1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.QUESTIONS REGARDING THIS DOCUMENT: (412) 772-8512 FAX: (412) 776-0243TO PLACE A DOCUMENT
3、 ORDER; (412) 776-4970 FAX: (412) 776-0790SAE WEB ADDRESS http:/www.sae.orgCopyright 1968 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001INFORMATIONREPORTJ792aREV.JUN68Issued 1954-06Revised 1968-06Superseding
4、J792 JUL54(R) SAE MANUAL ON BLAST CLEANINGForewordThis Document has not changed other than to put it into the new SAE Technical Standards BoardFormatThis report on blast cleaning is a companion to the SAE report on Shot Peening. It is intended to help engineers,management, and shop personnel to incr
5、ease their knowledge of the process. The information contained hereinhas been submitted and edited by a group that has had extensive and varied experience with blast cleaning andwhose recommendations merit consideration.1. ScopeBlast cleaning may be defined as a secondary manufacturing process in wh
6、ich a suitable stream ofsolid particles is propelled with sufficient velocity against a work surface to cause a cleaning or abrading actionwhen it comes in contact with the workpiece.As indicated in the definition, blast cleaning may be employed for a variety of purposes. Ordinarily, it isconsidered
7、 as a method for removing sand from castings, burrs or scale from forgings, mill products, or heattreated parts; to promote machinability, and to minimize the possibility of interference in actual operation. Inaddition to this use, blast cleaning also produces an excellent surface for industrial coa
8、tings. All theseobjectives are often accomplished in the one operation.1.1 HistoryThe cleaning problem of removing sand and scale has always been associated with the casting,forging, and heat treating of metal. As recently as the beginning of the twentieth century, foundrymenconsidered the chisel, h
9、ammer, dull file, and wire brush the chief weapons for attacking this problem. Handtools were gradually augmented by “rattling“ or tumbling methods.Pressure blasting was first introduced in 1870 by Gen. Benjamin Chew Tilghman. He discovered that metals,stone, and glass could be shaded or etched by j
10、ets of sand. He took out patents covering pressure blastingwith sand driven by compressed air, steam, and water; with sand struck by a paddle wheel, throwncentrifugally, or dropped from a height through a tube. Thus, General Tilghman advanced the principles uponwhich modern blast cleaning is based.1
11、Tilghmans first commercial machine used a steam blast as a method of propelling the sand. This proved tohave several disadvantages. The steam moistened the sand, necessitating a drying operation. It also tendedto hide the work, break glass objects, and rust metals. As a result, Tilghman changed to a
12、 tank-typecompressed air machine, which proved more successful.1. See “Modern Blast Cleaning and Ventilation,“ by C.A. Reams, Cleveland, Ohio: Penton Publishing Co., 1939.SAE J792a Revised JUN68-2-Other men and companies entered the blast cleaning equipment field. A natural development was the blast
13、ingmachine in which sand could be refilled during operation. This was accomplished by pouring sand through astandpipe of sufficient height to overcome tank pressure.Cabinets and barrels featuring pressure air blasting nozzles were advertised in magazines in 1895. That sameyear W. W. Sly introduced t
14、he exhaust tumbling barrel, which also increased the dust removal problem. Thiswas partially solved by the first cloth screen dust arrester patented in 1897.Many industries recognized the superior surface quality of castings, forgings, heat treated parts, etc., cleanedby blast cleaning. However, the
15、 high operational cost and low productivity of the process at that time limited itsuse to the cleaning of large castings or products where high quality was necessary regardless of cost.An old leanto in back of the plant comprised the up-to-date blast cleaning department of 1915. A blower fanprovided
16、 the ventilation. Wooden walls which splintered were soon replaced by steel sheets. The sandblasting distorted the sheets and cut the nails. Brick was used next and proved more durable. However, thesilica dust produced was harmful to the operator.In 1917 humane sand blast rooms were developed in whi
17、ch the operator stayed out of the blast zone.Downdraft ventilation, rubber-lined steel walls, and better lighting all served to improve the sand blastingoperation.A new phase of development took place with the introduction of metallic abrasives in the 1920s. Acceptancewas slow, due to the availabili
18、ty and low first cost of sand. Industry soon recognized the improvement in thequality of the finish and the lower cost, through increased durability of the shot. Improvements in reclaiming themetal abrasive eventually won over most of industry. One of the chief benefitssavings in storage space andha
