Alloy and Carbon Steel Bolting For Use in The Petroleum and Natural Gas Industries
Alloy and Carbon Steel Bolting For Use in The Petroleum and Natural Gas Industries
Alloy and Carbon Steel Bolting For Use in The Petroleum and Natural Gas Industries
all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
1
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
Introduction
An introduction will have to be developed which will also contain a high-level overview of the changes that were
made to the 3rd edition.
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
Alloy and Carbon Steel Bolting for Use in the Petroleum and
Natural Gas Industries
1 Scope
1.1 Purpose
This standard specifies requirements for the qualification, production, and documentation of alloy and carbon
steel bolting used in the petroleum and natural gas industries.
1.2 Applicability
This standard applies when referenced by an applicable API equipment standard or otherwise specified as a
requirement for compliance.
This standard establishes requirements for three bolting specification levels (BSLs). These three BSL
designations define different levels of technical, quality, and qualification requirements, BSL-1, BSL-2, and BSL-
3. The BSLs are numbered in increasing levels of requirements in order to reflect increasing technical, quality,
and qualification criteria.
This standard covers the following finished product forms, processes, and sizes:
a) machined studs;
c) cold formed bolts, screws, and nuts with cut or cold formed threads (BSL-1 only);
d) hot formed bolts and screws <1.5 in. (38.1 mm) nominal diameter;
e) hot formed bolts and screws ≥1.5 in. (38.1 mm) nominal diameter;
f) roll threaded studs, bolts, and screws <1.5 in. (38.1 mm) diameter;
g) roll threaded studs, bolts, and screws ≥1.5 in. (38.1 mm) diameter;
NOTE Alternate geometry bolting made in accordance with this specification may be specified by the purchaser, provided
the bolting can be classified under one of the categories above.
2 Normative References
The following documents contain provisions that, through reference in this text, constitute provisions of this
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
standard. For dated references, only the edition cited applies. For undated references, the latest edition of the
reference document (including amendments) applies.
API Specification Q1, Specification for Quality Management System Requirements for Manufacturing
Organizations for the Petroleum and Natural Gas Industry
API 6HT, 2nd Edition, Heat Treatment and Testing of Carbon and Low Alloy Steel Large Cross Section and
Critical Section Components
ASTM 1 A29/A29M, Standard Specification for General Requirements for Steel Bars, Carbon and Alloy, Hot-
Wrought
ASTM A193/A193M, Standard Specification for Alloy-Steel and Stainless Steel Bolting Materials for High
Temperature or High Pressure Service and Other Special Purpose Applications
ASTM A194/A194M, Standard Specification for Carbon Steel, Alloy Steel, and Stainless Steel Nuts for Bolts for
High Pressure or High Temperature Service or Both
ASTM A320/A320M, Standard Specification for Alloy-Steel and Stainless Steel Bolting Materials for Low
Temperature Service
ASTM A370, Standard Test Method and Definitions for Mechanical Testing of Steel Products
ASTM A540/A540M, Standard Specification for Alloy Steel Bolting for Special Applications
ASTM A751, Standard Test Methods, Practices, and Terminology for Chemical Analysis of Steel Products
ASTM A941, Standard Terminology Relating to Steel, Stainless Steel, Related Alloys and Ferroalloys
ASTM A962/A962M, Standard Specification for Common Requirements for Steel Fasteners or Fastener
Materials, or Both, Intended for Use at Any Temperature from Cryogenic to the Creep Range
ASTM A1100, Standard Guide for Qualification and Control of Induction Heat Treating
ASTM B850-98 (2015), Standard Guide for Post-Coating Treatments of Steel for Reducing the Risk of Hydrogen
Embrittlement
ASTM E10, Standard Test Method for Brinell Hardness of Metallic Materials
ASTM E18, Standard Test Method for Rockwell Hardness of Metallic Materials
ASTM E45, Standard Test Method for Determining the Inclusion Content of Steel
ASTM E112, Standard Test Method for Determining Average Grain Size
ASTM E381, Standard Method of Macroetch Testing Steel Bars, Billets, Blooms, and Forgings
ASTM E1268-01 (2016), Standard Practice for Assessing the Degree of Banding or Orientation of Microstructures
ASTM F606-19, Standard Test Methods for Determining the Mechanical Properties of Externally and Internally
Threaded Fasteners, Washers, Direct Tension Indicators, and Rivets
1
ASTM International, 100 Barr Harbor Drive, West Conshohocken, Pennsylvania 19428, www.astm.org.
