应力腐蚀试验的试样

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应力腐蚀及环境氢脆测试方法

K1-tF曲线
五、慢应变率法试验
慢应变率法，又称恒应变率法，它是将拉伸试样放在特定的介质中，然后在慢应变率试验机上，用一定的、缓慢的应变速度进行拉伸试验，直到拉断。
SERT型慢应变应力腐蚀试验机
六、应力腐蚀案例
不锈钢管与管板胀接部位的横向裂纹
管与管板连接方式很多，在应力腐蚀工程事故分析中，多遇到胀－焊连接，仅胀未焊连接还仅焊未胀连接三种。部分胀－焊连接方式见图。大量事故分析表明，不论是胀－焊还是仅胀未焊连接，不锈钢管束应力腐蚀裂纹多位于胀与未胀过渡区。这与滚胀连接时，局部变形，受有较大的纵向残余拉应力有关。实测表明，此处纵向应力一般高达相当于屈服强度的数值。
典型的da/dt－K曲线（K为应力强度因子）
8、破裂电位范围和临界破裂电位
大量的例子表明，对于某一特定体系应力腐蚀破裂只发生于一定的电位以上，低于这个电位则不会发生，这个电位值称为应力腐蚀破裂临界电位。
在沸腾的42％MgCl2 溶液中，18－8Ti 不锈钢的电位－断裂时间关系
二、试样及测试方法的类型
b、三点弯曲试样
恒应变三点弯曲试样及试验装置
恒载荷三点弯曲试验
1－棒；2－试样； 3－荷重
C、四点弯曲试样
恒应变四点弯曲试样及试样架
恒应变四点弯曲试样及试样架
1－棒；2－试样；3－荷重
d、双弯梁
3、U形弯曲试样
U形试样弯曲过程
常用的U形试样
1－焊接或缚紧；2－焊接；3－夹紧前；4－受力试样
水中Cl-浓度对 0Cr18Ni10钢SCC 敏感性的影响
5、应力腐蚀破裂敏感系数
在特定条件下，把应力腐蚀破裂时间的倒数，称为破裂敏感系数。当破裂敏感系数越大时，材料的应力腐蚀敏感性也越大。

氯化镁应力腐蚀试验标准

氯化镁应力腐蚀试验标准氯化镁应力腐蚀试验标准1.目的本标准旨在规定氯化镁应力腐蚀试验的方法和程序，以评估金属材料在氯化镁溶液环境下的应力腐蚀敏感性。

通过本试验，可以了解金属材料在特定条件下的应力腐蚀裂纹产生和发展情况，为提高材料的耐蚀性能提供依据。

2.适用范围本标准适用于金属材料在氯化镁溶液环境下的应力腐蚀试验。

试验对象包括但不限于钢铁、铝合金、铜合金等金属材料。

3.试验原理应力腐蚀是指在拉应力作用下，金属材料在腐蚀介质中发生的脆性断裂现象。

本试验通过将试样浸泡在氯化镁溶液中，并施加一定的拉应力，模拟实际使用条件下金属材料的应力腐蚀情况。

通过观察试样的破裂时间及破裂形态，评价金属材料的应力腐蚀敏感性。

4.试验步骤4.1 试样准备4.1.1 选择所需金属材料，制备成标准尺寸的试样，如平板、杆状等。

试样应具有足够的强度和刚度，以便在试验过程中保持稳定。

4.1.2 对试样进行研磨和抛光，确保表面光滑无瑕疵。

这一步骤可减少表面粗糙度对试验结果的影响。

4.2 试验溶液制备4.2.1 按照试验条件要求，配制适当浓度的氯化镁溶液。

根据需要，可添加适量的盐酸（续）其他离子或调节溶液pH值。

4.2.2 将配制好的氯化镁溶液倒入试验容器中，确保溶液深度适宜，一般为50mm至100mm。

根据试验要求，可选择采用恒温水浴或其他温度控制方法保持溶液温度稳定。

4.3 试样安装4.3.1 将试样固定在试验容器中，确保试样与容器轴线垂直。

可采用适当的支架或夹具进行固定。

4.3.2 对试样施加拉伸应力，使其产生预应力。

预应力的施加应按照试验条件要求进行控制，一般通过拉伸装置或特殊设计的夹具实现。

4.4 试验条件设定根据试验要求，设定试验温度、湿度和氯化镁溶液浓度等条件。

这些条件应根据实际使用环境和试验要求进行设定。

同时，设定试验时间为一定值，如24小时、48小时等，以便对不同材料的耐蚀性能进行比较和分析。

在设定试验条件时应注意控制变量的一致性，以保证试验结果的可靠性。

20#钢在30%NaOH溶液中应力腐蚀试验研究

效现象。通过模拟精丙酮塔再沸器中的介质成分及其浓度，试验研究
了２＃０钢在ＮＯａＨ溶液中应力腐蚀状况，为解决精丙酮塔再沸器失效
问题提供了依据。
应变率在１＾ＳＯｅ一左右较为合适。在这种情况下，如果试样未
选择应变速率是进行慢应变速率应力腐蚀试验的重要环
节。大量的资料和文献及我们已经研究的结果都证明，产生
应变率为１一秒～～１秒～在这一应变率范围内，将使裂ＯＯ。缝尖端的变形、溶解、成膜和扩散处于产生应力腐蚀破裂的临
界平衡状态。最初它应用于快速选材，判断不同合金成分和不同结构等对应力腐蚀的敏感性或对各类电化学参数的影响，或缓蚀剂效应等。近年来已应用于理论研究。
ＳＣＣ敏感的应变速率都集中在１－０％至１－一范围内。在此０７ｓ
实际工况直接相结合，快速、准确地进行抗应力腐蚀开裂（Ｃ能的评估。这个方法是将拉力试件放在一定环境中ＳＣＪ性
本次试验研究选用的试验温度为９￣压力为常压。０Ｃ。
３３试样．试验所用材料为２钢由５０７Ｘ４ｍｍ管。
３４沮度压力条件．

