Non-magnetic stainless steel heating process

Abstract

The present application relates to a kind of heating process of non-magnetic stainless steel, this process according to the steel grade characteristics of non-magnetic stainless steel, mainly utilize heating furnace heating temperature to non-magnetic stainless steel, both can reach traditional heating effect and can improve heating efficiency, reduce heating cost, the heating process of the present application has been maturely applied to non-magnetic stainless steel, and has been popularized to other steel grade, heating is a revolution for special steel, it is of great significance.

Description

Technical Field

[0001] This invention relates to a heating process for non-magnetic stainless steel that utilizes the residual heat of a heating furnace to heat the non-magnetic stainless steel based on its steel characteristics. Background Technology

[0002] Non-magnetic stainless steel has a simple microstructure, belonging to a face-centered cubic austenitic structure. Therefore, its heating curve is simpler than other steel grades. The ingot can be directly heated to the required temperature, while other steel grades generally require intermediate holding to ensure complete austenitization before heating to the required temperature. Its main chemical composition is: [C]≤0.05%, [Mn]≤16.0~22.0%, [Ni]≤4.50%, [Cr]≥18%, [N]≥0.50%, [Mo]≤4.0%. This steel grade has a high alloy content, making the forging surface extremely prone to cracking. The ingot requires surface treatment before heating. The traditional heating process generally involves placing the cold ingot in a cold heating furnace, heating the furnace to about 400℃, holding it for a certain time, then heating it to 1180℃, holding it for a certain time, and then removing the ingot from the furnace for forging. With increasingly fierce competition in the special steel industry, production efficiency and cost have become key to success. Therefore, there is an urgent need to innovate the original manufacturing process to improve quality and efficiency. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a non-magnetic stainless steel heating process that can significantly improve product production efficiency, save energy and reduce emissions, and reduce labor intensity. The steel ingot is directly loaded into a hot heating furnace, that is, a heating furnace that has just finished heating and still has residual heat in the furnace without steel ingots. After holding at the temperature for a certain period of time, the temperature is raised to 1180°C, held at the temperature, and then taken out of the furnace for forging.

[0004] The objective of this invention is achieved as follows: a non-magnetic stainless steel heating process, the specific heating process being as follows:

[0005] Step 1) Selecting a heating furnace: After the heating furnace is shut down and the furnace door is closed, the heating furnace should have a cooling rate of ≤80℃ / h in the temperature range of 500℃-800℃. There are no requirements for the cooling rate in other temperature ranges. The heating furnace should have a loading capacity of less than 100 tons.

[0006] Step 2) Load the surface-finished non-magnetic stainless steel ingots or electroslag ingots into the hot heating furnace in the form of cold ingots. That is, the heating furnace has just finished heating and there is still residual heat in the furnace without steel ingots. At this time, the heating furnace has stopped running, but the temperature inside the furnace is required to be in the range of 500℃-800℃. The furnace is sealed for heating for 5 hours.

[0007] Step 3) After the furnace is closed, the heating furnace is ignited and started, and the temperature is increased to 1180°C at a rate of 80°C per hour, and held for 6 hours.

[0008] Step 4) After heating is completed, the steel ingot or electroslag ingot is taken out of the furnace for forging.

[0009] The positive effects of the technical solution of the present invention are as follows:

[0010] 1. Significantly Improved Production Efficiency. Traditional heating processes, due to concerns about product quality, require steel ingots or electroslag ingots to be loaded into a cold heating furnace before undergoing heating, holding, and further heating operations. This not only results in a long heating cycle but also a lengthy furnace cooling period, significantly increasing the product manufacturing cycle and leading to low efficiency. This new process allows for the cyclical use of the heating furnace. After the previous batch of products has finished heating, the residual heat eliminates the need for cooling. Non-magnetic stainless steel can be directly loaded into the furnace for closed-furnace heating. Compared to traditional heating, no additional holding time is required, typically reducing heating time by 6 hours and furnace cooling time by 10 hours, resulting in a total increase in heating efficiency of 16 hours per unit.