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
ASTM F1470-12, Standard Practice for Fastener Sampling for Specified Mechanical Properties and
Performance Inspection
ANSI/ASME B1.1, Unified Inch Screw Threads (UN and UNR Thread Form)
ANSI/NCSL 2 Z540.3, Requirements for the Calibration of Measuring and Test Equipment
ISO 17020 3, Conformity assessment – Requirements for the operation of various types of bodies performing
inspection
ISO 17025, General Requirements for the Competence of Testing and Calibration Laboratories
For the purposes of this document, the following terms and definitions apply.
3.1.1
as-received condition
Raw material to be subsequently heat treated after receipt by the bolting manufacturer (excluding any
stress relief)
3.1.2
as-received heat-treated condition
Raw material received by the bolting manufacturer in its final austenitizing, quench, and tempered state
(excluding any stress relief)
3.1.3
banding
The separation of one or more phases or constituents in a two-phase or multiphase microstructure, or of
segregated regions in a single phase or constituent microstructure, into distinct layers parallel to the
deformation axis due to elongation of microsegregation.
3.1.4
bolting
All-thread studs, tap-end studs, double-ended studs, headed bolts, cap screws, screws, and nuts.
3.1.5
bolting manufacturer
An organization qualified for the production and marking of this bolting, who through the use of
manufacturing equipment and processes appropriate for the bolting product form, transforms raw
material into finished bolting and marks the bolting as meeting the specification.
2
American National Standards Institute, 25 West 43rd Street, 4th Floor, New York, New York 10036, www.ansi.org.
3 International Organization for Standardization, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva, Switzerland,
www.iso.org.
4 SAE International, 400 Commonwealth Drive, Warrendale, Pennsylvania 15096, www.sae.org.
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
3.1.6
cold formed bolts, screws, and nuts
Parts formed through the mechanical cold (at a temperature below the recrystallization temperature) up-setting
of wire, rod, or bar in order to generate the bolt or screw head (cold heading) or the configuration of the nut.
3.1.7
hard banding
A banded microstructure which exhibits a white, featureless phase when examined using etchants such as various
Nital solutions. These white, featureless bands have extremely high hardness levels (typically > 100HK difference
from adjacent bands) due to microsegregation.
3.1.8
heat
Material originating from a final melt, or for remelted alloys, the raw material originating from a single remelted ingot.
3.1.9
heat lot
a) Batch furnace: bolting or raw material of a single heat and diameter, heat treated together as a single
austenitizing, quenching, tempering, and stress-relieving charge.
b) Continuous furnace: bolting or raw material of a single heat and diameter heat treated without interruption
in a continuous charge (see 5.5.1).
3.1.10
hot formed bolts, screws, and nuts
Parts formed through the mechanical hot (at a temperature above the recrystallization temperature) up-setting
of wire, rod, or bar in order to generate the bolt or screw head (hot heading) or the configuration of the nut.
3.1.11
machined bolts, screws and nuts
Parts manufactured by machining from raw material to generate the bolt, screw head, or the configuration of
the nut.
3.1.12
manufacturing process specification
MPS
A written document describing the complete production sequence and method.
NOTE Manufacturing process specification is usually proprietary by manufacturer and not for general publication but is
available for review by customers or authorized third parties.
3.1.13
production lot
Bolting of a single nominal diameter and grade made from the same heat lot.
3.1.14
raw material
Bar, coil, rod, or wire used to manufacture bolting.
3.1.15
raw material supplier
The manufacturer of raw material used to produce qualified bolting defined as the steel mill or forging supplier.
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
3.1.16
sub-supplier
A provider of subcontracted products or services associated with the essential variables of this specification.
3.1.17
technical authority
A competent and technically qualified person or organization with evidence to demonstrate the expertise, skills,
and experience regarding quality and manufacturing processes necessary to perform the required verification(s).
NOTE Technical authority may also be considered a Subject Matter Expert (SME).
