CN108913992B

CN108913992B - Steel for bolt and application thereof

Info

Publication number: CN108913992B
Application number: CN201810699525.7A
Authority: CN
Inventors: 徐林丽
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-06-29
Filing date: 2018-06-29
Publication date: 2020-07-17
Anticipated expiration: 2038-06-29
Also published as: CN108913992A

Abstract

The invention discloses a bolt steel, which comprises iron and the following components in percentage by mass: 0.25 to 0.33 percent of carbon, 0.1 to 0.6 percent of silicon, 1.3 to 1.7 percent of manganese, less than or equal to 0.035 percent of phosphorus, less than or equal to 0.035 percent of sulfur, 0.04 to 0.10 percent of titanium, 0.0008 to 0.0035 percent of boron, 0.02 to 0.2 percent of aluminum, less than or equal to 0.5 percent of copper and less than or equal to 0.5 percent of nickel. The invention also correspondingly provides an application of the steel for the bolt. According to the invention, through adjusting the components of the bolt and the use amount of each component, the finally obtained bolt has high comprehensive performance such as high strength, excellent cold heading performance, excellent delayed fracture resistance and the like.

Description

Steel for bolt and application thereof

Technical Field

The invention belongs to the technical field of high-strength fasteners, and particularly relates to bolt steel and application thereof.

Background

The fastener is a mechanical part with wide application, and has wide application in the fields of vehicles, ships, railways, bridges, buildings and the like. The fastener is the mechanical industry foundation member, and the demand is very big, and the fastener includes various bolts, riveted joint, nut, rivet etc.. According to relevant standards, the performance grade of the bolt is 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9 and other 10 grades, wherein the bolt of 8.8 grade and above is obtained by heat treatment of low-carbon alloy steel or medium-carbon steel, and is generally called a high-strength bolt, and the rest is generally called a common bolt.

Because the bolt is used for connecting various structural materials and needs to bear large pressure and shearing force, the bolt needs to ensure high comprehensive performance such as high strength, excellent cold heading performance and the like. The existing material for the bolt is difficult to balance in the aspects of strength, cold heading performance and the like, and the use safety is influenced.

Disclosure of Invention

The invention aims to overcome the defects and shortcomings in the background technology and provide the bolt steel with excellent comprehensive performance and the application thereof. In order to solve the technical problems, the technical scheme provided by the invention is as follows:

the steel for the bolt comprises the following components in percentage by mass: 0.25 to 0.33 percent of carbon, 0.1 to 0.6 percent of silicon, 1.3 to 1.7 percent of manganese, less than or equal to 0.035 percent of phosphorus, less than or equal to 0.035 percent of sulfur, 0.04 to 0.10 percent of titanium, 0.0008 to 0.0035 percent of boron, 0.02 to 0.2 percent of aluminum, less than or equal to 0.5 percent of copper and less than or equal to 0.5 percent of nickel.

In the steel for bolt described above, it is preferable that the composition further contains at least one of the following elements: 0.02-1% of chromium, 0.002-0.25% of molybdenum, 0.1-0.3% of vanadium and 0.015-0.06% of niobium.

In the present invention, the main components act in the steel as follows: the carbon is used for forming a solid solution structure, the strength of the steel is improved, a carbide structure is formed, the hardness and the wear resistance of the steel can be improved, the lower the content of the carbon is, the better the plasticity of the steel is, the cold heading processing is facilitated, the higher the content of the carbon is, the lower the plasticity of the steel is, and the hardness is improved. Manganese can eliminate or weaken the hot brittleness of the steel caused by sulfur, thereby improving the hot workability of the steel, and the manganese can form solid solubility with iron, thereby improving the hardness and strength of ferrite and austenite in the steel; manganese is an element formed by carbide, enters cementite to replace part of iron atoms, and plays a role in refining pearlite due to the fact that the critical transformation temperature of manganese in steel is reduced, and also plays a role in indirectly improving the strength of pearlite steel. Silicon can improve the hardness of steel, but the plasticity and toughness of the steel can be reduced by excessively high content, and the content of silicon is not excessively high due to the requirement of cold heading. Titanium is one of strong ferrite forming elements, the A1 and A3 temperatures of steel are increased strongly, and titanium also has the effects of grain refinement and steel strength improvement. The main function of boron in steel is to increase the hardenability of steel and save part of precious metal addition, but too much boron can cause metal brittleness. The aluminum is mainly used for deoxidizing and refining grains, and the plasticity of the cold forging steel is improved. Chromium increases the hardenability of the steel and has a secondary hardening effect, which can improve the hardness and wear resistance of the steel. Copper and nickel can improve the strength of the steel. Molybdenum can refine grains, improve hardenability and hot strength, prevent temper brittleness, improve delayed fracture resistance and improve strength, but excessive molybdenum can deteriorate plasticity of steel, is not beneficial to cold heading, and also can increase cost. Vanadium can improve the strength of steel and the delayed fracture resistance, but excessive vanadium can deteriorate the plasticity of the steel and is not beneficial to cold heading. Niobium can refine grains and improve strength and hardenability of steel, but if niobium is excessive, cold heading property and delayed fracture resistance of steel may be deteriorated. In the invention, the mutual influence among all elements is obvious, and the steel for the bolt with the best comprehensive performance can be obtained by optimizing all the elements and the using amount thereof, and the steel for the bolt has excellent strength, cold heading property and delayed fracture resistance.