[0011] 2. Energy saving and emission reduction. The shortened heating time reduces the consumption of natural gas or coal gas, thus lowering carbon emissions. The heating method of this invention has no impact on product quality. Furthermore, this invention was first applied to easily cracked non-magnetic stainless steel, and after verifying that it had no impact on product quality, it has been fully extended to other products. Attached Figure Description

[0012] Figure 1 The heating process of this invention.

[0013] Figure 2 This is a traditional heating process. Detailed Implementation

[0014] The specific embodiments of the present invention will be further described below with reference to examples. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0015] A non-magnetic stainless steel heating process, the specific heating process is as follows:

[0016] Step 1) Select a heating furnace of suitable size and with good temperature control. The main performance characteristics of the heating furnace are: after the heating furnace is shut down and the furnace door is closed, the cooling rate in the temperature range of 500℃-800℃ is ≤80℃ / h; the cooling rate in other temperature ranges is not required; the heating furnace has a loading capacity of less than 100 tons.

[0017] Step 2) After surface finishing, the non-magnetic stainless steel ingots or electroslag ingots are cold-loaded into a hot heating furnace, i.e., a heating furnace that has just finished heating and still has residual heat without any steel ingots inside. At this time, the heating furnace has stopped running, but the temperature inside the furnace is required to be within the range of 500℃-800℃. The furnace is then sealed for heating for 5 hours.

[0018] Step 3) After the furnace is closed, the heating furnace is ignited and started to heat up to 1180°C or the required temperature at a rate of 80°C per hour, and then held for 6 hours.

[0019] Step 4) After heating is completed, the steel ingot or electroslag ingot is taken out of the furnace for forging.

[0020] Example 1: Steel grade: W2020NHS. Forging raw material: Φ600mm electroslag ingot, weighing 2.75 tons, number of pieces: 14.

[0021] The specific implementation steps of a non-magnetic stainless steel heating process are as follows:

[0022] Step 1) Select Heating Furnace No. 5. This furnace has a castable refractory structure, is a trolley-type regenerative furnace, and measures 7m*2.8m*2.5m. Its rated loading capacity is 100 tons, and its maximum heating temperature is 1250℃. After the furnace is shut down and the furnace door is closed, the cooling rate between 500℃ and 800℃ is 55℃ / h. Record the gas flow meter reading as 3,625,845 cubic meters before ignition.

[0023] Step 2) All 14 finished electroslag ingots were loaded into furnace No. 5. Furnace No. 5 had just finished unloading ZYNM9 steel and had stopped running. At this time, the furnace temperature was 1130℃. The furnace door was opened to cool down quickly. After the furnace temperature dropped to 800℃, the electroslag ingots were loaded into the furnace and the furnace was sealed for heating for 5 hours.

[0024] Step 3) After the furnace is closed, the heating furnace is ignited and started to heat up to 1180°C at a rate of 80°C per hour, and then held at that temperature for 6 hours.

[0025] Step 4) After heating is complete, the electroslag ingot is removed from the furnace for forging. Record the gas flow meter reading of the heating furnace at this time as 3,627,526 cubic meters.

[0026] The gas consumption using this invention method was 1681 cubic meters. No cracking occurred during the forging process of the 14 non-magnetic electroslag ingots. The performance results of the 14 products are shown in Table 1.

