ASTM A193 is a fastener specification covering alloy and stainless steel bolts and threaded studs for use with flanges, valves, pressure vessels, and fittings for high temperature and high pressure service. Common grades are below.
B7 Alloy steel, AISI 4140/4142 quenched and tempered
B8 Class 1 Stainless steel, AISI 304, carbide solution treated.
B8M Class 1 Stainless steel, AISI 316, carbide solution treated.
B16 A heat-treated chromium-molybdenum-vanadium steel for high-pressure, high-temperature service.
A193 Grade B7 Class Bolts are manufactured from AISI 4140/4142 low Carbon Alloy Steel Grades followed by quencing & tempering. We manufacture these Bolts with great precision & Quality. These grade bolts are also denoted as Grade 7 Bolts,B7 Bolts etc. We Also offer B7 Studs/B7 threaded bars/B7 Threaded rods. RS aslo offer Hex A193 B7 Bolt Fasteners in various sizes & Coatings.
ASTM A193 Grade B7 Heat treatment
Grade B7 is made out of Chromium Molybendum steel, normally AISI 4140, heat treated to 28-32 Rockwell Hardness, 125,000 PSI tensile strength, 105, 000 PSI yield. It will hold strength up to 1000 degrees F.
ASTM A193 Grade B7 Chemical Composition
| Elements | Range |
| Carbon | 0.37-0.49 % D |
| Manganese, max | 0.65-1.10 % |
| Phosphorus, max | 0.035 % |
| Sulfur, max | 0.040 % |
| Silicon | 0.15 - 0.35 % |
| Chromium | 0.75-1.20 % |
| Molybdenum | 0.15-0.25 % |
ASTM A193 Grade B7 Mechanical Properties - Metric Sizes
| Diameter mm | Min Tempering Temperature, °C | Tensile Strength min, MPa | Yield strength, min, 0.2% offset, MPa | Elongation in 4D min, % | Reduction of Area, min, % | Hardness, max |
| M64 and Under | 593 | 860 | 720 | 16 | 50 | 321 HBW or 35 HRC |
| over M64 to M100 | 593 | 795 | 655 | 16 | 50 | 321 HBW or 35 HRC |
| over M100 to M180 | 593 | 690 | 515 | 18 | 50 | 321 HBW or 35 HRC |
ASTM A193 Grade B7 Mechanical Properties - Inch Sizes
| Diameter Inch | Min Tempering Temperature, °C | Tensile Strength min, ksi | Yield strength, min, 0.2% offset, ksi | Elongation in 4D min, % | Reduction of Area, min, % | Hardness, max |
| 2.5 and under | 1100 | 125 | 105 | 16 | 50 | 321 HBW or 35 HRC |
| over 2.5 to 4 | 1100 | 115 | 95 | 16 | 50 | 321 HBW or 35 HRC |
| over 4 to 7 | 1100 | 100 | 75 | 18 | 50 | 321 HBW or 35 HRC |
Marking
Both the grade symbol and manufacturer’s identification are applied to the heads of bolts and one end of studs. Marking on very small diameter fasteners can be omitted
Dimensions
Unless otherwise specified by customers, headed bolts shall be heavy hex with dimensions covered under ASME B18.2.1.Length of fully thread studs is doesn’t included the chamfered ends, it is measured from first thread to first thread.
A193 Recommended Nuts,Bolts & Washer
| Bolt Grade | Nuts | Washers |
| A193 B7 | A194 2H | F436 |
| A193 B8 | A194 Grade 8 | SS304 |
| A193 B8M | A194 Grade 8M | SS316 |