CN116024499B - Steel for 10.9-grade bolt resistant to hydrogen-induced delayed fracture and preparation method of 10.9-grade bolt - Google Patents
Steel for 10.9-grade bolt resistant to hydrogen-induced delayed fracture and preparation method of 10.9-grade bolt Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 87
- 239000010959 steel Substances 0.000 title claims abstract description 87
- 230000003111 delayed effect Effects 0.000 title claims abstract description 58
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 52
- 239000001257 hydrogen Substances 0.000 title claims abstract description 52
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 50
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 239000000126 substance Substances 0.000 claims abstract description 21
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 14
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 13
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 13
- 229910052796 boron Inorganic materials 0.000 claims abstract description 8
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 8
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 7
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 7
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 7
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 7
- 238000005496 tempering Methods 0.000 claims description 38
- 230000000171 quenching effect Effects 0.000 claims description 31
- 238000010791 quenching Methods 0.000 claims description 30
- 238000001816 cooling Methods 0.000 claims description 20
- 238000004321 preservation Methods 0.000 claims description 19
- 238000005096 rolling process Methods 0.000 claims description 15
- 238000010438 heat treatment Methods 0.000 claims description 14
- 239000002994 raw material Substances 0.000 claims description 10
- 239000000956 alloy Substances 0.000 claims description 9
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 claims description 8
- 229910045601 alloy Inorganic materials 0.000 claims description 8
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 238000000034 method Methods 0.000 claims description 7
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- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 claims description 5
- 238000010521 absorption reaction Methods 0.000 claims description 5
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- 238000003723 Smelting Methods 0.000 claims description 3
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- 238000009749 continuous casting Methods 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 2
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- 239000000463 material Substances 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 16
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- 238000005275 alloying Methods 0.000 description 4
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- 238000012360 testing method Methods 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
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- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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Abstract
The invention provides steel for a 10.9-grade bolt with hydrogen-induced delayed fracture resistance and a preparation method of the 10.9-grade bolt, and belongs to the technical field of fastener materials. The steel for the 10.9-grade bolt comprises ：C：0.20～0.35％,Si：0.15～0.40％,Mn：0.5～0.9％,P：≤0.01％,S：≤0.003％,Cr：0.60～0.75％,Mo：0.10～0.25％,Nb：0.01～0.05％,V：0.01～0.10％,Ti：0.010～0.020％,Al：0.010～0.030％,B：0.001～0.004％,Ca：0.003～0.005％,RE：0.01～0.04％ mass percent of chemical components and the balance of Fe.
Description
Technical Field
The invention relates to the technical field of fastener materials, in particular to steel for a 10.9-grade bolt resistant to hydrogen-induced delayed fracture and a preparation method of the 10.9-grade bolt.
Background
With the gradual upsizing and large span of various buildings, bridge engineering and the like and the continuous improvement of the strength level of the used steel, the working stress level of the bolt parts serving as connecting pieces is obviously improved, and the working conditions are worse, so that the requirements on the strength, the service performance level and the like of the bolts are increasingly higher. An increase in the strength level of the bolt may lead to an increase in the load-bearing efficiency, but is at risk of a decrease in the resistance to hydrogen-induced delayed fracture, and particularly when the strength level exceeds about 1000 to 1200MPa, the resistance to delayed fracture may be significantly reduced.
The prior steel for the delayed fracture resistant bolt generally adopts a medium-low carbon composite alloying means, namely adopts a Cr-Mo system, and simultaneously adds V (less than or equal to 0.5 percent), nb (less than or equal to 0.1 percent) and Ti (less than or equal to 0.1 percent) to a certain extent, and also adds a certain amount of Cu and Ni according to the service condition of the bolt, such as a delayed fracture resistant 1040MPa level weather resistant bolt (application publication number CN 201711215120.3), a delayed fracture resistant high-strength bolt alloy material and a bolt manufacturing method (application publication number CN 201510461011.4) and the like; meanwhile, in order to meet the strength and the delayed fracture performance, a large amount of Mo is added to different bolts to improve the comprehensive performance, such as a high-strength bolt with excellent delayed fracture resistance and a manufacturing method thereof (application publication No. CN 200610105980.7), a wire rod for the bolt with excellent pickling performance and delayed fracture resistance after quenching and tempering (application publication No. CN 201680017865.60) and the like, and the cost is high. Part of the bolt steel is not added with Nb, V or the like, and has insufficient delayed fracture resistance, such as "high strength bolt steel excellent in delayed fracture resistance and cold workability" (application publication No. CN 2004100744100.7) or the like.
