Standards
ASTM A193 FASTENERS
Application in high temperature services or high pressure services or other special purposes.
DEGREE:
B5, B6, B7, B7M, B16, B8, B8A, B8C, B8CA, B8M, B8MA, B8M2, B8M3, B8P and B8PA
RAW MATERIALS USED:
ALLOY STEEL and STAINLESS STEEL
CONF DIMENSIONS:
ASME Standards:5 B18.2.1 Square and Hex Bolts and Screws
Metric Heavy Hex Bolts B18.2.3.3M
B18.3 Hexagonal and knurled screws
Metric Socket Head Cap Screws B18.3.1M
FASTENERS
ASTM A320
Application in low temperature services
DEGREES:
L7, L7M, L70 L7A, L71 L7B, L72 L7C, L73 L43 L1 B8, B8A B8C, B8CA B8T, B8TA B8P, B8PA B8F, B8FA B8M, B8MA RAW MATERIALS USED: ALLOY STEEL and STAINLESS STEEL
CONF DIMENSIONS:
B18.2.1 Square and hexagonal screws and bolts
B18.2.3.5M Metric Hex Bolts
B18.2.3.6M Metric heavy hex cap screws
B18.3 Hex and knurled socket screws
FASTENERS
A-490
Fasteners for use in structural applications Minimum 150 Ksi Tensile Strength.
DEGREES:
TYPE 1, TYPE 2 and TYPE 3
RAW MATERIALS USED:
CARBON STEEL AND ALLOY STEEL
DIMENSIONS CONF: B18.2.6
ASTM A325 FASTENERS
Fasteners for use in structural applications with a minimum tensile strength of 120/105 ksi
Degrees:
TYPE 1, TYPE 2 and TYPE 3
RAW MATERIALS USED:
CARBON STEEL AND ALLOY STEEL
CONF DIMENSIONS:
B18.2.6
Resistance Classes
1
Metric Screws
(ISO 898-01)
Class 8.8:
Medium carbon steel (e.g. (1038, 1045) or low carbon (1015, 1020) with additives of Boron, Manganese or chromium. Its tensile strength is at least 80 Kgf mm². The hardness specified for this class is contemplated in the standard (ISO 898-1) 22 / 32 Hrc up to M16 and 23 / 34 Hrc when greater than M16. They must be quenched and cooled in liquid media and subsequently tempered at a minimum temperature of 425 ºC.
Class 10.9
Alloy steels, e.g. (5135, 4140) have a tensile strength of at least 100 Kgf mm². The hardness specified for this strength class is also included in the standard (ISO 898-1), being 32/39 Hrc for all gauges.
They must be tempered and cooled in liquid media and subsequently tempered at a minimum temperature of 425 ºC.
Conclusion
The resistance classes covered by the standard (ISO 898-1) range from 3.6 to 12.9, the higher the resistance class the higher the tensile strength, that is, the first digit before the dot, e.g. (3.6) the “three” means in hundredths the tensile strength limit per mm² and the “six” the yield limit.
For resistance classes 3.6 to 5.8, a low carbon material (iron) can be used, for classes 8.8 and 9.8, medium carbon steels (1038, 1045) are used, and for classes 10.9 and above, the presence of alloy elements (Cr, Mo, etc.) in their composition is mandatory.
2
Inch Bolts (SAE J429)
GRADE 5
For this degree of resistance, the SAE J429 standard determines that 3 lines are engraved on the screw head, the hardness specified for this degree is 25/34 HRC for gauges up to 1” and larger than 1” the specified is 19/30 HRC.
The tensile strength for this Grade is a minimum of 120,000 psi (827 MPA) for gauges up to 1” and larger is 105,000 psi (724 MPA).
The minimum yield strength is 92,000 psi (634 MPA) for gauges up to 1” and larger, it is 81,000 psi (558 MPA). Medium carbon steels are used for this grade, for example (SAE1045 – SAE 1038), this strength grade is equivalent to metric class 8.8.
GRADE 8
For this degree of resistance, the SAE J429 standard determines that 6 lines are engraved on the screw head, the hardness specified for this degree is 33/39 HRC for all sizes.
The tensile strength for this Grade is a minimum of 150,000 psi (1034 MPA).
The minimum yield strength is at least 130,000 psi (896 MPA). Steels that have at least one alloy element in their composition are used for this grade. For example, (SAE 4140 – SAE 5140), this strength grade is equivalent to metric strength class 10.9.
Treatments
Electrolytic zinc
(White or Yellow)
A method of protecting metal parts from corrosion. Electrolytic zinc plating is based on surface treatment by immersion, unlike hot zinc plating. Electrolytic zinc plating involves a complete cleaning procedure such as pickling, washing, neutralization, and passivation.
Hot Galvanizing
It creates a thicker layer of protection, so it is more suitable for parts that will be exposed to more extreme weather or temperature conditions. Its cost can be higher, so it is more cost-effective in larger projects.
Organometallic Coating
Suitable for metal materials and parts that require high protection, free from hydrogen embrittlement. It is a superior coating to conventional coatings, such as electrolytic galvanizing, hot-dip galvanizing and others.