CN105779898B - Cold-work die steel plate and manufacturing method thereof - Google Patents

Abstract

The invention provides a cold working die steel plate, the components of the steel plate are as follows by weight percentage: C: 1.0-1.35%, Si: 0.7-1.0%, Mn: 0.4-0.5%, Cr: 9.0-10.5%, Mo: 0.7- 1.0%, V:0.6-1.0%, B:0.001-0.0012%, P<0.03, S<0.03, the balance is Fe and unavoidable impurities. Manufacturing method: The cast steel ingot is heated in a heating furnace. The heating process is two-stage heating. The rolled steel plate is rolled in multiple passes. The starting rolling temperature is 1050‑1100 °C, the final rolling temperature is 850‑930 °C, and the total reduction rate is 60‑85%; the rolled steel plate is slowly cooled, and the slowly cooled steel plate is quenched and tempered. The toughness of the steel can be improved by reducing the content of C in the steel, and at the same time, the hardenability of the steel can be further improved by adding cheap B elements, and a cold-work die steel plate with high hardness and toughness can be obtained, and its hardness can reach or even exceed Cr12 cold work die steel has higher toughness than Cr12 cold work die steel.

Description

A kind of cold working die steel plate and its manufacturing method

technical field

The invention belongs to the technical field of metal material production, and in particular relates to a cold-working die steel plate and a manufacturing method thereof.

Background technique

Mold is the foundation of industrial development and an indispensable forming tool for industrialization to realize mass production of products and research and development of new products. Die steel can be divided into cold work die steel, hot work die steel and plastic die steel according to its use and working conditions. Cold work die steel is mainly used for workpiece pressing, cold drawing, stamping and other molds in cold state. High-alloy cold-working die steel is the preferred material for high-precision and high-life cold-working dies, mainly Cr12-type cold-working die steel. This series of cold-working die steels are high-carbon and high-chromium die steels. This type of die steel has high hardness , strength and wear resistance, but due to the high carbon content, the eutectic carbides are severely inhomogeneous, which makes the impact toughness of the mold poor and easy to be brittle. And the traditional production process of Cr12 cold work die steel includes: electric furnace smelting-refining-ingot casting-ingot annealing treatment-heating-forging-post-forging heat treatment, resulting in the disadvantages of high production cost and complicated process. In view of the above existing problems, some patents for improving the above shortcomings have been produced.

"A Cold Work Die Steel and Its Preparation Method" (Application No.: 201210545009.1), the invention provides a cold work die steel, which reduces the carbon content in the steel on the basis of the Cr12 type die steel. It has the advantages of good abrasiveness, high hardness and small heat treatment deformation. However, the invention adds tungsten element to the steel, which increases the production cost.

"A Preparation Method of Cold Work Die Steel Material" (Application No.: 201310289985.X), the invention obtains a steel with good strength and toughness through melting, oxidation, detection of alloy composition and adjustment, refining, casting, heat treatment and other processes Cold work tool steel. However, the heat treatment process of this patent is relatively complicated, including cryogenic treatment processes such as 0°C water and liquid nitrogen, resulting in increased production costs.

"A High Alloy Cold Work Die Steel" (Application No.: 200810121969.9), the invention obtains a hardness and toughness reaching Cr12MoV in Cr12 type through electric arc furnace smelting-casting ingot-forging-stress relief annealing-cutting-storage and other processes , Cr12Mo1V1 die steel, but the steel has a high carbon content, up to 2.5%, which will inevitably reduce the toughness of the die steel and increase the brittle tendency of the die steel.

Compared with the above prior art, it can be known that the manufacture of cold work die steel mainly has the following deficiencies.

(1) The carbon content in steel is high, resulting in serious inhomogeneity of eutectic carbides, making it poor in impact toughness and prone to brittle cracks.

(2) Other precious elements are added, resulting in increased production costs.

(3) The production process is complicated and the production cost is higher.

Contents of the invention

The purpose of the present invention is to overcome the above problems and disadvantages and provide a cold work die steel with high strength and toughness and its manufacturing method, its hardness reaches or even exceeds Cr12 type cold work die steel, and its toughness is higher than Cr12 type cold work die steel steel.

