CN110983157A

CN110983157A - Smelting method for improving mechanical property of ZG40Mn2

Info

Publication number: CN110983157A
Application number: CN201911252315.4A
Authority: CN
Inventors: 孙健; 陈革
Original assignee: Hubei Sanjiang Space Wanshan Special Vehicle Co Ltd
Current assignee: Hubei Sanjiang Space Wanshan Special Vehicle Co Ltd
Priority date: 2019-12-09
Filing date: 2019-12-09
Publication date: 2020-04-10

Abstract

The invention discloses a smelting method for improving the mechanical property of ZG40Mn2, which comprises the following steps: adding enough glass for forming a layer of glass film at the bottom in the hearth, and adding a steel material; in the smelting process, slag conglomeration agent is added and spread to cover the exposed metal liquid surface, and a deoxidizer is added for deoxidation and the smelting temperature is ensured not to be higher than 1700 ℃; discharging the smelted molten steel of 1620-1660 ℃ to a preheated casting ladle, putting aluminum strips into the casting ladle in advance, and stopping discharging when the aluminum content in the casting ladle reaches 0.05%; and (5) calming until the temperature of the molten steel in the casting ladle reaches 1520-1560 ℃ and pouring. By adopting the technical scheme, the qualified rate of the quenching and tempering mechanical properties of ZG40Mn2 is greatly improved.

Description

Smelting method for improving mechanical property of ZG40Mn2

Technical Field

The invention relates to the technical field of casting, in particular to a smelting method for improving the mechanical property of ZG40Mn 2.

Background

In the casting production, the smelting process is vital, the purity of the molten steel is related to whether the subsequent mechanical properties of the casting are qualified or not, and a plurality of enterprises do not have vacuum smelting technology and still adopt common intermediate frequency smelting technology.

The ZG40Mn2 material is favored by special vehicle industry all the time due to the superiority of the material, but the qualification rate of the final quenching and tempering mechanical property of the material is very low due to the particularity of the material, and the qualification rate of the industry is below 20 percent at present. At present, in the process of smelting ZG40Mn2 castings, a slag conglomeration agent is generally adopted to carry out slagging and slag striking on molten metal, and the harmful oxygen absorption effect of the molten steel is neglected in the whole smelting process, so that the molten steel is finally rich in harmful inclusions.

The purity of molten steel mainly comprises three aspects, namely, the excessive oxides, the inclusions in the molten steel and the overburning of the molten steel.

Disclosure of Invention

Aiming at least one of the problems, the invention provides a smelting method for improving the mechanical property of ZG40Mn2, which is characterized in that glass is added to form a glass film on the surface of molten steel in the smelting process, the oxygen absorption of the molten steel is effectively controlled, the tapping temperature and the pouring temperature are strictly controlled, and a casting ladle is preheated, so that the calming time of the casting ladle is effectively prolonged, inclusions are effectively reduced, the over-burning of the molten steel is effectively prevented by strictly controlling the smelting temperature to be not higher than 1700 ℃, and the qualified rate of the quenching and tempering mechanical property of ZG40Mn2 is greatly improved.

In order to achieve the above object, the present invention provides a smelting method for improving mechanical properties of ZG40Mn2, comprising: adding enough glass for forming a layer of glass film at the bottom in the hearth, and adding a steel material; in the smelting process, slag conglomeration agent is added and spread to cover the exposed metal liquid surface, and a deoxidizer is added for deoxidation and the smelting temperature is ensured not to be higher than 1700 ℃; discharging molten steel at 1620-1660 ℃ which is smelted into a preheated casting ladle, wherein aluminum strips are placed into the casting ladle in advance, and stopping discharging when the aluminum content in the casting ladle reaches 0.05%; and (5) calming until the temperature of the molten steel in the casting ladle reaches 1520-1560 ℃ and pouring.

In the technical scheme, preferably, in the smelting process, the slag conglomeration agent is added to the surface of the molten steel for slagging in three times, the slag is removed in time after the first two times of slagging, the temperature of the center of the liquid level is detected after the third time of slagging, and the chemical components are sampled and detected when the temperature reaches about 1530 ℃.

