CN-121992173-A - Medium carbon alloy structural steel full-flow closed-loop end hardenability process and quality control method

CN121992173ACN 121992173 ACN121992173 ACN 121992173ACN-121992173-A

Abstract

The invention relates to the technical field of metal material performance detection and heat treatment, and discloses a full-flow closed-loop end hardenability process and quality control method for medium carbon alloy structural steel, which comprises the steps of 1, sample preparation calibration, 2, heat treatment process parameter calibration, 3, heat treatment operation calibration, 4, detection process calibration and 5, wherein the method unifies process parameter standard, eliminates detection deviation and improves result comparability, and the method definitely determines the calibration range of heating temperature (835-865 ℃ and within +/-6 ℃) heating and heat preservation time (48-68 min), quenching water temperature (17-23 ℃) and water column height (63-67 mm) through the step 2, and fixes parameter execution precision through thermocouple real-time monitoring and thermostatic device control means, thereby solving the problem that 'the same material is incomparable in detection result due to different processes', avoiding misjudgment of enterprises on material quality, and reducing the risk of qualified raw material waste and unqualified material flowing into processing links.

Inventors

YUAN LIN
Hou quan
Pan Xiquan
WU MIN
YANG GENGCHAO
ZHANG JIE
YUAN YUAN
LUO XIAO

Assignees

湖南华菱湘潭钢铁有限公司

Dates

Publication Date: 20260508
Application Date: 20260123

Claims (10)

