1、 Bolt overview

螺栓，机械零件，配用螺母的圆柱形带螺纹的紧固件。螺栓：由头部和螺杆（带有外螺纹的圆柱体）两部分组成的一类紧固件，需与螺母配合，用于紧固连接两个带有通孔的零件。这种连接形式称螺栓连接。如把螺母从螺栓上旋下，又可以使这两个零件分开，故螺栓连接是属于可拆卸连接。

Bolts, mechanical parts, cylindrical threaded fasteners with nuts. Bolt: a kind of fastener composed of head and screw (cylinder with external thread), which needs to be matched with nut to fasten and connect two parts with through holes. This type of connection is called bolt connection. If the nut is unscrewed from the bolt, the two parts can be separated, so the bolt connection belongs to removable connection.

按连接的受力方式分：分普通的和有铰制孔用的。按头部形状分：有T形的，六角头的，圆头的，方形头的，沉头的等等。其中六角头是常用的。一般沉头用在要求连接的地方。应用非常广泛。

According to the stress mode of connection, it is divided into ordinary and reamed holes. According to the head shape: T-shaped, hexagonal, round, square, countersunk, etc. Hexagon head is commonly used. Generally, countersunk head is used where connection is required. It is widely used.

螺栓有很多叫法，每个人的叫法可能都不同，有人叫成螺钉，有人叫成螺栓钉，有人叫成标准件，有人叫成紧固件。虽然有这么多叫法，但意思都是一样的，都是螺栓。螺栓是紧固件的通用说法。螺栓的原理是利用物体的斜面圆形旋转和摩擦力的物理学和数学原理，循序渐进地紧固器物机件的工具。

There are many names for bolts, and everyone may have different names. Some are called screws, some are called bolt nails, some are called standard parts, and some are called fasteners. Although there are so many names, they all mean the same. They are all bolts. Bolt is a common term for fasteners. The principle of bolt is a tool for fastening utensils and mechanical parts step by step by using the physical and mathematical principles of inclined circular rotation and friction of objects.

螺栓在日常生活当中和工业生产制造当中，是少不了的，螺栓也被称为工业之米。可见螺栓的运用之广泛。螺栓的运用范围有：电子产品，机械产品，数码产品，电力设备，机电机械产品。船舶，车辆，水利工程，甚化学实验上也有用到螺栓。反正是超多地方都有用到螺栓的。特如数码产品上面用到的精密螺栓。DVD，照相机、眼镜、钟表、电子等使用的微型螺栓;电视、电气制品、乐器、家具等之一般螺栓;于工程、建筑、桥梁则使用大型螺栓、螺帽;交通器具、飞机、电车、汽车等则为大小螺栓并用。螺栓在工业上负有重要任务，只要地球上存在着工业，则螺栓之功能永远重要。

Bolts are indispensable in daily life and industrial production and manufacturing. Bolts are also known as the rice of industry. It can be seen that bolts are widely used. The application scope of bolts includes: electronic products, mechanical products, digital products, power equipment, electromechanical mechanical products. Bolts are also used in ships, vehicles, hydraulic engineering, and even chemical experiments. Anyway, bolts are used in many places. Such as precision bolts used in digital products. Micro bolts for DVD, camera, glasses, clocks, electronics, etc; General bolts for TV, electrical products, musical instruments, furniture, etc; As for engineering, construction and bridges, large bolts and nuts are used; Transportation equipment, aircraft, trams, automobiles, etc. are both large and small bolts. Bolts have important tasks in industry. As long as there is industry on the earth, the function of bolts will always be important.

二、螺栓标志、性能等级

2、 Bolt mark and performance grade

（1）、标志。六角头螺栓和螺钉（螺纹直径≥5mm）。需在头部顶面用凸字或凹字标志，或在头部侧面用凹字标志。包括性能等级、厂标。碳钢：强度等级标记代号由“·”隔开的两部分数字组成。标记代号中“·”前数字部分的含义表示公称抗拉强度，如4.8级的“4”表示公称抗拉强度400N/MM2的1/100。标记代号中“·”和点后数字部分的含义表示屈强比，即公称屈服点或公称屈服强度与公称抗拉强度之比。如4.8级产品的屈服点为320N/mm2。不锈钢产品强度等级标志由“—”隔开的两部分组成。标志代号中“—”前符号表示材料。如：A2，A4等标志“—”后表示强度，如：A2-70

(1) . signs. Hexagon head bolts and screws (thread diameter ≥ 5mm). It is necessary to mark the head with convex or concave characters on the top surface or concave characters on the side of the head. Including performance grade and factory standard. Carbon steel: the strength grade marking code consists of two parts separated by "·". The meaning of the number before "·" in the marking code indicates the nominal tensile strength. For example, "4" in grade 4.8 indicates 1 / 100 of the nominal tensile strength of 400N / mm2. The meaning of "·" and the number after the point in the marking code indicates the yield ratio, that is, the nominal yield point or the ratio of nominal yield strength to nominal tensile strength. For example, the yield point of grade 4.8 products is 320n / mm2. The strength grade mark of stainless steel products consists of two parts separated by "-". The symbol before "-" in the sign code indicates the material. For example, A2, A4 and other signs indicate strength after "-", such as A2-70

（2）、等级。碳钢：公制螺栓机械性能等级可分为：3.6、4.6、4.8、5.6、5.8、6.8、8.8、9.8、10.9、12.9共10个性能等级。不锈钢分为60,70,80(奥氏体)；50,70,80,110(马氏体)；45,60（铁氏体）三类。

(2) , grade. Carbon steel: the mechanical property grade of metric bolt 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 (austenite); 50,70,80110 (martensite); 45,60 (ferrite) three types.

