ASTM A193 Specification

• Scope
• Chemical Requirements
• Heat Treatment
• Mechanical Properties
• Nuts
• Marking of Ferritic Steels
• Marking of Austenitic Steels
• Keywords
• Supplementary Requirements
• Appendix
• Reference Documents

Standard Specification for Alloy-Steel and Stainless Steel Bolting for High Temperrature or High Pressure Service and Other Special Purpose Applications.

This specification covers alloy and stainless steel bolting for pressure vessels, valves, flanges, and fittings for high temperature or high pressure service, or other special purpose applications. See Specification A962/A962M for the definition of bolting. Bars and wire shall be hot-wrought and may be further processed by centerless grinding or by cold drawing. Austenitic stainless steel may be carbide solution treated or carbide solution treated and strain-hardened. When strain hardened austenitic steel is ordered, the purchaser should take special care to ensure that Appendix 1 is thoroughly understood. Several grades are covered, including ferritic steels and austenitic stainless steels designated B5, B8, and so forth. Selection will depend upon design, service conditions, mechanical properties, and high temperature characteristics.

Chemical Requirements(Composition, percent)^A

Each alloy shall conform to the chemical composition requirements prescribed in Table below.

Note:

^A Values are maximums unless a range or a minimum is indicated. Where ellipses appear in this table, there is no requirement and the element need not be determined or reported. The intentional addition of Bi, Se, Te, and Pb is not permitted.
^B Typical steel compositions used for this grade include 4140, 4142, 4145, 4140H,4142H, and 4145H.
^C For bar sizes over 31⁄2 in. [90 mm], inclusive, the carbon content may be 0.50 % max. For the B7M grade, a minimum carbon of 0.28 % is permitted, provided that the required tensile properties are met in the section sizes involved, the use of AISI 4130 or 4130H is allowed.
^D Total of soluble and insoluble.
^E Columbium and Niobium are alternate names for element 41 in the Periodic Table of the Elements.
^F For S34752 – Boron content shall be 0.001-0.005 for both heat and product analysis.

Heat Treatment

1. Ferritic Steels:
Ferritic steels shall be allowed to cool to a temperature below the cooling transformation range immediately after rolling or forging. Bolting materials shall then be uniformly reheated to the proper temperature to refine the grain (a group thus reheated being known as a quenching charge), quenched in a liquid medium under substantially uniform conditions for each quenching charge, and tempered. The minimum tempering temperature shall be as specified in Tables above.

Use of water quenching is prohibited for any ferritic grade when heat treatment is performed after heading or threading.

Except as permitted below for B6X; bolting material that is subsequently cold drawn for dimensional control shall be stress-relieved after cold drawing. The minimum stressrelief temperature shall be within not more than 100 °F [55 °C] below the tempering temperature. Tests for mechanical properties shall be performed after stress relieving.

B6 and B6X shall be held at the tempering temperature for a minimum time of 1 h. B6X bolting material may be furnished in the as-rolled-and-tempered condition. Cold working after heat treatment is permitted for B6X material provided the final hardness meets the requirements of Tables below.

B7 and B7M shall be heat treated by quenching in a liquid medium and tempering. For B7M bolting components, such as bolts, studs, or screws, the final heat treatment, which may be the tempering operation if conducted at 1150 °F [620 °C] minimum, shall be done after all machining and forming operations, including thread rolling and any type of cutting. Surface preparation for hardness testing, nondestructive evaluation, or ultrasonic bolt tensioning is permitted.

B7 and B7M shall be heat treated by quenching in a liquid medium and tempering. For B7M bolting components, such as bolts, studs, or screws, the final heat treatment, which may be the tempering operation if conducted at 1150 °F [620 °C] minimum, shall be done after all machining and forming operations, including thread rolling and any type of cutting. Surface preparation for hardness testing, nondestructive evaluation, or ultrasonic bolt tensioning is permitted.

Bolting material Grade B16 shall be heated to a temperature range from 1700 to 1750 °F [925 to 955 °C] and oil quenched. The minimum tempering temperature shall be as specified in Tables below.

2. Austenitic Stainless Steels:
All austenitic stainless steels shall receive a carbide solution treatment (2 para – 5 para for specific requirements for each class). Classes 1, 1B, 1C (Grades B8R and B8S only), 2, 2B, and 2C can apply to bar, wire, and finished bolting components. Class 1A (all grades) and Class 1C (grades B8RA and B8SA only) can apply to finished bolting components. Class 1D applies only to bar and wire and finished bolting components that are machined directly from Class 1D bar or wire without any subsequent hot or cold working.