Therefore, it is desirable to provide a steel for bolts that has excellent delayed fracture resistance and mechanical properties at low cost.
Disclosure of Invention
The invention aims to provide a 10.9-grade bolt steel resistant to hydrogen-induced delayed fracture and a preparation method of the 10.9-grade bolt, and the 10.9-grade bolt steel is low in cost, good in economical efficiency and excellent in hydrogen-induced delayed fracture resistance and mechanical property.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides steel for a 10.9-grade bolt resistant to hydrogen-induced delayed fracture, which comprises the following chemical components in percentage by mass, ：C：0.20～0.35％,Si：0.15～0.40％,Mn：0.5～0.9％,P：≤0.01％,S：≤0.003％,Cr：0.60～0.75％,Mo：0.10～0.25％,Nb：0.01～0.05％,V：0.01～0.10％,Ti：0.010～0.020％,Al：0.010～0.030％,B：0.001～0.004％,Ca：0.003～0.005％,RE：0.01～0.04％ and the balance of Fe.
Preferably, the 10.9-grade steel for bolts comprises ：C：0.22～0.33％,Si：0.16～0.38％,Mn：0.55～0.85％,P：≤0.009％,S：≤0.002％,Cr：0.65～0.70％,Mo：0.15～0.20％,Nb：0.015～0.045％,V：0.015～0.09％,Ti：0.015～0.018％,Al：0.015～0.025％,B：0.002～0.003％,Ca：0.003～0.004％,RE：0.015～0.035％ and the balance of Fe in percentage by mass.
Preferably, the sum of the mass percentages of Nb, V and Ti is 0.03-0.08%.
Preferably, the mass percentage of RE is 0.02-0.03%.
The invention also provides a preparation method of the 10.9-grade bolt, which comprises the following steps:
(1) The alloy raw materials of the 10.9-grade steel for the bolts are mixed and then are sequentially smelted, continuously cast and continuously rolled to obtain bolt billets;
(2) Sequentially carrying out hot heading, necking and thread rolling on the bolt billet obtained in the step (1) to obtain a formed bolt;
(3) And (3) carrying out quenching and tempering heat treatment on the formed bolt obtained in the step (2) to obtain a 10.9-grade bolt.
Preferably, the hot heading temperature in the step (2) is 950-1000 ℃.
Preferably, the tempering heat treatment in the step (3) includes quenching and tempering performed sequentially; the heat preservation temperature of the quenching is 850-880 ℃, and the heat preservation time of the quenching is 0.5-1.5 h.
Preferably, the quenching cooling mode is water cooling to room temperature.
Preferably, the heat preservation temperature of tempering is 530-580 ℃, and the heat preservation time of tempering is 30-50 min.
Preferably, the tempering cooling mode is air cooling to room temperature.
