{{Short description|ASTM standard}} '''ASTM A325''' is an [[ASTM International]] standard for heavy hex structural [[Bolt (fastener)|bolts]], titled ''Standard Specification for Structural Bolts, Steel, Heat Treated, 120/105 ksi Minimum Tensile Strength''. It defines mechanical properties for bolts that range from {{convert|1/2|to|1+1/2|in}} in diameter.<ref>{{Citation | title = ASTM A325 - 09 | url = http://www.astm.org/Standards/A325.htm | accessdate = 2009-06-13}}.</ref>
The equivalent metric standard is '''ASTM A325M''', which is titled ''Standard Specification for Structural Bolts, Steel, Heat Treated 830 MPa Minimum Tensile Strength''. It defines mechanical properties for sizes M12–36.<ref name="astm metric">{{Citation | title = ASTM A325M - 09 | url = http://www.astm.org/Standards/A325M.htm | accessdate = 2009-06-13}}.</ref>
This is a standard set by the standards organization [[ASTM International]], a voluntary standards development organizations that sets technical standards for materials, products, systems, and services.
In 2016, ASTM officially withdrew specification A325 and replaced it with ASTM F3125.<ref>{{cite web |url=https://www.a325bolts.com/ |title=A325 Structural Bolts |publisher=Portland Bolt |accessdate=2019-01-18}}</ref> To minimize confusion, bolt head markings are unchanged and the designation A325 is retained as a grade name within the new standard.<ref>{{cite journal |url=https://www.structuremag.org/?p=9252 |title=New Twists and Turns |last=Shaw |first=Robert E. Jr. |journal=STRUCTURE Magazine |date=Nov 2015}}</ref> In 1951, A325 bolts were recognized as equivalent to a hot driven ASTM A141 rivet.<ref>{{citation |url=https://www.aisc.org/products/publication/historic-standards/specifications-for-assembly-of-structural-joints-using-high-tensile-steel-bolts---january-1951/ |title=Specifications for Assembly of Structural Joints Using High Tensile Steel Bolts |publisher=American Institute of Steel Construction |date=Jan 1951 |author=Research Council on Structural Connections |author-link=Research Council on Structural Connections}}</ref>
==Types== The ''type'' refers to the type of material used to make the bolt. The standard currently defines two types, however it previously defined the following three:<ref name="portland">{{Cite web |title=ASTM A325 - Portland Bolt |url=http://www.portlandbolt.com/technicalinformation/astm/ASTM_A325.html |accessdate=2009-06-13}}.</ref>
*Type 1: [[Medium carbon steel]], [[boron steel]], or medium carbon [[alloy steel]] *Type 2: Low carbon [[martensitic]] steel<ref name="american">{{Citation | title = ASTM, SAE and ISO grade markings and mechanical properties for steel fasteners | url = http://www.americanfastener.com/technical/grade_markings_steel.asp | accessdate = 2009-06-06}}.</ref> (withdrawn from the standard in 1991) *Type 3: [[Weathering steel]] There is also a ''T'' version, which is used to refer to fully threaded bolts.<ref name="portland"/>
Note that independent of the material the bolt is [[quench]]ed and [[tempering (metallurgy)|tempered]].<ref name="american"/>
==Connection types== There are also three connection types defined:<ref name="portland"/>
*'''SC''': A slip critical connection. *'''N''': A bearing type connection where the threads are on the shear plane. *'''X''': A bearing type connection where the threads are not on the shear plane.
