阅读说明：本技术 测试钢材的回火脆性的方法及其应用 (Method for testing temper brittleness of steel and application thereof ) 是由 王金光 刘震宇 尹青锋 董汪平 于 2018-09-11 设计创作，主要内容包括：本公开涉及一种测试钢材的回火脆性的方法及其应用。本公开的方法通过选取多批次待测钢材中J值最大的批次钢材进行特定温度下的冲击强度测试,并计算冲击功W,如果该冲击功W大于判定值W<Sub>d</Sub>,则判定待测钢材的回火脆性全部合格。该方法可以避免传统方法中对每一批钢材都进行J值测试和步冷试验的繁琐程序,最大限度地减少测试试样的数量,简化测试程序,并能保证测试结果可靠。(The disclosure relates to a method for testing temper brittleness of steel and application thereof. The method disclosed by the invention comprises the steps of selecting the batch of steel with the maximum J value from multiple batches of steel to be tested to carry out impact strength test at a specific temperature, calculating impact energy W, and if the impact energy W is greater than a judgment value W d And judging that the temper brittleness of the steel to be detected is all qualified. The method can avoid the complicated procedures of J value test and step cooling test on each batch of steel in the traditional method, reduce the number of test samples to the maximum extent, simplify the test procedures and ensure the reliability of the test results.)

1. A method of testing the temper brittleness of a steel product, wherein the steel product comprises a plurality of batches of steel product, the method comprising the steps of:

s1, testing the weight percentage contents w of Si, Mn, P and Sn of each batch of steel respectively_Si％、w_Mn％、w_P% and w_SnPercent, and calculating the J value of the steel material of each batch according to the formula (1),

J＝(w_Si+w_Mn)×(w_P+w_Sn)×10⁴formula (1);

s2, comparing the J value of each batch of steel with the standard J value_sComparing, the J value is larger than the standard value J_sThe temper brittleness of the steel of the batch is unqualified, and the J value does not exceed a standard value J_sThe batches of steel materials are used as steel materials to be detected;

s3, selecting the batch of steel with the maximum J value in the steel to be detected as a reference batch of steel, performing an impact test on the reference batch of steel at an impact temperature, and calculating the impact energy W of the reference batch of steel;

if W is greater than the decision value W_dThe temper brittleness of the steel to be detected is all qualified; if W is less than or equal to W_dIf the temper brittleness of the batch of the steel with the largest J value is unqualified, selecting the batch of the steel with the second largest J value in the steel to be detected as the reference batch of the steel, and continuing the processing of the step S3;

wherein the impact temperature is-60 ℃ to-50 ℃; the determination value W_d47-54J; the standard value J_sIs 80 to 120.

2. The method according to claim 1, wherein the steel comprises n batches of steel, n being an integer of 2 to 10.

3. The method of claim 1, wherein the method further comprises: and before the impact test, performing simulated post-weld heat treatment on the reference batch of steel.

4. The method of claim 1, wherein the impact test is a V-notch impact test.

5. The method of claim 1, wherein the impingement temperature is-60 ℃.

6. The method according to claim 1, wherein the determination value W_dIs 54J.

7. The method of claim 1, wherein the method comprises: and 3-6 samples are taken from the reference batch of steel materials to carry out the impact test, and the average value of the impact energy of the 3-6 samples is calculated to be used as the impact energy W of the reference batch of steel materials.

8. The method according to claim 1, wherein the steel material is Cr-Mo steel.

9. The method of claim 8, wherein the Cr-Mo steel is at least one of 2.25Cr-1Mo, 2.25Cr-1Mo-1/4V, and 3Cr-1 Mo-1/4V.

10. Use of the method of any one of claims 1 to 9 in the manufacture of a Cr-Mo steel pressure vessel in hydrogen.

Technical Field

The invention relates to the field of a hydrogen Cr-Mo steel pressure container applied to petrochemical industry, coal chemical industry and the like, in particular to a method for testing the tempering brittleness of steel and application thereof.

