A kind of uniformly carbonized cold heading steel and preparation method thereof

Abstract

The invention discloses a uniformly carburized cold heading steel, which belongs to the technical field of cold heading steel, and comprises the following raw materials in weight percentage: carbon: 0.08%-0.12%; manganese: 0.46%-0.52%; aluminum: 0.034%-0.047%; cobalt oxide: 0.06%-0.14%; antimony trisulfide: 0.023%-0.057%; the rest is Fe and inevitable impurities. The uniformly carburized cold heading steel prepared by the invention has high tensile strength, which meets the market production demand; by optimizing the proportion of each component and the heat treatment process, the size of the grain is reduced, the generation of lamellar pearlite is reduced, and the uniformity of carbide distribution is improved, thereby improving the anti-cracking performance. In addition, the heat treatment process time of the invention is short, which significantly improves the production efficiency compared with the prior art.

Description

Technical Field

[0001] The invention relates to the technical field of cold heading steel, and in particular to uniformly carbonized cold heading steel and a preparation method thereof. Background Art

[0002] Cold heading steel is often used to manufacture fasteners, which can fasten parts or components into a whole. It is an important basic material and is widely used in machinery, automobiles, ships, railways, bridges, buildings, instruments and other fields.

[0003] For example, Chinese patent CN115198208B discloses a heat-resistant and corrosion-resistant cold heading steel and its heat treatment method, production method and application. The heat-resistant and corrosion-resistant cold heading steel includes the following chemical components: C, Si, Mn, Cr, Co, Ni, V, N, Se, and 33≤V / N≤46, and the corrosion resistance coefficient R value is ≥3.6; the room temperature Rm of the heat-resistant and corrosion-resistant cold heading steel is ≥960MPa, and Rp0.2 is ≥890MPa, which is suitable for making high-strength bolts for high-temperature industrial atmospheric corrosion environments such as engines and turbines.

[0004] However, the heat treatment steps in the above patent require multiple heat preservations, and the heat preservation time is as long as 7-13 hours, and the production efficiency needs to be improved; and in the above patent, the wire is first heated to 600-650°C, which is easy to generate lamellar pearlite; and then heated to 760-800°C, which is easy to cause secondary generation of lamellar pearlite; thus, the carbide distribution is uneven, affecting the crack resistance.

[0005] Based on this, the present invention designs a uniformly carbonized cold heading steel and a preparation method thereof to solve the above problems. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, the present invention provides a uniformly carbonized cold heading steel and a preparation method thereof.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] A uniformly carbonized cold heading steel comprises the following raw materials in weight percentage: carbon: 0.08%-0.12%; manganese: 0.46%-0.52%; aluminum: 0.034%-0.047%; cobalt oxide: 0.06%-0.14%; antimony trisulfide: 0.023%-0.057%; the rest is Fe and unavoidable impurities;

[0009] The following steps are also included:

[0010] Step 1: Mix the above raw materials evenly according to proportion, vacuum melt, continuously cast and hot roll to obtain cold heading steel blank;

[0011] Step 2: slowly heat the cold heading steel billet to 675-684℃ and keep it warm for 30-40min;

[0012] Step 3: Cool down to 600-610℃;

[0013] Step 4: Increase the cooling speed, cool down to 530-540℃, and keep warm for 0.5-1.5h;

[0014] Step 5: Heat to 620-630℃ at a rate of 80-90℃ / h;

[0015] Step 6: Increase the heating rate to 130-160℃ / h and heat to 650-680℃;

[0016] Step 7: Increase the heating rate to 180-200°C / h again, heat to 720-760°C, keep warm for 2-3h and then air cool to room temperature; obtain uniformly carbonized cold heading steel.

[0017] Furthermore, in step 2, the heating rate is 1-2°C / min.

[0018] Furthermore, in step three, the cooling rate is 80-90°C / h.

[0019] Furthermore, in step 4, the cooling rate is 130-160°C / h.

