CN108467986B

CN108467986B - Smelting method of cast iron for mold

Info

Publication number: CN108467986B
Application number: CN201810175108.2A
Authority: CN
Inventors: 谈军; 陈寿猛
Original assignee: Jiangsu Tengda Cylinder & Pump Machinery Co ltd
Current assignee: Jiangsu Tengda Cylinder & Pump Machinery Co ltd
Priority date: 2018-03-02
Filing date: 2018-03-02
Publication date: 2021-04-06
Anticipated expiration: 2038-03-02
Also published as: CN108467986A

Abstract

The invention provides a method for smelting cast iron for a die casting, which comprises the following steps: (1) mixing and melting scrap steel and pig iron in proportion; (2) adjusting the proportion of each element in the molten iron; (3) adding tin at 1360 and 1400 ℃, wherein the addition amount of the tin is 0.06-0.08 wt%; (4) electrolytic copper is placed at the bottom of the ladle, and the molten iron is used for blending. The invention only uses industrial waste steel as the main raw material, changes waste into valuable and obtains the cast iron material which has good mechanical property and cutting property and is suitable for die castings.

Description

Smelting method of cast iron for mold

Technical Field

The invention relates to the technical field of metallurgy, in particular to a method for smelting cast iron.

Background

The scrap steel produced in the production process of steel plants is called "returned scrap steel", "self-produced scrap steel" or "recycled scrap steel". The carbon content is generally less than 2.0%, and the contents of sulfur and phosphorus are not more than 0.05%. The steel products and the scrap steel produced in the industrial manufacturing process account for about 20-25% of the total amount of the scrap steel, and mainly comprise the head cutting, the tail cutting, the cutting scrap, the leftover material and the like of steel materials. Various waste equipment, steel structural parts, scrapped locomotives, vehicles, steel rails, automobiles, ships, tools, appliances and the like also generate a large amount of waste steel. The steel plate is 25-30% of the total amount of scrap steel in industrially developed countries, and 1-1.5% of the total amount of steel put in the society. Cast iron molds are common molds in the casting field, and the main component of the cast iron molds is pig iron which is close to the component of scrap steel. Therefore, a process for preparing a cast iron mold by utilizing scrap steel needs to be developed, so that the scrap steel is turned into wealth, and resources are saved.

Disclosure of Invention

The invention aims to provide a method for smelting cast iron for a die, which takes scrap steel and pig iron as raw materials and obtains a cast iron material which has good mechanical property and cutting property and is suitable for die castings by adding elements with specific mixture ratio and adjusting smelting steps.

A method for smelting cast iron for die castings comprises the following steps:

(1) firstly, putting the scrap steel into an electric furnace, then adding pig iron, adjusting the heating power to 400KW, keeping for 10 minutes, and then gradually increasing to 680KW within 15 minutes until the scrap steel and the pig iron are melted;

(2) after scrap steel and pig iron are completely melted, adjusting the element content of molten iron, wherein: carbon: 3.28-3.32 wt%, silicon: 1.6-1.9 wt%, manganese: 0.6-0.9 wt%, phosphorus: 0.03 to 0.05 wt%, sulfur: 0.08 to 0.1 wt%, chromium: 0.2-0.35%;

(3) adding tin at 1360 and 1400 ℃, wherein the addition amount of the tin is 0.06-0.08 wt%;

(4) electrolytic copper is placed at the bottom of the ladle, and is flushed by the molten iron in the step (3) when the molten iron is discharged, wherein the copper content is 0.8-1.0 wt%.

Preferably, in the step (1), the scrap steel accounts for 20-50% by weight.

Preferably, in the step (1), the heating power is adjusted to 400KW and kept for 10 minutes, and then the heating power is adjusted to 500KW and kept for 5 minutes; then the heating power is regulated to 600KW and kept for 6 minutes; the heating power was then adjusted to 680 KW.

Preferably, in step (2), chromium and manganese are put together in molten iron.

Preferably, the temperature of step (4) is 1500. + -. 20 ℃.

Wherein, various elements added mainly play the following roles:

chromium: can play a role of secondary hardening and enhance the strength and the hardness of the cast iron. When the chromium content is more than 0.35%, cementite is promoted in the matrix structure, thereby lowering the machinability of cast iron.

Silicon: can remove harmful gases such as oxygen in molten iron and refine matrix structure. When the silicon content is more than 2%, the strength and toughness of cast iron are significantly reduced.

Manganese: manganese is a good deoxidizer and desulfurizer, can promote the refinement of pearlite in cast iron, is beneficial to eliminating the harmful effect of sulfur, and has no obvious effect when the content of manganese is lower than 0.6 percent.

Copper: the content of refined pearlite is increased, and the cutting performance of cast iron is improved.

Sulfur: improve the cutting performance of the cast iron and enhance the inoculation effect of the cast iron. When the sulfur content is more than 0.1%, segregation occurs.

Phosphorus: the strength and hardness of the cast iron are improved, and when the phosphorus content is higher than 0.05%, the segregation is serious, so that the cast iron is easy to crack.

Tin: effectively improves the strength and the hardness of the cast iron and increases the pearlite content of the cast iron.