1. The full-flow closed-loop end hardenability process and quality control method for the medium carbon alloy structural steel comprise the steps of sample preparation calibration, heat treatment process parameter calibration, heat treatment operation calibration, detection process calibration and result verification and parameter adjustment, and are characterized in that the sample preparation calibration comprises the steps of 1.1 processing mode and size control, 1.2 surface quality treatment and 1.3 parallel sample preparation; The heat treatment process parameter calibration comprises the steps of 2.1 heating temperature calibration, 2.2 heating and heat preservation time calibration, 2.3 quenching medium parameter calibration and 2.4 decarburization/carburization prevention measure calibration; The heat treatment operation calibration comprises the steps of feeding the sample in the step 3.1, discharging the sample out of the furnace and quenching transfer in the step3.2 and monitoring the quenching process in the step 3.3; The detection process calibration comprises the steps of step 4.1 detection equipment calibration, step 4.2 detection position calibration and step 4.3 repeated detection calibration; The step 5 is to compare the result verification and parameter adjustment with the calibration result of step 5.1, adjust the process parameter of step 5.2, control the influence of the component 5.3 on the auxiliary control and record and period of step 5.4.
2. The full-flow closed-loop end hardenability process and quality control method for the medium carbon alloy structural steel are characterized in that the machining mode and the size control in the step 1.1 are adopted to prepare a sample by adopting a sawing, linear cutting or turning and grinding machine combined machining mode, so that the length deviation of the sample is controlled to be +/-2.5 mm, the diameter deviation is controlled to be +/-0.4 mm, and the basic size requirement of an end quenching detection standard is met; 1.2, surface quality treatment, namely, the surface of a sample detection surface needs to be finely polished, the surface finish is controlled to be 0.4-1.2 mu m, and no oxide scale, scratch, pit and decarburized layer are generated; Step 1.3, preparing parallel samples, namely preparing at least 5-8 parallel samples in each batch of calibration, reducing the influence of single sample processing errors on the whole calibration result, and ensuring data representativeness.
3. The full-flow closed-loop end hardenability process and quality control method for medium carbon alloy structural steel, as set forth in claim 1, is characterized in that the heating temperature calibration in step 2.1 is carried out, namely, the target temperature of a heating furnace is set to 835-865 ℃, and after the temperature is raised to the target temperature, the temperature in the furnace is kept for 12-18min to be uniform; Step 2.2, heating and heat preservation time calibration, namely after a sample is put into a furnace, heating at a speed of 5-8 ℃ per minute (if supported by the furnace body), controlling the heating time to 22-32 minutes to ensure that the core of the sample completely reaches a set temperature, then entering a heat preservation stage, setting the heat preservation time to 26-36 minutes, recording the furnace temperature every 5 minutes during heat preservation, and preventing temperature drift; Step 2.3, the quenching medium parameter calibration, wherein the quenching medium is industrial clean water, the water temperature is controlled at 17-23 ℃ through a constant temperature device, the height of a quenching water column is adjusted to 63-67mm, the water flow speed is controlled at 0.8-1.2m/s, the vertical and uniform impact of a water column on a sample detection surface is ensured, and no split flow or turbulence phenomenon exists; And 2.4, calibrating decarburization/carburization prevention measures, namely introducing inert gas (nitrogen) into the furnace or placing graphite powder oxidation prevention medium in the heating process, reducing the decarburization of the surface of the sample, detecting the thickness of the decarburization layer on the surface of the sample after calibration, and adjusting the consumption of the protection medium when the thickness is smaller than or equal to 0.12mm and exceeds the range.
4. The full-flow closed-loop end hardenability process and quality control method for the medium carbon alloy structural steel are characterized in that the step 3.1 sample feeding operation is that prepared samples are uniformly placed in an effective heating area in a furnace, the sample spacing is not less than 12mm, the samples are not in direct contact with a furnace wall and a heating element, and local temperature non-uniformity is avoided.
5. The full-flow closed-loop end hardenability process and quality control method for the medium carbon alloy structural steel are characterized in that the step 3.2 of sample discharging and quenching transfer is characterized in that after heat preservation is finished, a special clamp is adopted to rapidly take out samples, the discharging time is controlled to be less than or equal to 10 seconds, the samples are immediately transferred to a quenching device, the detection surface is ensured to be completely aligned with the impact center of a water column, the quenching duration is not less than 18 minutes, and the positions of the samples are not moved during the quenching.
6. The full-flow closed-loop end hardenability process and quality control method for medium carbon alloy structural steel according to claim 1, wherein the step 3.3 of quenching process monitoring is characterized in that water temperature, water column height and water flow speed are recorded every 6min during quenching, and if parameters exceed a set range (water temperature + -1 ℃ and water column height + -0.5 mm), the quenching conditions are immediately regulated by a thermostatic device or a valve, so that the stability of quenching conditions is ensured.
7. The full-flow closed-loop end hardenability process and quality control method for medium carbon alloy structural steel, as set forth in claim 1, is characterized in that the step 4.1 of detecting equipment calibration, before detection, precision calibration is carried out on the hardness detecting equipment (manual or automatic), verification is carried out by using a standard hardness block (hardness value is covered by 35-48 HRC), equipment error is required to be controlled within +/-1.2 HRC, and if the error exceeds the standard, the equipment pressure is required to be adjusted, and the position of a detecting head is required to be recalibrated; Step 4.2, calibrating the detection position, namely determining that an end quenching detection point is a 'center+annular area' of the end face of the quenching end of the sample, namely, a center 1 point, uniformly taking 3 points from the annular area with the distance of 4-6mm from the center, and marking the detection position by using a marker pen to avoid detection offset, and cleaning surface oxidation products before each point is detected; and 4.3, repeatedly detecting and calibrating, namely, after each sample completes primary detection, performing secondary detection (after the temperature of the sample returns to room temperature) at intervals of 8-12min, and repeatedly detecting the parallel samples, wherein the range of the detection result of the same sample for 3 times is less than or equal to 2.8HRC, and taking the average value as the final end quenching value of the sample.
8. The full-flow closed-loop end hardenability process and quality control method for medium carbon alloy structural steel, which are disclosed in claim 1, are characterized in that the step 5.1 of calibration results are compared, wherein average end quenching values of all parallel samples are compared with a target range (34-47 HRC), if more than 90% of sample results are in the target range and the dispersion is less than or equal to 3.5HRC, the calibration is judged to be qualified, and if the sample results are not qualified, the deviation (furnace temperature fluctuation and quenching water temperature exceeding standard) is executed by checking parameters.
9. The full-flow closed-loop end hardenability process and quality control method for medium carbon alloy structural steel, which are disclosed in claim 1, are characterized in that the step 5.2 of process parameter adjustment is that if the detection value is overall higher (average exceeds the target upper limit of 2 HRC), the heating temperature can be adjusted downwards by 5-12 ℃ or the heat preservation time can be shortened by 3-5min, if the detection value is overall lower (average is lower than the target lower limit of 2 HRC), the heating temperature can be adjusted upwards by 5-12 ℃ or the heat preservation time can be prolonged by 3-5min, and after adjustment, small-batch (3 samples) calibration verification is carried out again.
10. The full-flow closed-loop end hardenability process and quality control method for medium carbon alloy structural steel, as set forth in claim 1, is characterized in that the component influence auxiliary control in step 5.3 is performed by combining the influence of material components on hardenability, and the residual element content, namely Ti is less than or equal to 0.0065% and Mo is less than or equal to 0.028%, is synchronously controlled in the calibration process, so that the interference of component fluctuation on end quenching values is reduced, and raw materials or smelting processes are required to be adjusted when the components exceed standards; And 5.4, after the calibration is finished, recording sample information, process parameters, detection data and adjustment conditions in detail to form an end quenching detection heat treatment process calibration report, wherein the calibration period is set to be once every 5-7 months, and if obvious deviation occurs in equipment maintenance, process change or detection results, the calibration needs to be immediately recalibrated.