[0020] A method for preparing cold heading steel comprises the following steps:

[0021] Step 1: Weigh the raw materials: iron powder, carbon powder, manganese powder, aluminum powder, cobalt oxide powder, and antimony trisulfide powder;

[0022] Step 2: Mix the above raw materials evenly, then vacuum melt, continuously cast and hot roll to obtain cold heading steel blank;

[0023] Step 3: Slowly heat the cold heading steel billet to 675-684℃ and keep it warm;

[0024] Step 4: Cool down to 600-610℃ at a rate of 80-90℃ / h;

[0025] Step 5: Increase the cooling speed, cool down to 530-540℃, and keep warm;

[0026] Step 6: Heat to 620-630℃ at a rate of 80-90℃ / h;

[0027] Step 7: Increase the heating rate to 130-160°C / h and heat to 650-680°C;

[0028] Step 8: Increase the heating rate again, heat to 720-760°C, keep warm and then air cool to room temperature; obtain uniformly carbonized cold heading steel.

[0029] Furthermore, step three is specifically as follows: slowly heating the cold heading steel billet to 675-684°C at a rate of 1-2°C / min, and keeping the temperature for 30-40 minutes.

[0030] Furthermore, step five is specifically as follows: increasing the cooling rate to 130-160°C / h, cooling to 530-540°C, and keeping warm for 0.5-1.5h.

[0031] Furthermore, the heating rate is increased to 180-200°C / h again, heated to 720-760°C, kept warm for 2-3h and then air-cooled to room temperature; thus, uniformly carbonized cold heading steel is obtained.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The uniformly carbonized cold heading steel prepared by the present invention has high tensile strength and meets the market production demand; by optimizing the proportion of each component and the heat treatment process, the size of the grains is reduced, the generation of lamellar pearlite is reduced, the uniformity of carbide distribution is improved, and thus the crack resistance is improved.

[0034] The heat treatment process time of the present invention is shorter, and the production efficiency is significantly improved compared with the prior art. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Embodiment 1

[0037] This embodiment provides a method for preparing uniformly carbonized cold heading steel, comprising the following steps:

[0038] Step 1: weigh the raw materials: carbon powder: 0.12%; manganese powder: 0.52%; aluminum powder: 0.047%; cobalt oxide powder: 0.14%; antimony trisulfide powder: 0.057%; the rest is iron powder;

[0039] Step 2: Mix the above raw materials evenly, then vacuum melt, continuously cast and hot roll to obtain cold heading steel blank;

[0040] Step 3: slowly heat the cold heading steel billet to 684°C at a rate of 2°C / min and keep it at that temperature for 40 minutes;

[0041] Step 4: Cool down to 610°C at a rate of 90°C / h;

[0042] Step 5: Increase the cooling rate to 160℃ / h, cool to 540℃, and keep warm for 1.5h;

[0043] Step 6: Heat to 630°C at a rate of 90°C / h;

[0044] Step 7: Increase the heating rate to 160°C / h and heat to 680°C;

[0045] Step 8: Increase the heating rate to 200°C / h again, heat to 760°C, keep warm for 3h and then air cool to room temperature; obtain uniformly carbonized cold heading steel.

[0046] Embodiment 2

[0047] This embodiment provides a method for preparing uniformly carbonized cold heading steel, comprising the following steps:

[0048] Step 1: weigh the raw materials: carbon powder: 0.08%; manganese powder: 0.46%; aluminum powder: 0.034%; cobalt oxide powder: 0.06%; antimony trisulfide powder: 0.023%; the rest is iron powder;

[0049] Step 2: Mix the above raw materials evenly, then vacuum melt, continuously cast and hot roll to obtain cold heading steel blank;

[0050] Step 3: slowly heat the cold heading steel billet to 675°C at a rate of 1°C / min and keep it at that temperature for 30 minutes;

[0051] Step 4: Cool down to 600°C at a rate of 80°C / h;

[0052] Step 5: Increase the cooling rate to 130℃ / h, cool to 530℃, and keep warm for 0.5h;

[0053] Step 6: Heat to 620°C at a rate of 80°C / h;

[0054] Step 7: Increase the heating rate to 130°C / h and heat to 650°C;

[0055] Step 8: Increase the heating rate to 180°C / h again, heat to 720°C, keep warm for 2h and then air cool to room temperature; obtain uniformly carbonized cold heading steel.