Classes 1 and 1B, and Class 1C Grades B8R and B8S—After rolling of the bar, forging, or heading, whether done hot or cold, bolting material shall be heated from ambient temperature and held a sufficient time at a temperature at which the chromium carbide will go into solution and then shall be cooled at a rate sufficient to prevent the precipitation of the carbide.

Class 1D—Rolled or forged Grades B8, B8M, B8P, B8LN, B8MLN, B8CLNCuB, B8N, B8MN, B8R, and B8S bar shall be cooled rapidly immediately following hot working while the temperature is above 1750 °F [955 °C] so that grain boundary carbides remain in solution. Class 1D shall be restricted to applications at temperatures less than 850 °F [455 °C].

Class 1A and Class 1C Grades B8RA and B8SA — Finished bolting components shall be carbide solution treated after all rolling, forging, heading, and threading operations are complete. This designation does not apply to starting material such as bar. Components shall be heated from ambient temperature and held a sufficient time at a temperature at which the chromium carbide will go into solution and then shall be cooled at a rate sufficient to prevent the precipitation of the carbide.

Classes 2, 2B, and 2C—Bolting material shall be carbide solution treated by heating from ambient temperature and holding a sufficient time at a temperature at which the chromium carbide will go into solution and then cooling at a rate sufficient to prevent the precipitation of the carbide. Following this treatment the bolting material shall then be strain hardened to achieve the required properties.

If a scale-free bright finish is required; this shall be specified in the purchase order.

Mechanical Properties

^ATo meet the tensile requirements, the Brinell hardness shall be over 200 HBW (93 HRB).
^BClass 1 is solution treated. Class 1A is solution treated in the finished condition for corrosion resistance; heat treatment is critical due to physical property requirement. Class 2 is solution treated and strain hardened. Austenitic steels in the strain-hardened condition may not show uniform properties throughout the section particularly in sizes over 3⁄4 in. in diameter.
^CFor sizes 3⁄4 in. in diameter and smaller, a maximum hardness of 241 HBW (100 HRB) is permitted.
^D For diameters 1 1⁄2 and over, center (core) properties may be lower than indicated by test reports which are based on values determined at 1⁄2 radius.

Hardness Requirements:
The hardness shall conform to the requirements prescribed in Tables Mechanical Requirements. Hardness testing shall be performed in accordance with either Specification A962/ A962M or with Test Methods F606/ F606M.

Grade B7M — The maximum hardness of the grade shall be 235 HBW or 99 HRB. The minimum hardness shall not be less than 200 HBW or 93 HRB. Conformance to this hardness shall be ensured by testing the hardness of each stud or bolt by Brinell or Rockwell B methods in accordance. The use of 100 % electromagnetic testing for hardness as an alternative to 100 % indentation hardness testing is permissible when qualified by sampling using indentation hardness testing. Each lot tested for hardness electromagnetically shall be 100 % examined in accordance with Practice E566. Following electromagnetic testing for hardness, a random sample of a minimum of 100 pieces of each heat of steel in each lot shall be tested by indentation hardness methods. All samples must meet hardness requirements to permit acceptance of the lot. If any one sample is outside of the specified maximum or minimum hardness, the lot shall be rejected and either reprocessed and resampled or tested 100 % by indentation hardness methods.

Surface preparation for indentation hardness testing shall be in accordance with Test Methods E18. Hardness tests shall be performed on the end of the bolt or stud. When this is impractical, the hardness test shall be performed elsewhere.

Nuts

Bolts, studs, and stud bolts shall be furnished with nuts, when specified in the purchase order. Nuts shall conform to Specification A194/A194M.

Product Marking

See Specification A962/A962M. The grade symbol shall be as shown in Table Marking of Ferritic Steels and Table Marking of Austenitic Steels. Grade B7M no longer requires a line under the grade symbol. However, a line is permitted.

Marking of Ferritic Steels

Marking of Austenitic Steels

Keywords

Alloy steel bars; alloy steel bolting; bolting components; bolting materials; hardness; heat treatment; stainless steel bolting.

Supplementary Requirements

These requirements shall not apply unless specified in the order and in the Ordering Information, in which event the specified tests shall be made before shipment of the product.

S1. High Temperature Tests
1. Tests to determine high temperature properties shall be made in accordance with Test Methods E21, E139, and E292, and Practices E150 and E151.

