Annealing heat treatment process of 23CrNi3MoA hot-rolled round steel

Abstract

The invention discloses an annealing heat treatment process for 23CrNi3MoA hot-rolled round steel, and relates to the technical field of steel production, the annealing heat treatment process comprises the following steps: dividing the hot-rolled round steel into first-specification round steel and second-specification round steel based on the diameter of the hot-rolled round steel, and the diameter of the second-specification round steel is greater than that of the first-specification round steel; the round steel of the first specification is put into a roller hearth furnace to be subjected to slow cooling annealing, the annealing temperature is controlled to be 530-700 DEG C, and the roller speed is 5 m / h; and the round steel of the second specification is put into the trolley furnace to be annealed at the temperature, the annealing temperature is controlled to be 680-690 DEG C, and the heat preservation time is larger than or equal to 18 h. By designing an annealing temperature curve, including annealing temperatures and holding time in different stages, the requirements that the product hardness is smaller than or equal to 240 HB and the cross section hardness deviation is smaller than or equal to 10 HB are met, the tensile strength is larger than or equal to 1450 MPa, the yield strength is larger than or equal to 1050 MPa, A is larger than or equal to 10%, Z is larger than or equal to 45%, and the impact toughness AKU is larger than or equal to 78 J.

Description

Technical Field

[0001] The invention relates to the technical field of steel production, in particular to an annealing heat treatment process for 23CrNi3MoA hot-rolled round steel. Background Art

[0002] With the development of China's industrialization and infrastructure construction, a large number of road construction, mining, tunnel and other projects require the use of large-scale excavation equipment, which requires the use of steel for drill tools; in view of the complex use environment of drill tool steel, the service life and reliability requirements of drill tool steel, especially 23CrNi3MoA for heavy-duty drill rods, are very high. Therefore, the raw material quality of drill tool steel is of paramount importance, especially the hardness and uniformity of the raw material steel for drill tools, which affects the machinability of drill tool drill rods and provides good organizational conditions for the hot processing of finished products. The 23CrNi3MoA material produced by the process of the present invention has the advantages of good and uniform hardness value, good machinability, good organizational foundation, good comprehensive strength and plasticity after quenching and tempering, and good impact toughness. The product quality hardness value and uniformity of other similar drill rods cannot meet the requirements at the same time. The hardness requirement of domestic similar products 23CrNi3Mo is ≤270HB, and there is no hardness uniformity requirement. The performance obtained after heat treatment cannot meet the high fatigue strength requirements. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the disadvantages of the prior art and provide an annealing heat treatment process for 23CrNi3MoA hot-rolled round steel.

[0004] In order to solve the above technical problems, the technical solution of the present invention is as follows: An annealing heat treatment process for 23CrNi3MoA hot-rolled round steel comprises: Based on the diameter of the hot-rolled round steel, it is divided into first-specification round steel and second-specification round steel, and the diameter of the second-specification round steel is greater than the diameter of the first-specification round steel; Put the first specification round steel into the roller hearth furnace for slow cooling annealing, control the annealing temperature to 530℃~700℃, and the roller speed to 5m / h; Place the second specification round steel into the trolley furnace for hot annealing, control the annealing temperature to 680-690℃, and keep the temperature for ≥18h.

[0005] As a preferred solution of the annealing heat treatment process of the 23CrNi3MoA hot-rolled round steel of the present invention, the diameter of the first specification round steel is less than 130 mm, and the diameter of the second specification round steel is greater than or equal to 130 mm.

[0006] As a preferred scheme of the annealing heat treatment process of 23CrNi3MoA hot-rolled round steel described in the present invention, the annealing temperature of the first heating zone and the second heating zone in the roller hearth furnace is 640°C~700°C, the annealing temperature of the second heating zone is 640°C~700°C, the annealing temperature of the third heating zone to the ninth heating zone is 675°C~700°C, the annealing temperature of the tenth heating zone is 645°C~680°C, the annealing temperature of the eleventh heating zone is 610°C~650°C, the annealing temperature of the twelfth heating zone is 580°C~620°C, and the annealing temperature of the thirteenth heating zone is 530°C~570°C.