ASTM G39 - 99(2011)

Designation:G39–99(Reapproved 2011)Standard Practice forPreparation and Use of Bent-Beam Stress-Corrosion Test Specimens 1This standard is issued under the ﬁxed designation G39;the number immediately following the designation indicates the year of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon (´)indicates an editorial change since the last revision or reapproval.1.Scope1.1This practice covers procedures for designing,prepar-ing,and using bent-beam stress-corrosion specimens.1.2Different specimen conﬁgurations are given for use with different product forms,such as sheet or plate.This practice applicable to specimens of any metal that are stressed to levels less than the elastic limit of the material,and therefore,the applied stress can be accurately calculated or measured (see Note 1).Stress calculations by this practice are not applicable to plastically stressed specimens.N OTE 1—It is the nature of these practices that only the applied stress can be calculated.Since stress-corrosion cracking is a function of the total stress,for critical applications and proper interpretation of results,the residual stress (before applying external stress)or the total elastic stress (after applying external stress)should be determined by appropriate nondestructive methods,such as X-ray diffraction (1).21.3Test procedures are given for stress-corrosion testing by exposure to gaseous and liquid environments.1.4The bent-beam test is best suited for ﬂat product forms,such as sheet,strip,and plate.For plate material the bent-beam specimen is more difficult to use because more rugged speci-men holders must be built to accommodate the specimens.A double-beam modiﬁcation of a four-point loaded specimen to utilize heavier materials is described in 10.5.1.5The exposure of specimens in a corrosive environment is treated only brieﬂy since other practices deal with this aspect,for example,Speciﬁcation D1141,and Practices G30,G36,G44,G50,and G85.The experimenter is referred to ASTM Special Technical Publication 425(2).1.6The bent-beam practice generally constitutes a constant strain (deﬂection)test.Once cracking has initiated,the state of stress at the tip of the crack as well as in uncracked areas has changed,and therefore,the known or calculated stress or strain values discussed in this practice apply only to the state of stress existing before initiation of cracks.1.7The values stated in SI units are to be regarded as standard.The inch-pound values in parentheses are provided for information.1.8This standard does not purport to address all of the safety concerns,if any,associated with its use.It is the responsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.(For more speciﬁc safety hazard information see Section 7and 12.1.)2.Referenced Documents 2.1ASTM Standards:3D1141Practice for the Preparation of Substitute Ocean WaterG30Practice for Making and Using U-Bend Stress-Corrosion Test SpecimensG36Practice for Evaluating Stress-Corrosion-Cracking Re-sistance of Metals and Alloys in a Boiling Magnesium Chloride SolutionG44Practice for Exposure of Metals and Alloys by Alter-nate Immersion in Neutral 3.5%Sodium Chloride Solu-tionG50Practice for Conducting Atmospheric Corrosion Tests on MetalsG85Practice for Modiﬁed Salt Spray (Fog)Testing 2.2NACE Documents:4NACE TM0177-96Laboratory Testing of Metals for Resis-tance to Speciﬁc Forms of Environmental Cracking in H 2S Environments 3.Terminology3.1Deﬁnitions of Terms Speciﬁc to This Standard:3.1.1cracking time —the time elapsed from the inception of test until the appearance of cracking.3.1.1.1Discussion —The test begins when the stress is applied and the stressed specimen is exposed to the corrosive environment,whichever occurs later.1This practice is under the jurisdiction of ASTM Committee G01on Corrosion of Metals and is the direct responsibility of Subcommittee G01.06on Environmen-tally Assisted Cracking.Current edition approved March 1,2011.Published April 2011.Originally approved in st previous edition approved in 2005as G39–99(2005).DOI:10.1520/G0039-99R11.2The boldface numbers in parentheses refer to a list of references at the end of this standard.3For referenced ASTM standards,visit the ASTM website,,or contact ASTM Customer Service at service@.For Annual Book of ASTM Standards volume information,refer to the standard’s Document Summary page on the ASTM website.4Available from NACE International (NACE),1440South Creek Dr.,Houston,TX 77084-4906,.Copyright.C ASTM International.100Barr Harbou r Drive,PO box C-700West Conshohocken,Pennsylvania 19428-2959,United StatesWe expertize in translation of technical documents and also deliver procurement service of Chinese versions. Information is available from /2896501387 . Please contact us if you need any help.3.1.1.2Discussion—The specimen is considered to have failed when cracks are detected.Presence of cracks can be determined with or without optical,mechanical,or electronic aids.However,for meaningful interpretation,comparisons should be made only among tests employing crack detection methods of equivalent sensitivity.3.1.2stress-corrosion cracking—a cracking process requir-ing the simultaneous action of a corrodent and sustained tensile stress.This excludes corrosion-reduced sections that fail by fast fracture.It also excludes intercrystalline or transcrystalline corrosion which can disintegrate an alloy without either applied or residual stress.4.Summary of Practice4.1This practice involves the quantitative stressing of a beam specimen by application of a bending stress.The applied stress is determined from the size of the specimen and the bending deﬂection.The stressed specimens then are exposed to the test environment and the time required for cracks to develop is determined.This cracking time is used as a measure of the stress-corrosion resistance of the material in the test environment at the stress level utilized.5.Signiﬁcance and Use5.1The bent-beam specimen is designed for determining the stress-corrosion behavior of alloy sheets and plates in a variety of environments.The bent-beam specimens are de-signed for testing at stress levels below the elastic limit of the alloy.For testing in the plastic range,U-bend specimens should be employed(see Practice G30).Although it is possible to stress bent-beam specimens into the plastic range,the stress level cannot be calculated for plastically-stressed three-andfour-point loaded specimens as well as the double-beam specimens.Therefore,the use of bent-beam specimens in the plastic range is not recommended for general use.6.Apparatus6.1Specimen Holders—Bent-beam specimens require a specimen holder for each specimen,designed to retain the applied stress on the specimen.Typical specimen holder conﬁgurations are shown schematically in Fig.1.N OTE2—The double-beam specimen,more fully described in10.5,is self-contained and does not require a holder.N OTE3—Specimen holders can be modiﬁed from the constant