1、Designation: B600 11Standard Guide forDescaling and Cleaning Titanium and Titanium AlloySurfaces1This standard is issued under the fixed designation B600; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、 number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This guide covers a cleaning and descaling procedureu
3、seful to producers, users, and fabricators of titanium andtitanium alloys 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 be mandatory forremoval of a
4、ny of the indicated soils but rather serve as a guidewhen titanium and titanium alloys are being processed in thewrought, cast, or fabricated form.1.3 It is the intent that these soils be removed prior tochemical milling, joining, plating, fabrication, and in anysituation where foreign substances in
5、terfere with the corrosionresistance, stability, and quality of the finished product.1.4 Acid etching may be required following cleaning whenthe surface has an oxygen-contaminated layer or alpha casepresent.1.5 The values stated in inch-pound units are to be regardedas standard. The values given in
6、parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.6 This standard does not purport to address the safetyconcerns, if any, associated with its use. It is the responsibilityof the user of this standard to consult and establish a
7、ppropriatesafety and health practices and determine the applicability ofregulatory limitations prior to use.2. Processing Soil Removal2.1 It is recommended that grease, oil, and lubricantsemployed in machining, forming, and fabricating operations ontitanium and titanium alloys be removed by alkaline
8、 oremulsion soak-type cleaners and electrolytic alkaline cleaningsystems. In the electrolytic system the work may be eitheranodic or cathodic polarity. Removal of these soils is recom-mended prior to heat treatment or application of acid treatmentdesignated in 4.2. When electrolytic systems are empl
9、oyed, thevoltage should be controlled to prevent the occurrence of sparkdischarge and subsequent pitting.3. Blast Cleaning3.1 Mechanical descaling methods such as sandblasting,shot blasting, and vapor blasting may be used to remove hotwork scales and lubricants from titanium surfaces if followedby t
10、horough conditioning and cleaning as described in Section4.3.2 The sand used for blasting should be a high-grade,washed, iron-free, silica sand. If carbon or low-alloy steelproducts are sandblasted in the same facility, the sand used forcleaning these products should not be used on titanium surfaces
11、and a separate sand supply should be provided.3.3 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 procedures.3.4 Blast
12、 cleaning that utilizes steel grit, steel shot, or sandcontaining appreciable amounts of iron should be followed byacid pickling to remove any embedded steel particles on thesurface of the titanium.3.5 Any abrasive or shot blast cleaning may induce residualcompressive stresses in the surface of the
13、material or titaniumstructure. Warpage may occur in sections that are subsequentlychemical milled or contour machined.3.6 In most cases, blast cleaning is not intended to eliminatepickling procedures completely. Abrasives will not removesurface layers contaminated with interstitial elements such asc
14、arbon, oxygen, and nitrogen. When these elements are presentin excessive amounts, they are preferably removed by con-trolled acid pickling in accordance with 4.3.4. Pickling, Cleaning, and Descaling4.1 Recommended post treatment of shot or abrasive blastedtitanium surfaces may include acid pickling
15、as described in4.3.2, or acid cleaning as described in 4.3.3. If the product is tobe chemical milled for the removal of the oxygen-contaminated layer, salt bath conditioning may be required to1This guide is under the jurisdiction of ASTM Committee B10 on Reactive andRefractory Metals and Alloys and
16、is the direct responsibility of SubcommitteeB10.01 on Titanium.Current edition approved Sept. 1, 2011. Published September 2011. Originallyapproved in 1974. Last previous edition approved in 2009 as B600 09. DOI:10.1520/B0600-11.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West
