ASTM A561-08(2020)

Standard Practice for Macroetch Testing of Tool Steel Bars

ABSTRACT
This practice covers macroetch testing used for evaluating the quality of tool steel bars. This test shall be used as a quality control and inspection test to reveal by deep acid etching, the macrostructure in specimens cut from bars and to show the presence, absence, and severity of the following internal, surface, or subsurface conditions: pipe, bursts, carbide or alloy segregation, nonmetallic inclusion concentrations, porosity, cracks or thermal flakes, seams, laps, ingot corner segregation, pinholes, foreign material, and ingot pattern. Macroetching may be performed in a vessel of borosilicate glass, porcelain, corrosion-resistant metals, or some other acid resisting material. The etching reagent, specimen sampling, specimen preparation, and testing procedure including etching temperature, etching time, and macroetching technique are detailed.
SCOPE
1.1 This practice for macroetch testing has been found to be a useful and reliable method for evaluating the quality of tool steel bars. It is used as a quality control and inspection test to reveal by deep acid etching the macrostructure in specimens cut from bars and to show the presence of such conditions as pipe, cracks, porosity, segregation, or foreign material. The etched surface is generally examined visually, but magnification up to about 10× is occasionally employed.  
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 29-Feb-2020
• ICS: 77.140.60 - Steel bars and rods
• Technical Committee: A01 - Steel, Stainless Steel and Related Alloys
• Drafting Committee: A01.29 - Tool Steels

Relations

• Replaces: ASTM A561-08(2014) - Standard Practice for Macroetch Testing of Tool Steel Bars
• Effective Date: 01-Mar-2020
• Referred By: ASTM A681-08(2022) - Standard Specification for Tool Steels Alloy
• Effective Date: 01-Mar-2020
• Referred By: ASTM A600-92a(2016) - Standard Specification for Tool Steel High Speed
• Effective Date: 01-Mar-2020
• Referred By: ASTM A686-92(2016) - Standard Specification for Tool Steel, Carbon
• Effective Date: 01-Mar-2020

Overview

ASTM A561-08(2020): Standard Practice for Macroetch Testing of Tool Steel Bars provides an established procedure for evaluating the quality of tool steel bars through macroetch testing. Developed by ASTM International, this standard outlines how to use deep acid etching to expose the macrostructure of sections cut from steel bars. The primary goal is to identify internal and surface conditions such as pipe, porosity, segregation, cracks, and other structural irregularities. Macroetch testing serves as a critical inspection and quality control tool in the manufacturing and processing of tool steels, ensuring products meet performance and reliability requirements.

Key Topics

• Macroetch Testing Process: Outlines specimen sampling, preparation, etching procedures, and recommended inspection techniques, including the use of hydrochloric acid and temperature control for effective results.
• Identification of Flaws: Enables detection of internal and external flaws such as:
  • Pipe
  • Bursts
  • Carbide or alloy segregation
  • Inclusions
  • Porosity
  • Cracks or thermal flakes
  • Seams, laps, and pinholes
  • Ingot corner segregation and ingot pattern
• Surface Examination: Typically performed visually, with optional magnification up to 10x for enhanced detail.
• Safety and Equipment: Recommends use of acid-resistant containers such as borosilicate glass, porcelain, or metal and cautions regarding proper ventilation and handling of reagents.
• Specimen Guidelines: Details on specimen size, location, and preparation methods to ensure accurate and consistent results.

Applications

Macroetch testing according to ASTM A561 is widely used in the tool steel manufacturing industry and associated sectors, providing practical value in:

• Quality Assurance: Ensuring each batch or lot of tool steel bars conforms to required internal and surface quality standards before further processing or delivery.
• Process Control: Allowing steel mills and forging facilities to monitor and optimize melting, casting, and rolling practices, reducing the risk of defects.
• Supplier Verification: Supporting steel purchasers and end-users in verifying that received tool steel bars meet specified macrostructural quality and conformance to contractual requirements.
• Failure Analysis: Aiding engineers and investigators in failure analysis by revealing macrostructural origins of defects or discontinuities in steel components.

Because this practice reveals critical details like segregations and inclusions, it plays a key role in industries such as automotive, aerospace, and heavy machinery, where the integrity and performance of tool steels are essential.

Related Standards

Organizations working with ASTM A561 often rely on or reference related international steel testing and quality standards for a comprehensive quality assurance approach, including:

• ASTM E45: Standard Test Methods for Determining the Inclusion Content of Steel
• ASTM E381: Standard Method of Macroetch Testing Steel Bars, Billets, Blooms, and Forgings
• ASTM A370: Standard Test Methods and Definitions for Mechanical Testing of Steel Products
• ISO 4967: Steel - Determination of Content of Non-metallic Inclusions - Micrographic Method Using Standard Diagrams

By integrating ASTM A561 with these related standards, manufacturers and quality assurance professionals can ensure a robust inspection regime for tool steel production.