In the above technical solution, preferably, for the detected chemical components, the chemical components of the molten steel in the hearth are adjusted to a preset ratio according to the principle of adjusting the element C and then adjusting the elements Si and Mn, and the ratio of each component is: 0.35 to 0.4 percent of C, 0.25 to 0.3 percent of Si, 1.65 to 1.75 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.01 percent of S, 0.05 to 0.15 percent of Cr, 0.05 to 0.10 percent of Ni, 0.10 to 0.15 percent of Mo, less than or equal to 0.03 percent of Cu, less than or equal to 0.02 percent of V, and less than or equal to 0.04 percent of Al.

In the technical scheme, preferably, after the chemical composition adjustment is finished, 0.10-0.15% of aluminum is scattered into the molten steel, and then the molten steel is discharged when the temperature reaches 1620-1660 ℃ after the slag conglomeration agent is scattered.

In the above technical solution, preferably, after tapping is stopped when the aluminum content in the ladle reaches 0.05%, the surface of the molten steel is immediately covered with a slag conglomeration agent.

In the technical scheme, preferably, 2-3 times of aluminum strips are added in the smelting process for deoxidation, manganese and aluminum are added for pre-deoxidation after smelting is completed, and the aluminum strips are added again for deoxidation before molten steel is discharged from a furnace.

In the above technical solution, preferably, the ladle is preheated by baking and heating the ladle or by returning the first ladle of molten steel to the furnace after the ladle is completely tapped to preheat the ladle, so that the ladle has a quiescent time of 3-5 minutes.

In the technical scheme, preferably, the slag conglomeration agent is a light 10-30 mesh slag conglomeration agent.

In the above technical solution, preferably, a rapid contact type temperature measuring instrument is used for detecting the temperature of the molten steel and the temperature of the ladle.

Compared with the prior art, the invention has the beneficial effects that: the glass is added to form a glass film on the surface of molten steel in the smelting process, so that oxygen absorption of the molten steel is effectively controlled, the tapping temperature and the pouring temperature are strictly controlled, and a casting ladle is preheated, so that the calming time of the casting ladle is effectively prolonged, inclusions are effectively reduced, the smelting temperature is strictly controlled to be not higher than 1700 ℃, the molten steel is effectively prevented from being over-burnt, and the quality-adjusting mechanical property qualification rate of ZG40Mn2 is greatly increased.

Drawings

FIG. 1 is a schematic block diagram of a smelting process for improving the mechanical properties of ZG40Mn2 according to one embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

The invention is described in further detail below with reference to the attached drawing figures:

as shown in FIG. 1, the smelting method for improving the mechanical properties of ZG40Mn2 provided by the invention comprises the following steps: adding enough glass for forming a layer of glass film at the bottom in the hearth, and adding a steel material; in the smelting process, slag conglomeration agent is added and spread to cover the exposed metal liquid surface, and a deoxidizer is added for deoxidation and the smelting temperature is ensured not to be higher than 1700 ℃; discharging the smelted molten steel of 1620-1660 ℃ to a preheated casting ladle, putting aluminum strips into the casting ladle in advance, and stopping discharging when the aluminum content in the casting ladle reaches 0.05%; and (5) calming until the temperature of the molten steel in the casting ladle reaches 1520-1560 ℃ and pouring.

In the embodiment, glass is added to form a glass film on the surface of molten steel in the smelting process, oxygen absorption of the molten steel is effectively controlled, the tapping temperature and the pouring temperature are strictly controlled, and a ladle is preheated, so that the calming time of the ladle is effectively prolonged, inclusions are effectively reduced, the smelting temperature is strictly controlled to be not higher than 1700 ℃, the molten steel is effectively prevented from being over-burnt, and the qualified rate of the quenching and tempering mechanical properties of ZG40Mn2 is greatly improved.

