CN108707842A - A kind of Ni hardening high hardness wear-resisting alloy and its casting method - Google Patents

Abstract

A Ni-hardened high-hardness wear-resistant alloy and its casting method. The mass percent content of each element in the alloy is Cr: 9.0-13.0, B: 2.6-2.9, C: 0.7-0.9, Ni: 0.6-1.5%, Nb : 0.4~0.8, V: 0.4~0.8, Mn is less than 0.3, Si is less than 0.07, and the balance is Fe. After weighing the corresponding raw materials according to the composition requirements, the alloy is prepared by melting in an induction furnace with a melting temperature of 1550-1650°C; then the power of the electric furnace is reduced to reduce the melt temperature to 1300-1350°C, and the total amount of ingredients is 0.1-0.15 % pure aluminum deoxidation; continue to keep warm for about 5 to 10 minutes, and cast the alloy. The average hardness of the ingot prepared by the invention is HRC68.8-70.9, the impact toughness is 10.2-13.8J/ ^cm2 , and the bending strength is 910-1021MPa.

Description

A kind of Ni-hardened high-hardness wear-resistant alloy and casting method thereof

technical field

The invention belongs to the field of high-hardness and wear-resistant cast iron, and relates to a wear-resistant and corrosion-resistant cast iron alloy containing ultrafine hard phase, supersaturated solid solution and martensitic matrix phase and a method for preparing components thereof, which can be widely used in electric power, metallurgy Manufacture of mechanical wear-resistant parts in , machinery, chemical and other industries.

technical background

Fe-Cr-BC wear-resistant casting alloy is based on Fe ₂ B or M ₂ B hard phase, which has good toughness, high hardness, high corrosion resistance, good smelting-casting processability, and has a very wide range of applications. Application prospects.

Patent document 1: Authorized announcement number CN 105695884 B, the prepared wear-resistant alloy has a hardness of HRC66-70 and an impact toughness of 4-9J/cm ² . The hardness of this type of alloy is high, but the impact toughness is insufficient, the strength index is low, and the bending strength is low, ranging from 346 to 477 MPa, which limits the application of this alloy to some occasions where the external load is large and impact resistance is required.

Document 2: Rapid cooling microstructure and properties of eutectic Fe-Cr-BC alloy, Casting, 2017, 66(10): 1053-1056. The rapidly cooled microstructure of as-cast Fe-Cr-BC alloy consists of martensite + retained austenite matrix and (Fe,Cr) ₂ (B,C)+(Fe,Cr) ₂₃ ( B,C) Composition of ₆ hard phases. The microhardness of the matrix phase of the fast cooling structure is 800-880HV, the microhardness of the hard phase is 1150-1400HV, the macroscopic hardness is HRC68, and the impact toughness reaches 13.6J/ ^cm2 ; It transforms into ferrite and granular cementite, the hard phases (Fe,Cr) ₂ (B,C) and (Fe,Cr) ₂₃ (B,C) ₆ are dissolved in a small amount, and the network is broken in some areas, and new phases appear (Fe,Cr) ₃ (B,C), the microhardness of the matrix phase after annealing is 330~400HV, the hard phase is 850~1250HV, the macrohardness is reduced to HRC46, and the impact toughness is reduced to 3.4J/cm ² .

The results obtained in Document 2 reflect that the hardness of the matrix phase plays an important role in the hardness and impact toughness of this type of material; compared with Patent Document 1, this type of alloy has the possibility of improving impact toughness and other properties.

Contents of the invention

The object of the present invention is to provide a Ni-hardened high-hardness wear-resistant alloy and its casting method. The alloy uses Fe ₂ B or M ₂ B as the hard phase, and the matrix is a high-hardness multi-component supersaturated solid solution hardened by Ni element, Martensite It has good toughness, high hardness and high strength index, good processability in smelting, casting and heat treatment, and has very broad application prospects.

In the invention, the Fe-Cr-B-C alloy with high wear resistance and high corrosion resistance is selected as the basic alloy, and 0.6-1.5% Ni element is added. Form a multi-element eutectic alloy containing Fe, Cr, B, C, Nb, V, Ni and other elements, the mass percentage of each element is Cr: 9.0~13.0, B: 2.6~2.9, C: 0.7~0.9, Ni : 0.6-1.5%, Nb: 0.4-0.8, V: 0.4-0.8, Mn content is less than 0.3, Si content is less than 0.07, S, P: ≤0.01, and the balance is Fe. The total mass percentage of C and B is 3.3-3.6; the C/Cr mass ratio is 0.06-0.08; the total mass percentage of Nb and V is 0.5-1.0.

