In late December 2025, we received an email from one customer in Jordan. He asked several pieces of bolts and nuts separately and sent us customized drawing at the same time. Reviewing drawing and goods description, we made our offer and reply. In the following weeks, we kept discussing details in the drawing and achieved agreement on the specifications. Later on, we got purchase order of all the items.

Goods list

NO.	DESCRIPTION	SIZE	Qty	Unit
1	B-B Stud	A193-B7M M58*3.0P*1180L-70S/0S(Left)	18	pc
2	HEX Nut Left	S45C M58*3.0P*(60H)-(Left)	18	pc
3	Coverd Nut	S45C M58*3.0P*(122H)-(Left)	18	pc
4	B-B Stud (Right)	A193-B7M M58*3.0P*1180L-70S/0S(Right)	18	pc
5	HEX Nut ( Right)	S45C M58*3.0P*(60H)-(Right)	18	pc
6	Coverd Nut (Right)	S45C M58*3.0P*(122H)-(Right)	18	pc
7	Washer	SS400 OD95*ID58*8T	72	pc

B7M Stud Bolts Chemical Composition

ASTM A193 B7M is a chromium-molybdenum alloy steel stud bolt, designed for sour service and high-pressure applications. Its chemical composition (percent) shows as below:

Element	Content Range
Carbon (C)	0.38 – 0.48
Manganese (Mn)	0.75 – 1.00
Phosphorus (P)	≤ 0.035
Sulfur (S)	≤ 0.040
Silicon (Si)	0.15 – 0.35
Chromium (Cr)	0.80 – 1.10
Molybdenum (Mo)	0.15 – 0.25

B7M Mechanical Property

All B7M stud bolts undergo quenching and tempering heat treatment, with the following key mechanical properties (minimum requirements):

• Tensile Strength: 100 ksi (690 MPa)
• Yield Strength (0.2% offset): 80 ksi (552 MPa)
• Elongation in 2 inches: 18%
• Reduction of Area: 50%
• Hardness: 235 HBW or 99 HRB (max)
• NACE MR0175/ISO 15156 Compliance: Suitable for sour service environments

S45C Nuts Chemical Composition

S45C is a medium carbon steel, widely used for general industrial nuts due to its good machinability and cost-effectiveness. Chemical composition (percent):

Element	Content Range
Carbon (C)	0.42 – 0.48
Silicon (Si)	0.15 – 0.35
Manganese (Mn)	0.6 – 0.9
Phosphorus (P)	≤ 0.03
Sulfur (S)	≤ 0.035

Compatibility of B7M Stud Bolts & S45C Nuts

ASTM A193 B7M stud bolts and S45C nuts (Grade 8) are highly compatible for most industrial applications, with the following advantages:

• Strength Matching: S45C Grade 8 nuts match the tensile and yield strength of B7M stud bolts, avoiding thread slipping or breakage under load.
• Processing Adaptability: Both materials have good machinability, ensuring precise thread fit and easy installation.
• Cost-Effective: S45C nuts are more affordable than alloy steel nuts (e.g., ASTM A194 2H), reducing assembly costs without compromising performance.
• Applicable Scenarios: Suitable for general industrial, mechanical, piping, and non-sour service high-pressure environments (for sour service, use NACE-compliant nuts).

Note: For extreme sour service (H2S-containing environments), S45C nuts should be replaced with NACE MR0175-compliant nuts to ensure corrosion resistance.

Inspection Photos

Customization Supported

In addition to standard-sized ASTM A193 B7M stud bolts and S45C nuts, we support customization according to your drawings or specifications. Customization options include:

• Custom sizes (thread diameter, length, nut thickness)
• Special heat treatment requirements
• Surface treatment (zinc plating, hot-dip galvanizing, Xylan coating)
• Special thread standards (UNC, UNF, metric etc)

Our professional engineering team provides technical support for customization, ensuring that the products meet your specific application needs.

Choose Us

Zizi Engineering Co Ltd is committed to providing one-stop solutions from drawing design, manufacturing to finished product delivery.

We welcome inquiries or drawing from project developers, contractors and enterprise clients and will offer professional technical support and efficient manufacturing services. 

Look forward to being your reliable partner.

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