ASTM A193 Specifications

During rolling or forging, ferritic steels are supposed to be left to cool at temperatures which are below the cooling transformation range. The bolting materials are then evenly warmed up to the correct temperature in order to straighten the grain. A group whose reheating is of this type is referred to as a quenching charge. The charge is then extinguished in a liquid medium under relatively homogenous conditions per batch and tempered. The lowest temperature of tempering should not be less than those given in the corresponding tables.

No ferritic grade may be quenched using water when the heat treatment is carried out after either heading or threading.

In the case of B6X material, cold-drawn dimensional control would be stress-relieved after cold drawing by bolting. The lowest permissible stress-relief temperature should be between 100°F (55°C) and the tempering temperature. Post-stress relieving should be followed by mechanical property tests.

The materials (B6 and B6X) will be left at the tempering temperature for at least 1 hour. B6X bolting can be in the condition of being as-rolled-and-tempered. B6X material can be cold worked following heat treatment as long as the end product hardness of the material corresponds to the requirements of a hardness table.

B7 and B7M bolting materials will be quenched in a liquid medium and then tempered. In the case of B7M components, such as bolts, studs, or screws, final heat treatment, which may be the tempering process at a minimum of 1150°F (620°C), shall, in any case, follow all machining and forming operations, including thread rolling and any form of cutting. Hardness testing, nondestructive testing or ultrasonic tensioning of the bolts has to be performed using a surface that has been prepared.

Grade B16 bolting material is to be heated between the temperatures of 1700 and 1750°F (925 to 955°C) and oil quenched. Minimum temperature will be in accordance with the requirements of the corresponding tables.

The austenitic stainless steels will all be subjected to carbide solution treatment (2 para -5 para based on the requirements of each category). Classes 1, 1B, 1C (B8R, B8S only), 2, 2B and 2C may be used on bar, wire and finished bolt components. Bolting components that have been finished may be covered by Class 1A (all grades) or Class 1C (grades B8RA and B8SA only). Class 1D is limited to bar and wire and finished bolting components which are machined directly out of Class 1D bar or wire and which have not undergone any subsequent hot or cold working.

Class 1 and 1B, and Class 1C Grades B8R and B8S: Following rolling of the bar, forging, or heading, both hot and cold, bolting material shall be heated to an ambient temperature and maintained a sufficient time at a temperature in which the chromium carbide will go into solution and then cooled at a rate which will avoid the formation of the carbide.

Class 1D: Rolled or forged grades B8, B8M, B8P, B8LN, B8MLN, B8CLNCuB, B8N, B8MN, B8R, and B8S bars shall be cooled quickly following hot working but when the temperature is not below 1750°C [955°C] so as to leave grain boundary carbides in solution. Class 1D will be limited to uses with temperatures below 850 °F [455 °C].

Class 1A and Class 1C Finished bolting components B8RA and B8SA: Components will be heated at ambient temperature, and maintained long enough at a temperature where the carbide of chromium will go to solution, after which it will be cooled at a rate adequate to inhibit the formation of the carbide.

Classes 2, 2B and 2C: Bolting material will be the carbide solution which is treated by heating to ambient temperature and retained for an adequate length of time at the temperature in which the chromium carbide will go into solution, and then at a rate sufficient to prohibit the precipitation of the carbide. After this treatment the bolting material will then be strain hardened to bring about the necessary properties.

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

Grade	Diameter (in.)	Min Tempering Temp (°F)	Tensile Strength (ksi)	Yield Strength (ksi)	Elongation in 4D (%)	Reduction of Area (%)	Hardness (max)
B5	Up to 4	1100	100	80	16	50	–
B6	Up to 4	1100	110	85	15	50	–
B6X	Up to 4	1100	90	70	16	50	20 HRC
B7	≤2.5	1100	125	105	16	50	321 HBW / 35 HRC
B7	>2.5–4	1100	115	95	16	50	321 HBW / 35 HRC
B7	>4–7	1100	100	75	18	50	321 HBW / 35 HRC
B7M	≤4	1150	100	80	18	50	235 HBW / 99 HRB
B7M	>4–7	1150	100	75	18	50	235 HBW / 99 HRB
B16	≤2.5	1200	125	105	18	50	321 HBW / 35 HRC
B16	>2.5–4	1200	110	95	17	45	321 HBW / 35 HRC
B16	>4–8	1200	100	85	16	45	321 HBW / 35 HRC