Ni element is a solid-solution strengthening element of steel, which can be infinitely solid-soluble with Fe and expand the austenite phase region. Ni does not form compounds with C, nor does it act with B, and can be solid-dissolved in the Fe matrix at the same time as Cr. It can strengthen ferrite and refine pearlite. Only when the nickel content in conventional steel is greater than 1.0% will it play a significant role in the hardenability and tempering stability of the steel. In sinter hardened steel, that is, an alloy that can cause martensitic transformation under the general industrial furnace cooling rate (about 60°C/min), the content of Ni is about 1.5-3.0%. However, if the Ni content is too high, the martensitic transformation temperature will drop. Therefore, when the Ni element is introduced into the hardened alloy, the Ni content should not be too high. Because there is a large amount of _Fe2B or _M2B in the present invention as a hard phase, the volume ratio of the matrix phase is about 50-60%, and the added Ni is mainly dissolved in the matrix phase, so the Ni content should be controlled In 0.6 ~ 1.5%.

Referring to Patent Document 1, in specific preparation of alloys, ferrochrome (high carbon, medium carbon, micro carbon), ferroboron, ferroniobium, ferrovanadium, metallic nickel and pure iron can be used as ingredients according to compositional requirements. Table 1 lists the raw materials and their components.

Table 1 can be applied to the raw material and composition of preparation invention alloy

The raw material composition in Table 1 is not unique, and the specific composition is determined by the actually available raw materials. Among them, ferrochrome, metal chromium, ferroboron, ferroniobium and ferrovanadium provide the content of Cr, B, Nb and V of the invention alloy, and high carbon ferrochrome is used to balance the C content. The pure iron can be electrical pure iron, electromagnetic pure iron or industrial pure iron.

The specific melting and casting process is as follows:

After weighing the corresponding raw materials according to the composition requirements, induction furnaces, vacuum induction furnaces, etc. can be used to smelt and prepare alloys. First melt ferrochrome, metallic chromium, ferroboron, ferroniobium, ferrovanadium, metallic nickel and pure iron at a melting temperature higher than 1550-1650°C to fully melt pure iron, metallic nickel and metallic chromium; then reduce the power of the electric furnace, After the melt temperature is lowered to 1300-1350°C, deoxidize with 0.1-0.15% of the total amount of pure aluminum; continue to keep warm for about 5-10 minutes, and quickly cast the alloy. The casting temperature range is 1250-1300°C.

Since the designed alloy is a eutectic composition, the melt has very good fluidity and can be cast by various methods, such as ordinary sand mold casting or investment casting, lost foam casting, metal mold casting, ceramic mold Casting, die casting, centrifugal casting and other special casting methods.

The designed alloy has a deep eutectic composition, and can form a non-equilibrium matrix structure, such as amorphous, nanocrystalline or martensitic structure, under ordinary sand casting conditions. In order to promote the non-equilibrium transformation of the matrix, the cooling rate from the solidification temperature to 600 °C should not be lower than 60 °C/min, which can be achieved by means of water cooling, iron molds, and cold iron placed in the mold. However, because the non-equilibrium transformation will cause volume changes, stress cracking will occur due to temperature inconsistency when preparing large castings. Therefore, castings should be released from the mold at 600-800 °C.

Subsequent ingot casting can adopt a stress relief annealing process below 600 °C and necessary machining processes.

The main feature of the invention is that it forms a deep eutectic composition through multi-element alloying, has low melting point, good fluidity, and simple casting process requirements. The matrix phase of the ingot structure is a non-equilibrium structure strengthened by Cr, B, C and Ni with high hardness, and the hard phase is boron and carbon compounds with high hardness. Due to the further solid solution strengthening effect of Ni on the matrix phase, the horse The effect of the tentensitic transformation temperature and the promotion of the martensitic transformation makes the martensite phase refinement and the hardness increase, so that the stress-strain between the hard phase and the matrix phase can be coordinated. On the premise of a slight increase in hardness Under this condition, the impact toughness and flexural strength of the alloy are improved. The average hardness of the ingot reaches HRC68.8-70.9, the impact toughness reaches 10.2-13.8J/cm ² , and the bending strength reaches 910-1021MPa.

Description of drawings

Fig. 1 casting structure chart of example 1 of the present invention;

The EDS collection of illustrative plates and composition of Fig. 2 example 4 casting hard phases of the present invention;

Fig. 3 is the EDS spectrum and composition of the casting matrix phase of Example 4 of the present invention.

Detailed ways

Various smelting methods and casting methods of the present invention are not limited by the following examples, and any improvements and changes within the scope of the claims of the present invention are within the protection scope of the present invention.