The invention provides steel for a 10.9-grade bolt resistant to hydrogen-induced delayed fracture, which comprises the following chemical components in percentage by mass, ：C：0.20～0.35％,Si：0.15～0.40％,Mn：0.5～0.9％,P：≤0.01％,S：≤0.003％,Cr：0.60～0.75％,Mo：0.10～0.25％,Nb：0.01～0.05％,V：0.01～0.10％,Ti：0.010～0.020％,Al：0.010～0.030％,B：0.001～0.004％,Ca：0.003～0.005％,RE：0.01～0.04％ and the balance of Fe. The 10.9-grade steel for the bolts does not need to be added with two alloying elements of Cu and Ni, and simultaneously, the content of Cr, V, B, mo and Ti is relatively low, so that the steel has lower alloying degree and can effectively reduce the cost; meanwhile, the content of Si, mn and Nb elements is also added and regulated under the condition of lower C content, so that the steel for the bolt has higher hydrogen-induced delayed fracture resistance under the condition of meeting the 10.9-grade bolt performance, and meanwhile, 0.01-0.04% of RE is added, so that the metallurgical quality of the steel for the bolt is improved, the inclusion level in the steel for the bolt is reduced, and the delayed fracture resistance is obviously improved. The results of the examples show that the room temperature tensile strength of the 10.9-grade bolt for resisting hydrogen-induced delayed fracture is 1086-1148 MPa; the non-proportional extension strength is 1006-1071 MPa; the elongation after breaking is 12.5-14%; the area reduction rate is 58-67%; the KV 2 impact absorption power is 98-137J at the temperature of minus 20 ℃; the core hardness is 34.5-37.5 HRC; the notch constant load critical fracture stress ratio n is 0.80-0.83; the class A sulfide fine system, the class D spherical oxide fine system and the class D spherical oxide coarse system inclusion are of 0.5 grade, the class B alumina fine system inclusion is of 0-1 grade, the class B alumina coarse system inclusion is of 0-1 grade, and the class A sulfide coarse system, the class C silicate fine system, the class C silicate coarse system and the class DS single particle spherical inclusion are not contained.
Drawings
FIG. 1 is a schematic diagram of the constant load notched tensile test pieces of examples 1 to 6 and comparative examples 1 to 6 of the present invention.
Detailed Description
The invention provides steel for a 10.9-grade bolt resistant to hydrogen-induced delayed fracture, which comprises the following chemical components in percentage by mass, ：C：0.20～0.35％,Si：0.15～0.40％,Mn：0.5～0.9％,P：≤0.01％,S：≤0.003％,Cr：0.60～0.75％,Mo：0.10～0.25％,Nb：0.01～0.05％,V：0.01～0.10％,Ti：0.010～0.020％,Al：0.010～0.030％,B：0.001～0.004％,Ca：0.003～0.005％,RE：0.01～0.04％ and the balance of Fe.
The chemical components of the steel for the 10.9-grade bolt with the hydrogen-induced delayed fracture resistance comprise the following components in percentage by mass: 0.20 to 0.35%, preferably 0.22 to 0.33%, more preferably 0.25 to 0.30%. The C in the 10.9-grade steel for the bolts is a main strengthening element, and the content of the C is controlled within the range, so that the steel for the bolts has higher plasticity and toughness and higher strength and hardness.
The chemical components of the steel for the 10.9-grade bolt with the hydrogen-induced delayed fracture resistance comprise the following components in percentage by mass: from 0.15 to 0.40%, preferably from 0.16 to 0.38%, more preferably from 0.20 to 0.35%, most preferably from 0.25 to 0.30%. According to the invention, si element is added as a reducing agent and a deoxidizing agent, and the content of the Si element is controlled within the range, so that oxides in a steel structure for the bolt can be removed, and inclusions can be reduced; and Si can also play a solid solution strengthening role, thereby effectively improving the mechanical property of the steel for the bolt.
The chemical components of the steel for the 10.9-grade bolt with the hydrogen-induced delayed fracture resistance comprise Mn: from 0.5 to 0.9%, preferably from 0.55 to 0.85%, more preferably from 0.60 to 0.80%, most preferably from 0.65 to 0.75%. According to the invention, mn element is added as a deoxidizer, and the content of Mn element is controlled within the range, so that oxides in a steel structure for the bolt can be removed, and inclusions are reduced; mn can form stable MnS with harmful element S in the steel for the bolt, so that the harmful effect of S is reduced; mn can also play a remarkable role in solid solution strengthening and grain refinement in the steel for bolts, and can remarkably improve the strength and toughness of the steel for bolts.
The chemical components of the steel for the 10.9-grade bolt with the hydrogen-induced delayed fracture resistance comprise the following components in percentage by mass: less than or equal to 0.01%, preferably less than or equal to 0.009%, more preferably less than or equal to 0.006%. In the present invention, the P is an impurity element, and by controlling the content of P in the above-described range, the detrimental effect of P can be reduced, inclusions can be reduced, and the mechanical properties of the steel for bolts can be improved.