Grade, Diameter, in.	Heat Treatment	Tensile Strength, min, ksi	Yield Strength, min, 0.25% offset ksi	Elongation in 4D, min %	Reduction of Area, min %	Hardness, max
Classes 1 and 10D: BB, B8M, B8BN, B8N, B8CN1, all diameters	carbide solution treated	75	30	30	50	223 HRB W or 85 HRB
Classes 1 and 10D: B8, B8C, B8LC, all diameters	carbide solution treated	75	30	30	50	223 HRB W or 85 HRB
Class 1: B8C, B8T, all diameters	carbide solution treated	75	30	30	50	223 HRB W or 85 HRB
Class 1: B8BA, B8CA, B8CB, B8CN1, B8CA, B8CA1, all diameters	carbide solution treated in finished condition	75	30	30	50	223 HRB W or 85 HRB
Class 1: B8M, B8ML, B8MC, B8MCLn, all diameters	carbide solution treated	80	35	35	55	271 HRB W or 88 HRB
Class 1: B8, B8B, B8C, B8L, all diameters	carbide solution treated	75	35	30	50	223 HRB W or 85 HRB
Class 1B: B8L, B8M, all diameters	carbide solution treated	80	35	30	45	271 HRB W or 88 HRB
Class 1C: B8B, B8BN, B8T, all diameters	carbide solution treated	90	40	30	60	271 HRB W or 88 HRB
Class 2: B8B, B8B, B8T, B8L, D, or under	carbide solution treated	105	45	35	55	312 HRB W or 100 HRB
Class 2: B8M, B8M2, B8M2L, B8M4	carbide solution treated and strain hardened	115	50	35	60	312 HRB W or 100 HRB
Class 2B, B8M2, 2 and under	carbide solution treated and strain hardened	100	40	30	55	350 HRB W or 110 HRB
Class 2B: B8M2, B8M2L	carbide solution treated and strain hardened	85	35	30	45	360 HRB W or 110 HRB

A To satisfy the tensile specifications, Brinnel hardness will be more than 200 HBW (93 HRB).

B Class 1 is solution treated. Class 1A refers to a solution that is treated in the finished state to be resistant to corrosion; the reason is that heat treatment is important as per physical property demands. Class 2 solution hardened and strain hardened. Strain-hardened austenitic steels do not necessarily possess uniform properties across the section, especially in sizes greater than 3/4 in. in diameter.

C Maximum hardness of 241 HBW (100 HRB) is allowed at sizes ⅝ in. in diameter and lower.

D Center (core?) properties can be less than test report values, which are based on 1/2 radius.

The hardness will be in accordance with the requirements in the Tables of Mechanical Requirements. Testing Hardness testing will be conducted in accordance with either Specification A962/A962M or Test Methods E10/E18/F606/F606M.

Grade B7M - The grade will have a maximum hardness of 235 HBW or 99 HRB. The lowest hardness will not be lower than 200 HBW and 93 HRB. This hardness shall be checked by conducting testing of the hardness of each stud or bolt, according to Brinell or Rockwell B. Alternative testing 100% electromagnetic testing may be used to determine hardness provided that it is qualified by sampling by indentation hardness testing. All lots subjected to electromagnetic hardness are to be 100% inspected according to Practice E566. After electromagnetic testing has been completed on the hardness, a selected sample of at least 100 pieces of each steel heat in every lot shall be subjected to indentation hardness tests. All the samples should be as hard as required to allow acceptance of the lot.

In case any single sample falls below or beyond the given maximum or minimum hardness, the lot will be rejected and either reprocessed and retested or indentation hardness tested 100%.

Preparation of the surface to be tested on indentation hardness shall be done in accordance with Test Methods E18. The end of the bolt or stud shall be subjected to hardness tests. In the event that this is not practical, hardness tests will be carried out otherwise.

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

Bolt Specification	Nut Specification	Washer Specification
ASTM A193 Grade B5	ASTM A194 Grade 3	ASTM A36 Mild Steel
ASTM A193 Grade B6	ASTM A194 Grade 6	ASTM A240 Grade 410
ASTM A193 Grade B7	ASTM A194 Grade 2H	ASTM F436 Type 1
ASTM A193 Grade B7M	ASTM A194 Grade 2HM	ASTM F436 Type 1
ASTM A193 Grade B16	ASTM A194 Grade 16	ASTM F436 Type 1
ASTM A193 Grade B8	ASTM A194 Grade 8	ASTM A240 Grade 304
ASTM A193 Grade B8M	ASTM A194 Grade 8M	ASTM A240 Grade 316
ASTM A193 Grade B8T	ASTM A194 Grade 8T	ASTM A240 Grade 321

Austenitic steel fasteners are classified into classes and grades with defined grade symbols as per ASTM A193.