S2. Charpy Impact Tests
1. Charpy impact tests based on the requirements of Specification A320/A320M, shall be made as agreed between the manufacturer and the purchaser. When testing temperatures are as low as those specified in Specification A320/A320M, bolting should be ordered to that specification in preference to this specification.

S3. 100 % Hardness Testing of Grade B7M
1. Each Grade B7M bolt or stud shall be tested for hardness by indentation method and shall meet the requirements specified in Tables.

S4. Hardness Testing of Grade B16
1. For bolts or studs 21⁄2 in. [65 mm] or smaller, the hardness for Grade B16 shall be measured on or near the end of each bolt or stud using one of the methods prescribed in 9.2.1 for the Brinell or Rockwell C test. The hardness shall be in the range 253–319 HBW or 25–34 HRC.

S5. Product Marking
1. Grade and manufacturer’s identification symbols shall be applied to one end of studs and to the heads of bolts and screws of all sizes. (If the available area is inadequate, the grade symbol may be marked on one end and the manufacturer’s identification symbol marked on the other end.) For bolts and screws smaller than 1⁄4 in. [6 mm] in diameter and studs smaller than 3⁄8 in. [10 mm] in diameter and for 1⁄4 in. [6 mm] in diameter studs requiring more than a total of three symbols, the marking shall be a matter of agreement between the purchaser and the manufacturer.

S6. Stress Relieving
1. A stress-relieving operation shall follow straightening after heat treatment.
2. The minimum stress-relieving temperature shall be 100 °F [55 °C] below the tempering temperature. Tests for mechanical properties shall be performed after stress relieving.

S7. Magnetic Particle Inspection
1. Bars shall be magnetic particle examined in accordance with Guide E709. Bars with indications of cracks or seams are subject to rejection if the indications extend more than 3 % of the diameter into the bar.

S8. Stress-Relaxation Testing
1. Stress-Relaxation Testing, when required, shall be done in accordance with Test Methods E328. The test shall be performed at 850 °F [454 °C] for a period of 100 h. The initial stress shall be 50 M psi [345 MPa]. The residual stress at 100 h shall be 17 M psi [117 MPa] minimum.

S9. Grain Size Requirements for Non H Grade Austenitic Steels Used Above 1000 °F
1. For design metal temperatures above 1000 °F [540 °C], the material shall have a grain size of No. 7 or coarser as determined in accordance with Test Methods E112. The grain size so determined shall be reported on the Certificate of Test.

S10. Hardness Testing of Class 2 Bolting for ASME Applications
1. The maximum hardness shall be Rockwell C35 immediately under the thread roots. The hardness shall be taken on a flat area at least 1⁄8 in. [3 mm] across, prepared by removing threads, and no more material than necessary shall be removed to prepare the flat areas. Hardness determinations shall be made at the same frequency as tensile tests.

S11. Thread Forming
1. Threads shall be formed after heat treatment. Application of this supplemental requirement to grade B7M or the grades listed is prohibited.

S12. Stress Rupture Testing of Grade B16
1. One test shall be made for each heat treat lot. Testing shall be conducted using a combination test bar in accordance with Test Methods E292.Rupture shall occur in the smooth section of each test specimen. The test shall be conducted at 1100 °F [595 °C] and 20 ksi [140 MPa]. The test shall be continued until the sample ruptures. Rupture life shall be 25 h minimum. Testing is not required on material less than 1⁄2 in. [12 mm] thick.
2. When a purchase order for bolting components invokes S12, the grade symbol applied shall be “B16R.”

S13. Coatings on Bolting Components
1. It is the purchaser’s responsibility to specify in the purchase order all information required by the coating facility. Examples of such information may include but are not limited to the following:
1.1. Reference to the appropriate coating specification and type, thickness, location, modification to dimensions, and hydrogen embrittlement relief.
1.2. Reference to Specifications A153/A153M, B633, B695, B696, B766, or F1941/ F1941M, F2329/ F2329M, or Test Method F1940, or other standards.

S14. Marking Coated Bolting Components
1. Bolting components coated with zinc shall have ZN marked after the grade symbol. Bolting components coated with cadmium shall have CD marked after the grade symbol.

S15. Requirements for Service Temperature Exceeding 1000°F
For bolting of Class 1 Grades B8, B8C, B8M, and B8T, to be used in service at temperatures exceeding 1000°F, the following shall apply:
The minimum carbon content shall be 0.04 %.
Carbide solution treatment shall be between 1900°F and 1950°F followed by quenching in water or rapid cooling by other means.