3.1.18
wrought structure
Structure that contains no cast dendritic elements.
3.2 Abbreviations
4 Qualification Bolting
4.1 General
4.1.1 The manufacturer shall have a quality management system that at a minimum meets the requirements of
API Q1.
4.1.2 The manufacturer may qualify to one or more of the nine bolting types listed in 1.4 and to one or more of
the three BSLs.
4.1.4 Bolting shall be produced from raw material procured from a qualified supplier as defined in 4.7 and
manufactured in accordance with an applicable manufacturing process specification (MPS) from a bolting
material grade listed in 4.4. The MPS shall address all of the processes that contain essential variables as listed
in section 4.2.
4.1.5 If no products manufactured in accordance with this standard are produced to a qualified MPS within three
years, requalification is required. Additionally, if any changes are made to the essential variables associated
with a bolting manufacturing process, requalification is required.
4.1.6 The manufacturer shall retain and have available an MPS (see 5.2) and qualification records (see 4.6) for
each product qualified. The qualification records shall show all of the products, processes, and sizes qualified
in addition to all of the results of tests and inspections required per Table 2.
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
For final product manufacturing, raw materials supplier, and sub-supplier qualifications to remain valid, all
production shall be within the essential variables listed in Table 1. Changes to any of the parameters listed
requires requalification of the final product. Essential variables applicable to each bolting specification level are
identified with an X in the column for that BSL.
4.3.1 Bolting shall be tested and evaluated by the bolting manufacturer in order to establish qualification to the
bolting types listed in 1.4 and a BSL.
4.3.2 Qualification parts shall meet all the requirements indicated in Table 2 for the applicable sections of this
standard. Qualification may be performed on parts specifically manufactured for qualification or random parts
selected from a production lot. Enough parts shall be supplied to provide material for all qualification testing
required by this section.
4.3.3 All tests, including those certified by the raw material supplier, shall be performed by a laboratory
accredited to ISO 17025. For subcontracted NDE, the sub-supplier’s QMS, ultrasonic examination, magnetic
particle inspection, and liquid penetrant inspection, shall be accredited to either ISO 17020 or ISO 17025.
Forge/ Dimensional
NDE NDE
BSL Material Heat Chemistry Mechanical Metallurgical Hardness and Visual
Surface Volumetric
Treat Inspection
BSL-2 5.3.2 5.2.3 5.4 5.5.2 5.6.3 5.7.2.3 5.8.2.1 5.8.2.2 5.9.3
BSL-3 5.3.3 5.2.4 5.4 5.5.2 5.6.4 5.7.2.4 5.8.3.1 5.8.3.2 5.9.4
4.4.1 The following bolting material grades are covered by this standard:
ASTM A194 Grades 7, 7M, 2H (BSL-1 only) & 2HM (BSL-1 only);
4.4.2 All requirements of the referenced ASTM specifications or the equipment manufacturer’s proprietary
bolting material specification shall be met except as modified by this standard. In the case of conflict
between the requirements of referenced specifications and this standard, the requirements of this
standard shall apply. Bolting manufactured from proprietary materials shall conform to the requirements
of this standard.
4.4.3 Internal and external threads shall not be over or undersized, respectively, and welding is not permitted.
4.5.1 General
Results of the tests specified in Table 2 shall conform with the acceptance criteria specified in Section 5 and
the bolting manufacturer’s written specification. Results shall be documented in accordance with 4.6.
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
4.5.2.1 Samples failing to meet acceptance criteria shall be cause for reevaluation of the MPS and the
processes and procedures used, and requalification is required.
4.5.2.2 When a qualification sample selected from a production lot, defined in 3.1.13, fails to meet acceptance
criteria, the entire lot shall be rejected.
4.5.2.3 Should the manufacturer choose to continue the qualification process with the same lot, the entire lot
shall be reprocessed. A maximum of two full reheat treatments is permitted.
4.5.2.4 For reprocessed lots, all qualification tests shall be repeated. Should any of the qualification tests fail
to meet the acceptance criteria, the entire lot shall be rejected.
