Part 2: Large Screws

Chapter 1 Product Classification

1、 Product categories

（1） Hexagonal bolt (HEXAGON HEAD BOLTS)

1. The reference standard for British bolts is ANSI/ASME B18.2.1, and the reference standard for Japanese bolts is JIS B1180 (Weibull's Tooth). The British system refers to BSW916 (Webster's Tooth).

(1) HEX MACHINE BOLT: Non Hua Si, with bundled tail, half tooth hexagonal bolt,

(2) HEX TAP BOLT: No Hua Si, No Bundle Tail, Full Tooth Hexagonal Bolt,

(3) HEX CAP SCREWS: with Huasi, bundled tail, half tooth hexagonal bolts,

2. The reference standards for metric bolts are as follows, and their differences are shown in the table:

（2） Carriage bolts/round headed square neck bolts:

ANSI/ASME B18.5；DIN603 ； ISO 8677；GB12；GB14

（3） Hexagon socket head cap screws:

DIN912 ； GB70 ； ISO4762 ； ANSI /ASME B18.3

（4） Hexagon Head Lag Screws:

ANSI/ASME B18.2.1 DIN 571

（5） Furniture screws: according to customer standards

（6） Hexagon Flange Bolt: IFI 111 GB 5787 DIN 921

2、 Product identification

（1） Diagram of each part of the bolt:

（2） Identification of bolts:

3、 Logo and performance level

(1) Sign. Hexagonal head bolts and screws (thread diameter ≥ 5mm). Use raised or recessed lettering on the top of the head, or recessed lettering on the side of the head. Including performance level and factory standards. Carbon steel: The strength grade marking code consists of two numbers separated by a "·". The meaning of the number before the "·" in the tag code represents the nominal tensile strength, such as the "4" in 4.8 grade representing 1/100 of the nominal tensile strength of 400N/MM2. The meaning of the "·" and the numerical part after the dot in the marking code represents the yield strength ratio, which is the ratio of the nominal yield point or nominal yield strength to the nominal tensile strength. The yield point of a 4.8 grade product is 320 N/mm2. The strength grade mark of stainless steel products consists of two parts separated by a "-". The symbol before "-" in the symbol code indicates the material. For example, the symbol "-" after A2, A4, etc. indicates strength, such as A2-70

(2) Level. Carbon steel: The mechanical performance grades of metric bolts can be divided into 10 performance grades: 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9, and 12.9. Stainless steel is divided into 60, 70, and 80 (austenitic); 50,70,80110 (martensite); 45, 60 (ferrite) three types.

Chapter 2 Process Flow

1、 Production process:

（1） Pan Yuan:

1. Disk element refers to the original disk strips purchased from the manufacturer, and a disk element mainly includes the following parameters:

A、 Brand B, Product Name C, Specification D, Material

E、 Furnace number or batch number F, quantity/weight

2. The main chemical components in steel are: C Mn、P、S、Si、Cu、Al， The lower the content of Al and Cu, the better.

（2） Annealing: Eliminating internal stress during wire processing and increasing its malleability.

（3） Acid washing: Remove a layer of oxide film on the surface of the wire, and lubricate the surface of the wire to facilitate wire extraction.

（4） Wire drawing: In order to achieve the desired wire diameter.

Hydrochloric acid water washing, grass washing (60-80 ℃), phosphate salt water washing, lubricant washing

（5） Starting (forming) and rolling teeth: completing the product shape and shaping the tooth shape.

（6） Heat treatment: changing the mechanical properties of screws.

（7） Electroplating: Surface treatment carried out to meet customer requirements while also enhancing certain properties of screws. Such as rust prevention, aesthetics, etc.

（8） Packaging: Pack the product into boxes/boxes according to standards or customer requirements.

（9） The above processes are detailed in Part 5.