Background

With the increasing amount of high-sulfur and high-acid crude oil processed in China and the increasing demand for clean energy, hydrogenation units of oil refining and coal chemical plants are largely used, wherein a large amount of Cr-Mo steel, such as 2.25Cr-1Mo, 2.25Cr-1Mo-1/4V and 3Cr-1Mo-1/4V, is used. These materials are characterized by a phenomenon called temper embrittlement, in which the toughness of the material deteriorates when the steel is kept at about 343 to 593 ℃ for a long time or cooled slowly from this temperature range due to metallurgical changes. The reason why the temper brittleness is generated is that harmful impurity elements (such As P, Sn, Sb, As) and certain alloy elements (such As Si, Mn) in the steel segregate to the prior austenite grain boundary, so that the grain boundary cohesive force is reduced.

For the assessment of temper embrittlement, two qualitative and quantitative methods are ubiquitous in the industry, i.e., a qualitative determination method is a J coefficient, i.e., (Si + Mn) (P + Sn). times.10⁴. The Step Cooling or stepwise Cooling (Step Cooling) processing method is an approximate quantitative determination method, and is widely used in engineering. The step cooling method is step cooling, the temperature is reduced by one step, the temperature is kept for a longer time, the steel generates the maximum temper brittleness, then a series of impact tests are carried out, and curves of the temper embrittlement degree before and after the step cooling test are drawn to determine the transformation temperature of the temper brittleness. When the step cooling test is carried out, a part of the material to be tested is directly subjected to the Charpy (V-shaped notch) impact test, 8 impact temperatures are set in total, a plurality of samples are taken at each temperature for testing, a temperature-impact energy curve is drawn, and the corresponding transition temperature VTr54 when the impact energy is 54J is calculated. And performing embrittlement treatment on the other part of the material according to an embrittlement procedure, namely heating to a specific temperature and then cooling step by step, keeping the temperature for a longer time after the temperature is reduced by one step to ensure that the steel generates the maximum temper brittleness within 300h, then performing impact test on the material subjected to the embrittlement procedure, similarly setting 8 impact temperatures, taking a plurality of samples at each temperature for testing, and drawing a temperature-impact work curve. When the calculated impact work is 54JThe corresponding transition temperature Δ VTr 54. VTr54 and Δ VTr54 need to satisfy a specific relationship. In general, the number of samples required for the step cold test is as many as several tens of samples per batch of steel.

As is known to all, the existing engineering industry requires qualitative and quantitative evaluation on materials for reactors, including steel plates, forgings and welding materials, in batches, one reactor is hundreds of tons in weight and 3000 tons in weight, the using amount is very large, if each batch of materials is tested, particularly a step cooling test, the number of samples is very large, the consumed time is very long, the delivery date of equipment and the project construction period are limited, and the test cost is very high.

Disclosure of Invention

The method is small in test sample quantity, simple to operate and capable of rapidly detecting whether the temper brittleness of large-batch steel is qualified or not.

In order to achieve the above object, a first aspect of the present disclosure provides a method of testing temper brittleness of a steel material, the steel material including a plurality of batches of the steel material, the method including the steps of: s1, testing the weight percentage contents w of Si, Mn, P and Sn of each batch of steel respectively_Si％、w_Mn％、w_P% and w_Sn% and calculating the J value of each batch of steel according to formula (1), J ═ w_Si+w_Mn)×(w_P+w_Sn)×10⁴Formula (1); s2, comparing the J value of each batch of steel with the standard J value_sComparing, the J value is larger than the standard value J_sThe temper brittleness of the steel of the batch is unqualified, and the J value does not exceed a standard value J_sThe batches of steel materials are used as steel materials to be detected; s3, selecting the batch of steel with the maximum J value in the steel to be detected as a reference batch of steel, performing an impact test on the reference batch of steel at an impact temperature, and calculating the impact energy W of the reference batch of steel; if W is greater than the decision value W_dThe temper brittleness of the steel to be detected is all qualified; if W is less than or equal to W_dIf the tempering brittleness of the steel products of the batch with the maximum J value is unqualified, and the steel products of the batch with the second largest J value in the steel products to be detected are selected asContinuing the processing of step S3 on the reference batch of steel; wherein the impact temperature is-60 ℃ to-50 ℃; the determination value W_d47-54J; the standard value J_sIs 80 to 120.

Optionally, the steel comprises n batches of steel, and n is an integer of 2-10.

Optionally, the method further comprises: and before the impact test, performing simulated post-weld heat treatment on the reference batch of steel.

Optionally, the impact test is a V-notch impact test.

Optionally, the impact temperature is-60 ℃.