三、目前市场螺栓标准件主要有碳钢、不锈钢、铜三种材料。

3、 At present, the bolt standard parts in the market mainly include carbon steel, stainless steel and copper.

（一）碳钢。我们以碳钢料中碳的含量区分低碳钢，中碳钢和高碳钢以及合金钢。

（1） Carbon steel. We distinguish low carbon steel, medium carbon steel, high carbon steel and alloy steel by the content of carbon in carbon steel.

1、低碳钢C%≤0.25%国内通常称为A3钢。国外基本称为1008，1015，1018，1022等。主要用于4.8级螺栓及4级螺母、小螺栓等无硬度要求的产品。（注：钻尾钉主要用1022材料。）

1. Low carbon steel C% ≤ 0.25% is commonly referred to as A3 steel in China. It is basically called 1008101510181022 abroad. It is mainly used for grade 4.8 bolts, grade 4 nuts, small bolts and other products without hardness requirements（ Note: the drill tail nail is mainly made of 1022 material.)

2、中碳钢0.25%

2. Medium carbon steel 0.25% < C% ≤ 0.45%   It is generally called No. 35 and No. 45 steel in China and 1035, ch38f, 1039, 40ACr, etc. in foreign countries. It is mainly used for Grade 8 nuts, grade 8.8 bolts and grade 8.8 hexagon socket products.

3、高碳钢C%>0.45%。目前市场上基本没使用

3. High carbon steel C% > 0.45%. It is basically not used in the market at present

4、合金钢：在普碳钢中加入合金元素，增加钢材的一些特殊性能：如35、40铬钼、SCM435，10B38。芳生螺丝主要使用SCM435铬鉬合金钢，主要成分有C、Si、Mn、P、S、Cr、Mo。

4. Alloy steel: alloy elements are added to ordinary carbon steel to increase some special properties of steel, such as 35, 40 chromium molybdenum, SCM435, 10b38. The aromatic screw mainly uses SCM435 chromium molybdenum alloy steel, and the main components are C, Si, Mn, P, s, Cr and mo.

（二）不锈钢。

（2） Stainless steel.

主要分奥氏体（18%Cr、8%Ni）耐热性好，耐腐蚀性好，可焊性好。A1，A2，A4

It is mainly divided into austenite (18% Cr, 8% Ni) with good heat resistance, corrosion resistance and weldability. A1，A2，A4

马氏体、13%Cr耐腐蚀性较差，强度高，耐磨性好。C1，C2，C4铁素体不锈钢。18%Cr镦锻性较好，耐腐蚀性强于马氏体。目前市场上进口材料主要是日本产品。按级别主要分SUS302、SUS304、SUS316。

Martensite and 13% Cr have poor corrosion resistance, high strength and good wear resistance. C1, C2, C4 ferritic stainless steel. 18% Cr has better upsetting property and stronger corrosion resistance than martensite. At present, the imported materials on the market are mainly Japanese products. It is mainly divided into SUS302, SUS304 and SUS316 by level.

（三）铜。常用材料为黄铜…锌铜合金。市场上主要用H62、H65、H68铜做标准件。

（3） Copper. Common materials are brass... Zinc copper alloy. H62, H65 and H68 copper are mainly used as standard parts in the market.

螺栓按照材料分：碳钢的级别与不锈钢的级别不一样。

Bolts are divided according to material: the grade of carbon steel is different from that of stainless steel.

碳钢常用的有：3.6级，4.6级，4.8级，5.6级5.8级6.8级8.8级9.8级10.9级12.9级，可以查GB/T3098.1-2000版。

Commonly used carbon steels are: grade 3.6, grade 4.6, grade 4.8, grade 5.6, grade 5.8, grade 6.8, grade 8.8, grade 9.8, grade 10.9 and grade 12.9. You can refer to GB / t3098.1-2000.

每种级别都有自己的规定，包括材料牌号，产品硬度，抗拉强度，屈服强度，破坏扭力等。

Each grade has its own regulations, including material grade, product hardness, tensile strength, yield strength, failure torque, etc.

比如以9.8级螺栓为例：9指材料的公称抗拉强度为900N/mm2，8指屈服强度与抗拉强度的比值0.8（取小数点后的一位8），这两个数中间加点就表示9.8。其硬度HV290-360.

For example, take grade 9.8 bolt as an example: 9 refers to the nominal tensile strength of the material is 900N / mm2, and 8 refers to the ratio of yield strength to tensile strength of 0.8 (take the eighth place after the decimal point). The addition of a point between these two numbers means 9.8. Its hardness is hv290-360

四、各种螺栓技术参数

4、 Technical parameters of various bolts

依相关标准，螺栓性能等级分3.6、4.6、4.8、5.6、6.8、8.8、9.8、10.9、12.9等10余个等级，其中8.8级及以上螺栓材质为低碳合金钢或中碳钢并经热处理（淬火、回火），通称为高强度螺栓，其余通称为普通螺栓。螺栓性能等级标号有两部分数字组成，分别表示螺栓材料的公称抗拉强度值和

According to relevant standards, the performance grades of bolts are divided into more than 10 grades, such as 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9 and 12.9. Among them, bolts of grade 8.8 and above are made of low-carbon alloy steel or medium carbon steel and are generally called high-strength bolts after heat treatment (quenching and tempering), and the rest are generally called ordinary bolts. The bolt performance grade is composed of two numbers, which respectively represent the nominal tensile strength value and