[0056] Embodiment 3

[0057] This embodiment provides a method for preparing uniformly carbonized cold heading steel, comprising the following steps:

[0058] Step 1: weigh the raw materials: carbon powder: 0.09%; manganese powder: 0.49%; aluminum powder: 0.041%; cobalt oxide powder: 0.12%; antimony trisulfide powder: 0.042%; the rest is iron powder;

[0059] Step 2: Mix the above raw materials evenly, then vacuum melt, continuously cast and hot roll to obtain cold heading steel blank;

[0060] Step 3: slowly heat the cold heading steel billet to 680°C at a rate of 1.5°C / min and keep it at that temperature for 34 minutes;

[0061] Step 4: Cool down to 606°C at a rate of 86°C / h;

[0062] Step 5: Increase the cooling rate to 140℃ / h, cool to 538℃, and keep warm for 1h;

[0063] Step 6: Heat to 624°C at a rate of 84°C / h;

[0064] Step 7: Increase the heating rate to 150°C / h and heat to 670°C;

[0065] Step 8: Increase the heating rate to 188°C / h again, heat to 750°C, keep warm for 2.5h and then air cool to room temperature; obtain uniformly carbonized cold heading steel.

[0066] Comparative Example 1

[0067] Different from the third embodiment, the raw material does not contain antimony trisulfide.

[0068] This embodiment provides a method for preparing uniformly carbonized cold heading steel, comprising the following steps:

[0069] Step 1: Weigh the raw materials: carbon powder: 0.09%; manganese powder: 0.49%; aluminum powder: 0.041%; cobalt oxide powder: 0.12%; the rest is iron powder;

[0070] Step 2: Mix the above raw materials evenly, then vacuum melt, continuously cast and hot roll to obtain cold heading steel blank;

[0071] Step 3: slowly heat the cold heading steel billet to 680°C at a rate of 1.5°C / min and keep it at that temperature for 34 minutes;

[0072] Step 4: Cool down to 606°C at a rate of 86°C / h;

[0073] Step 5: Increase the cooling rate to 140℃ / h, cool to 538℃, and keep warm for 1h;

[0074] Step 6: Heat to 624°C at a rate of 84°C / h;

[0075] Step 7: Increase the heating rate to 150°C / h and heat to 670°C;

[0076] Step 8: Increase the heating rate to 188°C / h again, heat to 750°C, keep warm for 2.5h and then air cool to room temperature; obtain uniformly carbonized cold heading steel.

[0077] Comparative Example 2

[0078] The difference from the third embodiment is that the temperature is raised to 670° C. in step three.

[0079] This embodiment provides a method for preparing uniformly carbonized cold heading steel, comprising the following steps:

[0080] Step 1: weigh the raw materials: carbon powder: 0.09%; manganese powder: 0.49%; aluminum powder: 0.041%; cobalt oxide powder: 0.12%; antimony trisulfide powder: 0.042%; the rest is iron powder;

[0081] Step 2: Mix the above raw materials evenly, then vacuum melt, continuously cast and hot roll to obtain cold heading steel blank;

[0082] Step 3: slowly heat the cold heading steel billet to 670°C at a rate of 1.5°C / min and keep it at that temperature for 34 minutes;

[0083] Step 4: Cool down to 606°C at a rate of 86°C / h;

[0084] Step 5: Increase the cooling rate to 140℃ / h, cool to 538℃, and keep warm for 1h;

[0085] Step 6: Heat to 624°C at a rate of 84°C / h;

[0086] Step 7: Increase the heating rate to 150°C / h and heat to 670°C;

[0087] Step 8: Increase the heating rate to 188°C / h again, heat to 750°C, keep warm for 2.5h and then air cool to room temperature; obtain uniformly carbonized cold heading steel.

[0088] Comparative Example 3

[0089] Different from the third embodiment, the cooling rate in step 5 is still 86° C. / h.

[0090] This embodiment provides a method for preparing uniformly carbonized cold heading steel, comprising the following steps:

[0091] Step 1: weigh the raw materials: carbon powder: 0.09%; manganese powder: 0.49%; aluminum powder: 0.041%; cobalt oxide powder: 0.12%; antimony trisulfide powder: 0.042%; the rest is iron powder;

[0092] Step 2: Mix the above raw materials evenly, then vacuum melt, continuously cast and hot roll to obtain cold heading steel blank;

[0093] Step 3: slowly heat the cold heading steel billet to 680°C at a rate of 1.5°C / min and keep it at that temperature for 34 minutes;

[0094] Step 4: Cool down to 606°C at a rate of 86°C / h;

[0095] Step 5: Heat at a rate of 86°C / h to 538°C, and keep warm for 1h;

[0096] Step 6: Heat to 624°C at a rate of 84°C / h;

[0097] Step 7: Increase the heating rate to 150°C / h and heat to 670°C;

[0098] Step 8: Increase the heating rate to 188°C / h again, heat to 750°C, keep warm for 2.5h and then air cool to room temperature; obtain uniformly carbonized cold heading steel.