High-carbon ferrochrome, micro-carbon ferrochrome, metal chromium, ferroboron, ferroniobium, ferrovanadium, industrial pure iron, metal nickel, etc. are selected as raw materials, and the alloy is formulated within the composition range required by the invention.

Embodiment 1. Select high-carbon ferrochrome, microcarbon ferrochrome, ferroboron, ferro-niobium, ferro-vanadium, metallic nickel and industrial pure iron as raw materials, and the composition range is as follows: Cr: 10.0wt.%; B: 2.9wt.% ; C: 0.7wt.%; Ni: 0.6wt.%; Nb: 0.4wt.%; V: 0.2wt.%;

After weighing the corresponding raw materials according to the composition requirements, induction melting and sand mold casting are adopted. The specific steps are:

First, high-carbon ferrochrome, micro-carbon ferrochrome, ferroboron, ferroniobium, ferrovanadium, metallic nickel and industrial pure iron are melted at 1650°C; then the power of the electric furnace is reduced to 1300°C, and then Deoxidize pure aluminum with a total amount of 0.15% of the ingredients; continue to keep warm for about 5 minutes, and quickly cast the alloy with a casting temperature range of 1250°C.

About 6 minutes after casting, the sand mold is opened. At this time, the ingot temperature is lower than 800°C, and the cooling rate from the solidification temperature to 800°C is about 70°C/min. Air cool to room temperature.

The metallographic spectrum of the ingot is shown in Figure 1. It is basically a dual-phase structure, and the structure is fine and uniform, which is a eutectic structure. A large number of squares appeared in the matrix phase, and the hard phase and the matrix phase were eutectic precipitation, and the hard phase did not appear a continuous network structure. It can be seen that the Ni element is beneficial to destroy the network structure of the hard phase, which can greatly improve the toughness and strength of the material.

The average hardness of the obtained ingot reaches HRC68.8, the impact toughness reaches 13.8J/cm ² , and the bending strength reaches 1021MPa.

Embodiment 2. Select high-carbon ferrochrome, metal chromium, ferroboron, ferroniobium, metal nickel and industrial pure iron as raw materials, and the composition range is as follows: Cr: 10.0wt.%; B: 2.7wt.%; C: 0.7wt .%; Ni: 0.9wt.%; Nb: 0.5wt.%; See Table 2 for the control of impurity elements.

After weighing the corresponding raw materials according to the composition requirements, the vacuum induction furnace can be used for melting and water-cooled iron mold casting. The specific steps are:

First, high-carbon ferrochromium, metallic chromium, ferroboron, ferro-niobium, metallic nickel and industrial pure iron are melted at a temperature of 1550°C; then the power of the electric furnace is reduced to lower the melt temperature to 1350°C, and the total amount of ingredients is 0.1%. Deoxidize pure aluminum; continue to keep warm for about 10 minutes, and quickly cast the alloy, the casting temperature range is 1300 ℃.

About 10 minutes after casting, the water-cooled iron mold was opened, and the ingot temperature was lower than 600°C at this time, and the cooling rate from the solidification temperature to 600°C was about 70°C/min. Air cool to room temperature.

The hardness of the obtained ingot reaches HRC69.2, the impact toughness reaches 12.4J/cm ² , and the bending strength reaches 954MPa.

Embodiment 3. select high-carbon ferrochrome, microcarbon ferrochrome, ferroboron, ferro-niobium, metallic nickel and industrial pure iron as raw materials, and the composition range is as follows: Cr: 10.0wt.%; B: 2.7wt.%; C: 0.8wt.%; Ni: 1.2wt.%; Nb: 0.6wt.%; See Table 2 for the control of impurity elements.

After weighing the corresponding raw materials according to the composition requirements, induction melting and investment casting are adopted. The specific steps are:

First, high-carbon ferrochrome, micro-carbon ferrochrome, ferroboron, ferro-niobium, metallic nickel and industrial pure iron are melted at a melting temperature of 1620°C; then the power of the electric furnace is reduced to lower the melt temperature to 1320°C, and then the Deoxidize with 0.12% pure aluminum; continue to keep warm for about 8 minutes, and quickly cast the alloy with a casting temperature range of 1280°C.

About 10 minutes after casting, open the sand mold. At this time, the temperature of the ingot is lower than 700°C, and the cooling rate from the solidification temperature to 700°C is about 60°C/min. Air cool to room temperature.

The hardness of the obtained ingot reaches HRC69.8, the impact toughness reaches 12.8J/cm ² , and the bending strength reaches 954MPa.