The purpose of the invention is achieved in this way:

A cold-working die steel plate, the composition of which is as follows by weight percentage: C: 1.0-1.35%, Si: 0.7-1.0%, Mn: 0.4-0.5%, Cr: 9.0-10.5%, Mo: 0.7-1.0 %, V:0.6-1.0%, B:0.001-0.0012%, P<0.03, S<0.03, the balance is Fe and unavoidable impurities.

The steel composition design reason of the present invention is as follows:

C: High carbon content can ensure the formation of a large number of alloy carbides. When quenching and heating, part of it dissolves into austenite to improve its stability. At the same time, it also increases the content of alloy elements in martensite to ensure its hardness. Undissolved carbides can refine grains, improve toughness, and improve the wear resistance of steel; but when the carbon content is too high, it will increase the inhomogeneity of carbides and seriously affect its toughness. The optional addition range of the present invention is 1.0-1.35%.

Si: An essential element for steelmaking and deoxidation. It has a strong solid solution ability in steel and can play a certain role in strengthening; in tool and die steel, with the increase of Si content, the size and number of eutectic carbides increase. The secondary hardening ability is improved, and the toughness of steel will be seriously reduced if the content is too high. The optional addition range of the present invention is 0.7-1.0%.

Mn: An appropriate amount of Mn can delay the transformation of ferrite and pearlite in steel, greatly increase the hardenability of steel, and improve impact toughness. The optional addition range of the present invention is 0.4-0.5%.

Cr: Chromium can increase the hardenability of steel, improve tempering stability, and produce secondary hardening; chromium is a medium-strong carbide-forming element, which can form carbides with carbon in steel, and can also be dissolved in solid solution and Fe3C Medium; in high carbon steel, with the increase of chromium content, the amount of carbide formed and the amount dissolved into the matrix increase, so that the strength and wear resistance of the steel become larger; but when the content is too high, it is easy to form too much Ledeburite eutectic and bulk carbides. The optional addition range of the present invention is 9.0-10.5%.

Mo: Molybdenum in steel can improve the hardenability and heat strength of steel, prevent temper brittleness, increase the ability to resist temper softening, and can produce secondary hardening during high temperature tempering, improve carbide stability, and improve Steel toughness and improved wear resistance, in the presence of chromium can also enhance the secondary hardening effect. The optional addition range of the present invention is 0.7-1.0%.

V: Vanadium is a strong carbide forming element, forming VC in steel, which can refine grains and improve the plasticity and toughness of steel. In tool and die steel, V is the main factor to improve wear resistance. But too high V content will reduce the grindability of tool steel. Considering comprehensively, the optional addition range of the present invention is 0.6-1.0%.

B: Boron can improve the hardenability of the matrix; refine the martensite substructure and improve the toughness of the matrix; during the annealing process, solid solution B preferentially guides the precipitation of secondary compounds, increases the number of secondary precipitates, and improves Me(C,B ) shape, improve material uniformity; B solid solution in austenite, reduce the high temperature yield strength of the matrix, improve the thermal deformation ability of the matrix, and reduce rolling or forging cracks. But the eutectic boride is not good for the toughness of steel, and it is not good for hot deformation. The optional addition range of the present invention is 0.001-0.0012%.

A method for manufacturing cold-work die steel plates, including smelting, casting, heating in a heating furnace, rolling, heat treatment,

(1) Smelting the steel with the above composition in a vacuum melting furnace, and casting the smelted molten steel into steel ingots;

(2) Put the steel ingot obtained in (1) into a heating furnace for heating, the heating process is two-stage heating, the first stage is heated to 700-800°C, the heating rate is 50-100°C/h, and the holding time is 0.5-2h; In the second stage, heat to 1100-1200°C, the heating rate is 50-100°C/h, and keep warm for 2-4h;

(3) rolling the heated steel ingot through multiple passes to obtain a rolled steel plate, the starting rolling temperature is 1050-1100°C, the final rolling temperature is 850-930°C, and the total reduction ratio is 60-85%;

(4) slow cooling the steel plate after rolling, the slow cooling start temperature is 700-800°C, and the slow cooling time is greater than 24h;

(5) Carry out heat treatment to the steel plate after the slow cooling is completed, and the heat treatment process is as follows:

a) Quenching, the heating process is two-stage heating, the first stage is heated to 800-850°C, the heating rate is 50-100°C/h, and the holding time is 1-2h; the second stage is heated to 950-1050°C, and the heating rate is 50- 100℃/h, holding time 1-3h; Quenching cooling method adopts oil cooling, cooling to oil temperature;

b) Tempering, the tempering temperature is 380-450°C, and the holding time is 1-3h.