The chemical components of the steel for the 10.9-grade bolt with the hydrogen-induced delayed fracture resistance comprise the following components in percentage by mass: less than or equal to 0.003%, preferably less than or equal to 0.002%, more preferably less than or equal to 0.001%. In the invention, S is an impurity element, and the harmful influence of S can be reduced by controlling the content of S in the range, so that inclusions are reduced, and the mechanical property of the steel for the bolt is improved.
The chemical components of the steel for the 10.9-grade bolt with the hydrogen-induced delayed fracture resistance comprise Cr:0.60 to 0.75%, preferably 0.65 to 0.70%, more preferably 0.66 to 0.68%. The present invention can improve the hardenability of the steel for bolts by adding Cr and controlling the content thereof within the above-mentioned range, thereby improving the strength and hardness.
The chemical components of the steel for the 10.9-grade bolt with the hydrogen-induced delayed fracture resistance comprise the following components in percentage by mass: 0.10 to 0.25%, preferably 0.15 to 0.20%, more preferably 0.0.16 to 0.18%. According to the invention, the hardenability of the steel for the bolt can be improved by adding Mo and controlling the content of Mo in the range, and the tempering resistance and the tempering stability can be improved, so that the steel for the bolt is tempered at a higher temperature to refine a structure, and Mo can inhibit the formation of corrosion pits and reduce external hydrogen, thereby improving the delayed fracture resistance of the steel for the bolt.
The chemical components of the steel for the 10.9-grade bolt with the hydrogen-induced delayed fracture resistance comprise the following components in percentage by mass: 0.01 to 0.05%, preferably 0.015 to 0.045%, more preferably 0.020 to 0.040%, most preferably 0.025 to 0.035%. The invention can have extremely strong binding force with C, N, O and form extremely stable compound with C, N, O by adding Nb and controlling the content thereof in the range, thereby playing the roles of refining grains, improving strength and reducing overheat sensitivity and tempering brittleness of steel; meanwhile, a strong hydrogen trap is formed, and the delayed fracture resistance of the steel for the bolt is obviously improved.
The chemical components of the steel for the 10.9-grade bolt with the hydrogen-induced delayed fracture resistance comprise the following components in percentage by mass: 0.01 to 0.10%, preferably 0.015 to 0.09%, more preferably 0.020 to 0.08%, most preferably 0.030 to 0.070%. According to the invention, V is added as a microalloying element, the content of the V is controlled within the range, the V exists in the steel for the bolt in the form of VC, and VC is a strong trap of hydrogen in the steel, so that the hydrogen in the steel can be adsorbed, the diffusible hydrogen content in the steel is reduced, and the delayed fracture resistance of the steel is obviously improved.
The chemical components of the steel for the 10.9-grade bolt with the hydrogen-induced delayed fracture resistance comprise the following components in percentage by mass: 0.010 to 0.020%, preferably 0.015 to 0.018%, more preferably 0.016 to 0.017%. Ti is added as a very strong carbide forming element, and the content of the Ti is controlled within the range, so that the Ti can play a very strong solid solution strengthening role; meanwhile, ti is also a strong trap of hydrogen, has a grain refining effect, and reduces the delayed fracture sensitivity of the steel.
In the present invention, the sum of the mass percentages of Nb, V and Ti is preferably 0.03 to 0.08%, more preferably 0.04 to 0.07%. The invention can obviously improve the mechanical property and the hydrogen-induced delayed fracture resistance of the steel for the bolt under lower content by controlling the sum of the mass percentages of Nb, V and Ti.
The chemical components of the steel for the 10.9-grade bolt with the hydrogen-induced delayed fracture resistance comprise the following components in percentage by mass: 0.010 to 0.030%, preferably 0.015 to 0.025%, more preferably 0.016 to 0.020%. According to the invention, al is added as a deoxidizing nitrogen-fixing agent, and the content of Al is controlled within the range, so that grains can be refined, the oxidation resistance of the steel for the bolt can be improved, and the brittle transition temperature of the steel can be reduced.
