CN115780510A - Production process of Cr-Ni-Mo series medium-carbon high-alloy steel bar - Google Patents
Production process of Cr-Ni-Mo series medium-carbon high-alloy steel bar Download PDFInfo
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- CN115780510A CN115780510A CN202211487942.8A CN202211487942A CN115780510A CN 115780510 A CN115780510 A CN 115780510A CN 202211487942 A CN202211487942 A CN 202211487942A CN 115780510 A CN115780510 A CN 115780510A
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 18
- 229910000851 Alloy steel Inorganic materials 0.000 title claims abstract description 16
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 12
- 238000005096 rolling process Methods 0.000 claims abstract description 44
- 238000010438 heat treatment Methods 0.000 claims abstract description 29
- 238000001816 cooling Methods 0.000 claims abstract description 16
- 238000005266 casting Methods 0.000 claims abstract description 7
- 238000002791 soaking Methods 0.000 claims abstract description 4
- 239000000203 mixture Substances 0.000 claims abstract description 3
- 238000000034 method Methods 0.000 claims description 11
- 229910052720 vanadium Inorganic materials 0.000 claims description 5
- 239000000126 substance Substances 0.000 claims description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims 1
- 229910001566 austenite Inorganic materials 0.000 abstract description 14
- 229910000831 Steel Inorganic materials 0.000 abstract description 13
- 239000010959 steel Substances 0.000 abstract description 13
- 239000013078 crystal Substances 0.000 abstract description 2
- 238000000137 annealing Methods 0.000 description 11
- 239000000463 material Substances 0.000 description 11
- 238000009749 continuous casting Methods 0.000 description 6
- 229910052804 chromium Inorganic materials 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 238000005496 tempering Methods 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 229910052750 molybdenum Inorganic materials 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 229910000599 Cr alloy Inorganic materials 0.000 description 2
- 229910001182 Mo alloy Inorganic materials 0.000 description 2
- 229910000990 Ni alloy Inorganic materials 0.000 description 2
- 229910003296 Ni-Mo Inorganic materials 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000004321 preservation Methods 0.000 description 2
- 238000010583 slow cooling Methods 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 238000003723 Smelting Methods 0.000 description 1
- 229910000746 Structural steel Inorganic materials 0.000 description 1
- 229910001315 Tool steel Inorganic materials 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
- 238000005553 drilling Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
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Abstract
The invention relates to the technical field of high alloy steel production, in particular to the technical field of high alloy steel production, and particularly relates to a production process of a Cr-Ni-Mo series medium-carbon high alloy steel bar, which comprises the following steps: (1) rolling: the temperature of a casting blank heating soaking section is 1100-1250 ℃, the initial rolling temperature is 1050-1200 ℃, the rolling process is not controlled, the final rolling temperature is 900-1000 ℃, and the casting blank is air-cooled after rolling; (2) heat treatment: the rolled stock is heat treated at a selected temperature (A) 1 Cooling the mixture in a furnace after the temperature is kept at-20) DEG C for 20-25 h; and (3) finishing and delivering. The steel rolling process is optimizedThe temperature in the rolling process is increased to achieve the purpose of properly coarsening crystal grains, so that the stability of austenite is reduced, the residual austenite content in hot-rolled steel is reduced, and the subsequent heat treatment is facilitated to reduce the delivery hardness of the product.
Description
Technical Field
The invention relates to the technical field of high alloy steel production, in particular to a production process of a Cr-Ni-Mo series medium-carbon high alloy steel bar.
Background
The Cr-Ni-Mo alloy structural steel bar has high hardenability and excellent comprehensive mechanical property, and is widely applied to the fields of engineering machinery, automobile parts and the like, such as 30CrNiMo, 36CrNiMo, 40CrNiMo, 30Cr2Ni4Mo and the like. With the increase of the content of Cr, ni and Mo alloy elements, the bar stock becomes hard gradually and the processing performance becomes poor, so that customers often require annealing heat treatment in a steel mill to reduce the hardness and deliver the steel to Cr-Ni-Mo high alloy steel.
At present, a plurality of heat treatment processes for reducing the hardness are available, such as a spheroidizing annealing process, a high-temperature tempering process and the like, and for alloy steel with high Cr, ni and Mo contents, the austenite stability is high, and the low-temperature annealing process is found to be effective for reducing the hardness as found in articles 23CrNi3MoA drilling tool steel heat treatment process influence on mechanical properties and microstructures, 30CrNi4MoA steel annealing process research and the like. However, as the annealing time of the bar stock increases, the impact properties after hardening and tempering tend to decrease.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: in order to solve the problems that the bar is gradually hardened and the processing performance is poor along with the increase of the content of Cr, ni and Mo alloy elements in the prior art, the production process of the Cr-Ni-Mo series medium-carbon high-alloy steel bar is provided.
