ASTM A370-21 Test Methods and Definitions for Mechanical Testing of Steel Products

Scope:

ASTM A370-21 is used to determine the mechanical properties of steel, stainless steel, and related alloy products to ensure that the properties conform to the product specification. Besides conformance testing, the tests are also used for acceptance testing of incoming materials, and evaluation of components after service exposure. 

Test Procedure: 

ASTM A370-21 covers several mechanical tests to determine several mechanical properties such as tensile strength, flexural strength, and hardness. 

Tension test: Steel specimens are subjected to a controlled tension until failure. Properties that are directly measured via a tensile test are ultimate tensile strength, breaking strength, maximum elongation, and reduction in area.

Bend test: Bend tests are used to evaluate the ductility of a material. A sample is placed horizontally upon two points and a force is applied to the top of the sample through a single point or two points. 

Hardness test: Hardness tests are used in mechanical engineering to determine the hardness of a material to deformation. It is employed to obtain a quick approximation of tensile strength. 

1. Brinell Test:

Brinell hardness is determined by forcing a hardened steel or carbide ball of known diameter under a known load into a surface and measuring the diameter of the indentation with a microscope. The Brinell hardness number is obtained by dividing the load, in kilograms, by the spherical area of the indentation in square millimeters; this area is a function of the ball diameter and the depth of the indentation.

2. ROCKWELL TEST:

An indenter applies a minor load on the metal, causing a dent. The depth of the dent establishes the baseline depth. Without removing the minor load, a major load is applied for a specific time, and the depth of the indentation produced by it is measured. The harder the metal, the shallower the penetration, and vice versa. The Rockwell hardness value is derived from the difference in the two depths: the baseline depth and final depth. This distance is converted to a hardness number. 

3. Portable Hardness Test:  

When the specimen is too big and heavy, or because of other logistical reasons, specimens cannot be tested with a fixed instrument. In such cases, a portable hardness tester is used for hardness testing. 

Charpy Impact Testing:

The machine has a pendulum-type hammer. The notched specimen is held securely at each end. The pendulum is pulled to a height and released. The hammer strikes opposite the notch and breaks the specimen into two. Because of the impact, the pendulum doesn’t swing as far. It has lost energy. That lost energy is the energy that was needed to break the specimen. The specimen must break into two. Results from instances in which the pendulum doesn’t have enough energy to toss the specimen into two are not reported as a standard result. The quantitative result of the impact tests the energy needed to fracture a material and can be used to measure the toughness of the material.

Data: 

The data obtained from tension test, bend test, hardness tests, and impact test are reported.