defor-mation type shown in Fig.1to give a constant-load type of stressing.For instance,the loading bolt can be supplanted by a spring or deadweight arrangement to change the mode of loading.6.1.1The holder shall be made of a material that would withstand the inﬂuence of the environment without deteriora-tion or change in shape.N OTE4—It should be recognized that many plastics tend to creep when subjected to sustained loads.If specimen holders or insulators are made of such materials,the applied stress on the specimen may change appreciably with time.By proper choice of holder and insulator materials,however, many plastics can be used,especially in short-time tests.6.1.2When the stress-corrosion test is conducted by immer-sion in an electrolyte,galvanic action between specimen and holder(or spacer)shall be prevented(see Note5).This is accomplished by(1)making the holder of the same material as the individual specimens,(2)inserting electrically insulating materials between specimen and holder at all points of contact (see Note4),(3)making the entire holder out of a nonmetallic material(see Note4),or(4)coating the holder with an electrically nonconducting coating that effectively prevents contact between holder and electrolyte.6.1.3Crevice corrosion may occur in an electrolyte at contact points between specimen and holder(or spacer).In these instances the critical areas should be packed with a hydrophobicﬁller(such as grease or wax).N OTE5—In atmospheres(gas)galvanic action between specimen and holder either does not exist or is conﬁned to a very small area as experienced in outdoor exposure tests.6.2Stressing Jigs—Three-point and four-point loaded specimen holders,Fig.1(b and c),contain a stressing feature in the form of a loading screw.To stress two-point loaded specimens(Fig.1(a)),a separate stressing jig shall be used.A convenient stressing jig is shown in Fig.2.N OTE6—The double-beam specimen,described in10.5,requires a mechanical or hydraulic stressing frame(a universal tension testing machine can also be used)as well as welding equipment.6.3Deﬂection Gauges—Deﬂection of specimens is deter-mined by separate gages or by gages incorporated in a loading apparatus as shown in Fig.3.In designing a deﬂection gageto FIG.1Schematic Specimen and HolderConﬁgurationssuit individual circumstances care must be taken to reference the deﬂection to the proper support distance as deﬁned in 10.2-10.5.7.Hazards7.1Bent-beam specimens made from high-strength materi-als may exhibit high rates of crack propagation and a specimen may splinter into several pieces.Due to high stresses in a specimen,these pieces may leave the specimen at high velocity and can be dangerous.Personnel installing and examining specimens should be cognizant of this possibility and be protected against injury.8.Sampling8.1Test specimens shall be selected so that they represent the material to be tested.In simulating a service condition,the direction of load application in the specimen shall represent theanticipated loading direction in service with respect to process-ing conditions,for example,rolling direction.8.2Paragraphs 9.4and 9.5deal speciﬁcally with specimen selection as related to the original material surface.9.Test Specimen9.1The bent-beam,stress-corrosion specimens shall be ﬂat strips of metal of uniform,rectangular cross section,and uniform thickness.9.2The identiﬁcation of individual specimens should be permanently inscribed at each end of the specimen because this is the area of lowest stress and cracking is not expected to be initiated by the identiﬁcation markings.If stenciling is used for identiﬁcation,this shall be done only on softened material before any hardening heat treatments to prevent cracking in the stenciled area.Care must be taken to prevent the identiﬁcation from being obliterated by corrosion.9.3Mechanical properties should be determined on the same heat-treatment lot from which stress-corrosion specimens are obtained.9.4The specimens can be cut from sheet or plate in such a fashion that the original material surface is retained.This procedure is recommended when it is desired to include the effect of surface condition in the test.9.5If,however,it is desired that surface conditions should not inﬂuence the test results of several materials with different surface conditions,the surfaces of all specimens must be prepared in the same way.It is recommended that grinding or machining to a surface ﬁnish of at least 0.7µm (30µin.)and to a depth of at least 0.25mm (0.01in.)be utilized for surface preparation.It is desirable to remove the required amount of metal in several steps by alternately grinding opposite surfaces.This practice minimizes warpage due to residual stresses caused by machining.All edges should be similarly ground or machined to remove cold-worked material from previous shearing.Chemical or electrochemical treatments that produce hydrogen on the specimen surface must not be used on materials that may be subject to embrittlement by hydrogen or that react with hydrogen to form a hydride.9.6Immediately before stressing,the specimens should be degreased and cleaned to remove contamination that occurred during specimen preparation.Only chemicals appropriate for the given metal or alloy should be used.Care must be exercised not to contaminate cleaned specimens.Also,it is suggested that specimens be examined for cracks before exposure to the test environment.10.Stress Calculations10.1The equations given in this section are valid only for stresses below the elastic limit of the material.At stresses above the elastic limit,but below the engineering yield strength (0.2%offset)only a small error results from use of the equations (see Note 1).The equations must not be used above the yield strength of the material.The following paragraphs give relationships used to calculate the maximum longitudinal stress in the outer ﬁbers of the specimen convex surface.Calculations for transverse stress or edge-to-edge variation of longitudinal stress are not given;the specimen dimensions are chosen to minimize these stresses consistent withconvenientFIG.2Stressing Jig and Two-Point Loaded Specimen with Holder(approximately 1⁄4actualsize)FIG.3Specimen Loading Apparatus for Three-Point LoadedBeam Specimens with Integral DeﬂectionGageuse of the specimens.The specimen dimensions given here can be modiﬁed to suit speciﬁc needs.However,if this is done,the approximate specimen proportions should be preserved to give a similar stress distribution (for instance,if the length is doubled the width should be doubled also).10.1.1When specimens are tested at elevated temperatures,the possibility of stress relaxation should be investigated.Relaxation can be estimated from known creep data for the specimen,holder,and insulating materials.Differences in thermal expansion also should be considered.10.1.2The applied stress is determined by specimen dimen-sions and the amount of bending deﬂection.Thus,the errors in the applied stress are related to those inherent in the use of measuring instruments (micrometers,deﬂection gages,strain gages,and so forth).For the two-point loaded specimens,most measured values lie within 5%of the values calculated in accordance with the procedures given in 10.2.1-10.2.3,as reported by Haaijer and Loginow (4).The calculated stress applies only to the state of stress before initiation of cracks.Once cracking is initiated,the stress at the tip of the crack,as well as in uncracked areas,has changed.10.2Two-Point Loaded Specimens —This specimen can be used for materials that do not deform plastically when bent to (L −H)/H =0.01(see section 10.2.5).The specimens shall be approximately 25by 254-mm (1-by 10-in.)