19、ndlingwas not appreciated until some years after the adoption of metal abrasives.The development of metallic abrasives began with the use of chilled cast iron shot. The comparatively shortshot life of chilled cast iron lead to the development of malleabilized and annealed cast iron shot. Next to bei
20、ntroduced into the metallic abrasive field was cast steel shot and more recently cut wire shot. Although theselatest shot have a higher initial cost than the iron shot, their life is much greater. In many instances, they haveproved to be more economical than the iron shot. These newer shot demand th
21、at the blasting equipment beoperated to minimize shot losses.As more companies produced metallic abrasives, more and more name and classification systems were used.This resulted in the need for standardization of abrasive classification for the entire blasting industry. A big stepin this direction w
22、as taken in 1943 when a group of shot producers, users, and equipment manufacturers met inDetroit and formed the Shotpeening Committee of the SAE. This committee established size andnomenclature standards for shot and grit (SAE Handbook). Also, the committee has worked, and is stillworking, on a sta
23、ndard testing procedure for the endurance and wear of metallic abrasives.With the introduction and acceptance of metallic abrasives, the blast cleaning suppliers were able to offerindustry their next big improvementthe use of centrifugal force for blast cleaning. Here the abrasive is thrownby a revo
24、lving wheel, which propels the abrasive mechanically. The idea was first proposed in the 19th centurybut abandoned. The large volume of sand that even the smallest machines required, plus the excessive wearof sand on metals, made its use prohibitive. In 1933 the American Foundry Equipment Co. demons
25、trated atBenton Harbor, Mich., the use of a barrel-type machine using a wheel to propel the abrasive. Later, thePangborn Corp. introduced a similar unit at Detroit, and another was introduced by the W. W. Sly Mfg. Co. inCleveland. Among later improvements was the construction by the Cargill Detroit
26、Co. of operatorless single-purpose equipment to provide process control on certain high production parts.SAE J792a Revised JUN68-3-Mechanization of blasting equipment, metallic abrasives, and the use of centrifugal force led to thedevelopment of more high productive cleaning equipment to meet growin
27、g production demands. The improvedblasting equipment developed includes the tumble type batch cabinets, continuous monorail cabinets, rotatingtables, and the latest developmentthe continuous barrel type.In the field of general cleaning the centrifugal or airless type is by far the most popular means
28、 of metallicabrasive propulsion. However, in the case of specialized or precision cleaning, air propulsion of metallicabrasives is more adaptable because of its ease of control and great flexibility. As parts become more complexin size and shape, specialized cleaning becomes more and more necessary.
29、Work in the development of abrasives, blasting equipment, processes, and standization goes on. The blastcleaning history has closely paralleled that of mass production. The blast cleaning industry has made manyvaluable contributions to the industrial growth of America, and will continue to do so.1.2
30、 Present StatusThe present trend of blast cleaning, with few exceptions, is to use the continuous-barrel typeof equipment with centrifugal blast wheels for all small castings that can be handled as bulk material. The useof the continuous-monorail type of blast cabinet equipment with centrifugal abra
31、sive propulsion for largecastings and forgings is very extensive. These two types of equipment are fast replacing the old pressure blastequipment. The centrifugal type of blast equipment has proved more economical per ton of cleaned castingsthan the previously used pressure blast equipment, with few
32、 exceptions. An exception to the precedingstatement is the specific specialized type of pressure blast equipment on a part that has internal pockets andon which it is necessary to direct the blast stream at a small area that cannot be reached with the widely usedcentrifugal-type equipment.The presen
33、t trend in ferrous metal blasting abrasives is toward material having superior breakdown resistance.The result of this progressive change is a lower cost per ton of cleaned castings with reduced abrasive materialbreakdown provided adequate auxiliary equipment can be installed adjacent to the blast c
34、leaning machine tosalvage the blast material that otherwise would be carried out in pockets of the cleaned work and lost.1.3 Secondary Effects1.3.1 Combined Cleaning And PeeningCombined cleaning and peening is applicable to parts where it isnecessary to remove scale, provided there is no subsequent