==Mechanical properties== === Mechanical properties, imperial === These types of bolts are designed to be tightened to near their [[proof strength]], in order to create significant bolt tension. The standard states that the bolts must be tightened to at least 70% of the [[tensile yield strength]]. These bolts use the same material as their common cousins ([[ASTM F568M]] for metric bolts), but have a thicker and wider head to more effectively distribute the load. This modified geometry is often referred to as ''heavy hex'' geometry.<ref name="uiowa"/> Nuts must meet ASTM A563, which also uses heavy hex geometry.<ref>{{cite book |last1=Kulak |first1=Geoffrey L. |url=http://www.boltcouncil.org/files/2ndEditionGuide.pdf |title=Guide to Design Criteria for Bolted and Riveted Joints |edition=2nd |publisher=American Institute of Steel Construction |year=2001 |pages=37 |isbn=978-1564240750}}</ref> Dimensions of heavy hex geometry are per document ANSI/ASME B18.2.6, which uses "coarse" threads as defined by [[Unified Thread Standard]].
ASTM 325 bolts can be considered equivalent to Grade 8.8 bolts according to [[ASTM F568M]].{{Citation needed |date=January 2019}}
For a higher strength version of this type of bolt, see [[ASTM A490]].
{| class="wikitable" border="1" style="text-align:center" |+Head markings and mechanical properties for imperial sizes<ref name="american" /> !Head marking !Grade !Nominal size range [in] !Proof strength [ksi] !Yield strength (min) [ksi] !Tensile strength (min) [ksi] !Core hardness [Rockwell]<ref name="fastspec">{{Citation|title=Grade Markings: Carbon Steel Bolts|url=http://www.fastspecinc.com/technical/technical.html|accessdate=2009-05-30}}.</ref> |- | rowspan="2" |[[File:Hex_cap_screw-ASTM_A325.svg|75x75пкс]]<br>or<ref name="fastspec" /><br>[[File:Hex_cap_screw-ASTM_A325_lines.svg|75x75пкс]] | rowspan="2" |'''Type 1''' |{{Frac|1|2}}–1 (inc.) |85 |92 |120 |C24–35 |- |1–{{Frac|1|1|2}} |74 |81 |105 |C19–31 |- |[[File:Hex_cap_screw-ASTM_A325_type_2.svg|74x74пкс]] |'''Type 2''' |{{Frac|1|2}}–1 |85 |92 |120 |C24–35 |- | rowspan="2" |[[File:Hex_cap_screw-ASTM_A325_type_3.svg|75x75пкс]]<ref name="crnote">Other markings may be used to denote atmospheric corrosion resistant material</ref> | rowspan="2" |'''Type 3''' |{{Frac|1|2}}–1 |85 |92 |120 |C24–35 |- |1–{{Frac|1|1|2}} |74 |81 |105 |C19–31 |}
=== Mechanical properties, metric === {| class="wikitable" border="1" style="text-align:center" |+Head markings and mechanical properties for metric sizes<ref name="uiowa">{{Cite web |title=Metric structural fasteners |url=http://www.icaen.uiowa.edu/~sdesign1/Text/fasteners_si.html |publisher=University of Iowa |accessdate=2009-06-06 |archive-url= https://web.archive.org/web/19990421064802/http://www.icaen.uiowa.edu/%7Esdesign1/Text/fasteners_si.html |archive-date=1999-04-21 |url-status=dead}}.</ref> |- ! Head marking !! Grade !! Nominal size range [mm] ! Proof strength [MPa] ! Yield strength (min) [MPa] ! Tensile strength (min) [MPa] ! Core hardness [Rockwell] |- | [[File:Hex cap screw-ASTM A325M 8S.svg|83x83px]] || | '''Type 1''' || rowspan=3 | 12–36<ref name="astm metric"/> || rowspan=3 | 600 || rowspan=3 | 660 || rowspan=3 | 830 || rowspan=3 | C23–34 |- | [[File:Hex cap screw-ASTM A325M type 2.svg|83x83px]] || '''Type 2''' |- | [[File:Hex cap screw-ASTM A325M 8S3.svg|83x83px]] || '''Type 3''' |}/mm
== See also == * [[ASTM F568M]]
==References== {{Reflist|2}}
{{ASTM standards}}
[[Category:ASTM standards]] [[Category:Screws]]