2010-04-28 | 金卫忠 | Flexible pipe hardness tester |
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