ﬂat strips cut to appropriate lengths to produce the desired stress after bending as shown in Fig.1(a ).10.2.1Calculate the elastic stress in the outer ﬁber at midlength of the two-point loaded specimens from relation-ships derived from a theoretically exact large-deﬂection analy-sis (4),as follows:´54~2E 2K !F k 222E 2K 12S tHD Gt H(1)and~L 2H !/H 5[K /2E 2K !#21(2)where:L =length of specimen,H =distance between supports (holder span),t =thickness of specimen,´=maximum tensile strain,K =*0p /2(1−k 2sin 2z )−1/2d z (complete elliptic integral ofthe ﬁrst kind),E =*0p /2(1−k 2sin 2z )1/2d z (complete elliptic integral of thesecond kind),k =sin u /2,u =maximum slope of the specimen,that is,at the end ofthe specimen,andz =integration parameter (4).10.2.2The mathematical analysis establishes that Eq 1and Eq 2deﬁne the relationship between the strain ´and (L −H)/H in parameter form.The common parameter in these equations is the modulus k of the elliptic integrals.Thus,the following procedure can be used to determine the specimen length L that is required to produce a given maximum stress s :10.2.2.1Divide the stress s by the modulus of elasticity E m to determine the strain ´.´5s /E m10.2.2.2From Eq 1determine the value of k corresponding to the required value of ´.10.2.2.3By using appropriate values of k ,evaluate Eq 2for L .To facilitate calculations,a computer can be used to generate a table for a range of strain ´and H/t with resultant values of (L −H)/H .10.2.3Calculate the deﬂection of the specimen as follows:y /H 5k /~2E 2K !(3)where:y =maximum deﬂection.The other quantities are given in 10.2.1.This relationship can be used as a simple check to ensure that the maximum stress does not exceed the proportional limit.If it should exceed the proportional limit,the measured deﬂection will be greater than that calculated from Eq 3.10.2.4As an alternative method the following approximate relationship can be used for calculating specimen length:L 5~ktE /s !sin 21~H s /ktE !(4)where:L =specimen length,s =maximum stress,E =modulus of elasticity,H =holder span,t =thickness of specimen,and k = 1.280,an empirical constant.This equation can be solved by computer,by trial and error,or by using a series expansion of the sine function.Eq 4shall be used only when the quantity (H s /ktE)is less than 1.0.10.2.5Choose specimen thickness and length and holder span to obtain a value for (L −H)/H of between 0.01and 0.50,thus keeping the error of stress within acceptable limits.A specimen thickness of about 0.8to 1.8mm (0.03to 0.07in.)and a holder span of 177.8to 215.9mm (7.00to 8.50in.)has been very convenient when working with very high strength steels and aluminum alloys with applied stresses ranging from about 205MPa (30ksi)for aluminum to 1380MPa (200ksi)for steel.The specimen dimensions given here can be modiﬁed to suit speciﬁc needs.However,if this is done,approximate dimensional proportions shall be preserved.10.2.6In two-point loaded specimens the maximum stress occurs at midlength of the specimen and decreases to zero at specimen ends.10.2.7The two-point loaded specimen is preferred to three-point loaded specimens because in many instances crevice corrosion of the specimen occurs at the central support of the three-point loaded specimen.Since this corrosion site is very close to the point of highest tension stress,it may cathodically protect the specimen and prevent possible crack formation or cause hydrogen embrittlement.Furthermore,the pressure of the central support at the point of highest load introduces biaxial stresses at the area of contact and could introduce tension stresses where normally compression stresses are present.N OTE 7—Occasionally two-point loaded specimens having a nonuni-form cross section are used for special purposes.A description of such a specimen is given by Wilson and Spier (5).10.3Three-Point Loaded Specimens—The specimen shall be aﬂat strip typically25to51-mm(1to2-in.)wide and127 to254-mm(5to10-in.)long.The thickness of the specimen is usually dictated by the mechanical properties of the material and the product form available.Support the specimen at the ends and bend the specimen by forcing a screw(equipped with a ball or knife-edge tip)against it at the point halfway between the end supports in a fashion shown in Fig.1(b).The specimen dimensions given here can be modiﬁed to suit speciﬁc needs. However,if this is done,approximate dimensional proportions shall be preserved.10.3.1Calculate the elastic stress at midspan in the outer ﬁbers of three-point loaded specimens from the relationship:s56Ety/H2(5) where:s=maximum tensile stress,E=modulus of elasticity,t=thickness of specimen,y=maximum deﬂection,andH=distance between outer supports.10.3.2The above relationship is based on small deﬂections (y/H less than0.1).In sheet-gage,bent-beam specimens the deﬂections are usually large,and thus,the relationship is only approximate.To obtain more accurate stress values,use a prototype specimen,equipped with strain gages,for calibra-tion.This prototype should have the same dimensions as the test specimens and should be stressed in the same way. 10.3.3In three-point loaded specimens the maximum stress occurs at midlength of the specimen and decreases linearly to zero at the outer supports.10.3.4For limitation in the use of three-point loaded speci-mens see10.2.7.10.4Four-Point Loaded Specimens—The specimen shall be aﬂat strip typically25to51-mm(1to2-in.)wide and127to 254-mm(5to10-in.)long.The thickness of the specimen is usually dictated by the mechanical properties of the material and the product form available.Support the specimen at the ends and bend the specimen by forcing two inner supports against it in a fashion shown in Fig.1(c).The two inner supports shall be located symmetrically around the midpoint between the outer supports.The specimen dimensions given here can be modiﬁed to suit speciﬁc needs.However,if this is done,approximate dimensional proportions shall be preserved.10.4.1Calculate the elastic stress for the midportion of the specimen(between contact points of the inner support)in the outerﬁbers of four-point loaded specimens from the following relationship:s512Ety/~3H224A2!