Description

Medium carbon alloy structural steel full-flow closed-loop end hardenability process and quality control method Technical Field The invention relates to the technical field of metal material performance detection and heat treatment, in particular to a full-flow closed-loop end hardenability process and a quality control method for medium carbon alloy structural steel. Background The end quenching detection is a core means for evaluating the hardenability of the structural steel, and the result directly determines the subsequent tempering process selection of the material and the use safety of the product, especially when the medium carbon alloy structural steel is used for manufacturing key parts (such as a knuckle and a shaft part) bearing complex loads, the end quenching value (such as J9) is a key index for judging whether the material meets the processing and service requirements. However, in the current end quenching detection process, non-uniformity and non-standardization of heat treatment process parameters have become core problems that cause deviation of detection results and affect data comparability. Under different detection scenes, key process links such as heating temperature, heat preservation time, quenching medium parameters and the like lack unified calibration standards, namely, on one hand, the temperature of a heating furnace is set to be 5-15 ℃ fluctuated, the heat preservation time difference can reach 10-20min (for example, the total time length of heating and heat preservation of part of scenes is only 35min, and the process which meets the national standard needs is more than 50 min), so that the core of a sample is insufficiently austenitized or austenitized, and on the other hand, the control precision of the quenching water temperature is insufficient (the fluctuation range is often more than +/-5 ℃) and the height deviation of a water column is more than +/-3 mm, so that the dispersion of the quenching degree detection result is further increased. The process is not standard, the detection deviation is directly caused, the difference of end quenching values (J9) of the same materials can reach 3-11HRC due to the heat treatment process difference, the misjudgment of enterprises on the quality of the materials (such as judging qualified materials to be unqualified or vice versa) is caused, the cracking risk (such as exceeding the upper limit of 5% of protocol requirements after tempering) in the subsequent processing process is possibly caused, meanwhile, stock raw material backlog (such as the fact that high-hardenability materials cannot be digested in time) and terminal customer complaints are caused, and the production stability and the supply chain reliability are seriously influenced. In addition, the influence of residual elements (such as Ti and Mo) of materials on hardenability is not fully related in the prior art, and component control is not included in a process calibration system, so that uncertainty of a detection result is further amplified. Disclosure of Invention (One) solving the technical problems Aiming at the defects of the prior art, the invention provides a full-flow closed-loop end hardenability process and a quality control method for medium carbon alloy structural steel, which have the advantages of unifying process parameter references, eliminating detection deviation, improving comparability of results and the like, and solve the problem of larger detection deviation. (II) technical scheme In order to achieve the purposes of unifying the process parameter references, eliminating detection deviation and improving comparability of results, the invention provides a technical scheme that the whole-flow closed-loop end hardenability process and quality control method of medium carbon alloy structural steel comprise the steps of 1, sample preparation and calibration, 2, heat treatment process parameter calibration, 3, heat treatment operation calibration, 4, detection process calibration and 5, result verification and parameter adjustment, wherein the step 1 comprises the steps of 1.1 processing mode and size control, 1.2 surface quality treatment and 1.3 parallel sample preparation; The heat treatment process parameter calibration comprises the steps of 2.1 heating temperature calibration, 2.2 heating and heat preservation time calibration, 2.3 quenching medium parameter calibration and 2.4 decarburization/carburization prevention measure calibration; The heat treatment operation calibration comprises the steps of feeding the sample in the step 3.1, discharging the sample out of the furnace and quenching transfer in the step3.2 and monitoring the quenching process in the step 3.3; The detection process calibration comprises the steps of step 4.1 detection equipment calibration, step 4.2 detection position calibration and step 4.3 repeated detection calibration; The step 5 is to compare the result verification and parameter adjustment with the calibration