CN115901525A - Comprehensive evaluation method for purity of ultrahigh steel grade pipeline steel - Google Patents

Abstract

The invention provides a comprehensive evaluation method of the purity of ultra-high steel grade pipeline steel, which comprises the steps of sampling on the ultra-high steel grade pipeline steel to obtain a first sample, obtaining inclusion parameters in the first sample by adopting a metallographic method, and grading the inclusions in the first sample according to the inclusion parameters; when the impurity level in the first sample is more than or equal to 2.0 or the ultra-size impurities exist, a second sample is taken from the ultra-high steel grade pipeline steel, the second sample is electrolyzed by adopting an electrolysis method, the impurities in the second sample are collected and weighed, and the total weight of the impurities in the second sample is obtained; and comparing the weight of the inclusions in the second sample with a standard level value to obtain a comprehensive evaluation result. The method integrates the simplicity, intuition and rapidness of a metallographic method and the accuracy of an electrolytic method, and can objectively and fairly evaluate the damage of the inclusions and the purity of the high-grade steel pipeline steel with the oversized inclusions.

Description

Comprehensive evaluation method for purity of ultrahigh steel grade pipeline steel

Technical Field

The invention belongs to the technical field of material physical property detection, and particularly relates to a comprehensive evaluation method for the purity of ultra-high steel grade pipeline steel.

Background

Pipeline transportation with the advantages of high efficiency, economy, safety and the like has become the preferred mode of long-distance oil and gas transportation. In recent years, the petroleum and natural gas industry in China develops rapidly, and in order to improve the conveying capacity of pipelines and reduce the construction cost of the pipelines, the requirements of high-grade pipeline steel in the petroleum and natural gas industry are expected to show a steadily increasing trend in the future. The oversized inclusions are usually present in the pipeline steel in the form of independent phases, which destroy the continuity of a steel matrix and increase the nonuniformity of a steel structure, thereby inevitably having various adverse effects on the service performances of the pipeline steel, such as bearing capacity, plasticity, impact toughness, corrosion resistance and the like, as shown in fig. 1.

Based on the evaluation of potential harm of the oversized inclusions to the service performance of the high-steel-grade pipeline steel, the accurate evaluation of the content of the large-sized inclusions in the high-steel-grade pipeline steel becomes an important means for further improving the performance of the pipeline steel and the safety and reliability of an oil and gas conveying pipeline.

Due to the advantages of simplicity, intuition, rapidness and the like, the conventional method for evaluating the inclusion content in the acceptance standard of high-grade steel pipeline steel generally adopts the method A in ASTM E45 (worst view field method) or the method A in GB/T10561, technicians generally divide the types of inclusions according to forms in the process of evaluating the inclusion content in the high-grade steel pipeline steel by using the two metallographic methods, and generally require to limit the grades of various inclusions in the acceptance standard of the high-grade steel pipeline steel. However, for some oversize inclusions with the thickness exceeding the coarse critical value, only the size of the oversize inclusions is required to be recorded separately in the currently common metallographic evaluation method, and no method for further evaluating the harm of the oversize inclusions and the inclusion content in high-grade pipeline steel is provided. Therefore, many pipeline steel manufacturers fail to pay enough attention to the oversized inclusions found in metallographic detection, and are not favorable for acceptance and evaluation personnel to evaluate the purity of the high-grade pipeline steel with the oversized inclusions, so that potential risks are brought to the safe operation of a pipeline system. Although the electrolytic (or non-aqueous solution electrolytic) method has higher accuracy for evaluating the content of the inclusions in the high-steel-grade pipeline steel and is beneficial to comprehensively evaluating the content of the large inclusions in the high-steel-grade pipeline steel, the method has the defects of long evaluation period, complex operation process, complexity and the like, and does not have the conditions for completely popularizing and using in the evaluation process of the inclusions of the pipe at present.

For ultrahigh steel grade pipeline steel, the wall thickness of the pipe is thin, and the potential hazard degree of large inclusions is higher than that of pipeline steel products such as X70 and X80, so that a comprehensive evaluation method suitable for the content of the large inclusions in the ultrahigh steel grade pipeline steel (X90 and X100) needs to be provided.