Keywords

Tool steel bars, macroetch testing, ASTM A561, steel inspection, steel quality control, macrostructure, steel defects, porosity, segregation, inclusions, etching test, steel standards, metallurgical testing.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: A561 − 08 (Reapproved 2020)
Standard Practice for
Macroetch Testing of Tool Steel Bars
This standard is issued under the fixed designation A561; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope and the fumes are corrosive and irritating, although nontoxic.
The solution may be reused within limits. With use, the
1.1 This practice for macroetch testing has been found to be
concentration of dissolved iron and other metals increases and
a useful and reliable method for evaluating the quality of tool
the acidity of the solution decreases retarding the etching
steel bars. It is used as a quality control and inspection test to
action.Spentsolutionshallbereplacedwithfreshsolution,not
reveal by deep acid etching the macrostructure in specimens
replenished with concentrated acid.
cut from bars and to show the presence of such conditions as
pipe, cracks, porosity, segregation, or foreign material. The
5. Sampling
etched surface is generally examined visually, but magnifica-
tion up to about 10× is occasionally employed.
5.1 The selection of specimens for macroetch testing must
be done with care for interpretations to be of value.
1.2 The values stated in inch-pound units are to be regarded
5.1.1 Specimens are usually cut from hot-rolled annealed
as standard. The values given in parentheses are mathematical
bars, but may be cut from machined or ground bars if the bars
conversions to SI units that are provided for information only
are to be finish machined or ground.
and are not considered standard.
5.1.2 Thespecimenshouldbelocatedatasufficientdistance
1.3 This international standard was developed in accor-
from the end of the bar to avoid end effects.
dance with internationally recognized principles on standard-
1 1
5.1.3 For ease in handling, use specimens ⁄4 in. to ⁄2 in.
ization established in the Decision on Principles for the
(6.35 mm to 12.7 mm) thick.
Development of International Standards, Guides and Recom-
5.1.4 Cut specimens to expose a transverse section of the
mendations issued by the World Trade Organization Technical
bar; however, the test is occasionally performed on a longitu-
Barriers to Trade (TBT) Committee.
dinal section.
5.1.5 Specimens may be taken from one or both ends of a
2. Referenced Documents
bar. Each bar may be sampled, or a few typical specimens may
2.1 ASTM Adjuncts:
be tested as representative of a large number of bars.
Six Photomacrographs
6. Specimen Preparation
3. Apparatus
6.1 In all cutting and grinding operations on the specimen,
3.1 Etching Containers—Macroetching may be performed
care must be exercised to avoid heating the surface to an
in a vessel of borosilicate glass, porcelain, corrosion-resistant
excessively high temperature. Specimens are cut from bars by
metals, or some other acid-resisting material.
sawing, machining, abrasive wheel cutting, or other means.
4. Reagent
Cutting should be controlled to prevent smearing the cut face
and masking the structure.
4.1 Etching Reagent—A solution of equal volumes of con-
6.1.1 The“as-cut”surfaceofaspecimenmaybesufficiently
centrated hydrochloric acid (HCl, sp gr 1.19) and water is
smooth to reveal the defects for which the examination is
commonly used for macroetching tool steels. This solution
conducted. No additional surface preparation may then be
must be used under a ventilating hood because HCl is volatile
necessary.
6.1.2 Additional surface preparation may be required to
This practice is under the jurisdiction of ASTM Committee A01 on Steel,
remove cutting marks and to allow details to be revealed by
Stainless Steel and Related Alloysand is the direct responsibility of Subcommittee
etching. In such circumstances, machining, grinding, or pol-
A01.29 on Tool Steels.
Current edition approved March 1, 2020. Published March 2020. Originally
ishing may be necessary. Generally, the degree of surface
approvedin1966.Lastpreviouseditionapprovedin2014asA561–08(2014).DOI:
smoothness required is greater the finer the detail that must be
10.1520/A0561–08R20.
resolved. When the action of the etchant is drastic, a coarser
Available from ASTM International Headquarters. Order Adjunct No.
ADJA0561. Original adjunct produced in 1984. surface finish may be used.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A561 − 08 (2020)
6.1.3 The surface must be free of adhering grease and oil. 8. Interpretation of Results
There should be no scale or oxide on the surface which will be
8.1 Examine the etched surface visually or at up to 10×
examined after etching.
magnification to determine its structure. Note the presence,
absence, and severity of the following conditions:
7. Procedure
8.1.1 Internal:
7.1 Temperature for Macroetching—Etching characteristics
8.1.1.1 Pip
...