What is the difference between A2 and A4 stainless steel bolts?

A2 (304) is ideal for standard outdoor and industrial use, while A4 (316) contains molybdenum, offering higher corrosion resistance for marine, chemical, and salt-spray environments.

Will stainless steel bolts rust over time?

Under severe chemical or chloride exposure, A2 may develop slight surface corrosion. A4/316 performs better in harsh environments. We also offer passivation treatment for enhanced protection.

China Fastener Black Alloy Steel Hexagon Hex Socket Flat Countersunk Head Screw DIN7991

Name: China Fastener Black Alloy Steel Hexagon Hex Socket Flat Countersunk Head Screw DIN7991
Brand: Ningbo Mianxuan Import &Export Co., Ltd.
SKU: 2116368435

Zhejiang, ChinaNingbo Mianxuan Import &Export Co., Ltd.

US$0.10

10,000-49,999 Pieces

US$0.05

50,000-99,999 Pieces

US$0.002

100,000+ Pieces

Sample price:US$0.00/piece.Request sample

Product profile

Customization

Available

Material

Alloy Steel

Type

Countersunk Head

Model NO.

DIN 7991

Groove

Hexagon

Connection

Common Bolt

Head Style

Counter Sunk Bolt

Standard

DIN, GB, ANSI, BSW, JIS, ISO

Grade

8.8

Thread

Unc, Unf, Un, Metric Coarse, Fine

Surface

Plain, Zinc Plated (Blue, White, Black, Yellow), N

Quality

100% Tested

Price

Factory Price

Lead Time

15-30 Days

Package

Standard Package or Customer's Packing

Box

Customer's Brand Box/Plain Box

MOQ

Can Be Negotiated

Shipment

by Sea / Truck / Plane / Express

Exterior Finish

Customized

Sample

Available

Customized

Available

Service

One-Stop Service

Online Sales

24 Hours Online

OEM/ODM

Available

Transport Package

Bulk Packaging, Small Box(Glue Box, Color Box)

Specification

M3 - M24

Trademark

Mianxuan, Customized

Origin

Ningbo, China

HS Code

7318159001

Production Capacity

1000tons Per Month

Key features

Comprehensive Standard Compliance: Meets DIN, ISO, ANSI, JIS, GB, and BSW standards for global compatibility.

Customizable Exterior Finish: Available in Plain, Black, Zinc, Yellow Zinc, HDG, and Dacromet finishes.

Wide Size Range: Standard sizes M3-M24 available with non-standard options upon request.

High Grade Strength: Offers Grade 8.8 strength with materials including Alloy, Carbon, and Stainless Steel.

Rigorous Quality Testing: 100% tested for torque, hardness, thread precision, and salt spray resistance.

OEM and ODM Services: Full customization for samples, drawings, packaging, and labeling available.

Flexible Lead Time: Production time ranges from 15 to 30 days depending on season and order volume.

Sample Availability: Free or low-cost samples provided for quality and dimension confirmation.

Company profile

High Repeat Buyers ChoiceYears of Export ExperienceR&D CapabilitiesODM Services

Ningbo Mianxuan Import &Export Co., Ltd.

Zhejiang, China

Business Type: Manufacturer/FactoryExport Year: 2014-07-01Nearest Port: Ningbo, Zhapu, ShanghaiAverage Response Time: ≤4.43hTerms of Payment: LC, T/T, Western UnionInternational Commercial Terms(Incoterms): FOB, EXW, CFR, CIF

AI-Powered supplier vetting

SummaryNingbo Mianxuan Import & Export Co., Ltd. is identified as a China-based manufacturer/factory offering vehicle parts, CNC machining, stamping, casting, die-casting, fasteners, plastic, and rubber products. It reports TS 16949 and ISO 9001 certifications, more than 10 production lines, 6–10 quality-control staff, and shipment inspection reports with material certificates. The supplier provides 3D software design, ODM, and several customization options, but reports no new products in the past year, no SDK, and no OEM service for popular brands. Service-management documentation is weak: no written procedures or records are reported for assessments, corrective actions, or complaint handling. It has no in-stock capability, overseas warehouse, or overseas showroom. Financial records are indicated for 2023–2025, but their results are not provided, so financial credibility cannot be determined. No customer cases are supplied.

Supplier typeThe supplier is explicitly identified as a manufacturer/factory and limited company in Ningbo, Zhejiang, China. Its stated scope covers fasteners, metal products, machinery, vehicle parts, CNC machining, stamping, casting, die-casting, plastic, and rubber parts, indicating broad manufacturing and industrial-product coverage.

CertificationsThe supplier reports holding TS 16949 and ISO 9001 management-system certifications. It also states that each shipment will include an effective inspection report and corresponding material certificate, providing explicit evidence of documented quality-related controls.

After-Sales capabilityThe supplier reports no written procedures or records for service-capability assessment, corrective and preventive actions, or effective customer-complaint handling. It also lacks in-stock service, overseas warehouse, and overseas showroom capabilities, indicating a documented weakness in after-sales and service infrastructure.

Production capacityThe supplier reports more than 10 production lines, 6–10 quality-control staff, and a product range spanning vehicle parts, CNC machining, stamping, casting, die-casting, fasteners, plastic, and rubber parts. It is located near Ningbo and Shanghai ports and reports 21 qualified suppliers, but has no inventory capability and peak-season lead-time data is inconsistent or unclear.

Customization capabilityThe supplier explicitly offers customization from samples, customization from designs, full customization, minor customization, 3D software design services, and ODM services. These statements provide direct evidence of broad product and design customization capability.

Product Q&A

Q:What thread standards do you follow?

Our screws comply with DIN, ISO, ANSI, and JIS standards, and can also be customized according to customer drawings.

Q:What stainless steel grades do you supply for bolts?

We supply multiple grades including A2-70, A2-80, A4-70, A4-80, 304, 316, and 410SS, suitable for different mechanical strength and corrosion-resistance requirements.

Q:Do you provide samples before mass production?

Yes, we offer free or low-cost samples for quality and dimension confirmation prior to order.

Q:How do you control product quality?

Every batch is tested for torque, hardness, thread precision, and salt spray corrosion resistance, following ISO 9001 quality system standards.

Q:Do you offer OEM or customized production?

Yes. We can produce screws according to samples, technical drawings, or specific drive/head combinations, and offer custom packaging and labeling.