Disclosure of Invention

In order to solve the problems in the prior art, the invention aims to provide a comprehensive evaluation method for the purity of the ultra-high steel grade pipeline steel, which can evaluate the damage of large-scale inclusions and the purity of the high steel grade pipeline steel with the large-scale inclusions, and can be widely applied to the evaluation of the content of the large-scale inclusions in various ultra-high steel grade pipeline steels.

In order to achieve the purpose, the invention provides the following technical scheme: a comprehensive evaluation method for the purity of ultra-high steel grade pipeline steel comprises the following specific steps:

s1, sampling on ultrahigh steel grade pipeline steel to obtain a first sample, obtaining inclusion parameters in the first sample by adopting a metallographic method, and grading the inclusions in the first sample according to the inclusion parameters;

s2, when the impurity level in the first sample is more than or equal to 2.0 or oversized impurities exist, taking a second sample from the ultra-high steel level pipeline steel, electrolyzing the second sample by adopting an electrolysis method, collecting the impurities in the second sample, and weighing to obtain the total weight of the impurities in the second sample;

and S3, comparing the weight of the inclusions in the second sample with a standard level value to obtain a comprehensive evaluation result.

Further, in step S1, the sampling is performed according to the specifications of ASTM E45 or GB/T10561.

Further, in step S1, the grade of the inclusions is determined according to ASTM E45 method A or GB/T10561 method A.

Further, in step S2, the second sample is sampled at a position 1/4 of the inner arc side in the width direction on the ultra-high steel grade pipeline steel.

Further, in step S2, the second sample is 2Kg.

Further, in step S2, during electrolysis, the anode is the second sample, the cathode is a stainless steel sheet, and the electrolyte is an organic solution using anhydrous methanol as a solvent.

Further, in step S2, during electrolysis, ice bath treatment is performed.

Further, in step S2, the inclusions in the obtained second sample are subjected to ultrasonic cleaning, elutriation, magnetic separation, washing, drying, and then weighed.

Further, in step S3, the standard level value is an average value of weights of the electrolyzed inclusions in the X90 and X100 products produced by a plurality of domestic large-scale pipeline steel manufacturers, and the standard level value is 0.423mg/1kg.

Further, in step S3, the comprehensive evaluation result specifically includes:

when the weight of inclusions in the second sample is > 0.423+ (0.423 × 35%), the comprehensive evaluation result is high grade;

when the weight of inclusions in the second sample was < 0.423- (0.423X 5%), the overall evaluation was low;

when the weight of inclusions in the second sample was 0.423- (0.423X 35%) ≦ 0.423+ (0.423X 35%), the comprehensive evaluation result was medium.

Compared with the prior art, the invention has at least the following beneficial effects:

the invention provides a comprehensive evaluation method for the purity of ultrahigh steel grade pipeline steel, which integrates the characteristics of simplicity, intuition and rapidness of a metallographic method, and introduces a main means of quantitative detection of inclusions, namely an electrolytic method, so that the accuracy of analysis of inclusions in the ultrahigh steel grade pipeline steel is effectively improved, the objectivity and justice of an evaluation result is ensured to a great extent, further quality disputes between pipeline steel manufacturers and users are effectively avoided, meanwhile, the analysis result of large inclusions and data such as the appearance, the size and the like obtained by using the evaluation method can provide a basis for further evaluating the harm of the large inclusions for the users, and the further effective improvement of the purity of the ultrahigh steel grade pipeline steel by the manufacturers is facilitated.

Drawings

FIG. 1 shows the macroscopic appearance of hydrogen bubbles on the surface of a sample after HIC test of an X100 steel pipe body sample with certain impurities exceeding the standard.

FIG. 2 is a schematic diagram of a sampling position.

FIG. 3 is a flow chart for evaluating the content of large inclusions in ultra-high grade pipeline steel.

Detailed Description

The invention is further described with reference to the following figures and detailed description.