The technical scheme adopted by the invention for solving the technical problems is as follows: a production process of a Cr-Ni-Mo series medium-carbon high-alloy steel bar comprises the following chemical components in percentage by weight: 0.20-0.40%, si:0.1-0.5%, mn:0.40-1.00%, cr:1.00-2.00%, ni:2.00-4.30%, mo:0.15-0.80 percent and V is less than or equal to 0.20 percent;
the production process comprises the following steps: (1) rolling: the temperature of a casting blank heating soaking section is 1100-1250 ℃, the initial rolling temperature is 1050-1200 ℃, the rolling process is not controlled, the final rolling temperature is 900-1000 ℃, and the casting blank is air-cooled after rolling;
(2) And (3) heat treatment: the rolled stock is heat treated at a selected temperature (A) 1 Cooling the mixture in a furnace after the temperature is kept at-20) DEG C for 20-25 h;
(3) And (6) finishing and delivering.
Further comprises the step (1) that the rod specification is 14-50mm.
The beneficial effects of the invention are: the invention provides a production process of a Cr-Ni-Mo series medium-carbon high-alloy steel bar;
(1) The steel has high Cr, ni and Mo contents and high austenite stability, so that a round bar in a hot rolling state contains certain residual austenite, the residual austenite in the steel has great influence on the hardness after heat treatment, a single-pass low-temperature annealing (the annealing temperature is below Ac 1) heat treatment process is adopted, the residual austenite is difficult to transform and decompose, the residual austenite is converted into a martensite structure when cooled after the heat treatment, and the delivery hardness is difficult to meet the requirement;
(2) With the increase of the alloy content in the steel, the transformation rate of the hot rolled structure in the high-temperature tempering process is slow, and a relatively long-time heat treatment is needed to achieve the required delivery hardness, but if the heat treatment time is too long, the coarsening of carbide precipitated in the steel is serious, and the impact toughness of the product is influenced, so the method combines the optimization of the rolling process and designs the heat treatment time, thereby meeting the requirements of the product on the impact toughness and the delivery hardness.
Drawings
The invention is further illustrated with reference to the following figures and examples.
FIG. 1 is a metallographic representation of residual austenite in a hot rolled material according to example 1;
FIG. 2 is a metallographic representation of residual austenite in a hot rolled material of comparative example 1;
FIG. 3 is a metallographic representation of the carbide particle size in example 1;
fig. 4 is a metallographic representation of the particle size of the carbide in comparative example 2.
Detailed Description
The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic views illustrating only the basic structure of the present invention in a schematic manner, and thus show only the constitution related to the present invention.
A production process of a Cr-Ni-Mo series medium-carbon high-alloy steel bar comprises the following chemical components in percentage by weight: 0.20-0.40%, si:0.1-0.5%, mn:0.40-1.00%, cr:1.00-2.00%, ni:2.00-4.30%, mo:0.15-0.80 percent of V and less than or equal to 0.20 percent of V;
the production process comprises the following steps: (1) rolling: the temperature of a heating soaking section of the casting blank is 1100-1250 ℃, the rolling temperature is 1050-1200 ℃, and if the rolling temperature is too high, decarburization is accelerated; the temperature is too low, the uniformity of components is poor, rolling is not controlled in the rolling process, and water cooling is not carried out in the rolling process, so that the temperature in the rolling process is relatively high, crystal grains can be coarsened properly, the stability of an austenite structure is improved, the transformation amount of residual austenite in the subsequent cooling process is reduced, a foundation is laid for the next annealing heat treatment, the final rolling temperature is 900-1000 ℃, air cooling is carried out after rolling, if water cooling is carried out after rolling, the thermal stress is large, the bending of a rolled material is severe, so that air cooling is carried out after rolling, and the specification of the rod in the step (1) is 14-50mm;
(2) And (3) heat treatment: the rolled stock is heat treated at a selected temperature (A) 1 Point-20) DEG C, keeping the temperature for 20-25h, then cooling along with the furnace, wherein the part is low-temperature annealing treatment, converting the martensite structure of the rolled material into a high-temperature tempering structure, reducing the hardness of the material and improving the subsequent processing performance, A 1 The point is the critical point, namely the temperature at which austenite, ferrite and cementite coexist in a balanced manner in an equilibrium state;
(3) And (6) finishing and delivering.
Example 1:
this example illustrates the practical control effect of the present invention on delivery hardness and product impact performance in the production process of a high Cr, ni, mo steel for construction machinery, rolled bar gauge phi 30mm.
(1) The smelting components of the steel grade comprise 0.32 percent of C, 0.20 percent of Si, 0.60 percent of Mn, 1.50 percent of Cr, 3.40 percent of Ni, 0.40 percent of Mo and 0.08 percent of V.