Embodiment 4. Select high-carbon ferrochromium, metallic chromium, ferroboron, ferro-niobium, ferrovanadium, metallic nickel and industrial pure iron as raw materials, and the composition range is as follows: Cr: 11.0wt.%; B: 2.7wt.%; C : 0.7wt.%; Ni: 1.5wt.%; Nb: 0.2wt.%; V: 0.4wt.%; See Table 2 for the control of impurity elements.

After weighing the corresponding raw materials according to the composition requirements, induction melting and sand casting are adopted. The specific steps are:

First, melt high-carbon ferrochrome, metallic chromium, ferroboron, ferro-niobium, ferro-vanadium, metallic nickel and industrial pure iron at a melting temperature of 1600°C; then reduce the power of the electric furnace to lower the melt temperature to 1300°C, and then use ingredients The total amount of 0.14% pure aluminum is deoxidized; the heat preservation is continued for about 7 minutes, and the alloy is cast rapidly, and the casting temperature range is 1250°C.

About 7 minutes after casting, the sand mold was opened. At this time, the ingot temperature was lower than 800°C, and the cooling rate from the solidification temperature to 800°C was about 60°C/min. Air cool to room temperature.

The average hardness of the obtained ingot reaches HRC70.9, the impact toughness reaches 10.2J/cm ² , and the bending strength reaches 910MPa.

The EDS composition analysis of the ingot hard phase and matrix phase is shown in Figure 2 and Figure 3, respectively. It can be seen that the amount of solid solution of Ni element in the hard phase is low, and it is mainly enriched in the matrix phase, which plays a role in strengthening the matrix phase. effect.

Embodiment 5. select high-carbon ferrochrome, microcarbon ferrochrome, ferroboron, ferro-niobium, ferro-vanadium, metallic nickel and industrial pure iron as raw materials, the composition range is as follows: Cr: 10.0wt.%; B: 2.6wt.% ; C: 0.6wt.%; Ni: 0.6wt.%; Nb: 0.3wt.%; V: 0.1wt.%;

After weighing the corresponding raw materials according to the composition requirements, induction melting and lost foam casting are adopted. The specific steps are as follows:

First, high-carbon ferrochrome, micro-carbon ferrochrome, ferroboron, ferroniobium, ferrovanadium, metallic nickel, and industrial pure iron are melted at a melting temperature of 1580°C; then the power of the electric furnace is reduced to 1320°C, Deoxidize with pure aluminum of 0.12% of the total amount of ingredients; continue to keep warm for about 9 minutes, and quickly cast the alloy, and the casting temperature range is 1250 ° C.

About 8 minutes after casting, open the lost foam sand mold. At this time, the temperature of the ingot is lower than 700°C, and the cooling rate from the solidification temperature to 700°C is about 70°C/min. Air cool to room temperature.

The hardness of the obtained ingot reaches HRC69.4, the impact toughness reaches 13.2J/cm ² , and the bending strength reaches 1016MPa.

Embodiment 6. Select high-carbon ferrochrome, micro-carbon ferrochrome, ferroboron, ferro-niobium, metallic nickel and industrial pure iron as raw materials, and the composition range is as follows: Cr: 10.0wt.%; B: 2.6wt.%; C: 0.8wt.%; Ni: 0.9wt.%; Nb: 0.8wt.%; See Table 2 for impurity element control.

After weighing the corresponding raw materials according to the composition requirements, vacuum induction melting and iron mold casting are adopted. The specific steps are as follows:

First, high-carbon ferrochrome, micro-carbon ferrochrome, ferroboron, ferro-niobium, metallic nickel and industrial pure iron are melted at 1600°C; then the power of the electric furnace is reduced to lower the melt temperature to 1350°C, and the total amount of ingredients is used 0.15% pure aluminum deoxidation; continue to keep warm for about 10 minutes, quickly cast the alloy, the casting temperature range is 1300 ℃.

About 10 minutes after casting, the sand mold is opened. At this time, the ingot temperature is lower than 600°C, and the cooling rate from the solidification temperature to 600°C is about 70°C/min. Air cool to room temperature.

The hardness of the obtained ingot reaches HRC69.8, the impact toughness reaches 12.2J/cm ² , and the bending strength reaches 962MPa.