In the steel for bolt, the component preferably contains 0.02-1% of chromium, 0.002-0.25% of molybdenum, 0.1-0.3% of vanadium and 0.015-0.06% of niobium. Experimental research shows that the bolt steel with excellent comprehensive performance can be finally obtained by simultaneously adding chromium, molybdenum, vanadium and niobium and controlling the proportion of the chromium, the molybdenum, the vanadium and the niobium.

In the above steel for bolt, preferably, the mass percentages of the molybdenum, the vanadium and the niobium are respectively: 0.15 to 0.25 percent of molybdenum, 0.2 to 0.3 percent of vanadium and 0.04 to 0.06 percent of niobium. More preferably, the mass ratio of molybdenum, vanadium and niobium is 1: 1.2: 0.24. experimental research shows that molybdenum, vanadium and niobium have certain influence on the comprehensive performance of the final bolt steel, the molybdenum can improve delayed fracture resistance and strength, but excessive molybdenum can deteriorate the plasticity of the steel and is not beneficial to cold heading. Vanadium can improve the strength of steel and the delayed fracture resistance, but excessive vanadium can deteriorate the plasticity of the steel and is not beneficial to cold heading. Niobium may improve strength and hardenability of the steel, but if it is excessive, cold heading property and delayed fracture resistance of the steel may be deteriorated. Experimental research shows that not only can the respective dosage of molybdenum, vanadium and niobium influence the performance of the final product, but also the mixture ratio of the molybdenum, vanadium and niobium has certain influence on the performance of the final product, when the mass percentages of the molybdenum, the vanadium and the niobium are respectively 0.15-0.25%, 0.2-0.3% and 0.04-0.06%, the molybdenum, the vanadium and the niobium are mutually cooperated with other elements, the steel for the bolt with better comprehensive performance can be obtained, and more preferably, when the mass ratio of the added molybdenum, the vanadium and the niobium is 1: 1.2: when 0.24, the steel for bolts has better comprehensive performance.

As a general technical concept, the invention also provides an application of the steel for the bolt.

In the above application, preferably, the steel for bolt is used for preparing 8.8-grade bolt, and the preparation process comprises the steps of firstly carrying out iron making, steel making and hot rolling on the steel component for bolt to obtain a wire rod, and then carrying out wire drawing and cold heading treatment on the wire rod to obtain 8.8-grade bolt. According to the invention, through the adjustment of the formula, when the bolt is prepared by obtaining the wire rod through iron making, steel making and hot rolling, the 8.8-grade bolt can be obtained by directly carrying out wire drawing and cold heading treatment, spheroidization and subsequent heat treatment are not required in the whole process, and the processing procedure of the 8.8-grade bolt can be greatly shortened.

In the above application, preferably, the steel for bolt is used for preparing a 12.9-grade bolt, and the preparation process comprises the steps of firstly carrying out iron making, steel making and hot rolling on the steel component for bolt to obtain a wire rod, and then carrying out spheroidizing, descaling, wire drawing, cold heading, quenching and tempering on the wire rod to obtain the 12.9-grade bolt.

In the application, the process parameters in the processes of iron making, steel making, hot rolling, spheroidizing, descaling, wire drawing, cold heading, quenching, tempering and the like in the processing procedure are correspondingly changed according to the grade, the model and the like of the bolt.