4.5.2.5 If reprocessing results in any changes to the MPS, the MPS shall be revised to reflect the new process
control variables.
a) ASTM specification number, edition, and grade or the equipment manufacturer’s proprietary bolting material
specification;
b) heat number;
c) steel manufacturer;
e) size;
g) MPS;
h) forming, as applicable;
i) heat treatment;
j) machining, as applicable;
m) inspection;
n) personnel qualifications;
q) sub-supplier(s) name and address and records of qualification for each subcontracted process.
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
4.7 Sub-suppliers
4.7.1 General
4.7.1.1 The bolting manufacturer shall have a documented and fully implemented procedure for qualifying sub-
suppliers of operations associated with the essential variables listed in section 4.2.
4.7.1.3 For BSL-2 and BSL-3 product, the initial qualification process shall include an onsite audit and technical
evaluation performed by a technical authority.
4.7.1.5 The essential variables listed in section 4.2, associated with each applicable BSL, shall be evaluated as
part of the technical evaluation.
4.7.1.6 Sub-suppliers shall be re-audited, at a minimum, by a technical authority at the frequency specified in
Table 3.
4.7.1.7 Sub-suppliers shall have an onsite technical authority with documented competency.
4.7.1.8 Qualification of subcontracted processes used to produce BSL-3 products shall be qualified with a first
article evaluation of each subcontracted process per the manufacturer’s documented procedure.
4.7.1.9 Sub-supplier shall have a quality management system in conformance with ISO 9001 or API Q1.
4.7.1.10 For BSL-2 and BSL-3 product, sub-suppliers of NDE services shall have a quality management
system accredited to ISO 17020 or ISO 17025 and lab service providers shall have a quality management
system accredited to ISO 17025.
4.7.1.11 For NDE or lab services, verifying current accreditation to ISO 17020 or ISO 17025, specific to the
testing performed by the supplier, may be used in lieu of onsite audits.
4.7.2.1 The bolting manufacturer shall qualify raw material suppliers for each grade and heat treat condition of
material supplied by the raw material supplier.
4.7.2.2 The raw material supplier shall maintain documented evidence of technical capability to produce
materials meeting this standard and shall have documented procedures that demonstrate capability to
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
4.7.2.3 For BSL-1 raw material suppliers, qualification of product shall consist of testing per section 4.7.3
4.7.2.4 For BSL-2 and BSL-3 raw material suppliers, in addition to the requirements of section 4.7.3, a technical
audit shall be performed and shall follow the requirements of Annex A.
4.7.3.1 Raw material may be supplied to the bolting manufacturer in either the heat-treated condition or a
condition requiring further heat treatment. At the frequency specified in Table 3, a technical verification of the
supplied raw material must be performed for each raw material supplier, per the requirements of Table 4. For
the purposes of this specification, the only supplied raw material conditions to be considered are:
4.7.3.2 For condition H material, testing shall be performed on a random heat for each bolting grade used by
the manufacture in section 4.4, as applicable to the raw material supplier. Additionally, the bolting manufacturer
shall verify all heat treatment processes used meet the requirements for the applicable BSL.
4.7.3.3 For condition A material, testing shall be performed on a random heat for each UNS designation
associated with the bolting grades listed in section 4.4, as applicable to the raw material supplier.
4.7.3.4 Testing of material in supplied condition H shall also qualify supplied condition A. Testing of material in
supplied condition A shall not qualify supplied condition H.
Table 4 – Raw Material Retesting & Validation Requirements for Technical Verification
Supplied Heat
BSL Chemistry Tensile Charpy Hardness Metallurgical
Condition Treatment
H 5.3.3.5 5.2.2 5.5.2 5.5.2 5.7.2.2 ASTM A962
BSL-1
A 5.3.3.5 --- --- --- --- ASTM A962
Note Testing may be performed on parts specifically manufactured for raw material qualification or random parts selected
from a production lot.
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
5.1.1 In addition to the requirements of 4.3, the bolting manufacturer shall prepare and document raw material
requirements in the form of a material specification. For BSL-1, this may be the applicable ASTM specification.
For BSL-2 and BSL-3, material specifications shall include the following:
5.1.2 The bolting manufacturer shall document acceptance of incoming raw material to the requirements of the
material specification prior to use in the production of bolting.
