ASTM A991/A991M-22

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Designation: A991/A991M − 17 A991/A991M − 22
Standard Test Method for
Conducting Temperature Uniformity Surveys of Furnaces
Used to Heat Treat Steel Products
This standard is issued under the fixed designation A991/A991M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 This test method covers the procedures used to conduct a temperature uniformity survey on a furnace used to heat treat steel
products. This method is used to determine the capability of the furnace to meet the permissible temperature variation specified
in the applicable product specification, or as agreed to by the purchaser and supplier of heat treat services. Survey documentation
requirements, and the procedure used to subsequently establish the furnace working zone, are defined in this test method.
1.2 This test method covers heat treat furnaces in any of the following categories:
1.2.1 Continuous or semi-continuous conveyance furnaces,
1.2.2 Batch furnaces, and
1.2.3 Salt or liquid baths and fluidized beds.
1.3 This test method only applies when specified in the product specification or the purchase order.
1.4 Controlling a heat treatment of steel products using thermocouples attached to the extremities of each load is an alternative
to performing a furnace survey. The producer shall adhere to Annex A1.
1.5 By mutual agreement between the purchaser and the supplier of heat treat services, more stringent and/or additional
requirements may be specified. The acceptance of any such additional requirements shall be dependent on negotiations with the
supplier and must be included in the order as agreed upon by the purchaser and supplier.
1.6 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
This test method is under the jurisdiction of ASTM Committee A01 on Steel, Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee A01.13
on Mechanical and Chemical Testing and Processing Methods of Steel Products and Processes.
Current edition approved April 15, 2017April 15, 2022. Published April 2017May 2022. Originally approved in 1998. Last previous edition approved in 20152017 as
A991/A991M – 10 (2015).A991/A991M – 17. DOI: 10.1520/A0991_A0991M-17.10.1520/A0991_A0991M-22.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A991/A991M − 22
1.8 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.
2. Referenced Documents
2.1 ASTM Standards:
E207 Test Method for Thermal EMF Test of Single Thermoelement Materials by Comparison With Reference Thermoelement
of Similar EMF-Temperature Properties
E220 Test Method for Calibration of Thermocouples By Comparison Techniques
E230 Specification for Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples
E608/E608M Specification for Mineral-Insulated, Metal-Sheathed Base Metal Thermocouples
2.2 SAE Standard:
AMS 2750 Pyrometry
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 batch furnace, n—heating device in which material may be stationary or oscillating during the processing cycle.
3.1.2 continuous conveyance furnace, n—heating device through which material is moved intentionally at a constant rate during
the processing cycle.
3.1.3 extremities, n—as referring to furnace working zone; outer boundaries in all three dimensions (length, width, and height) of
the material being processed.
3.1.4 operating range, n—expected range of temperature over which a furnace will be controlled to heat treat steel products.
3.1.5 primary survey, n—initial evaluation of the furnace, or an evaluation triggered by the initiation of a major furnace
modification.
3.1.6 secondary survey, n—evaluation of the furnace triggered by the expiration of a time requirement.
3.1.7 semi-continuous conveyance furnace, n—heating device through which material is moved intentionally with a predetermined
start-stop-start pattern during the processing cycle.
3.1.8 working zone, n—maximum volume and location in the furnace that meet the permissible temperature variation.
4. Significance and Use
4.1 Furnaces for heat treatment of steel products are used in many industries, in many ways. Regardless of heat treat furnace type,
or processing cycle, it may be necessary for users to know the temperature uniformity in the furnace and whether the material is
processed in a zone within the furnace that is capable of meeting the applicable permissible temperature variation requirements.
4.2 The procedures in this test method may be used by those using, manufacturing, and providing calibration service for, heat treat
furnaces used to process steel products.
5. Furnace Survey Equipment
5.1 Thermocouples:
5.1.1 Metal sheathed thermocouples shall be in accordance with Specification E608/E608M.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from Society of Automotive Engineers (SAE), 400 Commonwealth Dr., Warrendale, PA 15096-0001, http://www.sae.org.
A991/A991M − 22
5.1.2 The use of extension wires is permitted when compensated connectors, plugs, jacks, and terminal strips are used.
5.1.3 Thermocouples made from spool wire shall meet the requirements of AMS 2750.
5.1.4 The use of spliced extension wire is prohibited.
5.1.5 Thermocouples may be reused if the requirements of AMS 2750 (except Paragraphs 3.1.1.10 and 3.1.1.11 of Rev. D) are met.
5.2 Calibration:
5.2.1 All reference, primary, secondary, test and working equipment, instrumentation and sensors used in conjunction with this test
method shall meet the requirements of calibration defined by Test Methods E207 and E220.
5.2.2 Temperature measuring devices shall be calibrated within three months prior to use.
5.2.3 Calibration shall be traceable to the National Institute of Standards Technology standards, or equivalent national standards.
Calibration to such national standards shall be done at least once every two years.
5.2.4 Calibration shall be within the temperature range to be used in the survey and at intervals not greater than 200°F
[100°C]200 °F [100 °C] for primary and secondary standards.
5.2.5 Correction factors, limits of error, and deviations shall be in accordance with Specification E230.
6. Requirements
6.1 Uniformity Survey Test Conditions:
6.1.1 The furnace to be surveyed shall be capable of being tested at set point temperature(s) typical for the normal operating range.
6.1.1.1 If the operating range does not exceed a spread of 300°F [150°C],300 °F [150 °C], the midpoint temperature shall be
selected for the survey.
6.1.1.2 If the operating range exceeds a spread of 300°F [150°C],300 °F [150 °C], survey at the minimum and maximum set point
temperature for the normal operating range, except that the maximum temperature need not be higher than 2000°F
[1100°C].2000 °F [1100 °C].
6.1.2 Either typical or maximum production size and weight furnace loads shall be utilized during the survey. Use of representative
material to simulate product during survey is permitted.
6.1.3 The furnace atmosphere and operating conditions shall be representative of those used in production.
6.2 Frequency of Uniformity Surveys:
6.2.1 Primary Surveys:
6.2.1.1 A primary survey shall have been performed within twelve months prior to, or run concurrently with, the first production
heat treatment to which this test method applies.
6.2.1.2 A primary survey shall have been conducted when a major furnace modification is completed. A major furnace
modification includes, but is not limited to, the installation of the following: a different burner type, a new heating element design,
a different type of insulation system, and, a different type of temperature controlling device.
6.2.1.3 Replacement of worn parts with similar parts or patching of insulation that does not change the furnace characteristics does
not constitute a major furnace modification.
6.2.1.4 The survey shall be conducted within twelve months prior to, or run concurrently with, the first production heat treatment
performed after the modification.
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6.2.2 Secondary Surveys:
6.2.2.1 To maintain conformance with this test method, a secondary survey shall be conducted within twelve months after the
primary survey and additional surveys within every twelve month period thereafter.
6.2.2.2 Secondary surveys shall be conducted at a typical furnace set point temperature within the normal operating range. All
other conditions described in 6.
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