(6) where:s=maximum tensile stress,E=modulus of elasticity,t=thickness of specimen,y=maximum deﬂection(between outer supports),H=distance between outer supports,andA=distance between inner and outer supports.The dimensions are often chosen so that A=H/4.10.4.2An alternative method of calculating the elastic stress between the inner supports is as follows:s54Ety8/h2(7) where:h=distance between inner supports,andy8=deﬂection between inner supports.(This equation is a special case of10.4.1when A=0.) 10.4.3The above relationships are based on small deﬂec-tions(y/H less than0.1).In sheet-gage bent-beam specimens the deﬂections are usually large,and thus,the relationships are only approximate.To obtain more accurate stress values,use for calibration a prototype specimen equipped with strain gages.This prototype specimen should have the same dimen-sions as the test specimens and should be stressed in the same way.10.4.4In four-point loaded specimens the maximum stress occurs between the contact points with the inner supports;in this area the stress is constant.From the inner supports the stress decreases linearly toward zero at the outer supports. 10.5Double-Beam Specimen—The specimen shall consist of twoﬂat strips25to51-mm(1to2-in.)wide and127to 254-mm(5to10-in.)long.Bend the strips against each other over a centrally located spacer until both ends of the specimens touch.Hold them in this position by welding the ends together as shown in Fig.1(d)(see Note8).An equivalent procedure for bolted specimens is described on pp.319–321of Ref(2).N OTE8—If the test is to be conducted in an electrolyte,the spacer shall be made of the same material as the specimen(or of an electrically nonconducting material such as glass,ceramic,and so forth)to prevent galvanic action between specimen and spacer.See also6.1.2and Note4 and Note5.10.5.1Calculate the elastic stress for the midportion of the specimen(between contact points of the spacer)in the outer ﬁbers of the doublebeam specimens from the following rela-tionship:s53EtsH2@12~h/H!#@11~2h/H!#(8)where:s=maximum tensile stress,E=modulus of elasticity,t=thickness of specimen strip,s=thickness of spacer,H=see Fig.1(d),andh=length of spacer.10.5.2When the length of the spacer h is chosen so that H=2h the equation in10.5.1is simpliﬁed to:s53Ets/H210.5.3The above relationships are based on small deﬂec-tions(s/H being less than0.2).In sheet-gage bent-beam specimens the deﬂections are usually large,and thus,the relationships are only approximate.To obtain more accurate stress values,use a prototype specimen,equipped with strain gages,for calibration.The prototype specimen should have the same dimensions as the test specimens and should be stressed in the sameway.10.5.4In double-beam specimens the maximum stress oc-curs between the contact points with the spacer;in this area the stress is constant.From the contact with the spacer the stress decreases linearly toward zero at the ends of specimens. 11.Choice of Test Conditions11.1The purpose of stress-corrosion testing is to simulate on a small scale the conditions(materials,stress,and environ-ment)that exist in an engineering application.The stresses in an engineering structure can be varied between operational (design)stresses and residual stresses(from heat treatment or fabrication).Residual stresses are frequently the more impor-tant,primarily because current design practices and close control of processes have kept operational stresses well below the yield strength of the metal in use.On the other hand, magnitude and direction of residual stresses frequently are difficult to predict and also difficult to measure.Depending on the degree of restraint,residual stresses may even exceed the initial yield strength of the material.11.2Generally stress-corrosion testing falls into two broad categories:(1)evaluation of materials for a speciﬁc applica-tion,and(2)comparison of the relative behavior of several materials or environments.11.2.1To evaluate materials for speciﬁc applications,the testing conditions should be representative of the most severe conditions to which the materials would be subjected in service.Testing at nominal or design conditions could be misleading.An engineering structure,because of residual stresses,is expected to be stressed to its yield strength at some points even if the design stress for that structure is appreciably below yield strength.Thus,the use of the elastically stressed bent-beam specimens for materials evaluation is of limited value.11.2.2To compare materials or environments for relative stress-corrosion behavior,the test conditions may be only severe enough to produce varying degrees of cracking in the alloys of interest,in mechanical or thermal treatments used,or in sensitivity to speciﬁc environments investigated.By testing a set of specimens at a series of stress levels,the stress dependence of alloys can be assessed.The bent-beam speci-men is very well suited for establishing the relative merits of several alloys for the relative severity of several environments.11.3Ideally,the environmental test conditions should be the same that would prevail in the intended use of the alloys.In choosing a set of test conditions,it is important that they (environment and stress)be well deﬁned and reproducible.A detailed discussion is given by Loginow(6).11.4The presence of a machined notch in the middle of the tension side of a bent beam will induce a severe triaxial stress state at the root of the notch.The actual bending stress there will be greater by a concentration factor dependent on the notch geometry,than the minimal test stress,and generally, may be expected to be in the range of plastic stain.Advantages of such a notched specimen include the probable localized cracking in the notch and an acceleration of failure.However, unless directly related to practical conditions of usage,mis-leading failures may ensue.11.4.1Another type of stress concentration at the site of two drilled holes located half way between the end supports of a three-point loaded bent beam has been used in the evaluation of metals for oilﬁeld equipment.Details on the preparation and use of this specimen are described in NACE TM0177-96. Laboratory test data for carbon and low-alloy steels have been found to correlate withﬁeld data(7).12.Specimen Exposure12.1Expose the stressed specimens to the environment (gaseous or liquid)of interest.This can be accomplished by mounting the specimen holders on appropriate racks and exposing the entire rack to the environment.A typical atmo-spheric exposure rack is shown in Fig.4.As noted in7.1, bent-beam specimens may break violently and thus cause injury.To protect personnel and to prevent specimen loss,drill holes in specimen ends and holders and secure the specimens by wires to their holders.12.2Determination of cracking time is a subjective proce-dure involving visual examination that under someconditions FIG.4Bent-Beam Specimens on Atmospheric ExposureRack。