5.2.1 General
The bolting manufacturer shall prepare an MPS to include, as a minimum, allowable levels for all bolting
manufacturing parameters including the essential variables listed in Table 1.
5.2.2.1 Forging and hot heading shall be in accordance with the manufacturer’s standard procedure.
5.2.2.2 Heat treatment shall be in accordance with the applicable standard listed in 4.4.1.
5.2.2.3 Manufacturing processes shall be performed so as to avoid the introduction of stress risers that can occur
from sharp angles and tool marks. Threads may be cut or rolled. Unified National Threads shall be “R” (UNR
controlled radius series) for external threads and UN for internal threads (ANSI/ASME B1.1).
5.2.2.4 Furnace qualification and calibration shall be in conformance with API 6A, SAE AMS2750; or
SAE AMSH6875. Induction heat treatment qualification shall be in accordance with ASTM A1100. For forging
furnaces, qualification shall be in accordance with the manufacturer’s written procedures.
5.2.3.2 The manufacturer shall have a written forging procedure defining, at a minimum, the essential variables
defined in Table 1. When induction heating is used for forging, the manufacturer’s equipment shall include
temperature monitoring equipment and an automatic fail-safe system to prevent overheating.
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
5.2.3.3 ASTM A320 Grade L43, ASTM A540 Grade B23, and the equipment manufacturer’s proprietary bolting
material specification based on AISI 4340 material shall be double tempered.
5.2.3.4 When threads are rolled, parts shall subsequently be stress relieved at a temperature within
50 ºF (28 ºC) of, but not exceeding, the final tempering temperature, which is intended to establish mechanical
properties. This stress relief requirement is also met if the final temper heat treatment is done after any type of
thread forming.
5.2.3.5 Furnace loading shall be in accordance with API 6HT, Section 6.3.3.
5.2.3.6 Furnace loading diagram or photo shall be prepared for each load configuration.
5.2.3.7 Water, oil and polymer quenchant media shall be controlled in accordance with API 6HT, Section 6.2.2.
5.2.4.2 A minimum of one contact thermocouple attached to a part shall be used to verify heat treatment times
and temperatures. This referenced thermocoupled part shall be placed either in a location deemed to have the
slowest heating rate or centrally in the furnace load.
5.2.4.5 Induction and direct resistance heat treatments are prohibited for normalizing, austenitizing, tempering,
and stress relieving operations.
5.2.5.1 Plating and coating shall be provided only when specified in the purchase agreement.
5.2.5.2 Plating and coating shall be specified in accordance with industry or the equipment manufacturer’s
proprietary bolting material specification.
5.2.5.3 Zinc electroplating is not permitted for BSL-3 bolting used in splash zone or subsea service
All electroplated parts, except parts of Grades B7M, L7M, 2HM, and 7M, shall be baked within 2 hours after
plating at 375 ºF–425 ºF (191 ºC–218 ºC ) for 8 hours minimum at temperature.
The requirements of 5.2.2.4 shall apply to the ovens used for baking.
The validation of each plating process must include verification that the plating process does not induce
hydrogen embrittlement in API 20E bolting. A plating process is defined by the following variables
o Type of electroplating
o Minimum Thickness
o Baking Temperature
o Bath Type: Acid vs Alkaline
o Plating Process: Rack vs Barrel
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
o Plating Source
This verification shall consist of performing a sustained load test per ASTM F606-19 section 7, on an API
20E compliant fastener. The test shall be performed once for each plating process, as defined by the
variables listed above.
This verification shall be performed once every 3 years. A change to any of the variables listed above, will
require another verification test per this section. Record of this embrittlement verification testing shall be
kept by the bolting manufacturer.
5.2.5.5 The following shall be specified when ordering plating and coating:
a) part description;
c) description of plating/coating including type, thickness, finish, and other applicable requirements;
5.3.1 BSL-1
5.3.1.2 The reduction ratio based on starting material diameter shall be a minimum of 4:1.
5.3.1.3 The steel shall conform to the requirements of the standards listed in 4.4.1, as applicable.
5.3.2BSL-2
5.3.2.1 The requirements specified for BSL-1 are required for BSL-2.
5.3.2.2 Melting method of the raw material shall be fine grain practice as defined by ASTM A941. Steel shall be
produced by electric furnace or vacuum induction melting followed by secondary refining practices or ladle
refining.