Specifically, in order to reduce the oxygen content in the molten steel, a proper amount of glass is added at the bottom of a hearth at the initial stage of melting, specifically, a layer of small scrap steel and a proper amount of casting head are firstly added at the bottom of the hearth for melting and bottoming, the bottoming thickness is 200-300mm, then 3KG-4.5KG glass is added, then a large piece of scrap steel is continuously added, the glass is heated to 600-700 ℃ along with the hearth and starts to melt, a layer of glass film for isolating air is formed, the contact between the molten steel and the air can be reduced, the oxidation and the air suction of the molten steel are reduced, the absorption of N \ H \ O from the atmosphere by the molten steel is reduced, wherein N can react with deoxidizer aluminum, and Al3N is generated to cause the. Preferably, 2-3 times of aluminum strips are added for deoxidation in the smelting process, and the added aluminum strips are deoiled and dried, and meanwhile, a certain silicon content in the molten steel is kept, namely about 0.2-0.3%, so that the method is favorable for reducing oxygen in the molten steel. Because manganese can be deoxidized and desulfurized, manganese element is properly added in the metal melting period to ensure that the manganese element is burnt to achieve the effect of purifying the molten metal. Adding manganese and aluminum for pre-deoxidation after smelting, sampling and analyzing, then smelting and entering a fine adjustment period, wherein the main task is to eliminate oxygen and non-metallic inclusions in molten steel to the maximum extent and raise the temperature to tapping temperature. For effective deoxidation, the last deoxidation of the aluminum strip is carried out before the molten steel is taken out of the furnace, and meanwhile, a slag conglomeration agent is covered for heat preservation and impurity conglomeration, so as to fully melt alloy particles and fully float up a non-metal compound to enter furnace slag.

Specifically, a ladle filled with molten steel is hung to a sand mold pouring area for sedation waiting, the sedation time is about 3-5 minutes, and the molten steel in the ladle is detected to have the temperature of 1520-1560 ℃ for pouring. During the sedation, attention is paid to observe the molten film of the slag conglomeration agent on the surface of the molten steel, and if local rupture exists and the molten metal is exposed, the Japanese Ishikawa slag conglomeration agent is added to the exposed part in time to prevent air suction. In the casting production, the common smelting requirements of the common carbon steel are 'high-temperature tapping and low-temperature pouring', because the molten steel has good fluidity at high temperature, the molten steel is beneficial to the removal of gas in the molten steel and the floating of oxide inclusions, the defects of pores and slag inclusion of cast parts can be avoided, and the furnace temperature needs to be high; the pouring temperature cannot be too high, because too high leads to an increased tendency to shrinkage cavities during the solidification of the metal, and at the same time the pouring temperature cannot be too low, which leads to incomplete solidification of the molten steel, so that "low-temperature pouring" means a relatively low temperature with guaranteed filling of the casting mold. Considering that Mn element is seriously burnt at high temperature, the higher the temperature and the higher the content, the more serious the burning loss is, which is the difference between ZG40Mn2 material and common carbon steel, a certain tapping temperature needs to be controlled during smelting, the requirement of 'high temperature tapping' and the requirement of reducing Mn burning loss as much as possible require that proper tapping temperature and pouring temperature need to be established, after full test and exploration, the tapping temperature and the pouring temperature are respectively set at 1620 ℃ -1660 ℃ and 1520 ℃ -1560 ℃, and meanwhile, quick pouring is required to avoid Mn element burning loss caused by long-time pouring.

In the above embodiment, preferably, after the charge materials are completely melted, the nickel plate is finally added, and the melting is continued for 5min by increasing the power. The method comprises the following steps of using a slag ladle to remove a viscous glass film and slag on the surface of molten steel, adding a slag conglomeration agent to the surface of the molten steel for slagging for three times in the slagging process, adding about 0.7Kg each time, removing slag in time after the previous two times of slagging, carrying out temperature detection on the center of a liquid level after the third time of slagging, sampling and detecting chemical components when the temperature reaches about 1530 ℃, and observing whether the head of a test block has a shrinkage cavity or not. Secondly, during the smelting process, the power meter is closely observed, and if an abnormality is found or an adjacent value is exceeded, the smelting should be immediately stopped. If the local cooling water is cut off, the machine must be stopped immediately to dredge the pipeline and ensure the normal circulation of the cooling water.