The cast iron prepared by the smelting method increases the pearlite content of the matrix structure, improves the mechanical property and the machinability of the casting, and has the tensile strength of 283N/mm²Above, the Brinell hardness is 185 or more.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

A method for smelting cast iron for die castings comprises the following steps:

(1) firstly, putting scrap steel into an electric furnace, then adding pig iron, adjusting the heating power to 400KW, keeping for 10 minutes, then adjusting the heating power to 500KW, and keeping for 5 minutes; then the heating power is regulated to 600KW and kept for 6 minutes; the heating power was then adjusted to 680 KW. Until scrap and pig iron melt; wherein the scrap steel accounts for 20 percent of the total weight, and the pig iron accounts for 80 percent of the total weight.

(2) After scrap steel and pig iron are completely melted, adjusting the element content of molten iron, wherein: carbon: 3.31 wt%, silicon: 1.8 wt%, manganese: 0.75 wt%, phosphorus: 0.04 wt%, sulfur: 0.085 wt%, chromium: 0.32 percent;

(3) adding tin at 1400 ℃, wherein the addition amount of the tin is 0.07 wt%;

(4) electrolytic copper is placed at the bottom of the ladle, and the copper content is 0.9 wt%; and (4) pouring and blending by using the molten iron obtained in the step (3) during discharging, and keeping the temperature at 1490 ℃.

Through detection, the pearlite content in the cast iron material is 99%, and the tensile strength reaches 280N/mm²The Brinell hardness was 185.

Example 2

A method for smelting cast iron for die castings comprises the following steps:

(1) firstly, putting scrap steel into an electric furnace, then adding pig iron, adjusting the heating power to 400KW, keeping for 10 minutes, then adjusting the heating power to 500KW, and keeping for 5 minutes; then the heating power is regulated to 600KW and kept for 6 minutes; the heating power was then adjusted to 680 KW. Until scrap and pig iron melt; wherein the scrap steel accounts for 50 percent of the total weight, and the pig iron accounts for 50 percent of the total weight.

(2) After scrap steel and pig iron are completely melted, adjusting the element content of molten iron, wherein: carbon: 3.3 wt%, silicon: 1.75 wt%, manganese: 0.8 wt%, phosphorus: 0.035 wt%, sulfur: 0.09 wt%, chromium: 0.25 percent;

(3) adding tin at 1380 ℃, wherein the addition amount of the tin is 0.07 wt%;

(4) electrolytic copper is placed at the bottom of the ladle, and the copper content is 0.95 wt%; and (4) pouring and blending by using the molten iron obtained in the step (3) during discharging, and keeping the temperature at 1490 ℃.

The detection shows that the pearlite content in the cast iron material is 100 percent, and the tensile strength reaches 287N/mm²The Brinell hardness was 198.

Comparative example 1

A copper-nickel cast iron die material is prepared by melting and pouring the following components in percentage by weight:

3-4% of carbon, 0.4-0.7% of copper, 1.9-2.2% of silicon, 0.65-0.8% of manganese, 0.1-0.2% of molybdenum, 0.6-0.8% of nickel, 0.03-0.04% of phosphorus, 0.02-0.05% of sulfur, 0.12-0.2% of chromium, 0.18-0.2% of titanium, 0.03-0.05% of vanadium, and the balance of Fe and common impurities.

Firstly, preparing a new iron material and a scrapped die material, testing to obtain the content of specific components, adding elements according to the weight range of the components, and mixing to obtain a raw material.

Melting the raw material components, wherein the heating temperature range of the melting is 1480-1550 ℃, and the melting cannot be fully fused due to too low temperature. And pouring after full fusion, wherein the pouring temperature range is 1350-1400 ℃. The pouring is rapid so as to avoid the influence of temperature reduction on the fluidity and reduce defects.

The copper-nickel cast iron mold material also needs two annealing processes. The first annealing is to heat the formed die material in an annealing furnace to 1000 ℃, keep the temperature for 5 hours, cool the die material along with the furnace, carry out the second annealing after the temperature is reduced to 250 ℃, heat the die material to 800 ℃ by the second annealing, keep the temperature for 3 hours, and cool the die material along with the furnace to the normal temperature.

The detection shows that the pearlite content in the cast iron material is 95-98%, and the tensile strength is 250-272N/mm²The Brinell hardness is 145-160.

Claims

1. A method for smelting cast iron for die castings is characterized by comprising the following steps:

(1) firstly, putting scrap steel into an electric furnace, then adding pig iron, adjusting the heating power to 400KW, keeping for 10 minutes, then adjusting the heating power to 500KW, and keeping for 5 minutes; then the heating power is regulated to 600KW and kept for 6 minutes; then the heating power is increased to 680KW until the scrap steel and the pig iron are melted; wherein the scrap steel accounts for 50 percent of the total weight, and the pig iron accounts for 50 percent of the total weight;

(2) after scrap steel and pig iron are completely melted, adjusting the element content of molten iron, wherein: carbon: 3.3 wt%, silicon: 1.75 wt%, manganese: 0.8 wt%, phosphorus: 0.035 wt%, sulfur: 0.09 wt%, chromium: 0.25 wt%;

(3) adding tin at 1380 ℃, wherein the addition amount of the tin is 0.07 wt%;