Referring to fig. 3, the present invention includes the steps of:

1) Sampling the ultra-high steel grade pipeline steel which needs to be subjected to purity evaluation according to the specification of ASTM E45 or GB/T10561 to obtain a first sample, obtaining inclusion parameters in the first sample by adopting a metallographic method, grading the inclusions in the first sample by utilizing the A method (the worst field method) in the ASTM E45 or the A method in the GB/T10561 according to the inclusion parameters, finishing the evaluation if the grade of the inclusions is less than 2.0 (the acceptance condition usually adopted in the technical condition of the high steel grade pipeline steel for the current natural gas transmission pipeline engineering) or no oversized inclusions exist, and giving the grading result of the inclusions in the ultra-high steel grade pipeline steel according to the relevant specification of the ASTM E45 or the GB/T10561A method.

2) When the grade of the inclusions is more than or equal to 2.0 or when oversized inclusions exist, taking a second sample (the sampling position is shown in figure 2) with the total weight of 2Kg at a position which is positioned at the 1/4 side of the inner arc in the width direction on the ultrahigh steel grade pipeline steel, electrolyzing the second sample, collecting the inclusions in the second sample, and weighing to obtain the weight of the inclusions in the second sample;

preferably, the electrolytic bath is electrified for electrolysis, and during the electrolysis process, the second sample is an anode, the stainless steel sheet is a cathode, and the electrolyte is an organic solution taking anhydrous methanol as a solvent, and the composition of the electrolyte comprises: surfactant, complexing agent, buffer and proper reducing agent.

Preferably, nitrogen is continuously fed into the electrolytic cell during electrolysis in order to prevent oxygen in the air from affecting the electrolysis process.

Preferably, in order to reduce the surface activity of the inclusions, an ice bath device is adopted for treatment.

Preferably, the second sample is an electrolytic sample or a nonaqueous electrolytic sample.

Preferably, the main processes of the electrolytic separation of the inclusions in the second sample are as follows: sample electrolysis → ultrasonic cleaning anode → elutriation → magnetic separation → washing → drying → weighing to obtain the weight of the inclusion in the second sample, i.e. the quantitative result.

3) And comparing the weight of the inclusions in the second sample with a standard horizontal value, and checking and accepting the evaluation personnel to obtain three comprehensive evaluation results of high/medium/low purity of the ultrahigh steel grade pipeline steel.

Preferably, the mean value of electrolysis results of X90 and X100 products which are already developed by major domestic large-scale pipeline steel manufacturers is taken as a standard level value, so that the standard level value for comparing quantitative results of inclusions in the ultra-high steel grade pipeline steel is determined to be 0.423mg/1kg, and specific test values are shown in Table 1.

TABLE 1 quantitative analysis results of inclusions in X90, X100 pipeline steel samples of major manufacturers

The 8 manufacturers in the above table cover the major X90/X100 manufacturers of gem steel, saddle steel, etc., so that the resulting standard level values are very representative.

Example 1

The invention adopts a system analysis method to detect and evaluate the inclusion condition in the ultra-high steel grade pipeline steel, evaluates the cleanliness condition in the sample plate by adopting different detection modes, and quantitatively evaluates the inclusion level in the ultra-high steel grade pipeline steel in many aspects. The summary of the sample conditions of the domestic main X90 and X100 pipeline steel manufacturers is shown in Table 2:

TABLE 2 summary of samples from domestic major X90, X100 pipeline Steel manufacturers

In the first step, the typical steel products of the pipelines are sampled according to the GB/T10561, the inclusion parameters of the samples are measured by a metallographic method, the samples are graded according to the GB/T10561 method, and the evaluation results of each manufacturer are shown in tables 3 to 14.