In the above embodiment, preferably, for the detected chemical components, the chemical components of the molten steel in the hearth are adjusted to a preset ratio according to a principle that the element C is adjusted first and then the elements Si and Mn are adjusted, and the adjusted ratio of each component is as follows: 0.35 to 0.4 percent of C, 0.25 to 0.3 percent of Si, 1.65 to 1.75 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.01 percent of S, 0.05 to 0.15 percent of Cr, 0.05 to 0.10 percent of Ni, 0.10 to 0.15 percent of Mo, less than or equal to 0.03 percent of Cu, less than or equal to 0.02 percent of V, and less than or equal to 0.04 percent of Al.

In the above embodiment, preferably, after the adjustment of the chemical components is completed, the slag on the surface of the molten steel is removed, 0.10% to 0.15% of aluminum is sprinkled into the molten steel, about 0.7kg of slag conglomeration agent is sprinkled once, after half a minute, the temperature of the center of the liquid surface is detected, tapping is started when the temperature reaches 1620 ℃ to 1660 ℃, if the temperature deviates from the temperature, the adjustment can be performed by increasing or decreasing the smelting power, and the highest temperature is controlled not to exceed 1700 ℃.

In the above embodiment, preferably, the slag conglomeration agent is coated on the surface of the molten steel immediately after the tapping is stopped when the aluminum content in the ladle reaches 0.05%. Specifically, a casting ladle hung with a digital display lifting hook is lifted to the position below a water outlet nozzle, firewood ash in the ladle is poured, the intermediate frequency furnace is adjusted to be heat-preserving, discharging is started, and a forward tilting device is started to discharge. Recording the initial digital display weight of the ladle, putting an aluminum strip at the bottom of the ladle, pouring molten steel, observing the weight change, stopping discharging when the aluminum content ratio (0.05%) specified in the following table is met, and immediately covering the surface of the molten steel with about 0.4KG of Japanese rock slag conglomeration agent.

Specifically, the weight of the added aluminum and the weight of the molten steel can be referred to the following table:

weight/Kg of molten steel	Adding aluminum weight/g
		50	25
100	50
		200	100
300	150
		400	200
500	250
		600	300
700	350
		800	400
900	450
		1000	500

In the above embodiment, preferably, the ladle is preheated by baking and heating the ladle or by returning the ladle to the furnace after the ladle is fully tapped so as to preheat the ladle, so that the ladle has a calming time of 3-5 minutes. And sufficient time is provided for the impurities to float sufficiently by increasing the molten steel calming time.

In the above embodiment, preferably, the slag conglomeration agent is light 10-30 mesh slag conglomeration agent. In the casting production, the slag conglomeration agent is mainly used for conglomerating slag, so that impurities in molten steel are conglomerated together on the surface of the molten steel, slag striking of medium-frequency workers is facilitated, the domestic slag conglomeration agent is influenced by the performance of the domestic slag conglomeration agent, the conglomeration effect on fine impurities is not obvious, in the embodiment, the light 10-30-mesh Japanese Ishikawa No. 2 slag conglomeration agent (the density is lighter than that of the domestic slag conglomeration agent, washing separation is adopted during production, the cleanliness is high), and the slag conglomeration agent is added on the surface of the molten steel in a ladle, adsorbs impurities and reduces the. The slag conglomeration agent is an acidic composite salt which can form a high-melting-point neutral conforming salt with an alkaline oxide formed by oxidizing Mn in the molten steel, can consume the alkaline oxide in the molten steel, can adsorb various dispersed reactants in a slag layer, and reduces the total amount of inclusions in the molten steel, thereby realizing the purification of the molten steel.

