Can I use 2H nuts on B16 studs?

Specify A194 grade 7 for B16. Grade 7 is a Cr-Mo nut that holds up at the temperatures B16 is chosen for.

Is B7 suitable for cold service?

Not by itself: B7 has no mandatory impact test. Use A320 L7 with a Charpy test at −101 °C. Tell us the design temperature and we will advise.

B7 and L7 have the same strength – what is the difference?

The impact test. L7 is tested for toughness at low temperature; B7 is not. L7 costs more because of the testing.

Do you make inch and metric studs?

Yes. We cut, chamfer and mark stud bolts in-house to ASME B16.5 flange sizes with UNC / 8UN threads, and to DIN 976 / ISO metric threads.

Which certificate comes with the studs?

EN 10204 3.1 as standard, with heat number marked on every stud. 3.2 with a third-party inspector on request – see our certificate guide.

Can B7 studs be coated?

Yes: zinc, PTFE / Xylan, TAKECOAT-1000 or hot-dip galvanized. Check the coating's temperature limit, and use torque values matched to the coating.

Technical guide

B7, B7M, B16 or L7 – which stud bolt grade?

B7 is the default for flange bolting in high-pressure process service. Choose B7M for sour (H₂S) service where hardness must be limited, B16 for elevated temperatures, L7 for low-temperature service with impact testing down to −101 °C, and B8M when the bolt itself must resist corrosion.

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Short answer

B7 – Cr-Mo steel, the standard flange stud. Nut: A194 2H.
B7M – B7 tempered to max 235 HBW for sour service. Nut: 2HM.
B16 – Cr-Mo-V for elevated temperature; relaxes less than B7. Nut: A194 7.
L7 – B7 strength, Charpy-tested at −101 °C (−150 °F). Nut: A194 7, impact-tested.
B8M – 316 stainless for corrosive service. Nut: 8M.

Comparison

The grades side by side.

Minimum values up to M64 / 2½" (B7M up to M100 / 4"). Larger diameters have lower minimums – see the table in ASTM A193 or A320.

Grade	Standard	Material	Min. tensile	Min. yield	Max. hardness	Nut (A194)	Typical service
B7	ASTM A193	Cr-Mo alloy steel, quenched and tempered	860 MPa (125 ksi)	720 MPa (105 ksi)	321 HBW / 35 HRC	2H	General high-pressure and high-temperature flange bolting
B7M	ASTM A193	Cr-Mo alloy steel, tempered to lower hardness	690 MPa (100 ksi)	550 MPa (80 ksi)	235 HBW / 99 HRB	2HM	Sour service and hydrogen stress cracking environments
B16	ASTM A193	Cr-Mo-V alloy steel	860 MPa (125 ksi)	725 MPa (105 ksi)	321 HBW / 35 HRC	7	Elevated temperature – keeps preload better than B7
L7	ASTM A320	Cr-Mo alloy steel, impact-tested	860 MPa (125 ksi)	720 MPa (105 ksi)	321 HBW / 35 HRC	7 (impact-tested, marked L)	Low-temperature service, Charpy test at −101 °C
B8M Class 1	ASTM A193	Stainless 316, solution treated	515 MPa (75 ksi)	205 MPa (30 ksi)	223 HBW / 96 HRB	8M	Corrosive service, low strength
B8M Class 2	ASTM A193	Stainless 316, strain hardened	760 MPa (110 ksi) ≤ M20	655 MPa (95 ksi) ≤ M20	321 HBW / 35 HRC	8M	Corrosive service, higher strength – drops with diameter

How to choose

Four questions decide the grade.

01Is there H₂S or a risk of hydrogen cracking?Use the M grades: B7M with 2HM nuts. Their hardness is capped at 235 HBW and every piece is hardness tested – the usual choice where NACE MR0175 / ISO 15156 applies.
02Does the joint run hot?At elevated temperature B7 gradually loses preload. B16 (Cr-Mo-V) keeps its strength and relaxes less. Pair it with A194 grade 7 nuts.
03Does the joint run cold?B7 has no mandatory impact test. For low-temperature service specify A320 L7, Charpy-tested at −101 °C, with impact-tested grade 7 nuts.
04Must the bolt itself resist corrosion?Choose B8M (316). Class 1 is soft; Class 2 is strain hardened for more strength. Or keep B7 and add a coating – see our coatings guide. Note that a coating can lower the allowable service temperature.

FAQ

Questions we get every week.

Can I use 2H nuts on B16 studs?: Specify A194 grade 7 for B16. Grade 7 is a Cr-Mo nut that holds up at the temperatures B16 is chosen for.
Is B7 suitable for cold service?: Not by itself: B7 has no mandatory impact test. Use A320 L7 with a Charpy test at −101 °C. Tell us the design temperature and we will advise.
B7 and L7 have the same strength – what is the difference?: The impact test. L7 is tested for toughness at low temperature; B7 is not. L7 costs more because of the testing.
Do you make inch and metric studs?: Yes. We cut, chamfer and mark stud bolts in-house to ASME B16.5 flange sizes with UNC / 8UN threads, and to DIN 976 / ISO metric threads.
Which certificate comes with the studs?: EN 10204 3.1 as standard, with heat number marked on every stud. 3.2 with a third-party inspector on request – see our certificate guide.
Can B7 studs be coated?: Yes: zinc, PTFE / Xylan, TAKECOAT-1000 or hot-dip galvanized. Check the coating's temperature limit, and use torque values matched to the coating.

Next step

Configure, download or ask.

Reviewed October 2026 by HBS Solutions. Based on ASTM A193/A193M, ASTM A320/A320M and ASTM A194/A194M. Values are minimums from the standard; always check the edition and options named in your project specification.

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