The chemical components of the steel for the 10.9-grade bolt with the hydrogen-induced delayed fracture resistance comprise the following components in percentage by mass: 0.001 to 0.004%, preferably 0.002 to 0.003%. According to the invention, the quenching property of the steel for the low-carbon bolt can be remarkably improved by adding B and controlling the content of B within the range, and meanwhile, the B element is concentrated at the grain boundary, so that a diffusion channel of hydrogen can be reduced, and the content of diffusible hydrogen in a crystal is reduced.
The chemical components of the steel for the 10.9-grade bolt with the hydrogen-induced delayed fracture resistance comprise the following components in percentage by mass: 0.003 to 0.005%, preferably 0.003 to 0.004%. The invention can refine grains, partially desulfur, change the components, quantity and shape of nonmetallic inclusion, and improve the hydrogen induced cracking resistance and lamellar tearing resistance by adding Ca and controlling the content in the range.
The chemical components of the steel for the 10.9-grade bolt with the hydrogen-induced delayed fracture resistance comprise RE:0.01 to 0.04%, preferably 0.015 to 0.035%, more preferably 0.02 to 0.03%. The RE is added and the content is controlled in the range, so that the grain boundary can be obviously purified, the segregation is improved, the form of the inclusion is changed, and the harm caused by sulfide inclusion is eliminated.
The type of RE is not particularly limited in the present invention, and rare earth commonly used in the art may be used.
The chemical components of the steel for the 10.9-grade bolt with the hydrogen-induced delayed fracture resistance comprise the balance of Fe in percentage by mass.
The steel for the 10.9-grade bolt has low cost, good economy and excellent hydrogen-induced delayed fracture resistance and mechanical property.
The invention also provides a preparation method of the 10.9-grade bolt, which comprises the following steps:
(1) The alloy raw materials of the 10.9-grade bolt steel in the technical scheme are mixed and then are sequentially smelted, continuously cast and continuously rolled to obtain a bolt steel billet;
(2) Sequentially carrying out hot heading, necking and thread rolling on the bolt billet obtained in the step (1) to obtain a formed bolt;
(3) And (3) carrying out quenching and tempering heat treatment on the formed bolt obtained in the step (2) to obtain a 10.9-grade bolt.
The invention mixes alloy raw materials of 10.9-grade bolt steel, and then sequentially carries out smelting, continuous casting and continuous rolling to obtain a bolt steel billet.
The source of the alloy raw material of the 10.9-grade bolt steel is not particularly required, and the raw material is prepared by adopting the commercial raw materials or the conventional method for each element which are well known in the field.
The invention has no special requirements on the mixing of the alloy raw materials and the smelting, continuous casting and continuous rolling operation, and can obtain the steel for the bolt by adopting the conventional operation well known in the field.
After the bolt steel billet is obtained, the bolt steel billet is subjected to hot heading, necking and thread rolling in sequence to obtain the formed bolt.
Before the hot heading, the invention preferably performs pre-forming treatment on the bolt billet to obtain a pre-formed bolt; the pre-forming treatment preferably comprises pickling, drawing and blanking, which are performed sequentially. The invention has no special requirements on pickling, drawing and blanking, and can prepare the preformed bolt by adopting the conventional operation in the field.
In the present invention, the temperature of the hot heading is 950 to 1000 ℃, more preferably 960 to 990 ℃, and most preferably 980 ℃. According to the invention, by controlling the temperature of hot heading within the range, the bolt billet can obtain better thermoforming capability.
The present invention has no special requirement for the necking and thread rolling operation, and the forming bolt can be obtained by adopting the conventional necking and thread rolling operation in the field.
After the formed bolt is obtained, the formed bolt is subjected to quenching and tempering heat treatment to obtain the 10.9-grade bolt.
In the present invention, the tempering heat treatment preferably includes quenching and tempering performed sequentially; the quenching heat preservation temperature is preferably 850-880 ℃, more preferably 860-870 ℃; the holding time for the quenching is preferably 0.5 to 1.5 hours, more preferably 1 hour. According to the invention, the heat preservation temperature and the heat preservation time of quenching are controlled within the ranges, so that the formed bolt can obtain higher hardenability, and the strength and the hardness of the bolt are effectively improved.
In the present invention, the quenching is preferably performed by water cooling to room temperature. According to the invention, by adopting a quenching cooling mode from water cooling to room temperature, the bolt can be prevented from forming larger internal stress cracking, so that grains are refined and hardenability is improved under a higher cooling rate.