TABLE 3 metallographic evaluation of inclusion content in the manufacturer A sample

Sampling site	Non-metallic inclusions
		Plate roll head	A0.5，B0.5，D0.5
Coiled sheet tail part	A0.5，B0.5，D0.5

TABLE 4 metallographic evaluation of inclusion content in manufacturer B samples

Sampling site	Non-metallic inclusions
		Plate roll head	A0.5，B2.0，D1.5，D0.5e
Coiled sheet tail part	A0.5，B2.0e，DS0.5

TABLE 5 metallographic evaluation of inclusion content in manufacturer C samples

Sampling site	Non-metallic inclusions
		Plate roll head	A0.5，B0.5，D1.0，DS0.5
Coiled sheet tail part	A0.5，B0.5，D1.0

TABLE 6 evaluation results of impurity content in manufacturer D sample by metallographic method

Sampling site	Non-metallic inclusions
		Plate roll head	A0.5，B0.5，D0.5，DS1.5
Coiled sheet tail part	A0.5，B0.5，D1.0

TABLE 7 evaluation results of inclusion content in manufacturer E sample by metallographic method

Sampling site	Non-metallic inclusions
		Plate roll head	A0.5，B0.5，D1.0，DS1.0
Coiled sheet tail part	A0.5，B1.0e，D1.0

TABLE 8 metallographic evaluation of inclusion content in manufacturer F samples

Sampling site	Non-metallic inclusions
		Plate roll head	A0.5，B1.0，B1.0e，D0.5e，DS2.0
Coiled sheet tail part	A0.5，B1.0e，D0.5e，DS2.0

TABLE 9 metallographic evaluation of inclusion content in manufacturer G samples

Sampling site	Non-metallic inclusions
		Steel plate head	A0.5，B1.0，D0.5e，DS1.5
Steel plate tailPart (A)	A0.5，B2.0，B1.0e，D0.5e，DS2.0

TABLE 10 metallographic evaluation of inclusion content in factory H samples

Sampling site	Non-metallic inclusions
		Steel plate head	A0.5，B1.5，B1.5e，D0.5e，DS2.0
Steel plate tail	A0.5，B1.5，D0.5e

TABLE 11 metallographic evaluation of inclusion content in manufacturer I samples

Sampling site	Non-metallic inclusions
		Steel plate head	A0.5，B1.0e，D0.5，DS1.0
Steel plate tail	A0.5，B1.5，D0.5e

TABLE 12 metallographic evaluation of inclusion content in manufacturer J sample

Sampling site	Non-metallic inclusions
		Steel plate head	A0.5，B0.5，D0.5，D0.5e，DS1.5
Steel plate tail	A0.5，B0.5，D0.5，D0.5e，DS1.5

TABLE 13 metallographic evaluation of inclusion content in K samples from manufacturers

TABLE 14 metallographic evaluation of inclusion content in manufacturer L samples

Sampling site	Non-metallic inclusions
		Steel plate head	A0.5，B1.0，D0.5，DS0.5
Steel plate tail	A0.5，B1.0，B1.5s，D0.5，DS0.5

Note: the tail sample had oversized class B inclusions and had a maximum thickness of 26 μm.

And secondly, grading according to the evaluation result of a metallographic method and the regulation of the method A in GB/T10561, wherein inclusions with the grade of 2.0 appear in samples of a manufacturer F, a manufacturer G and a manufacturer H, and oversized inclusions appear in samples of a manufacturer L, so that the inclusion level of samples of the manufacturers needs to be further quantitatively evaluated.

Thirdly, for the X90, X100 ultra-high steel grade samples of manufacturer F, manufacturer G, manufacturer H and manufacturer L, a second sample with a total weight of 2Kg or a second non-aqueous solution sample is prepared at a position 1/4 of the inner arc side in the width direction, then the obtained sample is subjected to electrolytic analysis to obtain the quality of inclusions in the second sample, and the quality of the inclusions in the second sample is compared with a standard level value to obtain a comprehensive evaluation result, as shown in table 15:

TABLE 15 quantitative analysis and comparison conclusion of inclusions in ultra-high grade steel pipeline steel samples

Note: according to the quantitative analysis result of the inclusions in the steel sample of the X100 pipeline of the main manufacturer X90, the standard deviation of the data obtained by statistical analysis is 0.270, and the proportional relation between the standard deviation and the mean value is (0.423-0.270)/0.423 =36%, and the rounding is 35%.

