ASTM A490 and ASTM A490M are ASTM International

ASTM International

ASTM International, known until 2001 as the American Society for Testing and Materials , is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, and services...

 standards for heavy hex structural bolts

Screw

A screw, or bolt, is a type of fastener characterized by a helical ridge, known as an external thread or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or an object that has the...

 made from alloy steel. The imperial standard is officially titled Standard Specification for Structural Bolts, Alloy Steel, Heat Treated, 150 ksi Minimum Tensile Strength, while the metric

Metric system

The metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...

 standard (M) is titled Standard Specification for High-Strength Steel Bolts, Classes 10.9 and 10.9.3, for Structural Steel Joints.

Types

The type refers to the type of material used. The standard currently defines two types, however it previously defined the following three:

• Type 1: Medium carbon alloy steel
• Type 2: Low carbon martensitic steel for atmospheric temperature applications (withdrawn from the standard in 2002)
• Type 3: Weathering steel

Note that independent of the material the bolt is quench

Quench

In materials science, quenching is the rapid cooling of a workpiece to obtain certain material properties. It prevents low-temperature processes, such as phase transformations, from occurring by only providing a narrow window of time in which the reaction is both thermodynamically favorable and...

 and temper

Temper

Temperare is the Latin origin of words like "temperature" and "tempering"; it and "tempo" come, in turn, from tempus...

ed.

Connection types

There are also three connection types defined:

• 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

These bolts are equivalent to ASTM A325

ASTM A325

ASTM A325 is an ASTM International standard for heavy hex structural bolts, titled Standard Specification for Structural Bolts, Steel, Heat Treated, 120/105 ksi Minimum Tensile Strength...

 bolts in application and geometry, but are made to a higher strength. The imperial grades are made to the same strength specifications as ASTM A354

ASTM A354

ASTM A354 is an ASTM International standard that defines chemical and mechanical properties for alloy steel bolts, screws, studs, and other externally threaded fasteners...

 grade BD. The metric grades are made to the same strength specifications as ASTM F568M

ASTM F568M

ASTM F568M is an ASTM International standard for metric bolts, screws and studs that are used in general engineering applications. It is officially titled: Standard Specification for Carbon and Alloy Steel Externally Threaded Metric Fasteners...

 property class 10.9. Also, unlike their weaker counterparts they cannot be coated by hot-dip galvanization, mechanical deposition, or electroplating

Electroplating

Electroplating is a plating process in which metal ions in a solution are moved by an electric field to coat an electrode. The process uses electrical current to reduce cations of a desired material from a solution and coat a conductive object with a thin layer of the material, such as a metal...

.

Because these bolts are designed to be used in structural applications the threaded length of the bolts are shorter to keep the threads out of the joint.

Imperial head markings and mechanical properties

Head marking	Grade	Nominal size range [in]	Proof strength [ksi]	Yield strength (min) [ksi]	Tensile strength (min) [ksi]	Core hardness [Rockwell]
	Type 1	–1-	120	130	150 minimum 173 maximum	C33–38
	Type 2	–1
	Type 3	–1-

Head markings and strengths for metric hex-head cap screws

Head marking	Grade	Nominal size range [mm]	Proof strength [MPa]	Yield strength (min) [MPa]	Tensile strength (min) [MPa]	Core hardness [Rockwell]
	Type 1	12–36	830	940	1040	C33–39
	Type 2
	Type 3