不锈钢沸腾氯化镁应力腐蚀试验

不锈钢沸腾氯化镁应力腐蚀试验
不锈钢在氯离子的存在下，在高温和高压环境中会出现应力腐蚀现象。

氯离子可以进入不锈钢晶界并与晶体中的钢铁原子发生反应，形成氯化物。

在高温高压的作用下，氯化物会引起钢中的应力集中，导致晶格扩张和晶界腐蚀。

这种应力腐蚀破坏会导致不锈钢的力学性能下降，甚至导致不锈钢的断裂和破损。

沸腾氯化镁应力腐蚀试验是一种用于评估不锈钢在高温高压下抵抗应力腐蚀性能的试验方法。

在试验中，将不锈钢试样置于含有氯化镁的高温高压环境中，通常会加入一定的应力，例如通过拉伸试样。

通过观察不锈钢试样的外观变化、测量应力腐蚀裂纹的长度和宽度等方式，评估不锈钢在沸腾氯化镁环境下的耐蚀性能。

沸腾氯化镁应力腐蚀试验可以用于研究不同不锈钢材料的应力腐蚀性能差异，评估不同工艺条件下不锈钢材料的耐腐蚀性能，并指导不同领域的工程设计和材料选择。

应力腐蚀试验操作规程

应力腐蚀试验操作规程应力腐蚀试验（Stress Corrosion Cracking，SCC）是一种评价材料在应力作用下腐蚀敏感性的方法。

它可用于评估材料的工程性能和耐久性，尤其是在温度和湿度环境中。

以下是应力腐蚀试验的操作规程。

一、试验前准备1.选择试验材料和试样，并制备好试样，确保其符合要求。

2.准备好试验设备，包括应力装载设备、试样架和腐蚀介质等。

3.清洁试样和试验设备，确保无表面污染。

二、试验设备调试1.检查试验设备的安全性和可靠性，确保其能正常工作。

2.测试应力装载设备的标定和准确性，确保能正确施加设定的应力。

三、试样安装1.安装试样于试验设备中，并进行必要的校准。

2.确保试样能受到均匀的应力加载，并避免应力局部集中。

四、试验参数设定1.根据试验需求，确定试验的温度、湿度和应力等级。

2.设定试验时间，根据试验材料和环境的特性来确定。

五、试验开始1.开始应力腐蚀试验，并定期记录试验条件和观察试样情况。

2.进行必要的中期检查和维护，确保试验过程的稳定性。

六、试验结束1.达到设定的试验时间后，停止试验，并关闭试验设备。

2.取出试样，并进行表面检查和观察。

七、结果分析1.根据试样的表面情况和试验参数，判断试样是否产生了应力腐蚀开裂。

2.对试验结果进行统计和分析，给出相应的评价和建议。

八、资料整理1.将试验数据整理成报告，包括试验参数、观察结果和分析结论等。

2.保存好试样和试验设备等相关资料，以备后续的研究和使用。

总结：应力腐蚀试验是一项重要的材料评价方法，其可用于评估材料在应力作用下的腐蚀敏感性。

通过执行以上的操作规程，能够确保试验的准确性和可靠性，为材料性能的评估和材料选择提供有力的支持。

慢拉伸应力腐蚀试验测试标准

慢拉伸应力腐蚀试验测试标准慢拉伸应力腐蚀试验（Slow Strain Rate Testing，简称SSRT）是一种常用的材料力学性能测试方法，主要用于评估材料在应力腐蚀环境中的抗腐蚀性能。