As can be seen from Table 15, when the weight of inclusions in the second sample was > 0.423+ (0.423X 35%), the comprehensive evaluation result was high;

when the weight of inclusions in the second sample was < 0.423- (0.423X 35%), the overall evaluation was low;

when the weight of inclusions in the second sample was 0.423- (0.423X 35%) ≦ 0.423+ (0.423X 35%), the comprehensive evaluation result was medium.

The pipeline steel manufacturer and the user can comprehensively evaluate the purity level of the pipeline steel according to the evaluation conclusion, and can also use the evaluation method to obtain the analysis result of the large inclusions and the data of the appearance, the size and the like of the inclusions, so that a basis is provided for the user to further evaluate the damage of the large inclusions, and the manufacturer is required to further effectively improve the purity of the ultrahigh steel grade pipeline steel.

Claims (10)

1. A comprehensive evaluation method for the purity of ultra-high steel grade pipeline steel is characterized by comprising the following specific steps:

s1, sampling on ultrahigh steel grade pipeline steel to obtain a first sample, obtaining inclusion parameters in the first sample by adopting a metallographic method, and grading the inclusions in the first sample according to the inclusion parameters;

s2, when the impurity level in the first sample is more than or equal to 2.0 or oversized impurities exist, taking a second sample from the ultra-high steel level pipeline steel, electrolyzing the second sample by adopting an electrolysis method, collecting the impurities in the second sample, and weighing to obtain the total weight of the impurities in the second sample;

and S3, comparing the weight of the inclusions in the second sample with a standard level value to obtain a comprehensive evaluation result.

2. The comprehensive evaluation method for the purity of the ultra-high steel grade pipeline steel according to claim 1, wherein in the step S1, the sampling is performed according to the specification in ASTM E45 or GB/T10561.

3. The comprehensive evaluation method for the purity of the ultra-high steel grade pipeline steel according to claim 1, wherein in the step S1, the grade of the inclusions is determined according to the method A in ASTM E45 or the method A in GB/T10561.

4. The comprehensive evaluation method for the purity of the ultra-high steel grade pipeline steel according to claim 1, wherein in the step S2, the second sample is sampled at a position 1/4 of the inner arc side in the width direction on the ultra-high steel grade pipeline steel.

5. The comprehensive evaluation method for the purity of the ultra-high steel grade pipeline steel according to claim 1, wherein in the step S2, the second sample is 2Kg.

6. The method for comprehensively evaluating the purity of ultra-high steel grade pipeline steel according to claim 1, wherein in the step S2, the anode is the second sample, the cathode is the stainless steel sheet, and the electrolyte is an organic solution using anhydrous methanol as a solvent.

7. The comprehensive evaluation method for the purity of the ultra-high steel grade pipeline steel according to claim 1, wherein in the step S2, ice bath treatment is performed during electrolysis.

8. The comprehensive evaluation method for the purity of the ultra-high steel grade pipeline steel according to claim 1, wherein the impurities in the second sample obtained in the step S2 are subjected to ultrasonic cleaning, elutriation, magnetic separation, washing, drying and then weighing.

9. The comprehensive evaluation method for the purity of ultra-high steel grade pipeline steel according to claim 1, wherein in step S3, the standard level value is the average value of the weight of inclusions in the electrolyzed practical X90 and X100 products produced by a plurality of domestic large pipeline steel manufacturers, and the standard level value is 0.423mg/1kg.

10. The comprehensive evaluation method for the purity of the ultra-high steel grade pipeline steel according to claim 1, wherein in the step S3, the comprehensive evaluation result is specifically as follows:

when the weight of inclusions in the second sample was > 0.423+ (0.423 × 35%), the comprehensive evaluation result was high;

when the weight of inclusions in the second sample was < 0.423- (0.423X 5%), the overall evaluation was low;

when the weight of inclusions in the second sample was 0.423- (0.423X 35%) ≦ 0.423+ (0.423X 35%), the comprehensive evaluation result was medium.

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