5.3.2.3 The allowable sulfur content shall be 0.025 % maximum, and the allowable phosphorus content shall
be 0.025 % maximum.
5.3.3 BSL-3
5.3.3.1 The requirements specified for BSL-2 are required for BSL-3 except as specified below.
5.3.3.2 The reduction ratio based on starting material diameter shall be 10:1 minimum.
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
5.3.3.3 Allowable sulfur content shall be 0.015 % maximum, and the allowable phosphorus content shall be
0.015 % maximum.
5.3.3.5 In addition to the heat analysis performed by the raw material supplier, the bolting manufacturer shall
perform a product analysis in accordance with ASTM A29.
Methods and practices relating to chemical analysis shall be in accordance with ASTM A751. The frequency for
chemical analysis shall be one per heat. Results shall be documented on the test report.
5.5.1 General
Mechanical properties testing shall be performed by the raw material supplier or bolting manufacturer after all
thermal treatments including stress relief. When heat treated without interruption in continuous furnaces, as
defined in 3.1.9, testing shall be as follows: Not fewer than two tests for the first 20,000 lb. (9000 kg) or less, and
an additional test for every 10,000 lb. (4500 kg) or fraction thereof.
When any of the testing has been performed by the raw material supplier, the bolting manufacturer shall perform
a retest.
5.6.1 General
The following tests shall be performed, as applicable to the specified BSL. Any of the specified tests not
performed by the raw material supplier shall be performed by the bolting manufacturer. Results shall be
documented on the test report.
5.6.2 BSL-1
The microstructure and macrostructure shall conform to the requirements of the standards listed in 4.4.1, as
applicable.
5.6.3 BSL-2
5.6.3.1.1 General
Microstructure specimens shall be tested in accordance with ASTM E45, Method A, for inclusion content. For
other microstructure evaluations, the specimens shall be taken in the longitudinal direction at ¼T.
The microstructure shall conform to the requirements of Table 5. One test shall be conducted per heat.
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
Grain size shall be determined for each heat in accordance with ASTM E112 following etching with a suitable
reagent. Grain size shall conform to Table 5.
5.6.3.1.4 Microstructure
The microstructure shall be predominately tempered martensite. One test shall be performed per each heat.
5.6.3.1.5 Banding
Hard banding in microstructures, as shown in ASTM E1268-01 (2016), Figure A1.20, are not permitted. When a
banded microstructure is observed of questionable acceptability, a minimum of 3 Knoop micro-hardness readings
per test, in accordance with ASTM E384, shall be taken on the most predominate bands. The test load shall be
500 g, unless extremely thin bands are observed that will not permit an accurate 500 g test, in which case it is
permissible to reduce the test load to as low as 50 g to obtain an accurate reading. Individual readings shall not
exceed 470 HK. One test shall be conducted per heat.
Inclusion content, ASTM E45 Severity Level Number 2 for thin, 1.5 for Severity Level Number 2 for thin, 1.5 for
Method A thick, all categories thick, all categories
Inclusion test frequency One per heat One per heat
Grain size Size 5 or finer Size 5 or finer
Grain size test frequency One per each heat One per each heat lot
Microstructure Predominately tempered martensite Predominately tempered martensite
Microstructure test frequency One per each heat (after heat treat) One per each heat lot
Macrostructure testing ASTM E381 S1, R1, C2 ASTM E381 S1, R1, C2
Macrostructure test frequency One per heat One per heat
ASTM E1268-01 (2016) Figure A1.20 is ASTM E1268 Figure A1.20 is not
Banding
not permitted permitted
Banding test frequency One per each heat One per each heat lot
Macrostructure specimens shall be prepared and evaluated in accordance with ASTM E381 and ASTM A962.
The results shall meet the requirements of Table 5. One test shall be conducted per heat.
5.6.4 BSL-3
5.8.4.2 For grain size and banding, one test shall be performed per each heat lot.
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
5.8.4.3 When any hard banding is observed, the hardness test evaluation required under BSL-2 shall be
required for a minimum of 2 bands.