本文将介绍慢拉伸应力腐蚀试验的测试标准。

一、试验目的慢拉伸应力腐蚀试验的主要目的是评估材料在应力腐蚀环境中的抗腐蚀性能，包括抗氢脆性、抗应力腐蚀开裂性等方面。

二、试验原理慢拉伸应力腐蚀试验通过施加一定的应变速率和应力水平，使试样在应力腐蚀介质中进行慢速拉伸，以模拟材料在实际使用条件下的受力状态。

通过观察试样的断口形貌、测量其断裂应变等参数，可以评估材料在应力腐蚀环境中的抗腐蚀性能。

三、试验装置慢拉伸应力腐蚀试验通常采用电化学工作站进行测试。

电化学工作站包括电化学池、拉伸装置、电化学测量系统等组成部分。

其中，电化学池用于容纳试样和腐蚀介质，拉伸装置用于施加拉伸载荷，电化学测量系统用于监测试样的电化学行为。

四、试样制备慢拉伸应力腐蚀试验的试样通常为平行四边形形状，尺寸一般为长25mm、宽5mm、厚0.5mm。

试样表面应进行必要的打磨和清洗处理，以确保试样表面的光洁度和无杂质。

五、试验步骤1. 将试样放入电化学池中，并加入适量的腐蚀介质。

2. 设定拉伸速率和应力水平，并开始拉伸测试。

3. 实时监测试样的电化学行为，包括电位、电流等参数。

4. 在达到一定的拉伸应变后停止测试。

5. 取出试样，观察其断口形貌，并进行断裂应变测量。

六、试验结果分析通过观察试样的断口形貌和测量其断裂应变等参数，可以评估材料在应力腐蚀环境中的抗腐蚀性能。

常见的分析方法包括断口分析、断裂应变分析等。

七、注意事项1. 选择合适的腐蚀介质和拉伸速率，以模拟实际使用条件。

2. 保持试样表面的光洁度和无杂质，以减小外界因素对测试结果的影响。

3. 注意安全操作，避免发生意外事故。

八、总结慢拉伸应力腐蚀试验是一种常用的材料力学性能测试方法，可以评估材料在应力腐蚀环境中的抗腐蚀性能。

慢拉伸应力腐蚀标准

慢拉伸应力腐蚀标准一、试验条件1.试验环境：试验应在恒温、恒湿的环境中进行，以保证试验结果的准确性。

2.试验溶液：试验溶液应根据实际应用场景选择，如模拟海水、酸碱溶液等。

3.试验温度：试验温度应根据实际应用场景选择，一般为室温至50℃。

4.试验时间：试验时间应根据实际应用场景选择，一般为24小时至数天。

二、试样制备1.材料选择：试样应选择具有代表性的材料，如不锈钢、碳钢等。

2.形状与尺寸：试样应具有标准的形状与尺寸，以便进行对比试验。

3.表面处理：试样表面应平整光滑，无划痕、毛刺等缺陷，以保证试验结果的准确性。

4.加载装置：试样应安装有慢拉伸应力腐蚀试验的加载装置，以保证在试验过程中对试样施加一定的应力。

三、试验程序1.预处理：将试样放置在试验环境中，进行一定时间的预处理，以适应环境条件。

2.加载应力：按照规定程序对试样施加一定的应力，应力值应按照相关标准进行设定。

3.保持时间：在施加应力后，保持一定时间，以观察试样的变化情况。

4.卸载应力：在试验结束后，将试样卸载应力，以便进行后续观察。

5.观察与记录：观察试样的变化情况，并记录相关数据。

四、试验结果评定1.根据试验结果绘制应力腐蚀曲线，以评估试样的耐应力腐蚀性能。

2.根据观察结果判断试样是否发生断裂、变形等异常现象。

3.根据试验数据计算有关力学性能参数，如弹性模量、屈服强度等。

4.将试验结果与标准值进行对比，判断试样的耐应力腐蚀性能是否符合要求。

5.对试验结果进行分析，评估材料在实际应用中的耐应力腐蚀性能。

五、试验报告1.报告内容应包括试验名称、试验目的、试验条件、试样信息、试验程序、试验结果评定等内容。

2.报告应以严谨、客观的语言描述试验过程和结果，不得夸大或缩小事实。

3.报告中应附有试验曲线图和数据表等相关资料，以便读者更好地了解试验结果。

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3）预制裂纹试样
预裂纹 SCC 试样是预开机械缺口并经疲劳处理产生裂纹的试样，通过 SCC试验和断裂力学分析，测试结果可用于丁程设计、安全评定和寿命估计。这种基于断裂力学的预制裂纹试样，由于显著地缩短了孕育期而加速 SCC破坏，测试时间短；数据比较集中；便于研究裂纹扩展动力学过程。采用预裂纹试样，把线弹性断裂力学此用于 SCC 试验，可以确定金属材料在特定介质中的临界应力场强度因子 KISCC 和。
弹性应变试样
② C形环试样
② C形环试样