In the invention, the tempering heat preservation temperature is preferably 530-580 ℃, more preferably 540-570 ℃, and most preferably 550-560 ℃; the tempering heat preservation time is preferably 30-50 min, more preferably 35-45 min, and most preferably 40min. The invention can effectively relieve or even eliminate the internal stress in the quenching part by controlling the heat preservation temperature and the heat preservation time of tempering in the range, and ensures that crystal grains are not coarsened, thereby being more beneficial to obtaining higher mechanical property and hydrogen-induced delayed fracture resistance.
In the present invention, the tempering cooling mode is preferably air cooling to room temperature.
After finishing the tempering heat treatment, the invention preferably carries out surface treatment, re-rolling and packaging storage on the products subjected to the tempering heat treatment in sequence to obtain the 10.9-grade bolt. The surface treatment, re-rolling and packaging and storing operations are not particularly limited in the present invention, and may be performed by conventional operations in the art.
The 10.9-grade bolt prepared by the preparation method provided by the invention has the advantages of lower alloying degree, low cost, excellent hydrogen-induced delayed fracture resistance and higher strength, and can meet the use requirement of the 10.9-grade bolt; the preparation method is simple and feasible, the parameters are easy to control, the cost is low, and the method is suitable for mass production.
The technical solutions of the present invention will be clearly and completely described in the following in connection with the embodiments of the present invention. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Examples 1 to 6
The components and mass percentages of the 10.9 grade steel for bolts provided in examples 1 to 6 were composed of the components and mass percentages shown in table 1.
The preparation method of the 10.9-grade bolt for resisting hydrogen delayed fracture provided in examples 1 to 6 comprises the following steps:
(1) Alloy raw materials of 10.9-grade bolt steel are mixed and then are sequentially smelted, continuously cast and continuously rolled to obtain a bolt steel billet;
(2) Sequentially washing, drawing and blanking the bolt billet obtained in the step (1) to obtain a preformed bolt, and sequentially performing hot heading, necking and thread rolling to obtain a formed bolt; wherein the hot heading temperature is 980 ℃;
(3) Carrying out tempering heat treatment on the formed bolt obtained in the step (2), and then sequentially carrying out surface treatment, re-rolling, packaging and storage to obtain a 10.9-grade bolt; the quenching and tempering heat treatment is quenching and tempering which are sequentially carried out, the quenching cooling mode is water cooling to room temperature, the quenching heat preservation time is 1h, the tempering cooling mode is air cooling to room temperature, the tempering heat preservation time is 40min, and the quenching and tempering heat preservation temperatures are shown in table 2.
Table 1 Components and mass percentage (%)
Table 2 examples 1 to 6 provide heat treatment parameters for tempering and performance test results for 10.9 grade bolts
Comparative examples 1 to 6
The compositions and mass percentages of the bolt steels provided in comparative examples 1 to 6 are shown in Table 3.
The preparation method of the bolts provided in comparative examples 1 to 6 comprises the following steps:
(1) Alloy raw materials of bolt steel are mixed and then are sequentially smelted, continuously cast and continuously rolled to obtain bolt billets;
(2) Sequentially washing, drawing and blanking the bolt billet obtained in the step (1) to obtain a preformed bolt, and sequentially performing hot heading, necking and thread rolling to obtain a formed bolt; wherein the hot heading temperature is 980 ℃;
(3) Carrying out tempering heat treatment on the formed bolt obtained in the step (2), and then sequentially carrying out surface treatment, re-rolling, packaging and storage to obtain a bolt; the quenching and tempering heat treatment is quenching and tempering which are sequentially carried out, the quenching cooling mode is water cooling to room temperature, the quenching heat preservation time is 1h, the tempering cooling mode is air cooling to room temperature, the tempering heat preservation time is 40min, and the quenching and tempering heat preservation temperatures are shown in table 4.
