1、Designation: B614 16Standard Practice forDescaling and Cleaning Zirconium and Zirconium AlloySurfaces1This standard is issued under the fixed designation B614; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi
2、on. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers a cleaning and descaling procedureuseful to producers, users, and fabricators of zirconium andzirconium allo
3、ys for the removal of ordinary shop soils, oxides,and scales resulting from heat treatment operations and foreignsubstances present as surface contaminants.1.2 It is not intended that these procedures become manda-tory for removal of any of the indicated soils but rather serveas a guide when zirconi
4、um and zirconium alloys are beingprocessed in the wrought, cast, or fabricated form.1.3 It is the intent that these soils be removed prior tochemical milling, joining, plating, welding, fabrication, and inany situation where foreign substances interfere with thecorrosion resistance, stability, and q
5、uality of the finishedproduct.1.4 Unless a single unit is used, for example, solutionconcentrations in g/l, the values stated in either inch-pound orSI units are to be regarded separately as standard. The valuesstated in each system are not exact equivalents; therefore, eachsystem must be used indep
6、endently of the other. SI valuescannot be mixed with inch-pound values.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine th
7、e applica-bility of regulatory limitations prior to use. For specific hazardstatements, see Sections 3 and 7.2. Referenced Documents2.1 NFPA Standard:NFPA 484 Standard for Combustible Metals23. Processing Soil Removal3.1 Grease, oil, and lubricants employed in machining,forming, and fabricating oper
8、ations on zirconium and zirco-nium alloys should be removed by employing one of themethods or a combination of methods as listed: (1) alkaline oremulsion soak-type cleaners, (2) ultrasonic cleaning, (3)acetone, citrus based cleaners, or safety solvent immersionwashing or vapor degreasing, or (4) ele
9、ctrolytic alkalinecleaning system. In the electrolytic system, the work can beeither anodic or cathodic polarity provided voltage and currentdensity are controlled to avoid anodizing. Removal of thesesoils is recommended prior to heat treatment or application ofacid treatment designated in Section 5
10、. When electrolyticsystems are employed, the voltage should be controlled toprevent the occurrence of spark discharge and subsequentpitting. The use of trichloroethylene is not prohibited and canbe used; however its use is hazardous enough to preclude it asa recommended solvent in this standard. Car
11、e must be exer-cised when using chemical solvents. There are hazards associ-ated with their use, such as flammability, carcinogenicity, andozone depletion (see 7.1.)4. Blast Cleaning4.1 Mechanical descaling methods such as sandblasting,shot blasting, and vapor blasting may be used to remove hotwork
12、scales and lubricants from zirconium surfaces if followedby thorough conditioning and cleaning as described in Section5.4.2 Aluminum oxide, silicon carbide, silica sand, zirconsand, and steel grit are acceptable media for mechanicaldescaling. Periodic replacement of used media may be requiredto avoi
13、d excessive working of the metal surface by dullparticulate.4.3 Roughening of exposed surface areas may occur fromgrit or shot if cleaning of the entire surface is accomplished byblasting. Partial cleaning for preserving the surface finish is tobe preferred in conjunction with proper pickling proced
14、ures.4.4 Any abrasive or shot blast cleaning may induce residualcompressive stresses in the surface of the material or zirconiumstructure. Warpage may occur in sections that are subsequentlychemical milled or contour machined.1This practice is under the jurisdiction of ASTM Committee B10 on Reactive
15、and Refractory Metals and Alloys and is the direct responsibility of SubcommitteeB10.02 on Zirconium and Hafnium.Current edition approved May 1, 2016. Published May 2016. Originallyapproved in 1977. Last previous edition approved in 2010 as B614 10. DOI:10.1520/B0614-16.2Available from National Fire
16、 Protection Association (NFPA), 1 BatterymarchPark, Quincy, MA 02269, http:/www.nfpa.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.5 In most cases, blast cleaning is not intended to eliminatepickling procedures completely. How
17、ever, there are caseswhere blast cleaning does not need to be followed by a picklingoperation. Abrasives may not remove surface layers contami-nated with interstitial elements such as carbon, oxygen,hydrogen, and nitrogen. When these elements are present inexcessive amounts, they are preferably remo
18、ved by controlledacid pickling in accordance with 5.3.5. Pickling and Descaling5.1 Recommended post treatment of shot or abrasive blastedzirconium surfaces may include acid pickling as described in5.3 to ensure complete removal of metallic iron, oxide, scale,and other surface contaminants. Note that
19、 pickling does notneed to be the final surface conditioning. Mechanical methodsmay be acceptable as final conditioning steps.5.2 Scale and lubricant residues developed on mill, foundry,forged, or fabricated zirconium products usually require con-ditioning by one of the following commercial methods p
20、rior tofinal pickling as described in 5.3 to produce a completelyscale-free surface.5.2.1 Proprietary solutions of caustic- or organic-basedcompounds in tap water in accordance with the manufacturersrecommendation.5.2.2 Molten alkaline-based salt baths operating at 1200 to1300F (650 to 700C) in acco