Class	Grade	Grade Symbol
Class 1	B8	B8
	B8C	B8C
	B8M	B8M
	B8P	B8P
	B8P	B8P
	B8T	B8T
	B8LN	B8F or B8LN
	B8MLN	B8G or B8MLN
	B8CLN	B8Y or B8CLN
	B8CLNCuB	B8CLNCuB
	B8ML4CuN	B8YY or B8ML4CuN
Class 1A	B8A	B8A
	B8CA	B8B or B8CA
	B8MA	B8D or B8MA
	B8PA	B8H or B8PA
	B8TA	B8J or B8TA
	B8LNA	B8L or B8LNA
	B8MLNA	B8K or B8MLNA
	B8NA	B8V or B8MA
	B8MNA	B8W or B8MNA
	B8MLCuNA	B9K or B8MLCuNA
	B8CLNA	B8Z or B8CLNA
	B8CLCuBA	B8ZA or B8CLCuBA
	B8ML4CuNA	B8ZZ or B8MLCuNA
Class 1B	B8N	B8N
	B8MN	B8Y or B8MN
	B8MLCuN	B9J or B8MLCuN
Class 1C	B8R	B9A or B8R
	B8RA	B9B or B8RA
	B8S	B9D or B8S
	B8SA	B9F or B8SA
Class 1D	B8	B94
	B8M	B95
	B8P	B96
	B8LN	B97
	B8MLN	B98
	B8N	B99
	B8MN	B100
	B8R	B101
	B8S	B102
	B8CLN	B103
	B8ML4CuN	B104
B8CLNCuB	B105
Class 2	B8	B8SH
	B8C	B8CSH
	B8P	B8PSH
	B8T	B8TSH
	B8T	B8TSH
	B8N	B8NSH
	B8M	B8MSH
	B8MN	B8YSH
	B8MLCuN	B8JSH
Class 2B	B8M2	B9G or B8M2
	B8	B9
Class 2C	B8M3	B9H or B8M3

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

S1. High Temperature Tests
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
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 reference to this specification.

S3. Hardness Testing of Grade B7M
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
For bolts or studs ≤ ½ in. (16 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 203-319 HBRW or 25-34 HRC.

S5. Product Marking
Bars 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 ½ in. (6 mm) in diameter and studs smaller than ½ in. (10 mm) in diameter for any stud, the grade symbol and manufacturer’s identification symbol may be marked with fewer than 3 symbols. The marking shall be a matter of agreement between the purchaser and the manufacturer.

S6. Stress Relieving
A stress-relieving operation shall follow straightening after heat treatment.
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
Bars shall be magnetic particles 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
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 MPa [345 MPa]. The residual stress at 100 h shall be 17 MPa [117 MPa] minimum.

S9. Grain Size Requirements for Non-H Grade Austenitic Steels Used Above 1000°F
For design high temperatures above 1000 °F [540 °C], the material shall have a grain size of No. 7 or coarser as determined by 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
The maximum hardness shall be the Rockwell C15 indenture through the thread roots. The hardness shall be taken on an area of at least 1 in. [25 mm] across, prepared by removing threads, and no more material than necessary shall be removed to prepare the flat areas. Hardness determinations shall be at the same frequency as tensile tests.

S11. Thread Forming
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
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 time shall be continued until the sample ruptures. Rupture life shall be 25 min. Testing is not required on material less than ½ in. [12.7 mm] thick.

S13. When a purchase order for bolting components invokes S12, the grade symbol applied shall be “B16R.”

S14. Purchaser Requirements
It is the purchaser’s responsibility to specify in the purchase order all information required for mechanical testing. Examples of such information include but are not limited to the following:
Reference to the applicable material specification and type, thickness, location, modifications, and hydrogen embrittlement levels.

S15. Magnetic Bolting Components
Bolting components made with zinc shall have ZnM marked after the grade symbol. Bolting components coated with cadmium shall have a CD marked after the grade symbol.

S16. Requirements for Service Temperature Exceeding 1000°F
When bolting materials of Grades B8, B8C, and B8T, are used in service at temperatures exceeding 1000°F, the following shall apply:
Following the carbide solution treatment and cooling, the material shall then be strain hardened to achieve the required properties. The minimum carbon content shall be 0.04 %.
The minimum carbon content shall be above 1000°F and 1950°F followed by quenching in water or rapid cooling by other means.

Appendix

1. STRAIN HARDENING OF AUSTENITIC STEELS
Strain hardening refers to the increment in strength and hardness occasioned by plastic deformation, which occurs below the recrystallization temperature (cold work). It is achieved in austenitic stainless steels by cold drawing to the required finished size by means of either cold drawing or other methods of oversizing bars or wire. Strain hardening properties are what limits the level of strain hardening that can be attained on any alloy. Moreover, the yields of strain that can be generated depend also on the variables of the process, including the total cross-section reduction, the die angle, and the bar size. With bigger diameter bars, plastic deformation will take place mostly in the outer parts of the bar in such a way that the higher the strength and hardness brought about by strain hardness is attainable in the outer parts of the bar. In other words, the lower the bar, the higher the penetration of strain hardening.

And so, mechanical properties of a particular strain hardened bolting part are not only subject to alloy, but also the size of the bar that it is machined out of. The minimum direction of the bar that may be utilized, however, is determined by the setup of the component such that the setup may influence strength of the component.

An example of this is machining a stud of a certain alloy and size out of a smaller diameter bar than a bolt of the same alloy and size since a large diameter bar is needed to fit the head of the bolt. It is therefore likely that the stud will have a higher strength when compared to a similar size bolt in an alloy.

2. COATINGS AND APPLICATION LIMITS
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].