Alternatively, the determination value W_dIs 54J.

Optionally, the method comprises: and 3-6 samples are taken from the reference batch of steel materials to carry out the impact test, and the average value of the impact energy of the 3-6 samples is calculated to be used as the impact energy W of the reference batch of steel materials.

Optionally, the steel material is Cr — Mo steel.

Optionally, the Cr-Mo steel is at least one of 2.25Cr-1Mo, 2.25Cr-1Mo-1/4V, and 3Cr-1 Mo-1/4V.

In a second aspect of the present disclosure, there is provided a use of the method of the first aspect of the present disclosure in the production of a Cr — Mo steel pressure vessel.

Through the technical scheme, the method disclosed by the invention selects the batch of steel with the largest J value to test the impact strength at the specific temperature, so that the complicated procedures of J value testing and step cooling testing on each batch of steel in the traditional method can be avoided, the number of test samples is reduced to the maximum extent, the test procedures are simplified, and the reliability of the test result can be ensured.

Additional features and advantages of the disclosure will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure without limiting the disclosure. In the drawings:

fig. 1 is a schematic diagram of the temperature shock power curve obtained by performing the step cooling test in comparative example 1 of the present disclosure.

Detailed Description

The following detailed description of specific embodiments of the present disclosure is provided in connection with the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present disclosure, are given by way of illustration and explanation only, not limitation.

The present disclosure provides in a first aspect a method of testing the temper brittleness of a steel product, the steel product comprising a plurality of batches of steel product, the method comprising the steps of: s1, testing the weight percentage contents w of Si, Mn, P and Sn of each batch of steel respectively_Si％、w_Mn％、w_P% and w_Sn% and calculating the J value of each batch of steel according to formula (1), J ═ w_Si+w_Mn)×(w_P+w_Sn)×10⁴Formula (1); s2, comparing the J value of each batch of steel with the standard J value_sComparing, the J value is larger than the standard value J_sThe temper brittleness of the steel of the batch is unqualified, and the J value does not exceed a standard value J_sThe batches of steel materials are used as steel materials to be detected; s3, selecting the batch of steel with the maximum J value in the steel to be tested as a reference batch of steel, performing an impact test on the reference batch of steel at an impact temperature, and calculating the impact energy W of the reference batch of steel; if W is greater than the decision value W_dThe temper brittleness of the steel to be detected is all qualified; if W is less than or equal to W_dIf the temper brittleness of the steel products of the batch with the largest J value is unqualified, selecting the steel products of the batch with the second largest J value in the steel products to be detected as the reference batch of steel products, and continuing the processing of the step S3; wherein the impact temperature is-60 ℃ to-50 ℃; determination value W_d47-54J; standard value J_sIs 80 to 120.

The inventors of the present disclosure have found that, among a plurality of batches of steel materials, a batch of steel material having the largest J value is selected and subjected to an impact test at a specific temperature as long as the impact energy satisfies a condition of being greater than a determination value W_dThe other batches of steel with smaller J value can also meet the condition that the impact energy is larger than the judgment value W_dAnd is temper brittleThe properties all meet the qualified standards. By the method, only the batch of steel with the largest J value is selected for impact strength test, and the sample amount can be reduced to 3 at least. In contrast, the conventional test method performs a step cooling test on each batch of steel, measures the impact energy at 8 temperatures before and after the embrittlement procedure, and draws a temperature impact energy curve, wherein at least 48 samples need to be tested on each batch of steel, and if the number of the test samples is large, the number of the test samples can reach hundreds of thousands, which takes a long time. The method disclosed by the invention can avoid the complicated procedures of J value test and step cooling test on each batch of steel in the traditional method, only performs the impact test on the batch of steel with the maximum J value without embrittlement treatment, and only tests the impact power at one temperature, thereby reducing the number of test samples to the maximum extent, simplifying the test procedures and ensuring the reliability of the test result.

According to the present disclosure, different batches of steel refer to steel with different element contents, for example, steel from the same furnace in a steel making process generally has the same element contents because the same raw material composition is adopted and the same treatment process is carried out, and can be used as steel of the same batch. In the disclosure, the J value of a batch of steel can be determined by extracting 3-6 samples from the batch of steel and taking the average value of the test, wherein the average value is the J value of the batch of steel.