(2) The section of the continuous casting billet is 220mm and 260mm, the cold billet of the continuous casting billet is heated in a heating furnace, the temperature of a high-temperature section is 1180 ℃, and the start rolling temperature is 1100 ℃; rolling is not controlled in the rolling process, and the final rolling temperature is 950 ℃; air cooling is carried out after rolling, and the rolled material is put into a pit for slow cooling.
(3) And (4) performing heat treatment after the rolled material is taken out of the pit, wherein the heat treatment temperature is 670 ℃, and performing furnace cooling after heat preservation for 25 hours.
The measured delivery hardness and the impact property in a quenched and tempered state are shown in Table 1, the delivery hardness is 260-275HBW, and the impact toughness AKU2 in the quenched and tempered state is 140-170J.
Comparative example 1
The production process of the steel with similar chemical components and same specification as a comparison case is as follows:
(1) The section of the continuous casting billet is 220mm and 260mm, the cold billet of the continuous casting billet is heated in a heating furnace, the temperature of a high-temperature section is 1180 ℃, and the start rolling temperature is 1100 ℃; water is penetrated for controlled rolling in the rolling process, and the final rolling temperature is 830 ℃; air cooling is carried out after rolling, and the rolled material is put into a pit for slow cooling.
(2) And (4) performing heat treatment after the rolled material is taken out of the pit, wherein the heat treatment temperature is 670 ℃, and performing furnace cooling after heat preservation for 25 hours.
After the rolling temperature is reduced, the metallographic structure of the hot rolled material is shown in fig. 1, and compared with the example, the residual austenite in the structure is obviously increased, so that the hardness reduction difficulty for subsequent annealing is increased. The measured delivery hardness and the impact properties in a quenched and tempered state are shown in Table 1, the delivery hardness is 290-300HBW, and the impact toughness in a quenched and tempered state is AKU 2-160J.
Comparative example 2
The steel grades with the same components and the same specification are taken as comparison cases, and the production process is as follows:
(1) The section of the continuous casting billet is 220mm and 260mm, the cold billet of the continuous casting billet is heated in a heating furnace, the temperature of a high-temperature section is 1180 ℃, and the start rolling temperature is 1100 ℃; the rolling process does not need water penetration for controlled rolling, and the finishing temperature is 950 ℃; after rolling, air cooling, entering a pit and slowly cooling.
(2) And (4) performing heat treatment after the rolled material is taken out of the pit, selecting the heat treatment temperature of 670 ℃, preserving the heat for 45 hours, and then cooling along with the furnace.
After the annealing heat treatment time is prolonged, the metallographic structure is shown in fig. 2, and compared with the example, the carbide in the structure is obviously coarse, which is not beneficial to improving the impact toughness. The measured delivery hardness and the impact property in a quenched and tempered state are shown in Table 1, the delivery hardness is 240-250HBW, and the impact toughness in a quenched and tempered state is AKU 2-120J. The shock appears to decrease and the fluctuation is large.
TABLE 1 test results
In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.
Claims (2)
1. A production process of a Cr-Ni-Mo series medium-carbon high-alloy steel bar is characterized in that the medium-carbon high-alloy steel comprises the following chemical components in percentage by weight: 0.20-0.40%, si:0.1-0.5%, mn:0.40-1.00%, cr:1.00-2.00%, ni:2.00-4.30%, mo:0.15-0.80 percent of V and less than or equal to 0.20 percent of V;
the production process comprises the following steps: (1) rolling: the temperature of a casting blank heating soaking section is 1100-1250 ℃, the initial rolling temperature is 1050-1200 ℃, the rolling process is not controlled, the final rolling temperature is 900-1000 ℃, and the casting blank is air-cooled after rolling;
(2) And (3) heat treatment: the rolled stock is heat treated at a selected temperature (A) 1 Cooling the mixture in a furnace after the temperature is kept at-20) DEG C for 20-25 h;
(3) And (6) finishing and delivering.
2. The process for producing a medium carbon high alloy steel bar in the Cr-Ni-Mo series according to claim 1, wherein: the rod specification in the step (1) is 14-50mm.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211487942.8A CN115780510A (en) | 2022-11-25 | 2022-11-25 | Production process of Cr-Ni-Mo series medium-carbon high-alloy steel bar |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211487942.8A CN115780510A (en) | 2022-11-25 | 2022-11-25 | Production process of Cr-Ni-Mo series medium-carbon high-alloy steel bar |
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| CN202211487942.8A Pending CN115780510A (en) | 2022-11-25 | 2022-11-25 | Production process of Cr-Ni-Mo series medium-carbon high-alloy steel bar |
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