35、heat treatment. Parts that are being treated inthis manner include automotive connecting rods, axleshafts, and steering knuckles. However, on parts such asaxleshafts and steering knuckles, which require machining in critical areas, some of the effectiveness of thepeening is lost.Parts with small sur
36、face imperfections may be improved by lessening the effect of the stress-raisers during thecleaning operation.Some controversy exists on the question of the inspection of blast cleaned parts. It is thought by some thatsmall defects, ordinarily brought out by pickling, will be obscured by the blastin
37、g operation. Others claim thatthese small defects are made less detrimental by the peening action of the cleaning operation. Some surfacedefects may be concealed to the extent that an inspection other than visual may be necessary.1.3.2 USE AS AN INSPECTION TOOLBlasting is applied to facilitate inspe
38、ction of selectively hardened parts; thisblasting often serves as a cleaning operation as well. The inspection of chilled iron parts and decarburizedareas on hardened parts is made easier by blasting. It is also possible by blasting to show leaks in maskedareas after carburizing and hardening.SAE J7
39、92a Revised JUN68-4-2. References2.1 Applicable PublicationsThe following publications form a part of the specification to the extent specifiedherein. Unless otherwise indicated the lastest revision of SAE publications shall apply.2.1.1 SAE PUBLICATIONSAvailable from SAE 400 Commonwealth Drive, Warr
40、endale, PA 15096-0001.SAE J441Cut Wire ShotSAE J444Cast Shot and Grit Size Specifications for Peening and CleaningSAE J827Cast Steel ShotSAE Handbook2.1.2 OTHER PUBLICATIONS“Modern Blast Cleaning and Ventilation,” C.A. Reams, Cleveland, Ohio, Penton Publishing Company, 1939“Simplified Practic Recomm
41、endation 118-50Abrasive Grain Sizes,” U.S. Department of CommerceBulletin, June 1, 1950“Hyrdo-Finish and Hydro Sandblast,” W.I. Gladfelter, Pangborn Corporation“Fine Particle Blasting or MicroBlast Fluid Honing and Finishing,” E.E. Hawkinson, MicroBlastManufacturing Corporation“Fine Particle Blastin
42、gA.P. Neuman and V.W. Nichols, Vapor Blast Manufacturing Company3. Blast Cleaning MachinesBlast cleaning machines have any or all of the following components: abrasivepropelling mechanism; cabinet or enclosure; abrasive cycling and regenerative system; work holdingmechanism; load and unload mechanis
43、m; and controls.Abrasive blasting equipment is generally divided into air blast units, airless blast units, and wet blastingmachines, according to the method of propelling the abrasive. Air blasting and airless blasting machines aredry processes for general cleaning, while wet blasting is usually re
44、stricted to the cleaning and finishing ofprecision parts requiring special finishes or cleaning action.3.1 Air Blasting MachinesIn air blast equipment the abrasive material is forced by compressed air through asmall orifice or nozzle (Figure 1). The abrasive stream takes the shape of a small cone an
45、d asserts its effectover a small area. The two advantages of air blasting are its flexibility in cleaning specific areas with a highlyconcentrated blast pattern and its ability to use both metallic and nonmetallic abrasives. The narrow,coneshape stream of abrasive is ideal for cleaning interior cavi
46、ties, blind holes, and narrow recesses andlocalized areas of castings, forgings, and heat treated parts.FIGURE 1INDUCTION NOZZLESAE J792a Revised JUN68-5-Air blast cabinets are either of the suction feed, gravity feed, or direct pressure types, with the pressure typegiving the more powerful blast, w
47、hich is desirable for removing burned-in sand, heavy scale, etc. The mostcommon form of air blast equipment is that in which the blasting nozzle is manipulated by an operator, whomay be located outside or inside the blasting cabinet.In the large air blast rooms (Figure 2) the operator, in special ap
48、parel, manipulates a flexible air blast nozzle toclean large and intricate parts that, because of their size, must remain stationary.FIGURE 2HAND BLAST ROOMIn the smaller so-called hand blast cabinet (Figure 3) the operator reaches through the cabinet andmanipulates the nozzle and/or the work while
49、viewing his progress through a suitably protected glass window.Manual cabines, due to their flexibility, are generally used when only a few pieces or work constitute the entireproduction of that item. For cleaning high production items, single-purpose air blast machines are used,whereby the parts are automatically located in proper relation to the nozzles, blasted, and ejected into storageboxes and onto conveyor lines. These machines are able to use automatic loading devices and are able tooperate without an operator.3.2 Airless Blasting MachinesIn airless blasting mac