The method disclosed by the invention can be used for testing the temper brittleness of a plurality of batches of steel, for example, the steel can comprise n batches of steel, and n can be an integer from 2 to 10, preferably an integer from 3 to 6.

The method disclosed by the disclosure comprises the steps of firstly testing the J value of each batch of steel, and comparing the J value of each batch of steel with a standard value J_sAnd comparing, performing the first step of judgment to determine whether the element content of the steel is qualified, performing the second step of judgment only by using the steel with qualified element content as the steel to be detected, and directly judging the unqualified tempering brittleness of the steel in batches with unqualified element content to eliminate the steel. According toAccording to the method disclosed by the invention, the second step of judgment only needs to judge whether the impact energy of the batch of the steel with the maximum J value is qualified, if the impact energy of the batch of the steel with the maximum J value is qualified, the temper brittleness of all batches of the steel to be tested with qualified element content is qualified, namely the temper brittleness of the rest other batches of the steel to be tested can be judged to be qualified without the impact energy test of the second step, so that the number of test samples and the test time are greatly reduced; if the batch of steel with the largest J value is unqualified, the impact power test in the step (3) is carried out on the batch of steel with the second largest J value, if the batch of steel with the second largest J value is more than 2 batches of steel, if the temper brittleness of the batch of steel with the second largest J value is qualified, namely the temper brittleness of the rest batches of steel to be tested with smaller J values can be judged to be qualified without the impact power test in the second step, if the temper brittleness of the batch of steel with the second largest J value is unqualified, the batch of steel with the third largest J value is continuously searched for the impact power test, and the like, until whether the temper brittleness of all the steel to be tested is qualified or not can be judged; in other words, the method disclosed by the invention preferably adopts the J value to carry out the first round of screening on a plurality of batches of steel, carries out the second round of impact power test screening on the batches of steel with qualified J values, and sequentially carries out the impact power test screening on the batches of steel with qualified J values according to the sequence of the J values from large to small, and according to the sequence, when the impact power test of the steel with qualified J values of a certain batch is also qualified, the temper brittleness of the other batches of steel with qualified J values, which are smaller than the batch of steel with qualified J values or have the same J values, can be judged to be qualified.

According to the present disclosure, in order to further improve the test reliability, further, the impact temperature is preferably-60 ℃ to-50 ℃, more preferably-60 ℃; determination value W_dPreferably 47 to 54J, and more preferably 54J.

Standard value J according to this disclosure_sFor the conventional J value determination standard in the art, it is generally considered that the J value does not conform to the standard J value_sRange of off-spec steel samples, in this disclosure, standard value J_sPreferably 80 to 120, and more preferably 80 to 100.

The method of testing the weight percent content of Si, Mn, P and Sn of each batch of steel in accordance with the present disclosure may be conventional in the art, for example, using the methods specified in the GB/T223 series of standards.

According to the disclosure, in order to ensure that the steel material still meets the requirements after long-time post-weld heat treatment, the method may further comprise: and (3) before the impact test, performing simulated post-weld heat treatment on the reference batch of steel. The method of performing the simulated post-weld heat treatment may be conventional in the art and will not be described herein.

The method of performing the impact test according to the present disclosure may be a method conventional in the art, and preferably the impact test may be a V-notch impact test, for example an impact test performed with reference to GB/T229-2007 standard.

The method for performing the impact test on the batch of steel with the largest J value can take 3-6 samples, and preferably comprises the following steps: 3-6 samples are taken from the steel with the largest J value in the batch for impact test, so that the number of the samples is suitable, the test procedure is simple and convenient, and the test result can be ensured to be reliable.

According to the present disclosure, the steel subjected to the temper embrittlement test may be a steel of a kind conventional in the art, for example, a Cr-Mo steel, and further, the Cr-Mo steel is preferably at least one of 2.25Cr-1Mo, 2.25Cr-1Mo-1/4V, and 3Cr-1 Mo-1/4V.

The method of the present disclosure may be used for the testing of temper brittleness of conventional steel for welding, particularly in applications where large batches of welded steel are required, whereby the second aspect of the present disclosure provides the use of the method of the first aspect of the present disclosure in the production of a hydrogen bonded Cr-Mo steel pressure vessel.

The present disclosure is further illustrated by the following examples, but is not to be construed as being limited thereby.