Compared with the prior art, the invention has the advantages that:

1. according to the invention, through adjusting the components and the use amounts of the components of the bolt and the mutual synergistic effect of the components, the finally obtained bolt has high comprehensive properties such as high strength, excellent cold heading performance, excellent delayed fracture resistance and the like. Fasteners such as bolts and screws made of the steel for bolts also have excellent comprehensive performance.

2. The preparation method of the steel for the bolt is simple, the method for preparing the steel for the bolt into the fastener is also simple, the complex and tedious operation process is avoided, and the steel for the bolt is suitable for large-scale production and manufacturing, particularly when 8.8-grade bolts are prepared by using the steel for the bolt, spheroidization and subsequent heat treatment processes are not required, and the processing process of the 8.8-grade bolts can be greatly shortened.

Detailed Description

In order to facilitate an understanding of the present invention, the present invention will be described more fully and in detail with reference to the preferred embodiments, but the scope of the present invention is not limited to the specific embodiments described below.

Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

Example 1:

the steel for the bolt comprises the following components in percentage by mass: 0.31 percent of carbon, 0.25 percent of silicon, 1.47 percent of manganese, less than or equal to 0.015 percent of phosphorus, less than or equal to 0.003 percent of sulfur, 0.09 percent of titanium, 0.0022 percent of boron, 0.04 percent of aluminum, 0.025 percent of chromium, 0.02 percent of copper, 0.01 percent of nickel, 0.01 percent of molybdenum, and the balance of iron and inevitable impurities.

When the 12.9-grade bolt is prepared from the bolt steel, the bolt steel is subjected to iron making, steel making and hot rolling to obtain a wire rod, and then spheroidizing, descaling, wire drawing, cold heading, quenching, tempering and oiling are performed to obtain the bolt. Wherein, the spheroidization is carried out for 5h at 750 ℃, the descaling is carried out in acid liquor, the quenching is carried out for 60min at 890 ℃, the quenching medium is ultra-speed quenching oil, and the tempering is carried out for 60min at 450 ℃.

The wire rods produced in this example had diameters of 6.5mm, 8mm, 10mm, 12mm, and the bolts produced from the wire rods had specifications of M6 × 20mm (diameter × length), M8 × 30mm, M10 × 40mm, and M12 × 50 mm.

The physical properties of the wire obtained in this example were as follows: the tensile strength is 1165MPa, the yield strength is 1058MPa, the elongation is 13.5 percent, and the cold upsetting is as follows: 1/2, pass, total decarburized layer: 0.07, fully decarburized layer: 0.

the performance parameters of the bolts in this example are shown in table 1 below.

Table 1: performance parameters of the bolts in example 1

The bolt product in the embodiment meets various technical requirements of GB70.1-200012.9 grades, and the performance of the raw material reaches the performance requirement required by 12.9 grades of bolts.

When the 8.8-grade bolt is prepared from the bolt steel, the bolt steel is subjected to iron making, steel making and hot rolling to obtain a wire rod, and then the wire rod is subjected to wire drawing, cold heading and oiling treatment, so that the bolt steel can be obtained without heat treatment processes such as spheroidization, quenching, tempering and the like.

Example 2:

the steel for the bolt comprises the following components in percentage by mass: 0.28% of carbon, 0.11% of silicon, 1.3% of manganese, less than or equal to 0.015% of phosphorus, less than or equal to 0.003% of sulfur, 0.06% of titanium, 0.0012% of boron, 0.1% of aluminum, 0.01% of copper, 0.01% of nickel, 0.17% of molybdenum, 0.25% of vanadium, 0.048% of niobium, and the balance of iron and inevitable impurities.

In this example, a 12.9-grade bolt was produced from the bolt steel in the same manner as in example 1.

Example 3:

the steel for the bolt comprises the following components in percentage by mass: 0.31% of carbon, 0.25% of silicon, 1.47% of manganese, less than or equal to 0.015% of phosphorus, less than or equal to 0.003% of sulfur, 0.09% of titanium, 0.0022% of boron, 0.04% of aluminum, 0.025% of chromium, 0.02% of copper, 0.01% of nickel, 0.01% of molybdenum, 0.30% of vanadium, 0.05% of niobium, and the balance of iron and inevitable impurities.