Appendix

1. STRAIN HARDENING OF AUSTENITIC STEELS
Strain hardening is the increase in strength and hardness that results from plastic deformation below the recrystallization temperature (cold work). This effect is produced in austenitic stainless steels by reducing oversized bars or wire to the desired final size by cold drawing or other process. The degree of strain hardening achievable in any alloy is limited by its strain hardening characteristics. In addition, the amount of strain hardening that can be produced is further limited by the variables of the process, such as the total amount of crosssection reduction, die angle, and bar size. In large diameter bars, for example, plastic deformation will occur principally in the outer regions of the bar so that the increased strength and hardness due to strain hardening is achieved predominantly near the surface of the bar. That is, the smaller the bar, the greater the penetration of strain hardening.
Thus, the mechanical properties of a given strain hardened bolting component are dependent not just on the alloy, but also on the size of bar from which it is machined. The minimum bar size that can be used, however, is established by the configuration of the component so that the configuration can affect the strength of the componoent.
For example, a stud of a particular alloy and size may be machined from a smaller diameter bar than a bolt of the same alloy and size because a larger diameter bar is required to accommodate the head of the bolt. The stud, therefore, is likely to be stronger than the same size bolt in a given alloy.

2. COATINGS AND APPLICATION LIMITS
1. Use of coated bolting components at temperatures above approximately one-half the melting point (Fahrenheit or Celsius) of the coating is not recommended unless consideration is given to the potential for liquid and solid metal embrittlement, or both. The melting point of elemental zinc is approximately 780 °F [415 °C]. Therefore, application of zinc-coated bolting components should be limited to temperatures less than 390 °F [210 °C]. The melting point of cadmium is approximately 600 °F [320 °C]. Therefore, application of cadmium-coated bolting components should be limited to temperatures less than 300 °F [160 °C].

Referenced Documents

ASTM Standards:
A153/A153M Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware.
A194/A194M Specification for Carbon Steel, Alloy Steel, and Stainless Steel Nuts for Bolts for High Pressure or High Temperature Service, or Both A320/A320M Specification for Alloy-Steel and Stainless Steel Bolting for Low-Temperature Service.
A354 Specification for Quenched and Tempered Alloy Steel Bolts, Studs, and Other Externally Threaded Fasteners.
A788/A788M Specification for Steel Forgings, General Requirements.
A962/A962M Specification for Common Requirements for Bolting Intended for Use at Any Temperature from Cryogenic to the Creep Range.
B633 Specification for Electrodeposited Coatings of Zinc on Iron and Steel.
B695 Specification for Coatings of Zinc Mechanically Deposited on Iron and Steel.
B696 Specification for Coatings of Cadmium Mechanically Deposited.
B766 Specification for Electrodeposited Coatings of Cadmium.
E18 Test Methods for Rockwell Hardness of Metallic Materials.
E21 Test Methods for Elevated Temperature Tension Tests of Metallic Materials.
E112 Test Methods for Determining Average Grain Size.
E139 Test Methods for Conducting Creep, Creep-Rupture, and Stress-Rupture Tests of Metallic Materials.
E150 Recommended Practice for Conducting Creep and Creep-Rupture Tension Tests of Metallic Materials Under Conditions of Rapid Heating and Short Times (Withdrawn 1984).
E151 Recommended Practice for Tension Tests of Metallic Materials at Elevated Temperatures with Rapid Heating and Conventional or Rapid Strain Rates (Withdrawn 1984).
E292 Test Methods for Conducting Time-for-Rupture Notch Tension Tests of Materials.
E328 Test Methods for Stress Relaxation for Materials and Structures.
E566 Practice for Electromagnetic (Eddy Current/Magnetic Induction) Sorting of Ferrous Metals.
E709 Guide for Magnetic Particle Testing.
F606/F606M Test Methods for Determining the Mechanical Properties of Externally and Internally Threaded Fasteners, Washers, Direct Tension Indicators, and Rivets.
F1940 Test Method for Process Control Verification to Prevent Hydrogen Embrittlement in Plated or Coated Fasteners.
F1941/F1941M Specification for Electrodeposited Coatings on Mechanical Fasteners, Inch and Metric
F2329/F2329M Specification for Zinc Coating, Hot-Dip, Requirements for Application to Carbon and Alloy Steel Bolts, Screws, Washers, Nuts, and Special Threaded Fasteners.

ASME Standards:
B18.2.1 Square and Hex Bolts and Screws.
B18.2.3.3M Metric Heavy Hex Screws.
B18.3 Hexagon Socket and Spline Socket Screws.
B18.3.1M Metric Socket Head Cap Screws.