[0007] As a preferred solution of the annealing heat treatment process of 23CrNi3MoA hot-rolled round steel of the present invention, the loading capacity of the trolley furnace is less than or equal to 110 tons.

[0008] As a preferred solution of the annealing heat treatment process of the 23CrNi3MoA hot-rolled round steel of the present invention, the charging temperature of the trolley furnace is greater than or equal to 250°C.

[0009] As a preferred solution of the annealing heat treatment process of the 23CrNi3MoA hot-rolled round steel of the present invention, the speed of the cooling fan of the roller hearth furnace is less than or equal to 60r / min.

[0010] The beneficial effects of the present invention are: The present invention achieves the requirements of product hardness ≤240HB, cross-section hardness deviation ≤10HB, tensile strength ≥1450MPa, yield strength ≥1050MPa, A ≥10%, Z ≥45%, and impact toughness AKU ≥78J by designing an annealing temperature curve, including annealing temperatures and holding times at different stages. DETAILED DESCRIPTION

[0011] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific implementation methods.

[0012] The present application provides an annealing heat treatment process for 23CrNi3MoA hot-rolled round steel, which specifically comprises the following steps: Step S101: The hot-rolled round steel is divided into first-specification round steel and second-specification round steel based on its diameter, and the diameter of the second-specification round steel is greater than the diameter of the first-specification round steel.

[0013] Specifically, the diameter of hot-rolled round steel is generally 50mm~180mm. When the diameter of hot-rolled round steel is greater than or equal to 130mm, it is classified as the second specification round steel, i.e. large specification round steel, and the rest is classified as the first specification round steel, i.e. small specification round steel. Afterwards, different annealing heat treatment methods are used according to the specifications of the hot-rolled round steel.

[0014] It should be noted that before the annealing heat treatment, the annealing furnace needs to be prepared. In this embodiment, the annealing furnace uses a trolley furnace and a roller hearth furnace. Among them, the trolley furnace needs to check the annealing furnace burner and furnace door closure and other equipment conditions in advance to ensure that the annealing furnace operation process can ensure the execution of the temperature process. The roller hearth furnace needs to be scheduled in advance, prepare the material height and production rhythm, and check the operation of the fan and rollers.

[0015] Step S102: placing the first specification round steel into a roller hearth furnace for slow cooling annealing, controlling the annealing temperature to be 530° C. to 700° C. and the roller speed to be 5 m / h.

[0016] Specifically, the roller hearth furnace is divided into 13 heating zones, 1 to 13. Among them, the annealing temperature of the first and second heating zones is 640℃~700℃, the annealing temperature of the second heating zone is 640℃~700℃, the annealing temperature of the third to ninth heating zones is 675℃~700℃, the annealing temperature of the tenth heating zone is 645℃~680℃, the annealing temperature of the eleventh heating zone is 610℃~650℃, the annealing temperature of the twelfth heating zone is 580℃~620℃, and the annealing temperature of the thirteenth heating zone is 530℃~570℃.

[0017] In addition, the roller speed of the roller hearth furnace is controlled to 5m / h, and the speed of the cold spray fan is controlled to be less than or equal to 60r / min.

[0018] Step S103: placing the second specification round steel into a trolley furnace for hot annealing, controlling the annealing temperature to 680-690° C., and keeping the temperature for ≥18 h.

[0019] Specifically, in the trolley furnace annealing heat treatment process, the furnace loading capacity is controlled to be ≤110 tons, the furnace loading temperature is ≥250°C, the trolley annealing furnace is heated to 680-690°C, and the insulation time is ≥18h.

[0020] The following is further described by means of specific examples.