Table 3 comparative examples 1 to 6 provide bolt steels with the components and the mass percent (%)
Table 4 thermal treatment parameters and results of property measurements for bolts provided in comparative examples 1 to 6
The performance test criteria for each of tables 2 and 4 are as follows:
tensile strength, non-proportional elongation, elongation after break and reduction of area refer to GB/T228.1-2010 section 1 of Metal Material tensile test: room temperature test methods;
KV 2 impact absorption power at-20 ℃ refers to GB/T229-2007 Charpy pendulum impact test method for Metal materials;
core hardness reference GB/T230.1-2009 section 1 of rockwell hardness test for metallic materials: test methods;
Critical fracture stress ratio n the constant load notch tensile test is carried out by referring to ISO/FDIS 16573:2014 (E) method for evaluating hydrogen-induced delayed fracture resistance test of high-strength steel, and the tensile schematic diagram of the sample is shown in figure 1. In the test, the solution is Walpole (concentrated hydrochloric acid+anhydrous sodium acetate+deionized water or distilled water) corrosion inhibition solution with the pH value of 3.5+/-0.5, and the critical stress of notch fracture is defined according to the formula ① according to the minimum stress of fracture of a sample and the maximum stress of no fracture in a specified time (the specified time is 100 h):
Wherein sigma c is critical stress of fracture of the sample, and the unit is MPa; sigma 0 is the constant load notch tensile strength of the sample, and the unit is MPa; the test result meets the following technical requirements: the notch constant load critical fracture stress ratio n is not less than 0.8.
As can be seen from Table 2, the room temperature tensile strength of the bolts of examples 1 to 4 was 1086 to 1148MPa; the non-proportional extension strength is 1006-1071 MPa; the elongation after breaking is 12.5-14%; the area reduction rate is 58-67%; the KV 2 impact absorption power is 98-137J at the temperature of minus 20 ℃; the core hardness is 34.5-37.5 HRC; the notch constant load critical fracture stress ratio n is 0.80-0.83.
As can be seen from Table 4, the bolts of comparative examples 1 to 4 have room temperature tensile strengths of 975 to 1225MPa; the non-proportional extension strength is 928-1160 MPa; the elongation after breaking is 10.5-16%; the area reduction rate is 54-71%; the KV 2 impact absorption power is 75-120J at the temperature of 20 ℃ below zero; the core hardness is 31-42 HRC; the notch constant load critical fracture stress ratio n is 0.65-0.78. Meanwhile, as shown in Table 3, the bolt C of comparative example 1 has high content and poor hydrogen-induced delayed fracture resistance although the mechanical properties are qualified; the bolt of comparative example 2 has low V content, unqualified mechanical properties and poor hydrogen-induced delayed fracture resistance; the bolt of comparative example 3 has low Nb content and unqualified mechanical property; the bolts of comparative example 4 are not added with B, and the mechanical property and the hydrogen-induced delayed fracture resistance are not qualified; the bolts of comparative example 5 are not added with Nb and Ti, and the mechanical property and the hydrogen-induced delayed fracture resistance are not qualified; the bolts of comparative example 6 were not added with RE, but were not qualified in terms of hydrogen-induced delayed fracture resistance, although they were qualified in terms of mechanical properties.
In conclusion, the 10.9-grade bolt provided by the invention has low cost, good economy and excellent hydrogen-induced delayed fracture resistance and mechanical property.
The inclusion rating was carried out on the bolts of 10.9 grades provided in examples 1 to 6 and comparative examples 1 to 6 according to GB/T10561-2005 "Standard rating chart microscopic examination method for determination of nonmetallic inclusion content in Steel", and the evaluation results are shown in Table 5.
Table 5 inclusion grades of bolts provided in examples 1 to 6 and comparative examples 1 to 6
As can be seen from Table 5, the bolts provided in examples 1 to 6 were free from the A sulfide-based fine inclusions, the D-spherical oxide-based coarse inclusions, the B-alumina-based fine inclusions, the B-alumina-based coarse inclusions, and the DS-single-particle spherical inclusions, each of which was 0.5-grade, each of which was 0-1-grade; the bolts provided in comparative examples 1 to 6 were 0.5 to 1.5 in level of fine A sulfide-based inclusions, 0 to 1.5 in level of fine B alumina-based inclusions, 0 to 1.5 in level of coarse A sulfide-based inclusions, 0 to 1 in level of fine C silicate-based inclusions, 0 to 1 in level of coarse B alumina-based inclusions, 0 to 1 in level of fine D spherical oxides, 0.5 to 1 in level of coarse D spherical oxides and single-particle DS spherical inclusions. As can be seen by comparison, the bolt provided by the invention has the advantages of less impurity types, small size and better grading effect.