17、 Conshohocken, PA 19428-2959, United States.avoid selectively etched surfaces if configuration interfereswith uniform blasting.4.2 Scale and lubricant residues developed on mill, foundry,forged, or fabricated titanium products usually require condi-tioning by one of the following commercial methods
18、prior tofinal pickling as described in 4.3.2 to produce a completelyscale-free surface.4.2.1 Proprietary solutions of caustic-based compounds intap water in accordance with the manufacturers recommenda-tion.4.2.2 Molten alkaline-based salt baths operating at 750 to850F (399 to 454C) in accordance wi
19、th prescribed proce-dures.4.2.3 Molten alkaline-based salt baths operating at 400F(204C) in accordance with prescribed procedures.4.2.4 Oxides and heat tints developed below 1100F(593C) can frequently be removed by pickling in an acidsolution composed of 10 to 20 volume % (150 to 300 g/L) ofnitric a
20、cid (70 %) and 1 to 2 volume % (12 to 24 g/L) ofhydrofluoric acid (60 %) at 120F (49C).4.2.5 Forged and hot-worked titanium alloys that have thenormal heat-developed scale mixed with graphitic or glass-typelubricants may be conditioned in a molten alkaline-based saltbath operating at 850F (454C) to
21、effect complete solubility ofthe complex scale. Following conditioning, the part should bepickled as described in 4.3.2.4.2.6 It is recommended that heat-treatable alpha beta andbeta alloys in the solution-treated condition that have beenprocessed at temperatures above 1100F (593C), with gra-phitic
22、and molybdenum disulfide lubricant residues mixed withthe heat-developed scale, be conditioned in a molten alkaline-based salt bath operating at 400F (204C). After conditioning,the part may be pickled in accordance with the treatmentdescribed in 4.3.2.4.2.7 Abrasive methods such as wheel or belt gri
23、nding,segmented flapper wheels, and grit or shot blasting, whenavailable, may be used when surface configuration is such thatthe scaled areas are readily accessible.NOTE 1Conditioning of titanium in high-temperature oxidizing saltcan generate galvanic currents where the work is contacting ferrous ba
24、sematerials. Titanium is electrically positive or anodic with respect to theseferrous materials, having an open circuit potential of approximately 0.60V. The resulting discharge from the rack to the work piece can result insurface over-heating and eventual ignition. This effect can be minimizedby ma
25、intaining bath temperature at or below 850F (455C) and byproviding titanium fixtures or aluminum insulation between the work andthe fixture.NOTE 2Heavily scaled forgings or hot-rolled materials can be me-chanically abraded to remove excess surface contamination prior to saltbath conditioning.NOTE 3S
26、ilicon-based protective coatings used to minimize scaleformation during hot forming or annealing of titanium alloys are solublein the molten salt bath. All of the coating should be removed prior to anyacid treatment.4.3 Following mechanical abrading or chemical condition-ing, the material may be fur
27、ther treated to completely clean thesurface in one of the following solutions:4.3.1 After salt bath conditioning and water rinse, thetitanium or titanium alloy may be immersed in a sulfuric acidsolution to remove the converted scale product. It is recom-mended that the acid solution be maintained at
28、 150F (66C)and a concentration of 10 to 40 volume % of sulfuric acid(95 % solution by weight). Final brightening may be accom-plished by a short immersion in the acid solution of 4.3.2.4.3.2 To ensure complete removal of metallic iron, oxide,scale, and other surface contaminants, material that has b
29、eenmechanically abraded in accordance with 3.1 or chemicallyconditioned in accordance with 4.2.1, 4.2.2,or4.2.3 may befinish cleaned by immersion in an acid solution composed of10 to 30 volume % (150 to 450 g/L) of nitric acid (70 %) and1 to 3 volume % (12 to 36 g/L) of hydrofluoric acid (60 %) at12
30、0F (49C), maintaining a ratio of 10 parts nitric acid to 1part hydrofluoric acid.NOTE 4Hot-formed or heat-treated titanium fabrications or assem-blies that have a mixed surface contamination consisting of graphite ormolybdenum disulfide with titanium oxides should be conditioned in amolten salt bath