[0027] Table 1: Performance Results of Products Using the Closed Oven Heating Process

[0028] Furnace ingot number Rr（0.2） Rm A Z Grain size 7B22591 151 165 28 67 5.5 7B22592 159 173 24 65 4.5 7A22306 152 167 24 67 5.5 7B22570 151 164 23 68 4 9B22540 148 163 27 69 5 9B22541 148 165 24 66 3.5 7B22595 162 174 25 66 4 7A22253 160 173 22 64 5 7A22254 159 176 23 64 6.5 7A22255 158 173 23 65 4.5 7A22256 160 172 23 67 5.5 7A22257 162 174 27 66 6 7B22513 160 172 25 66 4.5 6A22592 154 171 28 66 3

[0029] Comparative implementation case of Example 1 (traditional heating process):

[0030] Steel grade: W2020NHS. Forging raw material: Φ600mm electroslag ingot, weighing 2.75 tons, 14 pieces.

[0031] The specific implementation steps of the traditional heating process for non-magnetic stainless steel are as follows:

[0032] Step 1) In order to make an accurate comparison, the traditional heating process still selects heating furnace No. 5, and records the gas flow meter reading as 3,865,246 cubic meters before the heating furnace is ignited.

[0033] Step 2) All 14 finished electroslag ingots were loaded into furnace No. 5. Furnace No. 5 was ignited and heated to 350°C at full power, then held at that temperature for 4 hours.

[0034] Step 3) After the heat preservation is completed, the temperature is increased to 1180℃ at a rate of 60℃ per hour, and kept warm for 6 hours.

[0035] Step 4) After heating is complete, the electroslag ingot is removed from the furnace for forging. Record the gas flow meter reading of the heating furnace at this time as 3,868,254 cubic meters.

[0036] The conventional heating process consumed 3008 cubic meters of gas. No cracking was observed during the forging process of the 14 non-magnetic electroslag ingots. The performance results of the 14 products are shown in Table 2.

[0037] Table 2: Performance Results of Products Using Traditional Heating Processes

[0038] Furnace ingot number Rr（0.2） Rm A Z Grain size 6A22582 159 172 25 65 4.5 7A22229 157 171 25 67 5 7A22261 156 172 24 67 5 7A22262 159 170 27 67 5.5 7A22258 161 175 23 67 4.5 7A22260 161 166 24 65 5 7B22521 148 171 27 68 3.5 7B22522 160 165 27 64 6 7B22523 158 172 25 75 4 9A22323 156 172 23 68 4.5 7B22525 149 167 24 63 5 7A22265 156 174 28 67 5.5 7A22296 156 168 26 68 3.5 7A22299 154 170 26 68 5

[0039] Compared with traditional heating processes, the heating process of this invention reduces gas consumption by 1327 cubic meters without affecting product quality.

Claims

1. A non-magnetic stainless steel heating process, characterized in that: The specific heating process is as follows: Step 1) Selecting a heating furnace: To ensure the furnace shut-off effect, select a heating furnace with a cooling rate of ≤80℃ / h in the 500℃-800℃ temperature range after the furnace is shut down and the furnace door is closed; the cooling rate is not required for other temperature ranges; the furnace should have a loading capacity of less than 100 tons. Step 2) Load the surface-finished non-magnetic stainless steel ingots or electroslag ingots into the hot heating furnace in the form of cold ingots. That is, the heating furnace has just finished heating and there is still residual heat in the furnace without steel ingots. At this time, the heating furnace has stopped running, but the temperature inside the furnace is required to be in the range of 500℃-800℃. The furnace is sealed for heating for 5 hours. Step 3) After the furnace is closed, the heating furnace is ignited and started, and the temperature is increased to 1180°C at a rate of 80°C per hour, and held for 6 hours. Step 4) After heating is completed, the steel ingot or electroslag ingot is taken out of the furnace for forging.

2. The non-magnetic stainless steel heating process according to claim 1, characterized in that, To ensure that the furnace remains sealed for 5 hours so that the non-magnetic stainless steel is thoroughly heated, if the temperature inside the furnace is below 500℃ during the sealing process, the heating furnace will be ignited and run to raise the temperature to 700℃±10℃. After holding the temperature for 1 hour, the furnace will be shut off and the sealing process will continue. This process will be repeated.

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