1、MILITARY STAND ARDIZ AT ION HANDBOOK GLASS ti THIS DOCUMENT CONTAINS 86 PAGES Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-DEPARTMENT OF DEFENSE WASHINGTON, D. C. - MIL-HDBK-722(blR) Glass 1 August 1969 1. This standardization handbook was develop
2、ed for the Department of Defense in accordance with est ab1 ished procedure. 2. lis puhlirurioii was npprovcd on i Aupusi 1369 for printing and inclusion in the miiitaiy s tiitid iirti xiit i 011 Iinndhook scar ie s. 3. Wiis handbook provides basic fundamcntnl information on Elass products for the g
3、uidance of engincers and designers of military matcricl. The handbook is not intended to be referenced in purchase specifications except for informational purposes, nor shall it supersede any specification requirements. 4. Every effort has been made to reflect the latest information on glass product
4、s. It is the intent to review this document periodically to insure its completeness and currency. Users of this document are encouraged to report any errors discovered and recommendations for changes or inclusions to tbe Director, Army Materials and Mechanics Research Center, Watertown, Massachusett
5、s 02172, ATTN: AMXMR-QS. . f , Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. . . - - MIL-HDBK-722 93 77977?0 001Ob11 b - Mll-HOBK-722(MR) 1 AUGUST 1969 Preface - This is one of a group of handbooks covering materials used in the design and constr
6、uction of militar y equi pmen t. The purpose of the handbook is to provide technical information and data about glass products for use in achieving the objectives of the Defense Standardization Program. The handbook is intended for use, as applicable, in engineering design, development, inspection,
7、procurement, maintenance, supply, and disposal of equipment and materials. Whenever ptacticable, the various types, classes, and- grades of materials arc identified with applicable government specifications. Corresponding technical society specifications and commercial designations are listed for re
8、ference. The numerical vaiucs for properties listed in this handbook are in agreement with values listed in the issues of specification in effect on the issue date of the handbook. The handbook values may, in some instances, differ from those listed in current specifications because of revisions or
9、amend- ments made to specifications after publication of the handbook. In connection with procurement, it should be understood that the issue of specifications listed in the contract govern requirements. Whenever specifications are referred to in this handbook, only the basic designation is given; a
10、ll revision and amendment symbols are omitted. This is done for simplification and also to avoid the necessity of correcting the handbook whenever specifications are revised or amended, Current issues of specifications should be determined by consulting the latest issue of the “Department of Defense
11、 Index of Specifications and Standards.“ Thr handbook was preparcd by Mr. Errol B. Shand, Technical Consultant on the use of Glass and Ccramic Materials, ximate because composi- tions of the various typcs tire not definitely fixed. d. Chapter 4. Chapter 4 incliides discussions I treatments of anneal
12、iag and tempering. Proce- durei for strength testing are ikluded because types of tests commonly applied to other ma- terials are not readily adaptable to brittle ma- terials. In addition to the conventional methods . of determining breaking stresses, the subject of fracture analysis of glass is dis
13、cussed. One unusual feature is that breaking stresses can usually be estimated from markings on the frac- ture surface with a fair degree of accuracy. The use of this method is particularly useful in the diagnosis of fractures which occur in service. The structural design of brittle materials impose
14、s limitations which may be of little im- portance for materials of a more conventional kind. Not only are the characteristics of mechani- cal failure different for glass, but the results of failure can be catastrophic. Although design principles ate similar to those for other materi- als, the genera
15、l philosophy of design and the direction of approach will be modified. Actual design procedures used constitute much more than the substitution of properties, including an assumed breaking stress, than in the procedures used for metals. These distinctions are dis- cuss e d briefly . e. Chapter 5. Th
16、is chapter discusses some representative applications of glass which are of military significance. The discussionattempts to show the engineering principles involved in the various designs rather than structural details. Many of the military uses of glass involve the transmission of light for purpos