[0021] Embodiment 1: furnace number: 23706542, specification φ80mm.

[0022] Process route: smelting → continuous casting → heating → rolling → annealing → straightening → finishing → finished product inspection → packaging → weighing → warehousing.

[0023] The annealing process is performed by roller hearth furnace slow cooling annealing process, the temperature is 685℃, and the roller speed is 5m / h.

[0024] The production results show that the finished product composition, alloy control, residual elements and gas composition, macro, inclusions, grain size, banding, flaw detection, performance, impact, etc. all meet the requirements. See Table 1 for hardness results. See Table 2 for performance and impact results.

[0025]

[0026] Table 1

[0027] Table 2 Embodiment 2: furnace number: 24700655, specification φ160mm.

[0028] Process route: smelting → continuous casting → heating → rolling → annealing → straightening → finishing → finished product inspection → packaging → weighing → warehousing.

[0029] The annealing process is performed in a trolley furnace with a temperature of 680°C and a holding time of 19.5h.

[0030] The production results show that the finished product composition, alloy control, residual elements and gas composition, macro, inclusions, grain size, banding, flaw detection, performance, impact, etc. all meet the requirements. See Table 3 for hardness results. See Table 4 for performance and impact results.

[0031]

[0032] Table 3

[0033] Table 4 Therefore, the technical solution of this application achieves the key indicators of low hardness, high strength and high toughness. The product hardness ≤ 240HB and the cross-sectional hardness deviation ≤ 10HB are met. The performance and impact toughness can meet the requirements: tensile strength ≥ 1450MPa, yield strength ≥ 1050MPa, A ≥ 10%, Z ≥ 45%, impact ≥ 78J.

[0034] In addition to the above embodiments, the present invention may also have other implementation modes; any technical solutions formed by equivalent replacement or equivalent transformation shall fall within the protection scope required by the present invention.

Claims

1. An annealing heat treatment process for 23CrNi3MoA hot-rolled round steel, characterized in that: include: Based on the diameter of the hot-rolled round steel, it is divided into first-specification round steel and second-specification round steel, and the diameter of the second-specification round steel is greater than the diameter of the first-specification round steel; Put the first specification round steel into the roller hearth furnace for slow cooling annealing, control the annealing temperature to 530℃~700℃, and the roller speed to 5m / h; Place the second specification round steel into the trolley furnace for hot annealing, control the annealing temperature to 680-690℃, and keep the temperature for ≥18h.

2. The annealing heat treatment process of 23CrNi3MoA hot-rolled round steel according to claim 1, characterized in that: The diameter of the first specification round steel is less than 130 mm, and the diameter of the second specification round steel is greater than or equal to 130 mm.

3. The annealing heat treatment process of 23CrNi3MoA hot-rolled round steel according to claim 1, characterized in that: The annealing temperature of the first heating zone and the second heating zone in the roller hearth furnace is 640°C~700°C, the annealing temperature of the second heating zone is 640°C~700°C, the annealing temperature of the third heating zone to the ninth heating zone is 675°C~700°C, the annealing temperature of the tenth heating zone is 645°C~680°C, the annealing temperature of the eleventh heating zone is 610°C~650°C, the annealing temperature of the twelfth heating zone is 580°C~620°C, and the annealing temperature of the thirteenth heating zone is 530°C~570°C.

4. The annealing heat treatment process of 23CrNi3MoA hot-rolled round steel according to claim 1, characterized in that: The loading capacity of the trolley furnace is less than or equal to 110 tons.

5. The annealing heat treatment process of 23CrNi3MoA hot-rolled round steel according to claim 1, characterized in that: The loading temperature of the trolley furnace is greater than or equal to 250°C.

6. The annealing heat treatment process of 23CrNi3MoA hot-rolled round steel according to claim 1, characterized in that: The speed of the cooling fan of the roller hearth furnace is less than or equal to 60r / min.

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