5.7.1 General
When inspecting or testing production lots, a sample that fails to meet the applicable requirements shall result in
the rejection of the entire lot. The rejected lot shall be scrapped, reworked, or, where practical, inspected 100 %
and the defective parts removed. In the case of rework or 100 % inspection, the lot shall be reinspected or tested
for the failed characteristic and any characteristic affected by rework.
5.7.2.1 General
Hardness testing, including specimen preparation, shall be performed in accordance with ASTM A370 including
Annex A3, except that testing shall also be in conformance with ASTM E10 or ASTM E18. Results shall be
documented on the test report.
5.7.2.2 BSL-1
The hardness test results shall conform to the requirements of ASTM A193, ASTM A194, ASTM A320, ASTM
A540 or the equipment manufacturer’s proprietary material specification as applicable, except that maximum
hardness for Grades B7, L7, 2H, 7, L43, B22, B23 and the equipment manufacturer’s proprietary material
specification shall not exceed 34 HRC (319 HBW). Test frequency shall conform to ASTM F1470, Table 6,
sample size A except when 100 % hardness testing is required by the ASTM specification for the grade.
Note Refer to API 21TR1, Annex A for additional information regarding strength and hardness limits in subsea environments.
5.7.2.2.2 Hardness Testing of Bars Heat Treated by Induction or Electric Resistance Methods
For bars heated by induction or electric resistance methods, a cross section of the bar shall be taken at the same
test frequency as the required for lot testing of the heat-treated bar per ASTM A193. The cross-section shall be
ground and a Rockwell hardness traverse performed with tests as close to the edge as permitted by ASTM E18,
approximately mid radius, and approximately center. All hardness measurements in the traverse shall meet the
acceptance criteria of 5.7.2.2.1.
5.7.2.3 BSL-2
Hardness testing requirements specified for BSL-1 are required for BSL-2 except that when a hardness traverse
for bars heat treated by induction or electric resistance methods is required, all readings shall be within 3 HRC.
Note Refer to API 21TR1, Annex A for additional information regarding strength and hardness limits in subsea environments.
For nuts not listed in ASTM A194 Tables 3 and 4, a sample nut from each heat lot shall be sectioned and the
cross-section hardness tested in accordance with ASTM F606-19 or ASTM A370. Hardness shall meet the
acceptance criteria of 5.7.2.2.1.
5.7.2.4 BSL-3
5.7.2.4.1 Hardness testing requirements and yield strength limits specified for BSL-2 are required for BSL-3.
5.8.1 BSL-1
5.8.2 BSL-2
5.8.2.1 Surface NDE is required. Either magnetic particle examination or liquid penetrant examination is
permitted. Magnetic particle examination shall be in accordance with ASTM A962 S55, including personnel
qualification. Liquid penetrant examination shall be in accordance with ASTM A962 S56, including personnel
qualification. Acceptance criteria shall be per ASTM A962 S57. Pieces examined shall be as stated in Table 6.
Results shall be documented on an examination report.
5.8.2.2 Ultrasonic examination is required on bar, rod, wire, or bolting with a diameter greater than 2.5 in.
(63.5 mm) nominal after heat treatment and prior to threading. Ultrasonic examination shall be performed in
accordance with API 6A volumetric NDE examination of stems (PSL-3 and PSL-4), including personnel
qualification. Each piece shall be examined. Results shall be documented on the test report.
5.8.3 BSL-3
5.8.3.1 Surface NDE requirements specified for BSL-2 are required for BSL-3 except each piece shall be
inspected.
5.8.3.2 Ultrasonic examination is required on bar, rod, wire, or on bolting of diameters 1 in. (25.4 mm) nominal
and larger after heat treatment and prior to threading. Ultrasonic examination shall be performed in accordance
with API 6A volumetric NDE examination of stems (PSL-3 and PSL-4), including personnel qualification. Each
piece shall be examined. Results shall be documented on the test report.
5.9.1 General
All dimensions and visual inspections shall meet the requirements of the applicable ASTM or the equipment
manufacturer’s proprietary material specification. Inspections shall be performed prior to coating. Results shall
be documented on an inspection report. Oversizing of nut threads or under sizing of bolt threads is not
permissible.
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
All testing shall be performed in accordance with this specification and the applicable material specifications.