In conclusion, the 10.9-grade bolt resistant to hydrogen delayed fracture provided by the invention has the advantages of reasonable component arrangement, simple and easily-realized production and manufacturing process, low cost, strong economy, remarkable hydrogen delayed fracture resistance, excellent comprehensive mechanical property, good inclusion grading effect, and better than that of a common high-strength bolt, and can be popularized and applied to the field of common high-strength connecting steel structures.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (10)
1. 10.9 Grade bolt steel resistant to hydrogen-induced delayed fracture comprises the following chemical components in percentage by mass of ：C：0.22~0.35%,Si：0.15~0.40%,Mn：0.5~0.9%,P：≤0.01%,S：≤0.003%,Cr：0.60~0.75%,Mo：0.10~0.25%,Nb：0.01~0.05%,V：0.01~0.10%,Ti：0.010~0.020%,Al：0.010~0.030%,B：0.001~0.004%,Ca：0.003~0.005%,RE：0.025~0.040% and the balance of Fe;
The room-temperature tensile strength of the 10.9-grade bolt resistant to hydrogen-induced delayed fracture is 1086-1148 MPa; the non-proportional extension strength is 1006-1071 MPa; the elongation after breaking is 12.5-14%; the area reduction rate is 58-67%; the KV 2 impact absorption power is 98-137J at the temperature of minus 20 ℃; the core hardness is 34.5-37.5 HRC; the notch constant load critical fracture stress ratio n is 0.80-0.83; the class A sulfide fine system, class D spherical oxide fine system and class D spherical oxide coarse system inclusion are of 0.5 grade, class B alumina fine system inclusion is of 0-1 grade, class B alumina coarse system inclusion is of 0-1 grade, and the class A sulfide coarse system, class C silicate fine system, class C silicate coarse system and DS single particle spherical inclusion are not contained.
2. The steel for 10.9-grade bolts according to claim 1, wherein the chemical composition is ：C：0.22~0.33%,Si：0.16~0.38%,Mn：0.55~0.85%,P：≤0.009%,S：≤0.002%,Cr：0.65~0.70%,Mo：0.15~0.20%,Nb：0.015~0.045%,V：0.015~0.09%,Ti：0.015~0.018%,Al：0.015~0.025%,B：0.002~0.003%,Ca：0.003~0.004%,RE：0.025~0.035% and the balance of Fe in mass percent.
3. The steel for 10.9-grade bolts according to claim 1 or 2, wherein the sum of the mass percentages of Nb, V and Ti is 0.03 to 0.08%.
4. The steel for 10.9-grade bolts according to claim 2, wherein the mass percentage of RE is 0.02 to 0.03%.
5. The preparation method of the 10.9-grade bolt comprises the following steps:
(1) Mixing alloy raw materials of the 10.9-grade bolt steel according to any one of claims 1-4, and then sequentially smelting, continuous casting and continuous rolling to obtain a bolt steel billet;
(2) Sequentially carrying out hot heading, necking and thread rolling on the bolt billet obtained in the step (1) to obtain a formed bolt;
(3) And (3) carrying out quenching and tempering heat treatment on the formed bolt obtained in the step (2) to obtain a 10.9-grade bolt.
6. The method according to claim 5, wherein the hot heading temperature in the step (2) is 950-1000 ℃.
7. The production method according to claim 5, wherein the tempering heat treatment in the step (3) comprises quenching and tempering performed sequentially; the heat preservation temperature of quenching is 850-880 ℃, and the heat preservation time of quenching is 0.5-1.5 h.
8. The method of claim 7, wherein the quenching is performed by water cooling to room temperature.
9. The method according to claim 7, wherein the tempering is performed at a temperature of 530 to 580 ℃ for 30 to 50 minutes.
10. The method of claim 7 or 9, wherein the tempering is performed by air cooling to room temperature.
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