Example 4:

the steel for the bolt comprises the following components in percentage by mass: 0.31 percent of carbon, 0.25 percent of silicon, 1.47 percent of manganese, less than or equal to 0.015 percent of phosphorus, less than or equal to 0.003 percent of sulfur, 0.09 percent of titanium, 0.0022 percent of boron, 0.04 percent of aluminum, 0.025 percent of chromium, 0.02 percent of copper, 0.01 percent of nickel, 0.012 percent of molybdenum, 0.30 percent of vanadium, 0.04 percent of niobium, and the balance of iron and inevitable impurities.

Example 5:

the steel for the bolt comprises the following components in percentage by mass: 0.31 percent of carbon, 0.25 percent of silicon, 1.47 percent of manganese, less than or equal to 0.015 percent of phosphorus, less than or equal to 0.003 percent of sulfur, 0.09 percent of titanium, 0.0022 percent of boron, 0.04 percent of aluminum, 0.025 percent of chromium, 0.02 percent of copper, 0.01 percent of nickel, 0.2 percent of molybdenum, 0.24 percent of vanadium, 0.048 percent of niobium, and the balance of iron and inevitable impurities.

Example 6:

the steel for the bolt comprises the following components in percentage by mass: 0.31 percent of carbon, 0.25 percent of silicon, 1.47 percent of manganese, less than or equal to 0.015 percent of phosphorus, less than or equal to 0.003 percent of sulfur, 0.09 percent of titanium, 0.0022 percent of boron, 0.04 percent of aluminum, 0.025 percent of chromium, 0.02 percent of copper, 0.01 percent of nickel, 0.24 percent of vanadium, 0.048 percent of niobium, and the balance of iron and inevitable impurities.

Example 7:

the steel for the bolt comprises the following components in percentage by mass: 0.31% of carbon, 0.25% of silicon, 1.47% of manganese, less than or equal to 0.015% of phosphorus, less than or equal to 0.003% of sulfur, 0.09% of titanium, 0.0022% of boron, 0.04% of aluminum, 0.03% of chromium, 0.02% of copper, 0.01% of nickel, 0.1% of molybdenum, 0.1% of vanadium, 0.02% of niobium and the balance of iron and inevitable impurities.

Comparative example 1:

the steel for the bolt comprises the following components in percentage by mass: 0.31% of carbon, 0.25% of silicon, 1.47% of manganese, less than or equal to 0.015% of phosphorus, less than or equal to 0.003% of sulfur, 0.09% of titanium, 0.0022% of boron, 0.04% of aluminum, 0.02% of chromium, 0.02% of copper, 0.01% of nickel, 0.40% of molybdenum, 0.30% of vanadium, 0.10% of niobium, and the balance of iron and inevitable impurities.

Comparative example 2:

the steel for the bolt comprises the following components in percentage by mass: 0.31% of carbon, 1.25% of silicon, 1.47% of manganese, less than or equal to 0.015% of phosphorus, less than or equal to 0.003% of sulfur, 0.09% of titanium, 0.0022% of boron, 0.04% of aluminum, 0.025% of chromium, 0.02% of copper, 0.01% of nickel, 0.35% of molybdenum, 0.5% of vanadium, 0.048% of niobium, and the balance of iron and inevitable impurities.

The relevant performance data for the wires and bolts of examples 1-7 and comparative examples 1-2 are shown in table 2 below.

Table 2: relevant Performance data for the wire and bolt of examples 1-7 and comparative examples 1-2

Claims

1. A12.9-grade bolt is characterized in that the steel for the bolt comprises the following components in percentage by mass: 0.31% of carbon, 0.25% of silicon, 1.47% of manganese, less than or equal to 0.015% of phosphorus, less than or equal to 0.003% of sulfur, 0.09% of titanium, 0.0022% of boron, 0.04% of aluminum, 0.025% of chromium, 0.02% of copper, 0.01% of nickel, 0.2% of molybdenum, 0.24% of vanadium, 0.048% of niobium, and the balance of iron and inevitable impurities;

after the steel for the bolt is subjected to iron making, steel making and hot rolling treatment to obtain a wire rod, and then spheroidizing, descaling, wire drawing, cold heading, quenching, tempering and oiling treatment are carried out to obtain a 12.9-grade bolt; wherein, the spheroidization is carried out for 5h at 750 ℃, the descaling is carried out in acid liquor, the quenching is carried out for 60min at 890 ℃, the quenching medium is ultra-speed quenching oil, and the tempering is carried out for 60min at 450 ℃.