17、es of glazing and vision through the medium. Such glazing com- ponents in widely different fields have been considered. It is shown that when requirements become more varied and more severe, both the type of glass and the structural design of com- ponents may be modified greatly. * It is noted that
18、glasses may be required to transmit or absorb radiations in parts of the electromagnetic spectrum beyond the visihle range. Glasses of special properties are often used for such purposes. Plastics reinforced with glass fibers may be used to overcome some of the mechanical limitations of massive but
19、for more distant neighbors the spacings are no longer constant and become more .variable as the distance between neighbors increases. From such work it has been concluded that the structure of glasses consists of a thrcc- dimensional network, of which the basic unit is the silica tetrahedron, a sili
20、con atom surroundcd by four oxygen atoms. Adjacent tetrahedra are linked together by common oxygen atoms. - _. The - linkages between tetrahedra are slightly irregu- lar, so that the long-range periodicity becomes lost. This structure of glass is called a random network. . . - - . - . . Provided by
21、IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-HDBK-722 73 7777770 - - OOLOb2L 9 m - - MIL-HDBK-7 22 I MR) 1 AUGUST 1969 - .- - _ . CHANGES DURING COOLING Although all physical properties change during the cooling process, those of dimension and vis- cosity
22、 are representative. Figure I compares the dimensionnl changes in a substance when it crystallizes and when it cools to a glassy state. Above the melting point it is a liquid with a relatively high coefficient of expansion with tem- perature. When it crystallizes at the melting point there is an abr
23、upt decrease in dimension. At lower temperatures the rate of contraction is much lowrr than in the liquid state. If crystalli- zation docs not occur the contraction will con- tinue as an extension of the liquid curve, and in this range the substance will be a supercooled liquid. For ench rate of coo
24、ling a temperature will be reached at which the structural adjust- ments will lag behind the equilibrium of the liquid state. The cutve AB shows this condition for rapid cooling. Below the point B no further structural rearrangements will occur and the sub- stance is now a glass. The intercept E cor
25、res- ponds to the structural arrangement in the glass if it remained in equilibrium with the liquid. The temperature of the intercept Tf is known as the fictive temperature.“ When cooled at a much lower rate, the substance remains a supercooled liquid to the lower temperature C and becomes a - _._.
26、- -_ LI auiD;J r- S! I 4; I TEMPERATURE FIGURE i. Comparison of the Linear Contraction of a Substance When Cooling from a Liquid to a Solid, and When Cooling to a Glass TEMPERATURE - - _-. . FIGURE 2. Viscosity Relations versus Tempera- tur of a Substanco When Coaling from a Liquid to a Wid, and Whe
27、n Cooling to a Glass . - - I_I- glass at the pointxY-It-has a-fifiE Tmeerakre Tf. The temperature intervals AB and CD are called the transformation ranges for the two con- ditions of cooling. - _ - . -_ . - - I .- _ - The cwves show that the dimensions of the glass, or specific volumes, are influenc
28、ed by the rate of cooling through the transformation range. The higher the rate of cooling, the larger the specific volume. _ I_ _-_ I_._ _ -_-.- Figure 2 illustrates the viscosity changes which occur on cooling. When crystallization occurs at the melting point, the viscosity rises abruptly, and fur
29、ther permanent deformation will result from plastic flow. As a supercooled liquid the viscosity rises rapidly as the temperature is lowered. The equilibrium conditionis represented by the curve ACG, When cooled rapidly, the vis- cosity will follow the line AR and for slow cool- ing tk. line CD. Cons
30、equently, the viscosities of glasses ate greatly affected by their rates of cooling through the transformation range. If the glasses are reheated to a temperature within the , transformation range, the viscosity will shift toward the equilibrium condition by an amo act as fluxes to bwer the temperat
31、ure required to melt the glass. They also reduce the stability of the glass, but this can be improved with the addition of lime (Cao), magnesia (MgO), and lead oxide (PbO). - - .- - . _-I . - - 8, Intermediates. There is B third group of oxides which cannot act as glass formers alone, but which can
32、enter the network of certain other glasses, and can produce desirable properties in them. included in these oxides are alumin: (A$03), zinc _- _._ oxide (Zno), and zirconia (ZrOz,). Alumina tends to prevent devitrification, while zirconia increases chemical durability. -_ - - - _I ._ _- . . - I I-_.