C 形环试样尺寸小，加载应力方法简单，可暴露于几乎仟何一种腐蚀性环境中。它可以定量测定各种合金的应力腐蚀断裂敏感性，特别适用于管材和棒材的横向试验及各种材料(如厚板)的短—横向试验。最准确的加载应力方法是：把电应变片贴在周向和横向问的拉仰表面上，紧固螺栓直到应变片指示达到所需应力为止。
弹性应变试样
① 弯梁试样这种方法可以用于任何金属的试样，外加应力应低于材料的弹性极限，其外加应力可精确计算或测定(ASTM G39)。弯梁试样通常是在恒应变条件下试验，但恒载荷条件也可用。在上述两种条件下，当裂纹发生时，试样曲率的局部变化会导致裂纹扩展过程中应力和应变的改变。因此“试验应力”是试验开始时(即发生SCC前)的最高表面拉伸应力。
3）预制裂纹试样 ① 恒载荷增K型试样 ② 恒位移降K型试样 ③ 恒载荷恒K型试样
预制裂纹试样
① 恒载荷增K型试样
目前测量KISCC最简单、最常用的是悬臂梁弯曲试验。试样为悬臂梁弯曲预裂纹试样，属于恒载荷增K型。
恒载荷增K型试样
预制裂纹试样
② 恒位移降K型试样
最常用的是改进后的楔形张开加载(改进的WOL)试样及双悬臂梁(DCB)试样，这两种试样都是通过裂纹张开到一定位移达到加载的目的。
恒位移降K型试样恒位移试样的优点
a) 由于用螺钉自行加载，因而不需要复杂设备，而且可在实际的腐蚀介质中作试验，从而可获得实际使用条件下的应力腐蚀数据； b) 用—个试样就可获得KISCC和da／dt的数据； c) 由于这类试样主要用于观察裂纹扩展和止裂，故对预制裂纹的要求可较宽。
预制裂纹试样
③ 恒载荷恒K型试样
在预制裂纹的试样中还有一种恒KI试样，这种试样是在研究裂纹亚临界扩展的动力学时，为了精确测定 da/dt 对 KI 的依赖关系，随着裂纹扩展KI保持恒定的试样。
③ Ｏ形环试样
Ｏ形环试样是一种模拟承受箍形应力的特定用途的 SCC试样。
④ 拉伸试样
当进行单向拉伸加载时，其应力图谱是简单而均匀的，而且外加应力的大小可以精确确定。试样的种类和尺寸、加载应力的方法利府力水平等都具有灵活性。小的横截面的试样得到了广泛的应用，它们对 SCC的发生有较大的敏感性，能比较快地得到试验结果，试验比较方便。除了试验丝状产品，不推荐使用标距小于10mm，、直役小于3mm的试样。
残余应力试样
② 焊接试样
焊缝附近发展的残余应力常常是服役中的SCC的起源。在单—焊缝附近的纵向应力似乎没有在塑性变形的焊件中出现的应力那样大，因为焊接合属中的应力受到热合属(冷却时会收缩)屈服强度的限制。但是当两个或更多的焊件组合成—个比较复杂的结构时会出现高应力。
2）带缺口试样
缺口试样是模拟金属材料中宏观裂纹和各种加工缺口效应以考察材料SCC敏感性的专门试样。优点： ① 缩短孕育期，加速SCC进程； ② 使SCC限定于缺口区域； ③ 改善测量数据的重现性； ④ 便于测量某些参数，如裂纹扩展速率。
塑性应变试样
U型弯曲试样
残余应力试样
① 塑性变形试样
在室温下包括局部塑性变形的一些加工过程(如成形、调直和模锻)所造成的残余应力可能超过材料的弹性极限。塑性变形试样可以是杯突试样、偏斜挤压试样、经冷加工的管节、具有剪切边、冲压孔或钢印的板材等。这类试样通常是定性的，不能确切知道应力的大小。
④ 拉伸试样
⑤ 音叉试样
音叉试样也是一种专门用途的试样，特别适用于沿纵向或长—横向取样的薄板材料的试验。
（2）塑性应变试样
许多加速 SCC 试验采用塑性变形的试样，因为其制造和使用既简单又经济。由于它们包含大量的弹性和塑性应变，所以能提供光滑试样所能得到的最苛刻的试验条件。这种试样通常用于筛选试验，用以检测一种合金在不同环境中、在给定环境中具有不同金相条件的合金以及在相同环境中不同台金之间在耐 SCC 性能方面的差别。
第五章局部腐蚀的试验方法
5.5 应力腐蚀开裂试验方法
5.5.2 应力腐蚀试验的试样
5.5.2 应力腐蚀试验的试样 1）光滑试样
2）带缺口试样
3）预制裂纹试样
1）光滑试样（1）弹性应变试样
（2）塑性应变试样
（3）残余应力试样
（1）弹性应变试样
为了控制通过变形加载所施加的表面拉伸应力，应变通常限定在试验材料的弹性范围，然后通过测量应变和弹性模量可以计算施加膨力的大小。在恒载荷加载的情况下，通常是直接测定载荷，并根据试样的几何条件和加载方法利用适当的公式计算应力。为施加载菏和监测载荷可能出现的变化，可使用测力传感器或校正弹簧。