The beneficial effect of the present invention is that: the toughness of the steel is improved by reducing the content of C element in the steel, and at the same time, the hardenability of the steel is further improved by adding cheap B element, and finally a cold-worked steel with high hardness and toughness is obtained. Die steel plate, its hardness reaches or even exceeds that of Cr12 cold work die steel, and its toughness is higher than that of Cr12 cold work die steel.

Description of drawings

Fig. 1 is a metallographic structure diagram of a steel embodiment of the present invention.

detailed description

Below by embodiment the present invention will be further described.

The embodiments of the present invention carry out smelting, casting, furnace heating, rolling and heat treatment according to the component ratio of the technical solution. The chemical composition of the steel of the embodiment of the present invention is shown in Table 1. The heating process of the steel ingot in the embodiment of the present invention is shown in Table 2. The ingot rolling process and slow cooling process of the embodiment of the present invention are shown in Table 3. The heat treatment process of the steel plate in the embodiment of the present invention is shown in Table 4. The test results of steel plate mechanical properties of the embodiment of the present invention are shown in Table 5.

The chemical composition (wt %) of the embodiment of the present invention of table 1

Example C Si mn Cr Mo V B P S 1 1.05 0.95 0.5 10.5 1.0 0.98 0.0011 0.028 0.015 2 1.21 0.9 0.43 9.7 0.8 0.75 0.0012 0.025 0.018 3 1.33 0.7 0.41 9.2 0.7 0.62 0.001 0.029 0.009 4 1.35 0.82 0.45 9.4 0.9 0.8 0.0011 0.024 0.014 5 1.15 0.9 0.48 9.5 0.8 0.9 0.001 0.023 0.017

Table 2 Heating process of steel ingot

Table 3 Ingot rolling process and slow cooling process

Table 4 Steel plate heat treatment process

Table 5 Test results of steel plate mechanical properties

Example Hardness/HRC Impact toughness/J 1 59 60 2 60 70 3 62 61 4 58 75 5 60 68

Claims (1)

1. a kind of manufacture method of cold work die steel plate, it is characterised in that the composition of the steel plate is as follows by weight percentage：C： 1.0-1.35%, Si:0.7-1.0%, Mn:0.4-0.5%, Cr:9.0-10.5%, Mo:0.7-1.0%, V:0.6-1.0%, B:0.001-0.0012%, P<0.03,S<0.03, surplus is Fe and inevitable impurity；

The manufacture method, including smelt, cast, heating stove heat, rolling, heat treatment, (1) is by the steel of mentioned component using true Empty smelting furnace is smelted, and the molten steel for smelting completion is cast into steel ingot；

(2) gained steel ingot in (1) is put into heating furnace and heated, heating process heats for two benches, first stage heating To 700-800 DEG C, 50-100 DEG C of programming rate/h, soaking time 0.5-2h；Second stage is heated to 1100-1200 DEG C, heating 50-100 DEG C of speed/h, is incubated 2-4h；

(3) steel ingot completed will be heated and obtains rolled plate, 1050-1100 DEG C of start rolling temperature, finishing temperature through multi- pass rolling 850-930 DEG C, total reduction 60-85%；

(4) steel plate after the completion of rolling is subjected to slow cooling, 700-800 DEG C of slow cooling start temperature, temperature retention time is more than 24h；

(5) steel plate after the completion of slow cooling is heat-treated, Technology for Heating Processing is as follows：

A) quench, heating technique is two-stage heat, the first stage is heated to 800-850 DEG C, and 50-100 DEG C of programming rate/h is protected Warm time 1-2h；Second stage is heated to 950-1050 DEG C, 50-100 DEG C of programming rate/h, soaking time 1-3h；Quenching cooling Mode uses oil cooling, is cooled to oil temperature；

B) it is tempered, 380-450 DEG C of temperature, soaking time 1-3h.