33、 - 9. Si!icatc Systems. The one -component glass of this system, silica glass, is difficult to manufacture so that its use is limited to spe- cial purposes, B2O3 another glass former, is sometimes added. It acts as a flux by reducing temperatures of melting, and also modifies other properties. in ce
34、rtain proportions, it maintains the thermal expansion coefficient at low values. Na20 and K20 are commonly used as fluxes, while Cao, MgO, and Al203 act as stabilizers. PbO increases density and refractive index and improves electrical properties. TABLE I. CHEMICAL COMPOSITION OF COMMERCIAL GLASSES
35、Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MlL=HDBK-722MR) 1 AUGUST 1969 . . - Table I lists representatiue compositions of a number of commercial glasses of the silica sys- tem. a. Silica Glass. This is sometimes known under the commercial name
36、s of fuzed silica or fuzed quartz, it is essentially pure silica. This glass is low in thermal expansion coefficient, has high values of light transmittance, and has good electrical properties and chemical dura- bility. It can be operated at higher temperatures than other silicate glasses. A modific
37、ation of this glass is known as 96 percent silica glass. It is made with a process which leaves a residue of about 3 percent of 2Oj in its composition. As A consequence, the viscosity characteristics are reduced materially. In general, its properties arc slightly less de- sirablc than thosc of the p
38、urer silica glass. -_. .- _- b. Soda-Lime Glossar. This type of glass is mclted in larger quantities than any other glass. It is an economical glass to melt and to form into many products. it is widely used for glazing, for glass containers, and electric lamps of vari- ous types. Proportions of the
39、various consti- tuents of a soda-lime glass will vary over a relatively narrow range to make it most suitable for the particular forming operating used, and to meet the requirements of different products. For instance, chemical durability is of unusual im- portance for glass containers, while ease o
40、f lamp working and the ability to seal to certain other glasses for electric lamp enclosures is important for these types. c. Lead-alkali Glasses. In these glasses, lead oxide may replace the lime of the soda-lime glasses, but in some of them the content of lead oxide may reach a value of 80 percent
41、 of thc total. For most electrical applications, such as parts of incandescent lamp bulbs, the lead-oxide content is limited to about 20 percent. High lead compositions are used to absorb I- and gamma radiations, and as solder glasses for sealing othcr glasses at relatively low temperatures. Lead-al
42、kali glasses are used for optical pur- poses and for decorative crystal because of their high refractive indexes. -_ - - - _ d. Borosilicate Glasses. Although there are many glasses of this general type, one of parti- cular interest is the low thermal expansion glass used for many industrial purpose
43、s. This glass has unusual resistance to thermal shock and has excellent properties of chemical durability. - - _ - - _ -. - . _. - - - - - _ . . . _ -_ - . The glass is well adapted for use in labora- tory apparatus. It is free of heavy metal oxides, so that contamination is reduced in makiag chemic
44、al analyses. - _ _ . _- - . e. Aluminosilicate Glasses. These glasses contain large amounts of Al203 and relatively large amounts of Ca0 and MgO. They are more highly viscous below ,OoOC than the more com- mon glasses, so that they are suitable for higher operating temperatures. Thermal coefficients
45、 of expansion lie between those of the low-espan- sion borosilicate glasses and soda-lime glasses. f. Chses for Fibers. Although most com- mercial glasses can be drawn into fibers, chemi- cal durability is of particular importance for most of these products, because many of the fibers range in diame
46、ter from values of less tan one micron to ten microns. The two glasses listed in Table I have high resistance against weathering. High softening points are also de- sirable, because the cooling rates of fibers are extremely high, so that the viscosities will be depressed to much lower temperatures t
47、han when the same glasses are cooled slowly. This cha- racteristic is shown in Figure2. Textile products and thermal insulation are frequently operated at relatively high temperatures. - - -I I- - _-_. _ _ _ - g. Other Glasses. Probably one thousand different commercial glass compositions are melted
48、 in any one year. Of these, a multitude of unusual compositions ate used for optical purposes alone. Many others arc iisccl for tcch- nical and scientific psrpoeca whir-h hmwI special propcrtics. hcw requirrmrrirs III glabi5fib arise from time to rime, so duit IEW coinpobi- rions must be developed t
49、o meet them. Surti glasses cannot be discussed within the scope of this manual. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MlL-HDBK-722( MR) 1 AUGUST 1969 . GLASS MANUFACTURE 10. General. The basic operations of glass manufacture include the fusion of the raw con- stiturnts into II molten mass and then the form- ing of thc viscous mass into desired sha