Embodiment 7. Select high-carbon ferrochrome, micro-carbon ferrochrome, ferroboron, ferro-niobium, ferro-vanadium, metallic nickel and industrial pure iron as raw materials, and the composition range is as follows: Cr: 11.0wt.%; B: 2.6wt.% ; C: 0.9wt.%; Ni: 1.2wt.%; Nb: 0.2wt.%; V: 0.2wt.%;

After weighing the corresponding raw materials according to the composition requirements, induction melting and lost foam casting can be used. Specific steps are as follows:

First, high-carbon ferrochrome, micro-carbon ferrochrome, ferroboron, ferroniobium, ferrovanadium, metallic nickel and industrial pure iron are melted at a melting temperature of 1580°C; then the power of the electric furnace is reduced to 1300°C, Deoxidize with pure aluminum of 0.10% of the total amount of ingredients; continue to keep warm for about 5 minutes, and quickly cast the alloy, and the casting temperature range is 1250 ° C.

About 9 minutes after casting, open the lost foam sand mold. At this time, the ingot temperature is lower than 600°C, and the cooling rate from the solidification temperature to 600°C is about 70°C/min. Air cool to room temperature.

The hardness of the obtained ingot reaches HRC69.9, the impact toughness reaches 11.9J/cm ² , and the bending strength reaches 1012MPa.

Embodiment 8. Select high-carbon ferrochrome, micro-carbon ferrochrome, ferroboron, ferroniobium, metallic nickel, ferrovanadium and industrial pure iron as raw materials, and the composition range is as follows: Cr: 13.0wt.%; B: 2.6wt.% ; C: 0.8wt.%; Ni: 1.5wt.%; Nb: 0.6wt.%; V: 0.4wt.%;

After weighing the corresponding raw materials according to the composition requirements, induction melting and lost foam casting are adopted. The specific steps are as follows:

First, high-carbon ferrochrome, micro-carbon ferrochrome, ferroboron, ferro-niobium, ferro-vanadium, metallic nickel and industrial pure iron are melted at a melting temperature of 1590°C; then the power of the electric furnace is reduced to a temperature of 1320°C, Deoxidize with pure aluminum of 0.13% of the total amount of ingredients; continue to keep warm for about 7 minutes, and quickly cast the alloy, and the casting temperature range is 1280 ° C.

About 9 minutes after casting, open the lost foam sand mold. At this time, the temperature of the ingot is lower than 700°C, and the cooling rate from the solidification temperature to 700°C is about 60°C/min. Air cool to room temperature.

The hardness of the obtained ingot reaches HRC70, the impact toughness reaches 11.8J/cm ² , and the bending strength reaches 988MPa.

The cast alloy performance detection prepared by each embodiment is as follows:

1. The HR-150A Rockwell hardness machine is used for the hardness test of the cast metal of the example, the load is 150Kg, and the average value is taken after five points are punched, which are listed in Table 2.

2. The JBS-300B impact testing machine is used to test the impact toughness of the cast metal of the example, the measuring range is 150J, and the average value is taken after five samples are made, which are listed in Table 2.

3. Conduct a three-point bending test on the electronic universal testing machine for cast metal materials in the example. The sample size is a rectangular sample of 2×5×50mm, and the span is 30mm. The average value of the bending strength of three similarly processed samples is listed in Table 2.

Composition and hardness, impact toughness and flexural strength of table 2 embodiment

Claims (3)

1. A Ni-hardened high-hardness wear-resistant alloy, characterized in that: the mass percentage of each element in the alloy is Cr: 9.0-13.0, B: 2.6-2.9, C: 0.7-0.9, Ni: 0.6-1.5% , Nb: 0.4-0.8, V: 0.4-0.8, the content of Mn is less than 0.3, the content of Si is less than 0.07, S, P: ≤0.01, and the balance is Fe. Among them, the sum of C and B: 3.3-3.6; the mass ratio of C/Cr: 0.06-0.08; the sum of Nb and V is 0.5-1.0. 2. the preparation method of Ni-hardened high-hardness wear-resistant alloy as claimed in claim 1 is characterized in that: after weighing the corresponding raw materials according to the composition requirement ratio, adopt induction furnace smelting to prepare alloy, first ferrochrome, metallic chromium , ferroboron, ferroniobium, ferrovanadium, metallic nickel and pure iron are melted at a melting temperature of 1550-1650°C; then reduce the power of the electric furnace, and after the melt temperature drops to 1300-1350°C, use 0.1-0.15% of the total amount of ingredients Deoxidize pure aluminum; continue to keep warm for about 5-10 minutes, cast alloy, the casting temperature range is 1250-1300 ℃; casting and molding by various methods, the cooling rate from solidification temperature to 600 ℃ should not be lower than 60 ℃/min . 3. The method for preparing a Ni-hardened high-hardness wear-resistant alloy as claimed in claim 2, characterized in that: when preparing a large casting, the casting is released from the constraints of the mold at 600-800°C.