31、. The 400F (204C) temperature is preferred for thesestructures to avoid any thermally induced distortion.NOTE 5In salt bath or alkaline water solution conditioning, thetitanium oxides present on the surface of the metal are chemically reactedto form sodium titanate. This material is soluble in the s
32、ulfuric andnitric-hydrofluoric acid pickles. The sulfuric acid solutions are notappreciably corrosive to titanium or titanium alloys and can be furtherinhibited by the addition of 0.25 to 1.0 % of cupric sulfate or ferroussulfate.NOTE 6Most of the acid pickling following molten salt bath condi-tioni
33、ng is accomplished in the sulfuric or nitric-hydrofluoric acid solution.The material is cycled through the salt bath, water rinse, and sulfuric aciduntil all of the scale has been completely removed. Final brightening isobtained by a brief cycle in the nitric-hydrofluoric solution (4.3.2).NOTE 7In t
34、he nitric-hydrofluoric pickling solution, the ratio of nitricacid to hydrofluoric acid is more important than the concentration of eitherof these two acids. When this ratio is maintained at 10 to 1, hydrogenabsorption during pickling is minimized.NOTE 8In the processing of titanium mill products and
35、 fabrications,an oxygen-rich layer is unavoidable where there is a combined exposureto high temperatures and an oxidizing atmosphere. In the removal of thisoxygen-rich layer or alpha case by pickling in strong solutions of nitricand hydrofluoric acids, it is extremely important that all residual oxi
36、de andscale has been removed to prevent preferential etching of the finishedproduct.NOTE 9Hydrogen in excess of the specified amount may be removedby vacuum annealing of the cleaned work piece.NOTE 10Hydrofluoric acid at 48 % concentration can be used in placeof the 60 % concentration. If this is do
37、ne, the ratio of nitric to hydrofluoricshould be 8 to 1.NOTE 11Turning, peeling, and centerless grinding have also beensuccessfully utilized as alternative descaling and cleaning methods forround bar.4.3.3 To ensure complete removal of metallic iron and othersurface contaminants, material that has b
38、een mechanicallyabraded in accordance with 3.1 or chemically conditioned inaccordance with 4.2.1, 4.2.2,or4.2.3 may be finish cleaned byimmersion in one of the following acid solutions and main-tained within the specified temperature range for the specifiedtime.4.3.3.1 The solution should contain 20
39、 to 25 volume percentof nitric acid. The parts should be immersed for a minimum of20 min at a temperature in the range from 120 to 140F (49 to60C) or 30 min at a temperature in the range from 70 to 90F(21 to 32C).B600 1124.3.3.2 The solution should contain 4 to 10 weight percentof citric acid. The p
40、arts should be immersed for a minimum of4 min at a temperature in the range from 140 to 160F (60 to71C), a minimum of 10 min at a temperature in the range from120 to 140F (49 to 60C), or a minimum of 20 min at atemperature in the range from 70 to 120F (21 to 49C).NOTE 12Acid cleaning (4.3.3) is not
41、intended to remove residualoxide and scale.5. Inspection5.1 Visual inspection of material cleaned in accordance withthis guide should show no evidence of paint, oil, grease, glass,graphite lubricant, scale, abrasive, iron, or other forms ofcontamination.5.2 Hydrogen absorption during the cleaning pr
42、ocess 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. A hydrogen increase greater than 20
43、 ppmover the original product analyses may be cause for replacingthe acids or adjusting the composition to reduce the extent ofhydrogen pickup.5.3 Additional evaluation of product cleanliness may beobtained by chemical milling of an expendable sample testpiece. It is recommended that approximately 0
44、.001 to 0.002 in.(0.025 to 0.05 mm) should be removed from each surface.After chemical milling, the surface should be uniformlysmooth and bright with the absence of peaks indicative ofresidual scale or contamination.6. Keywords6.1 alpha case; cleaning; descaling; pickling; titanium; tita-nium alloyA
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48、e on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).B600 113
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