Heat treatment method capable of realizing both precipitation strengthening and lower bainite phase-transformation strengthening

A heat treatment method and precipitation strengthening technology, which is applied in the field of heat treatment that takes into account both precipitation strengthening and lower bainite transformation strengthening, and can solve the problems that precipitation strengthening and lower bainite strengthening cannot be solved

Active Publication Date: 2020-11-03

JIANGSU UNIV

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AI-Extracted Technical Summary

Problems solved by technology

[0006] The purpose of the present invention is to provide a heat treatment method that takes into account both precipitation strengthening and lower bainite transformation strengthening. The iron-based alloy prepared by the heat treatment method provided by the present invention has the ch...

Method used

The present invention has adjusted the heat treatment method in the prior art, adopts the method flow process of pre-quenching+tempering+lower bainite transformation, has utilized precipitation strengthening, lower bainite transformation strengthening and complex phase (lower bainite body and martensite) fine-grain strengthening, while improving the strength and impact absorption energy of the material.

The process graph of new technique provided by the invention is as shown in Figure 1, first iron base alloy is heated to austenite phase region and quenched, then cooled to martensitic transition temperature, carries out martensitic pre-quenching, Then heat up to the temperature range that can produce precipitation strengthening for tempering, and finally cool down to the temperature range of the lower bainite transf...

Abstract

The invention provides a heat treatment method capable of realizing both precipitation strengthening and lower bainite phase-transformation strengthening, and belongs to the technical field of heat treatment of alloy materials. The heat treatment method provided by the invention comprises the following steps that an iron-based alloy is heated to an austenite phase interval for first heat preservation, then cooled to the martensitic transformation temperature for second heat preservation, then heated up to the temperature interval where precipitation strengthening can be generated for third heat preservation, finally cooled into the temperature range of a lower bainite phase-transformation temperature interval for fourth heat preservation, and then cooled to the room temperature. The methodprocess of pre-quenching, tempering and lower bainite transformation is adopted, and precipitation strengthening, lower bainite phase-transformation strengthening and multi-phase (lower bainite and martensite) fine-grained strengthening are utilized to improve the strength and impact absorption energy of materials. The result of the embodiment shows that the hardness of the iron-based alloy prepared by the heat treatment method provided by the invention is greater than or equal to 56 HRC, and the impact absorption energy Aku of the iron-based alloy is greater than or equal to 28 J.

Technology Topic

PhysicsHeat conservation +7

Image

Examples

Experimental program(3)
Comparison scheme(3)

Example Embodiment

[0051] Example 1

[0052] As attached figure 1 The process curve in the heat treatment of H13 steel (grade, 4Cr5MoSiV1, the composition is shown in Table 1), the parameters of H13 steel are obtained from the TTT diagram of H13 steel. It is 320℃, Mf is 180℃, and the lower bainite transformation temperature range is 320℃~400℃.

[0053] The heat treatment method is:

[0054] (1) Heat the H13 steel to 1050°C for 1 hour to obtain an austenitic alloy;

[0055] (2) The austenitic alloy obtained in the step (1) is water-cooled to 260° C. and held for 30 seconds to obtain a martensitic iron-based alloy;

[0056] (3) Raising the martensitic iron-based alloy obtained in the step (2) to 550°C for 0.5 hour to obtain a tempered iron-based alloy;

[0057] (4) The tempered iron-based alloy obtained in the step (3) is water-cooled to 340°C for 2 hours, and then naturally cooled to room temperature.

[0058] The properties of H13 steel after heat treatment: hardness 58HRC, impact absorption energy Aku30J.

[0059] Table 1 H13 steel composition

[0060]

Example Embodiment

[0061] Example 2

[0062] As attached figure 1 The process curve in the heat treatment of 42CrMo steel (the composition is shown in Table 2), the parameters of 42CrMo steel are obtained from the TTT diagram of 42CrMo steel, its Ac3 is 800℃, and its Ms is 310℃ in the case of austenitizing at 840℃ , Mf is 170℃, and the lower bainite transformation range is 310℃~420℃.

[0063] The heat treatment method is:

[0064] (1) Heat the 42CrMo steel to 840°C for 1 hour to obtain an austenitic alloy;

[0065] (2) Cooling the austenitic alloy oil obtained in the step (1) to 200° C. and holding it for 10 minutes to obtain a martensitic iron-based alloy;

[0066] (3) Raising the martensitic iron-based alloy obtained in the step (2) to 400°C for 0.5 hour to obtain a tempered iron-based alloy;

[0067] (4) The tempered iron-based alloy oil obtained in the step (3) is cooled to 340°C for 2 hours, and then naturally cooled to room temperature.

[0068] The properties of 42CrMo steel after heat treatment: hardness 56HRC, impact absorption work Aku28J.

[0069] Table 2 Composition of 42CrMo steel

[0070]

[0071]

Example Embodiment

[0072] Example 3

[0073] As attached figure 1 The process curve in the process curve for the heat treatment of Cr12MoV steel (the composition is shown in Table 3), the parameters of Cr12MoV steel are obtained from the TTT diagram of Cr12MoV steel, its Accm is 855 ℃, austenitizing at 1020 ℃, its Ms is 230 ℃, Mf It is 80℃, and the temperature range of lower bainite is 230℃~350℃.

[0074] The heat treatment method is:

[0075] (1) Heat Cr12MoV steel to 1020°C and keep it for 1 hour to obtain austenitic alloy;

[0076] (2) Cooling the austenitic alloy oil obtained in the step (1) to 190°C and holding it for 1 minute to obtain a martensitic iron-based alloy;

[0077] (3) Raising the martensitic iron-based alloy obtained in the step (2) to 500°C for 0.5 hour to obtain a tempered iron-based alloy;

[0078] (4) The tempered iron-based alloy oil obtained in the step (3) is cooled to 240°C for 2 hours, and then naturally cooled to room temperature.

[0079] The properties of Cr12MoV steel after heat treatment: hardness 56HRC, impact absorption work Aku28J.

[0080] Table 3 Composition of Cr12MoV steel

[0081]

[0082] The conventional heat treatment process includes the following steps:

[0083] (1) Quench and heat the iron-based alloy to obtain an austenitized alloy;

[0084] (2) After cooling the austenitic alloy obtained in step (1), perform martensitic pre-quenching to obtain a martensitic iron-based alloy;

[0085] (3) After raising the temperature of the martensitic iron-based alloy obtained in the step (2), performing lower bainite austempering to obtain the lower bainite transformation-strengthened iron-based alloy;

[0086] (4) The lower bainite transformation-strengthened iron-based alloy obtained in the step (3) is tempered one or more times, and then naturally cooled to room temperature.

PUM

Property	Measurement	Unit
Impact absorption energy	30.0	J
Impact absorption energy	28.0	J
Impact absorption energy	14.0	J

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