All required tests, including those certified by the raw material supplier, shall be performed by a laboratory
accredited to ISO 17025.
For subcontracted ultrasonic examination, magnetic particle inspection, and liquid penetrant inspection, ISO
17020 is an acceptable alternative to ISO 17025.
2 to 8 ALL
9 to 50 8
51 to 90 13
91 to 150 20
151 to 280 32
281 to 500 50
501 to 1200 80
6 Calibration Systems
Inspection, measuring, and testing equipment used for acceptance shall be identified, inspected, calibrated, and
adjusted at specific intervals in accordance with ANSI/NCSL Z540.3 and this standard. Calibration standards
shall be traceable to the applicable national or international standards agency and shall be no less stringent than
the requirements included herein. Inspection, measuring, and testing equipment shall be used only within the
calibrated range. Calibration intervals shall be established based on repeatability and degree of usage.
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
7 Test Report
7.1 General
The test report shall be supplied to the purchaser and shall include the following.
7.2 BSL-1
BSL-1 test reports are as required by the applicable ASTM or equipment manufacturer’s proprietary material
specification.
heat treat procedure including times, temperatures, quench media, and diagram or photo of furnace
loading;
8 Marking
8.1 ASTM Product Marking
Product marking shall be in accordance with ASTM A193, ASTM A194, ASTM A320, ASTM A540, ASTM A962
or the equipment manufacturer’s proprietary bolting material specification, as applicable.
NOTE The referenced ASTM specifications require marking of individual parts for headed bolting 1/4 in. nominal diameter
and larger, for studs 3/8 in. nominal diameter and larger and for nuts of all sizes.
Bolting shall be marked with unique heat lot identification and the following:
Each piece 1 in. nominal diameter and larger shall be marked. For bolting less than 1 in. nominal diameter, the
bolting shall be securely containerized to maintain heat lot identification and traceability. Multiple heat lots shall
not be mixed in a single container. Containers used in the processing, storing, and shipping of bolting not
individually marked shall be clearly labeled with all marking information required by the relevant ASTM or
equipment manufacturer’s proprietary bolting material specifications and this standard.
9 Record Retention
The bolting manufacturer shall establish and maintain documented procedures to control all documents and
data required by this standard. Records required by this standard shall be maintained for 10 years. Documents
and data may be in any type of media (hard copy or electronic) and shall be:
b) legible,
Annex A
(Normative)
A.1 General
A.1.1 As a part of the technical audit, the bolting manufacturer shall ensure that a raw material supplier has
implemented controls for the raw material essential variables in Table 1 for each grade of raw material
ordered.
A.1.2 On-site technical audits of the raw material supplier shall be performed and documented by the bolting
manufacturer’s technical authority. The bolting manufacturer shall document the approval of the technical
audit report.
A.1.3 Raw material suppliers shall be qualified to a specific grade listed in 4.4.1 per facility location.
The questions listed in Table A.1 shall be included, as a minimum, for a technical audit of the raw material
supplier for the given operations, as applicable to the intended grade listed in 4.4.1:
Annex B
(Normative)
The process control activities associated with the manufacturing of bolting shall be as identified in Table B.1 for
each manufacturing location. The manufacturer shall maintain equipment and personnel to ensure conformance
to the requirements listed in Table B.1 for all activities performed by the manufacturer.
Performed by:
Process Control Activity
Bolting Manufacturer Outsourced
Material Verification X Not Permitted
Forging X X
Heat treating X X
Machining X Not Permitted
Threading cutting and Rolling X Not Permitted
Tensile and impact testing X X
Metallography X X
Chemical Analysis X X
Hardness testing X X
NDE Surface X X
NDE Volumetric X X
Marking X Not Permitted
Coating X X
Final Inspection X Not Permitted
This document is not an API Standard; it is under consideration within an API technical committee but has not received all
approvals required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside
of API committee activities except with the approval of the Chairman of the committee having jurisdiction and staff of the
API Standards Dept. Copyright API. All rights reserved.
Bibliography
[1] ANSI/ASQ 5 Z1.4-2003 (R2013), Sampling Procedures and Tables for Inspection by Attributes
5
American Society for Quality, 600 North Plankinton Avenue, Milwaukee, WI 53203, https://asq.org.
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