In the above embodiment, it is preferable that the temperature of the molten steel and the temperature of the ladle be detected by using a rapid contact type temperature measuring instrument. The rapid contact type temperature measuring instrument effectively ensures that the molten steel smelting temperature is controlled, and the temperature in the smelting furnace is mastered at any time in a narrow casting temperature control interval and strict casting standard requirements. In the prior art, a far infrared temperature measuring instrument is often used for controlling the temperature in a furnace and a casting ladle, but because the far infrared temperature measuring instrument is greatly influenced by environmental factors, the display of smoke dust generated in intermediate frequency smelting and a method used by an operator can be influenced, and the measurement error is large. Therefore, in this embodiment, the rapid contact type temperature measuring instrument is adopted, the actual temperature of the molten steel can be displayed by only inserting the instrument into the molten steel, the operation is convenient, the data is effective, the temperature in the ladle can be grasped at any time, and preferably, the upper melting temperature limit is 1700 ℃.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A smelting method for improving the mechanical property of ZG40Mn2 is characterized by comprising the following steps:

adding enough glass for forming a layer of glass film at the bottom in the hearth, and adding a steel material;

in the smelting process, slag conglomeration agent is added and spread to cover the exposed metal liquid surface, and a deoxidizer is added for deoxidation and the smelting temperature is ensured not to be higher than 1700 ℃;

discharging molten steel at 1620-1660 ℃ which is smelted into a preheated casting ladle, wherein aluminum strips are placed into the casting ladle in advance, and stopping discharging when the aluminum content in the casting ladle reaches 0.05%;

and (5) calming until the temperature of the molten steel in the casting ladle reaches 1520-1560 ℃ and pouring.

2. The smelting method for improving the mechanical properties of ZG40Mn2 as claimed in claim 1, wherein in the smelting process, the slag conglomeration agent is added to the surface of the molten steel for slagging in three times, the slag is removed in time after the first two times of slagging, the temperature of the center of the liquid surface is detected after the third time of slagging, and the chemical components are sampled and detected when the temperature reaches about 1530 ℃.

3. The smelting method for improving the mechanical properties of ZG40Mn2 as claimed in claim 2, wherein the chemical components of the molten steel in the hearth are adjusted to a preset ratio according to the principle of adjusting C element first and then Si and Mn element for the detected chemical components, and the ratio of each component is as follows: 0.35 to 0.4 percent of C, 0.25 to 0.3 percent of Si, 1.65 to 1.75 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.01 percent of S, 0.05 to 0.15 percent of Cr, 0.05 to 0.10 percent of Ni, 0.10 to 0.15 percent of Mo, less than or equal to 0.03 percent of Cu, less than or equal to 0.02 percent of V, and less than or equal to 0.04 percent of Al.

4. The smelting method for improving the mechanical properties of ZG40Mn2 as claimed in claim 3, wherein the molten steel is tapped when the temperature reaches 1620 ℃ -1660 ℃ after the chemical composition adjustment is completed and 0.10% -0.15% of aluminum is added to the molten steel and then slag conglomeration agent is added.

5. The smelting method for improving the mechanical properties of ZG40Mn2 as claimed in claim 1, wherein the slag accretion agent is coated on the surface of the molten steel immediately after tapping is stopped when the aluminum content in the ladle reaches 0.05%.

6. The smelting method for improving the mechanical properties of ZG40Mn2 according to claim 1, wherein the aluminum strips are added for deoxidation 2-3 times in the smelting process, manganese and aluminum are added for pre-deoxidation after smelting is completed, and the aluminum strips are added again for deoxidation before molten steel is discharged from a furnace.

7. The smelting method for improving the mechanical properties of ZG40Mn2 as claimed in claim 1, wherein the ladle is preheated by baking and heating the ladle or by returning the ladle to the furnace after the ladle is completely tapped to preheat the ladle, so that the ladle has a quiescent time of 3-5 minutes.

8. The smelting method for improving the mechanical property of ZG40Mn2 according to any one of claims 1 to 5, wherein the slag conglomeration agent is a light 10-30 mesh slag conglomeration agent.

9. The melting method for improving the mechanical properties of ZG40Mn2 according to claim 1, wherein a rapid contact type temperature measuring instrument is used for detecting the temperature of the molten steel and the temperature of the ladle.