1、Designation: B 600 91 (Reapproved 2002)e1Standard Guide forDescaling and Cleaning Titanium and Titanium AlloySurfaces1This standard is issued under the fixed designation B 600; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.e1NOTEEditorial changes were made in 4.2.4
3、 and 4.3.2 in September 2006.1. Scope1.1 This guide covers a cleaning and descaling procedureuseful 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
4、surface contaminants.1.2 It is not intended that these procedures be mandatory forremoval of any 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 toch
5、emical milling, joining, plating, fabrication, and in anysituation where foreign substances interfere 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
6、.1.5 The values stated in inch-pound units are to be regardedas the standard. The values in parentheses are for informationonly.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 estab
7、lish appropriatesafety 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 al
8、kaline 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 ar
9、e employed, 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 follow
10、edby thorough 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 su
11、rfacesand 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
12、 Blast cleaning that utilizes steel grit or sand containingappreciable amounts of iron should be followed by acidpickling to remove any embedded steel particles on the surfaceof the titanium.3.5 Any abrasive or shot blast cleaning may induce residualcompressive stresses in the surface of the materia
13、l 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 ascarbon,
14、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 and Descaling4.1 Recommended post treatment of shot or abrasive blastedtitanium surfaces may include acid pickling as described in4.3
15、.2, to ensure complete removal of metallic iron, oxide, scale,and other surface contaminants. If the product is to be chemical1This guide is under the jurisdiction of ASTM Committee B10 on Reactive andRefractory Metals and Alloys and is the direct responsibility of SubcommitteeB10.01 on Titanium.Cur
16、rent edition approved March 15, 1991. Published May 1991. Originallypublished as B 600 74. Last previous edition B 600 74 (1985).1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.milled for the removal of the oxygen-contaminated layer,
17、 saltbath conditioning may be required to avoid selectively etchedsurfaces if configuration interferes with 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 pr
18、ior 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 with
19、 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 aci
20、d (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 ef
21、fect 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 an
22、d 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 grind
23、ing,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 base
24、materials. 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 main
25、taining 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 3Sil
26、icon-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 furth
27、er 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 1
28、50F (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 Material that has been mechanically abraded in accor-dance with 3.1 or chemically conditioned in accordance wit
29、h4.2.1, 4.2.2,or4.2.3 may be finish cleaned by immersion in anacid solution composed of 10 to 30 volume % (150 to 450 g/L)of nitric acid (70 %) and 1 to 3 volume % (12 to 36 g/L) ofhydrofluoric acid (60 %) at 120F (49C), maintaining a ratioof 10 parts nitric acid to 1 part hydrofluoric acid.NOTE 4Ho
30、t-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. The 400F (204C) temperature is preferred for thesestructures to avoid any thermally ind
31、uced 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 sulfuric andnitric-hydrofluoric acid pickles. The sulfuric acid solutions are notappreciab
32、ly 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-tioning is accomplished in the sulfuric or nitric-hydrofluoric acid solution.The material is c
33、ycled 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 the nitric-hydrofluoric pickling solution, the ratio of nitricacid to hydrofluoric acid is
34、 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 fabrications,an oxygen-rich layer is unavoidable where there is a combined exposureto hi
35、gh 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 oxide andscale has been removed to prevent preferential etching of the finishedproduct.NOTE
36、9Hydrogen in excess of the specified amount may be removedby vacuum annealing of the cleaned work piece.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 o
37、fcontamination.5.2 Hydrogen absorption during the cleaning 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 foll
38、owed bychemical analyses. A hydrogen increase greater than 20 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 expend
39、able sample testpiece. It is recommended that approximately 0.001 to 0.002 in.(0.025 to 0.05 mm) shall be removed from each surface. AfterB 600 91 (2002)e12chemical milling, the surface should be uniformly smooth andbright with the absence of peaks indicative of residual scale orcontamination.6. Key
40、words6.1 cleaning; descaling; pickling; titanium; titanium alloyASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any suc
41、h patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invite
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43、fair hearing you shouldmake your views known to the ASTM Committee 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).B 600 91 (2002)e13