[0099] Experimental example

[0100] The tensile strength test and the cross-sectional shrinkage test were respectively carried out on Examples 1 to 3 and Comparative Examples 1 to 3 according to GB / T 6478-2015 "Steel for Cold Heading and Cold Extrusion", and the grain size test was carried out on each group of products according to GB / T 6478-2015 "Method for Determination of Average Grain Size of Metals", and the results are as follows:

[0101] project Embodiment 1 Embodiment 2 Embodiment 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 tensile strength 485MPa 488Mpa 484MPa 460MPa 487MPa 486MPa Sectional shrinkage 68％ 67％ 69％ 66％ 57％ 65％ Grain size 9.5 9.5 9.5 9.5 Level 9 Level 9

[0102] The uniformly carbonized cold heading steel prepared by the present invention has high tensile strength and meets the market production demand; by optimizing the proportion of each component and the heat treatment process, the size of the grains is reduced, the generation of lamellar pearlite is reduced, the uniformity of carbide distribution is improved, and thus the crack resistance is improved.

[0103] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A uniformly carbonized cold heading steel, characterized in that: The raw materials include the following weight percentages: carbon: 0.08%-0.12%; Manganese: 0.46%-0.52%; Aluminum: 0.034%-0.047%; Cobalt oxide: 0.06%-0.14%; Antimony trisulfide: 0.023%-0.057%; The rest is Fe and unavoidable impurities; The following steps are also included: Step 1: Mix the above raw materials evenly according to proportion, vacuum melt, continuously cast and hot roll to obtain cold heading steel blank; Step 2: slowly heat the cold heading steel billet to 675-684℃ and keep it warm for 30-40min; Step 3: Cool down to 600-610℃; Step 4: Increase the cooling speed, cool down to 530-540℃, and keep warm for 0.5-1.5h; Step 5: Heat to 620-630℃ at a rate of 80-90℃ / h; Step 6: Increase the heating rate to 130-160℃ / h and heat to 650-680℃; Step 7: Increase the heating rate to 180-200°C / h again, heat to 720-760°C, keep warm for 2-3h and then air cool to room temperature; obtain uniformly carbonized cold heading steel.

2. The cold heading steel according to claim 1, characterized in that: In step 2, the heating rate is 1-2°C / min.

3. The cold heading steel according to claim 2, characterized in that: In step 3, the cooling rate is 80-90°C / h.

4. The cold heading steel according to claim 3, characterized in that: In step 4, the cooling rate is 130-160°C / h.

5. A method for preparing uniformly carbonized cold heading steel, characterized in that: The following steps are involved: Step 1: Weigh the raw materials in weight percentage: carbon powder: 0.08%-0.12%; manganese powder: 0.46%-0.52%; aluminum powder: 0.034%-0.047%; cobalt oxide powder: 0.06%-0.14%; antimony trisulfide powder: 0.023%-0.057%; the rest is Fe powder; Step 2: Mix the above raw materials uniformly, vacuum melt, continuously cast and hot roll to obtain cold heading steel blank; Step 3: slowly heat the cold heading steel billet to 675-684°C and keep it warm; Step 4: Cool down to 600-610℃ at a rate of 80-90℃ / h; Step 5: Increase the cooling speed, cool down to 530-540℃, and keep warm; Step 6: Heat to 620-630°C at a rate of 80-90°C / h; Step 7: Increase the heating rate to 130-160°C / h and heat to 650-680°C; Step 8: Increase the heating rate again, heat to 720-760°C, keep warm and then air cool to room temperature; obtain uniformly carbonized cold heading steel.

6. The preparation method according to claim 5, characterized in that: Step 3 is specifically as follows: slowly heating the cold heading steel billet to 675-684°C at a rate of 1-2°C / min, and keeping the temperature for 30-40 minutes.

7. The preparation method according to claim 6, characterized in that: Step 5 is specifically as follows: increase the cooling rate to 130-160°C / h, cool to 530-540°C, and keep warm for 0.5-1.5h.

8. The preparation method according to claim 7, characterized in that: The heating rate is increased again to 180-200°C / h, heated to 720-760°C, kept at this temperature for 2-3h, and then air-cooled to room temperature; thus, uniformly carbonized cold heading steel is obtained.