21、rdance with prescribed proce-dures.5.2.3 Oxides and heat tints developed below 1000F(540C) can frequently be removed by pickling in a nitric acid hydrofluoric acid solution. Common input acid strengthsused are 70 % by weight for HNO3acid and 48 % by weightfor HF acid. HF acid at 60 % strength has be
22、en used in the pastbut there are additional transportation restrictions on thishigher strength acid.5.2.4 The pickling acid solution is composed of 25 to 50 %by volume of 70 % strength HNO3acid and 3.8 to 8.8 % byvolume of 48 % strength HF acid. The balance is clean filteredwater. This yields a solu
23、tion having 350 to 700 mg/L of nitricacid and 36 to 84 mg/L of hydrofluoric acid. Pickling should bedone in a solution with a temperature less than 120F (50C)and preferably nearer to 90F (30C).5.2.5 Abrasive methods such as wheel or belt grinding,high-speed tool steel or carbide grinding, or both, s
24、egmentedflapper wheels, and grit or shot blasting, when available, maybe used when surface configuration is such that the scaled areasare readily accessible.NOTE 1The pickling rate (weight loss per unit time mg/dm2perminute) of zirconium and zirconium alloys is dependent on acid concen-trations and
25、temperature. The following table and Fig. 1 show theserelationships.Vol%HNO3Vol%HFTemp WT Loss80 1.0 100 1.0080 2.0 100 2.0080 3.0 100 3.0080 4.0 100 4.0080 5.0 100 5.0030 1.0 100 1.7530 2.0 100 2.7530 3.0 100 3.7530 4.0 100 4.7530 5.0 100 6.4039 3.5 110 5.0039 3.5 140 8.0039 3.5 160 11.005.2.5.1 Fo
26、r example, the use of 30 % HNO3with HF at100F increases the pickle rate compared to the use of an 80 %HNO3solution with the same HF concentration. Also, anincrease in temperature from 110 to 160F more than doublesthe pickle rate (5.0 to 11.0 mg/dm2in 7 min.).5.3 Following mechanical abrading or chem
27、icalconditioning, the material may be further treated to clean thesurface completely using the following solution:5.3.1 Material that has been mechanically abraded in accor-dance with 4.1, or chemically conditioned in accordance with5.2.1 and 5.2.2, may be finish-cleaned by immersion in an acidsolut
28、ion composed of 25 to 50 volume % (350 to 700 g/L) ofnitric acid (70 %) and 3 to 7 volume % (36 to 84 g/L) ofhydrofluoric acid (60 %) at 120F (50C) maintaining a ratio ofFIG. 1 WT Loss vs HF, HNO3and TemperatureB614 16210 parts nitric acid to 1 part hydrofluoric acid. Hydrofluoricacid at 48 % concen
29、tration can be used in place of the 60 %concentration. If this is done, the ratio of nitric to hydrofluoricshould be 8 to 1.NOTE 2Most of the acid pickling following molten salt bath condi-tioning is accomplished in the sulfuric or nitric-hydrofluoric acid solution.The material is cycled through the
30、 salt bath, water rinse, and acid until allof the scale has been completely removed. Final brightening is obtainedby a brief cycle in the nitric-hydrofluoric solution, in accordance with 5.3.NOTE 3In the nitric-hydrofluoric pickling solution, the ratio of nitricacid to hydrofluoric acid is more impo
31、rtant than the concentration of eitherof these two acids. When this ratio is maintained at 10 to 1, hydrogenabsorption during pickling is minimized. Hydrofluoric acid at 48 %concentration can be used in place of the 60 % concentration. If this isdone, the ratio of nitric to hydrofluoric should be 8
32、to 1.NOTE 4The components should be rinsed immediately and thor-oughly in cold tap water following pickling to avoid staining of thesurfaces with residual fluorides or chlorides which may be detrimental insome services.NOTE 5In the processing of zirconium mill products and fabrications,an oxygen-ric
33、h layer is unavoidable where there is a combined exposureto high temperatures and an oxidizing atmosphere. In the removal of thisoxygen-rich layer by pickling in strong solutions of nitric and hydrofluoricacids, it is extremely important that all residual oxide and scale have beenremoved to prevent
34、preferential etching of the finished product.6. Inspection6.1 Visual inspection of material cleaned in accordance withthis practice should show no evidence of paint, oil, grease,glass, graphite, lubricant, scale, abrasive, iron, or other formsof contamination.6.2 Hydrogen absorption during the clean
35、ing process shouldbe minimized and well within tolerable limits if the proceduresoutlined are followed. Periodic monitoring of the cleaningsystem can be accomplished by processing samples of knownhydrogen content through the complete system followed bychemical analyses.Ahydrogen increase greater tha
36、n 2 to 5 ppmover the original product analyses may be cause for replacingthe acids or adjusting the composition to reduce the extent ofhydrogen pickup.6.3 Additional evaluation of product cleanliness may beobtained by chemical milling of an expendable sample testpiece. It is recommended that approxi
37、mately 0.001 to 0.002 in.(0.025 to 0.05 mm) shall be removed from each surface. Afterchemical milling, the surface should be uniformly smooth andbright with the absence of peaks indicative of residual scale orcontamination.7. Hazards7.1 Cleaning using this practice involves the use of hazard-ous che
38、micals. These chemicals are as follows: acetone, nitricacid, hydrofluoric acid, molten cleaning salts, and alkalinecleaning solutions. Before using any of these materials consulta standard reference on safe use of chemicals or the manufac-turers recommendations for safe handling.7.2 Grinding and gri
39、t blasting of zirconium can create a finemetal dust that is flammable and dangerous if allowed toaccumulate. Precautions should be taken to manage such dustas described in NFPA 484.8. Keywords8.1 cleaning; descaling; zirconium; zirconium alloysASTM International takes no position respecting the vali
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